New Horizons to Pluto and The Kuiper Belt – Part 2

An Extraordinary Challenge
Unmanned missions to the planets are challenging undertakings at the best of times. As examples, until recently about half of all mission to Mars ended in failure; while the Voyager 1 & 2 Grand Tour of Jupiter, Saturn, Uranus and Neptune was only possible through the 1970’s and 80’s because of an alignment of the giant planets that only happens every 279 years, and which was needed to gravitationally assist the Voyager 1 & 2 spacecraft as they travelled from one planet to the next (called a gravitational sling-shot). We could not repeat such a grand tour of the outer planets today.

But as difficult as planetary missions can be, the challenges facing a mission to Pluto are even greater than those associated with virtually all other planetary missions.

The paramount issue is of course Pluto’s extreme remoteness, residing in the outermost regions of our planetary system. At 6 billion kilometres from the Sun, it takes Pluto 248 years to orbit the Sun just once. At it’s furthest from Earth it can be up to 7.5 billion kilometres away (we may even take license to state that distance as about 0.0008 light years – just shy of one thousandth of a light year!). A journey of such proportions presents extraordinary challenges – not least of which is getting there fast enough within a reasonable fraction of a human lifetime to make the mission practical.

An equally sever challenge is that of communicating with, and managing the spacecraft once it arrives at Pluto. While this is an issue for all missions beyond the Moon, it is particularly problematic with Pluto because of the 9-hour radio-communications round-trip time and for a close encounter lasting just 24 hours in total! In short, there can be no real-time communications with the spacecraft at closest approach, demanding a new capability in automated space exploration.

To set this in one final context: the first successful mission to Mars (Mariner 4) was 50 years ago, yet it has taken all of the intervening time for us to figure out how to devise a successful mission to Pluto. While missions have been proposed since the 1990’s, all were rejected until a proposed mission in 2001 which properly addressed the challenges and offered realistic solutions. That mission is the New Horizons Mission about to unfold – the brainchild of Principle Investigator Alan Stern of Southwest Research Institute in Texas, an astrophysicist and aeronautical engineer with experience in no less than twenty-four previous space and planetary missions.

Extraordinary Solutions
To achieve a successful flyby of Pluto, Stern and his team had to address an extensive set of challenges unique to travelling to Pluto.

Fastest launch in history
Firstly, to reach Pluto in a realistic time frame (deemed to be under ten years), the 2006 launch of New Horizons had to be so powerful as to push the space probe away from Earth faster than any other spacecraft in history – at a velocity of 60,000 kilometres per hour (kph). At that velocity, New Horizons would travel from Los Angeles to New York in just four minutes. Indeed, upon launch, it passed The Moon in only eight hours (it took Apollo 11 three days to reach the Moon), and yet, New Horizons’ journey to Pluto has still taken nine and a half years – and has travelled a journey equivalent to travelling to the Moon – and back – 8000 times.

Even the fastest launch in history was not sufficient to achieve a sub ten-year flight time to Pluto however; and so New Horizons, like the Voyagers, had to also avail of a gravitational slingshot assist around Jupiter in 2007 to boost its velocity by an extra 9000 kph. Otherwise New Horizons would still be seven hundred million kilometres from Pluto today, and would not arrive until September 2016 – fifteen months after its current July 2015 arrival. So successful was the Jupiter gravitational assist that New Horizons will indeed arrive at its closest point to Pluto at precisely 11.47 UTC on July 14th 2015 – exactly 50 years, to the day, after Mariner 4 arrived at Mars!

Efficiency in Space Probe and Science Payload Design
The only way to achieve such a high escape velocity from Earth and rapid transit to Pluto was to make the spacecraft as light and compact as possible. At 478 kilogrammes (kg), New-Horizons (see Figure 1) is one of the smallest probes ever sent to another planet – by comparison the Voyager 1 & 2 spacecraft are each over 700 kg, while the Mars Curiosity Rover has a mass of 900 kg. And while such a mass limitation would normally place severe constraints on the science payload, Stern and his team have devised a first rate science package:

LORRI – a stereo camera which will image features on the surface of Pluto as small as 70m across, and reveal the surface’s 3D topography

Ralph – an Infra-red camera that will analyse the chemical and geochemical composition of the surface of both Pluto and Charon

Alice – an Ultra-Violet camera that will analyse Pluto’s thin but intriguing atmosphere

SWAP & PEPSSI – Plasma and High Energy Particle Detectors that will measure radiation emanating from the Sun and Milky Way Galaxy, and how they affect Pluto and Charon

SDC – A Student (designed) Dust Collector – among the most important instruments because we currently have no details of dust strewn across space beyond Uranus. This instrument will provide significant new insight into the material composition of The Kuiper Belt

REX – An astounding Radio Science Experiment that will listen for radio waves sent from a radio telescope on Earth 4.5 hours before New Horizons’ closest approach to Pluto on July 14th; where upon the radio waves will bounce off Pluto’s surface and into the New Horizons REX detector at precisely the same time as it emerges from the dark side of Pluto, and where the radio ‘echoes’ from the surface will reveal details on Pluto’s surface and atmosphere.

Figure 1: New Horizons. A compact spacecraft suitable for the enormous voyage to Pluto (Click on image for larger view).
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Data Rate Constraints – imposing a New Kind of Planetary Encounter!
Despite the superlative efforts to make New Horizons a reality and a mission of scientific value, there is no getting away from the fundamental issue of how far away Pluto is and how that affects communications between Earth and the spacecraft. Even with a sizable 2.1 metre radio dish antenna, the best achievable reliable data link rate to Earth will be just 1-kilobit-per-second (1kbs) – tiny by broadband standards today, but the very best that can be achieved given the mass and size of the spacecraft, and its remoteness from Earth.

As a result, there is no way that New Horizons could transmit its new images and scientific data back to Earth in real time, and so the spacecraft has been equipped with two 8-Gigabyte solid-state recorders so that as it flies by Pluto it will record all data in real time and permanently, and subsequently transmit the data back to Earth in a steady stream over the next 16 months.

So this will not be like any previous planetary encounter. We will not experience a short burst of vast quantities of data on July 14th. Rather, New Horizons will deliver the images and data gathered in a 24-hour period centred on July 14th back to Earth in a constant stream for more than a year – imposing upon us a new kind of planetary mission – one where we will slowly learn about the planet and come to know it intimately over a prolonged period of time, as it we are there for that length of time.

Pluto Close Encounter – An Automated Event
As already indicated, as soon as New Horizon’s initiates its close encounter mission with Pluto, there is no possibility of direct intervention from Earth. Hence one of the most intriguing aspects to this mission has been the requirement for the entire 24-hour close encounter with the Pluto-Charon system to be completely automated.

The complex logistics associated with this have long since been worked out and have even been rehearsed by the New Horizons team many times in the last ten years on route to Pluto. For such a complicated set of events to be successful, there can be no unforeseen complications. As a result, The Hubble Space Telescope was called upon in the first few days of July 2015 to look ahead of New Horizons towards the Pluto-Charon system, to see if it could spot any hitherto undetected Kuiper Belt object in the flight path or within the Pluto-Charon system itself. To the resolution capabilities of Hubble, none were seen, and on July 4th the final instruction was transmitted to New Horizons to carry out a final course correction toward the heart of the Pluto,-Charon system, (Pluto has 5 moons in total: Charon and the four tiny moons Hydra, Nix, Kerberos and Styx); where the spacecraft will travel within the orbits of all the moons, between Pluto and Charon at a distance of just 12,500km from the surface of Pluto.

To demonstrate the precision to which the entire close encounter has been planned, the New Horizons team recently released for public view one of the many “Observation Playbooks” already predetermined for the LORRI optical camera; which reveal the extraordinary timing and planetary surface location details to be used by LORRI to image Pluto’s surface on closest approach (see Figure 2 for an example from the Playbook). You can download that Playbook by clicking appropriate link in the List of Resources at the end of this blog.

It is worth noting that in having designed such an automated mission, the New Horizons team have set out the first of a new kind of mission that can be used not only for Pluto, but which can serve future missions even further out into The Solar System (NASA’s new Space Launch System, due for first launch in 2018, will be capable of delivering space probes to a distance of 4 times the distance of Pluto in a 10 year time frame). Indeed, as described in more detail below below – it is hoped that New Horizons will itself travel to two other Kuiper Belt worlds in 2018 and 2019, and use its automated capabilities to explore those worlds too.

So let us look more closely at what are the specific mission goals for New Horizons at the Pluto-Charon system, and the time line of events to shortly unfold.

Figure 2: 1 page from the LORRI Camera “Playbook” indicating how New Horizons will image Pluto (Click on image for larger view).
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The New Horizons Mission Goals

Pluto-Charon Phase
Pluto is already known to be like no other world we have visited to date (See Figure 3 for New Horizons image of Pluto on July 10th). With a surface composed of nitrogen and other volatile ices at -229 oC, and with such an elliptical orbit about the Sun, we suspect that there is dynamism on the planetary surface as nitrogen and the other volatile materials change state from solid to liquid to gas. We even expect complex migrating terrains and an atmosphere with weather that varies greatly as the planet orbits the Sun.

Charon on the other hand, is more like the water-ice moons of Jupiter and Saturn, and exhibits none of the dynamic features of Pluto. Because of such differences, it is hypothesised that Charon is the result of a collision between Pluto and another rogue world billions of years ago, leading to the creation of the Pluto-Charon system we see today.

So there’s an extraordinary amount to examine in a very short amount of time; and all of its instruments will be operational at the same time, gathering as much data as possible. Among the planned operations are to:

• Map the surface morphology of both Pluto and Charon
• Take high resolution and 3D topography images of selected locations
• Map the geology and geochemistry of the surfaces of both worlds
• Characterise the atmosphere of Pluto and search for an atmosphere of Charon
• Search for rings and other moons orbiting Pluto
• Observe the behaviour of volatile materials across the surface of Pluto
• Measure the High Energy, Plasma and Dust environment across the Pluto-Charon space environment.

Kuiper Belt Phase
As has been emphasised in of both of these blogs, while originally we set out to visit The Planet Pluto, since the launch of New Horizons, Pluto has been reclassified as a type of world called a dwarf-planet, while the Kuiper Belt has taken on new relevance in our quest to understand the origin, evolution and nature of the entire Solar System.

But with limited on-board fuel and only a maximum of a one degree of arc gravitational sling-shot assist manoeuvring available from Pluto, it has become a priority in recent years to identify candidate Kuiper Belt worlds which New Horizons might visit as it exits the Solar System along its current path.

Once again the services of The Hubble Space Telescope were called upon, and on October 15 2014 Hubble’s search uncovered three potential targets provisionally designated PT1, PT2 and PT3 by the New Horizons team (See Figure 4). All are objects estimated to have diameters around 30–55 km, and at distances from the Sun of 43–44 Astronomical Units – approximately 7 billion km distance (AU – 1AU is about 150 million kilometres – the distance from the Earth to the Sun, and a unit often used to measure distances across The Solar System). It is now intended to send New Horizons to at least one, if not two of these Kuiper Belt objects, with encounters expected to occur over 2018–2019. A decision on which world (or worlds) to visit will be taken through 2016 – 2017.

071015_Puto_Image_Annotated (2)
Figure 3: New Horizons Image of Pluto from approximately 3 million kilometres on July 10th. Complex geology is already beginning to reveal itself, indicating an active surface and climate (Click on image for larger view).
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Figure 4: Hubble Space Telescope image of a Kuiper Belt world in the line of sight of Pluto, for exploration around 2018-2019 (Click on image for larger view).

Pluto-Charon Mission Timeline
So with such an enthralling mission almost upon us, here are some of the details of the close approach of the Pluto-Charon system over July 14th (See Figure 5):

Pluto Close Encounter 12 hours before and after 11.47 UTC, July 14th 2015

• Closest Approach, 12,500 km on July 14th 11:47 UTC (12:47 BST)

• The busiest part of the Pluto system flyby will last one full Earth day, from about 12 hours before closest approach to about 12 hours after. On approach, the spacecraft will study ultraviolet emissions from Pluto’s atmosphere and make global maps of Pluto and Charon both in visible light and in infrared light sensitive to methane frost on the surface. Such infrared measurements will also reveal details about Pluto’s and Charon’s surface chemical and geochemical compositions, as well as the variation in temperature across the surface. New Horizons will sample material coming from Pluto’s atmosphere, and will image all of Pluto’s moons during this period.

• At closest approach, the spacecraft comes within 12,500 kilometres of Pluto and approximately 29,000 kilometres from Charon. During the half-hour when the spacecraft is closest to Pluto and Charon, it will take close-up pictures at both visible and near-infrared wavelengths. The best pictures of Pluto will show surface features as small about 70 metres across. The spacecraft will also obtain stereo maps that will allow for the construction of 3D topography maps of Pluto.

• Upon circling the far side of Pluto, New Horizons will observe Earth and The Sun as they emerge from behind Pluto and pass though its thin atmosphere, allowing us to determine the composition of Pluto’s atmosphere.

• At the same time, radio transmissions which were sent from Earth 4.5 hours previously, will reflect off Pluto’s surface and be picked up by New Horizons as it emerges from Pluto’s dark side; in so doing revealing the composition, structure, and thermal profile of Pluto’s atmosphere in exquisite detail. This will requires precise timing in radio transmissions. The one-way light time delay — the time for a radio signal to reach New Horizons from Earth – will be precisely 4 hours and 25 minutes at the time of closest encounter; and so the New Horizons team must transmit the signals to bounce off Pluto’s surface precisely 4 hours and 25 minutes before the anticipated moment when New Horizons emerges from behind Pluto.

• Even after the spacecraft passes Pluto, Charon and their four smaller companion moons, its work is far from over. Looking back at the dark side of Pluto or Charon is the best way to spot haze in the atmosphere, to look for rings, and to determine whether their surfaces are smooth or rough; while the spacecraft will also obtain images of Pluto’s night side illuminated by Charon, which casts about as much light onto Pluto as a quarter moon does onto Earth.

Figure 5: New Horizons Close Encounter with Pluto & Charon (Click on image for larger view).
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Post Pluto Encounter
• July – Jan 2016 Departure Phase programme: Continued imaging and scientific measurements of beyond the Pluto-Charon system.
• July 2015 – December 2016 – all data to be returned to Earth by December 2016
• November 2017 – All data primary analysis complete. A major conference about Pluto to be held to reveal the results of scientific analysis; and next phase to Kuiper Belt to be planned

And so, as enthralling as the coming week will be, it is also the case that New Horizons will be delivering continuous new images and scientific measurements until December 2016.

If you are interested in following this extensive mission as it unfolds, there is an excellent App available for both iOS and Android devices; while Facebook, Twitter and Web site updates will also be issued on a regular basis over the coming years – see the List or Resources at the end of this blog, all of which will keep you up-to-date during the entire mission.

New Horizons Mission – Context, Value and Relevance

Since its discovery in 1930, Pluto has been nothing more to our collective consciousness than an utterly remote, unfathomably cold and tiny world in the far off reaches of our Solar System. Seemingly of little value to contemplate in any way, the purpose of a mission there was questioned even after its launch.

But like on so many occasions throughout history, what we encounter by bothering to explore is altogether different, and usually unimagined, to our starting point.

In the nine and a half years since New Horizons set off on its epic voyage, our understanding of Pluto and The Kuiper Belt has radically altered. We now know that region of The Solar System to be occupied by upwards of a trillion worlds, each a remnant of the earliest formation of our system, each with a story to tell, a contribution to make, about how our system, and perhaps life itself, came to be.

Irrespective of how far we have come however, the coming weeks and months will radically alter, if not revolutionize once again our perception and understanding of Pluto and its system of moons, of that region of The Solar System and of The Solar System at large.

And so the science, the insight, to be gleaned from this mission will significantly improve our understanding of the origin and evolution of our Solar System, as well as provide valuable new contexts on the origin of life on Earth and a cosmic context for the emergence of other planetary systems and life everywhere.

New Horizons will complete the First Reconnaissance of The Solar System. We will have visited all of the important worlds of our Solar System at least once. This gives us a more comprehensive perspective of Earth as a member of this planetary system. From the frozen depths of the outer rim of the system all the way in to sweltering Mercury, we can now fully appraise Earth’s environment in light of just how different, and hostile to us, planetary environments can be – and are. Nitrogen is a gas on Earth, but it is so cold on Pluto as to be rock solid. Understanding such environments acts as a powerful comparator on how benign Earth currently is, but how drastic changes to its surface environment can be.

Having visited Pluto, we can now see ourselves in a broader context; not for some immediate purpose or requiring some profound reaction by each and every one of us – just – to take on board the full extent and extremes of our entire Solar System, and to be mindful of them when making decisions that require the best context available. Visiting Pluto expands that context, and allows us to see ourselves from a broader perspective.

And so, although all planetary missions can seem similar to one another, this mission will reveal its unique identity in the coming weeks, as a new kind of mission with a brand new story to tell. This is the last major moment of discovery regarding a traditionally regarded major world, and the dawn of a new era of space exploration involving extremely long voyages and completely automated exploration – unleashing a new capacity that will not always require direct intervention, and which in the future may span full or perhaps even multiple human lifetimes.

The engineers working at a ferocious rate right now as you read this had no guidebook, no set of instructions on how to get to, or explore, Pluto. Rather, step-by-step they had to figure it out, and are in the process of writing a new guidebook for the next phase of exploration of space. From Clyde Tombaugh’s extraordinary dedication in discovering Pluto among a myriad of background stars, to the New Horizons teams across both institutions running this project on behalf of NASA (The Southwest Research Institute in Texas and The John Hopkins University), all have contributed to bringing all of humanity perceptively to the outer edge of our stellar system. That’s what can be achieved in 85 years of space exploration.

And so New Horizons is pushing the boundary of our awareness to the edge of our Solar System. For the next generation of space explorers, Pluto will not be their goal. We have achieved that. Their goal will be beyond Pluto, deeper into space and toward interstellar space. New Horizons will have laid the foundation, and they will figure the rest out.

Indeed the very beginnings of such a future are already being contemplated, both by the likes of NASA and other independent organisations. Today, you can go to Boeing’s website and download the brochure for the extraordinary new Space Launch System being build for NASA in 2018, where approximately twenty types of space journey are proposed – including the ability to reach 30 billion kilometres in about the time it took New Horizons to reach Pluto. Meanwhile, concepts for the first interstellar space probe to the nearest stars within the next 85 years are similarly being examined in practical and costed terms.

We can be confident that coming generations will build on what New Horizons has achieved, and will push the boundary of our exploration beyond Pluto, deeper into the Kuiper Belt and eventually to the nearest stars.

New Horizons – Links to Resources




App: Pluto Safari (iOS & Android)
Pluto Safari provides interactive views of the current locations of Pluto and New Horizons, lets you explore a 3D model of the spacecraft and the five-moon Pluto system and helps you find the dwarf planet in the sky. The app also features a multimedia guide to Pluto, a timeline of New Horizons’ milestones and updated news about the mission:




New Horizons Home Web site

Public Outreach Website:

New Horizons Pluto Close Encounter Play Book:

NASA New Horizons Web site

Interview with Clyde Tombaugh

New Horizons to Pluto and The Kuiper Belt – Part 1

Introduction – A Moment of Exploration and Discovery

Over the coming week a compact unmanned space probe called New Horizons will fly by the dwarf planet Pluto, making its closest approach on July 14th. This is the first time a spacecraft will have visited this far off world. So remote is Pluto, at almost six billion kilometres from the Sun, and so small is it (just two thirds the diameter of our Moon) that since its discovery in 1930 we have been unable to determine much about the character of this little but important world. That is about to change.

It is worth contemplating that, whether intimately involved in the New Horizons mission to Pluto, or a member of the public witnessing it unfold from afar, we will all share in this imminent transition from not knowing, to coming to know, Pluto. Nobody is excluded – we will all share the sense of discovery about to unfold.

This is the last moment of significant discovery of a traditionally regarded major world of The Solar System. So the time for engagement with this mission is from now – just before the flyby – to experience the full extent of the close encounter and transition from almost total ignorance about this world, to coming to know it as we have come to know the other planets.

And there are potent ways across numerous modes of communication and connectivity to follow New Horizons (see the “List of Resources” section in the second blog in this series “New Horizons to Pluto and The Kuiper Belt – Part 2”, for pointers on how to follow the New Horizons mission via smart-phone, social-media and online over the coming weeks and months, and next four years of the extended mission beyond Pluto).

The search for The Planet Pluto – A quest to understand The Solar System

The quest to find and characterise Pluto has been a one hundred and seventy year quest to understand the nature of The Solar System at large. It is a quest still incomplete to this day, and the primary reasons we are going there. To understand the nature of this quest, we must consider why a search for a ninth planet was initiated in the first place.

In Search of Planet X
Only five other planets are visible in the sky to the unaided eye – Mercury, Venus, Mars, Jupiter and Saturn. So it wasn’t until well after the invention of the telescope around 1600 that the seventh planet, the gas giant planet Uranus was discovered, in 1781. Over time, it became clear that Uranus’ orbit did not fit with Newton’s theory of gravity used to explain how the planets orbit the Sun; and while some questioned the legitimacy of Newton’s theory, thankfully others held off from throwing out the baby with the bath water, and a search was initiated for yet another (eight) planet that might be perturbing Uranus’ orbit and explain the discrepancy.

That search lead to the discovery of the gas giant planet Neptune in 1846. Although the presence of Neptune largely explained the irregularities in Uranus’ orbit, further studies suggested that the orbit of Neptune itself might also be irregular, perhaps because of yet another hitherto undiscovered planet – a ninth planet even further out in The Solar System. The extent of irregularity in Neptune’s orbit was less than for Uranus however, and doubt was expressed even at the time as to whether there was sufficient irregularity to require the existence of an external influence.

On occasion, lingering and unresolved scientific episodes like this capture the imagination of some from outside the field, and in this case the enigmatic character of Percival Lowell entered the story in the late nineteenth century. Lowell was a wealthy American businessman, a fervent amateur astronomer and the person most responsible for perpetuating the contention (which survived in some quarters until the 1960’s) that there were canals on Mars built by a race of Martians. Lowell set up a well equipped observatory in Flagstaff Arizona in 1894 from where he observed what he claimed to be dozens of planetary-scale Martian canals, and even claimed to see new ones where before none had been seen (a process he called ‘gemination’).

True to character in engaging a potentially sensational celestial story, Lowell also took up the challenge of searching for a ninth planet, which he designated as “Planet X” (where X means unknown, and not the Roman numeral for ‘10’).

Despite extensive searches over a number of years, Lowell found no trace of a ninth planet. He passed away in 1916, but in his will he left one million dollars both to his observatory and to the search for Planet X. After a decade of legal complications regarding that contentious aspect to his will, a new telescope was commissioned at Flagstaff in 1927 specifically for the task of finding Planet X. A young and enthusiastic amateur astronomer called Clyde Tombaugh (Figure 1) was hired to conduct the new search, which he did with dedication and precision. Starting in 1929, Tombaugh systematically took thousands of photographic plates of the night sky along the Ecliptic (the path around the sky along which the Sun, Moon and planets appear to move). He used a device called a blink comparator with which he could flick back and forth between any two photographic plates taken of the same patch of sky on different nights, examining them by eye to see if any object, such as a new planet, could be identified in different locations on each plate as it traversed the sky. Within one year, on February 18th 1930, Tombaugh spotted a new world moving among the background stars across two photographic plates he had taken on January 23rd and January 29th that year (Figure 2).

Figure 1: Clyde Tombaugh (1906 – 1997)

Figure 2: The Pluto discovery photographic plates taken by Clyde Tombaugh in January 1930.(Click on image for larger view)

Calculations quickly revealed the orbit of the new world to be beyond that of Neptune, while early estimates also suggested it might be as large as Earth (best estimates ranged between 0.1 and 0.9 Earth masses). And so it seemed that Planet X had been found, and was given the name Pluto – named in a competition by an eleven year old girl from Oxford called Venetia Burnley (1918-2009); though some claim it was named Pluto because the first two letters in the name are the initials of Percival Lowell!

Tombaugh lived from 1906 to 1997, and it was a pleasure to see him being interviewed by Sir. Patrick Moore on the BBC’s The Sky at Night in the 1980’s, where he described, in the most humble of terms, the extensive effort involved in discovering Pluto.

It is surely fitting that a container attached to New Horizons spacecraft due to pass by Pluto on July 14th carries a small amount of Clyde Tombaugh’s ashes. The inscription on the container reads “Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the Solar System’s ‘third zone’ Adelle and Muron’s boy, Patricia’s husband, Annette and Alden’s father, astronomer, teacher, punster, and friend: Clyde W. Tombaugh (1906-1997).”

And in that description – the mention of a “third zone” of The Solar System – lies the pointer to the continuation of the story of The Planet Pluto and why we are visiting it now. In 1978 it was discovered that Pluto had a moon, given the name Charon, the discovery of which finally allowed for an accurate determination of the size and mass of Pluto. It was found that Pluto was far smaller than previously thought, with a diameter of about 2500 kilometres and a mass far less than that of Earth (now known to be only 1/500th that of Earth). If there was a Planet X influencing the orbit of Neptune, Pluto wasn’t it. While some searches were conducted to find a tenth planet (a true “Planet X”) between 1978 and 1992, improved measurements of Neptune’s mass, by virtue of the Voyager 2 spacecraft passing Neptune in 1989, all but eliminated the need for any corrections to its orbit or for the need for a Planet X beyond Pluto.

The Discovery of The Kuiper Belt
But the more recent searches were not made in vein. Firstly, the 1978 and subsequent measurements of the Pluto-Charon system revealed Charon to be quite large, with a diameter of about 1200 km and orbiting at only a distance of about 20,000km from Pluto; making this an intriguing system of two small planet-like objects perfectly synchronized in their movements through gravitational resonance (also known as tidal locking). Both Pluto and Charon orbit about their common orbital barycentre (centre of mass, a point residing in space about one thousand kilometres beyond Pluto’s surface) every 6.4 Earth days; while a ‘day’ on each world is also 6.4 Earth-days long, with each world therefore only ever showing one face to the other, in much the same way that our Moon only shows one face to Earth.

Furthermore, visual detections began to emerge of a large number of other smaller objects beyond the orbit of Neptune. By the early 1990’s it was realised that stretching out in vast belts from just beyond Neptune at 4.5 billion kilometres, to a distance of more than 8 billion kilometres, are countless millions of minor worlds ranging in sizes from less than one kilometre to several thousand kilometres in diameter. This region is now called The Kuiper Belt, named in honour if the Dutch-American astronomer Gerard Kuiper, the foremost planetary scientist of the first half of the 20th century.

Today it is hypothesised that The Kuiper Belt contains upwards of one trillion tiny icy worlds, with a combined mass of two hundred times that of The Asteroid Belt between Mars and Jupiter. Indeed the Kuiper Belt may contain as many as one hundred thousand minor planet-like worlds with a diameter greater than 100km, and with some of them the size of Pluto. Several Kuiper Belt worlds about the same size as Pluto have been discovered in recent years, three of which are named Makemake, Haumea and Eris.

The Harmony of the Heavens

Multiple belts and types of worlds
Our recent studies of the Kuiper Belt, as incomplete as they are, have radically altered our understanding of not only the outer Solar System, but also of the origin and evolution of the entire Solar System itself.

For example, two distinct categories of objects within the Kuiper Belt have been identified – the so-called Plutinos or Hot-Population which orbit the Sun in highly elliptical orbits that on occasion come within the orbit of Neptune, and which tend to be grey in colour (and of which Pluto is the primary member); and the Cubewanos (pronounced Q-B-ones) or Cold-Population which reside in more circular orbits further out, which don’t cross the path of Neptune and which tend to be more red in colour (and of which the Kuiper Belt object Makemake is a member). We also see another, more dispersed belt of object called the Scattered Disk, made up of millions of tiny worlds scattered over a wide belt beyond Neptune but at steeply inclined orbits around the Sun, of which Eris is a member. It seems that the range of categories of worlds in our Solar System is far more diverse than ever realised.

It is also becoming increasingly evident that acquiring comprehensive details on the range, number and character of such worlds will provide important new insight into the origin, evolution and history of The Solar System. Why? – Because it appears that the worlds of the Kuiper Belt did not originate in their current locations, but were shepherded there over the ages through gravitational orbital resonance by the four giant planets Jupiter, Saturn, Uranus and Neptune. And so by understanding the full nature of the Kuiper Belt, we will uncover new details of the history and evolution of activity across entire Solar System since its birth.

We could regard the study of such worlds as a kind of “celestial taxonomy” – the classification of object types and characteristics as a way of coming to know the natural history of The Solar System. In biology, taxonomy has lead to a deep understanding of life on Earth – not just a description of life-types on Earth today, but also on why there is biodiversity in life and its relationship to its evolutionary natural history. Similarly, through the improving classification and characterization of the worlds within the Kuiper Belt, we will learn more about how they came about and evolved over time.

And so, in this recent and maturing perspective of The Solar System, Pluto has come to be regarded not as a planet like Earth or Jupiter; but as a newly identified category of world called a minor planet, and as a primary member of the Kuiper Belt. As a result, the International Astronomical Union (IAU), in 2006, officially moved Pluto into the newly designated category of minor planet called a dwarf-planet.

We might say that it was the search for Pluto that finally brought us to our first comprehensive view of true nature and history of The Solar System. It is the prime example among many newly discovered worlds that compel us to contemplate what are planets, and what aren’t planets; and in so doing push forward our understanding of the actual system we live in.

The old view of nine major planets orbiting the Sun in never-changing orbits is not correct. Rather, we live in a dynamic system containing a huge range of object types, all governed largely by planetary gravitational forces primarily from the four gas giant planets; which over the eons have interacted with one another as well as the countless smaller worlds – shepherding them into resonant orbits and belts based on close numerical or harmonic ratios (for example Pluto orbits the Sun twice for every three Neptune orbits), creating the extraordinary Harmony of the Heavens which we see today throughout the entire system. And by unravelling the precise sequencing of events on how this came about, we hope to gain a better perspective on the origin and history of all the worlds of our system.

Indeed we have made strides in that direction already. New models of The Solar System indicate that the so called Plutinos originated closer in to the Sun near Jupiter, and are therefore of totally different material makeup and origin to the Cubewanos which seem to have originated further out near Neptune. Meanwhile the orbits of all the major planets, and especially the four gas giants, have moved significantly throughout history, settling into harmonic resonances with one another (for example Jupiter orbits the Sun about twice for every one Saturn orbit); all the while the Kuiper Belt has been assembled from countless billions of world-lets from various parts of The Solar System and shepherded into regulated belts beyond Neptune.

In Search of Origins and a Cosmic Context

While such dynamism and harmonic movement is now known to have happened in the past and indeed continues today, we are far from a complete picture; and our best models contain significant inconsistencies. For example, current models predict fifty times more mass in The Kuiper Belt than we can see; while it is also unclear why many of the Plutino objects possess moons or are twinned with other objects, while none of the Cubewanos exhibit this feature.

So we are far from a complete picture. But we do have the means at our disposal to improve our understanding; from improved theoretical models to observations using the likes of The Hubble Space Telescope, and of course by travelling to The Kuiper Belt to investigate some of those far off worlds close up. This is an on-going quest.

The consequences to achieving a comprehensive understanding of origin and evolution of The Kuiper Belt are significant not only to understanding the natural history of our Solar System, but also toward a better understanding the origin of life on Earth. Not only will those ancient and far off worlds provide details on the water, other volatile materials such as methane and carbon dioxide and organic materials in the Sun’s proto-planetary disc during planet formation; but unravelling the full dynamics of our Solar System’s early history will provide powerful insights into the origin and evolution of all the worlds of our system, as well as the distribution and availability of biogenic materials.

Currently we are very much in the dark on whether life even originated on Earth, let alone on mechanism that originated life; but we know that the conditions of the early Solar System were critically important; and we now know that many of the answers we seek reside in space and in The Kuiper Belt. And, a more comprehensive understanding of our own Solar System will provide details on the formation and character of solar systems and planets everywhere, helping us to gain a better perspective on a broad context for solar systems – and life – elsewhere in the Universe.

And so it has turned out that the detailed investigation of the dwarf-planet Pluto and other Kuiper Belt objects is among the most important scientific investigations we can conduct, the answers to which will provide valuable new insights into some of our deepest questions on origins and a universal context for planetary systems and life itself.

Rosetta: Rendezvous with Comet 67P/Churyumov-Gerasimenko (“67P / CG”)

On Wednesday 6th of August 2014 and after a mammoth 10-year journey across the Solar System, the European Space Agency space probe Rosetta will rendezvous with a comet called “67P / Churyumov-Gerasimenko” (67P/CG) – a tiny icy worldlet just 4-5 kilometre long orbiting the Sun in an elliptical orbit and currently several hundred million kilometres distance from Earth.

By Wednesday 6th August, Rosetta will have settled into a 25-kilometer orbit around 67P/CG. In November 2014, a small automated Lander called Philae attached to Rosetta will be sent down to the surface. Both spacecraft will continue to travel with the comet for the next 16 months as it circles and approached the Sun (closest approach on August 13th 2015); scrutinizing its composition and behaviour as the Sun’s heat transforms the tiny frozen world into a hive of volatile activity that temporarily swells it into a gaseous entity many millions of kilometres in size.

By analysing the comet with a suite of 22 instruments, Rosetta and Philae will conduct a comprehensive analysis of the material makeup of the comet that will provide important new information regarding the origin of Earth, Earth’s oceans and life itself.

Overview and Objectives of the Rosetta Mission
Rosetta is a European Space Agency (ESA) mission to orbit and land on comet 67P /Churyumov-Gerasimenko (“67P/CG”) as it circles the Sun. The primary mission lasts from August 6th 2014 to December 31st 2015.

It is a mission made up of a main Rosetta space probe orbiter and a smaller lander attached to Rosetta named Philae. Rosetta will settle into orbit on August 6th 2014 and continue to orbit the comet over the next 16 months. In November 2014 Philae will land on the comet’s surface. Both will travel with the comet as it orbits the Sun and reaches closest approach to the Sun on August 13th 2015.

Comets are made up of icy volatile materials like water and carbon dioxide, as well as dust and other materials. So as 67P/CG approaches its closest point to the Sun in its orbit (called perihelion), its volatile materials will heat up and sublimate, forming a vast spherical gaseous coma and perhaps a tail, both of which will be more rarefied than the air we breathe and reach for millions of kilometres into space. Since 67P/CG does not approach the Sun too closely (as some other comets do), it is not likely to become as chaotic a ‘volatile cauldron’ as those which travel much closer to the Sun.

While Philae will measure the composition of, and activity on the comet directly from the surface; Rosetta, orbiting at a distance of just 25km, will also measure the volatile materials emanating from the comet into its immediate space vicinity, and indeed will be able to see how the comet changes and reacts to the Sun’s heat and solar wind as they move closer to the Sun in August 2015.

The data gleaned from the comet will reveal its internal makeup and composition, including any organic materials present, to the atomic and molecular levels; providing significant new insight into the origin of the Solar System, the origin of Earth and its oceans and the origin of life.

Journey to Comet 67P/Churyumov-Gerasimenko
Because no current rocket (including the powerful ESA Arianne-5 rocket upon which Rosetta was launched) has the capability to send such a large 3-Tonne spacecraft directly to a comet such as 67P/Churyumov-Gerasimenko, Rosetta was ‘bounced around the inner Solar System like a cosmic billiard ball’, during its ten-year trek to Comet 67P/Churyumov-Gerasimenko.

Since its launch in 2004 from Kourou in French Guiana, Rosetta has criss-crossed the inner Solar System four times, has travelled over 6 billion kilometres, including availing of three gravity-assist flybys of Earth (2005, 2007 and 2009) and one of Mars (2007); and is finally due to arrive at comet 67P/CG – just 4 to 5 kilometres in length – at a distance of several hundred million kilometres from Earth.

Hibernation and Wakeup
Rosetta’s 10 year deep-space odyssey comprised lengthy periods of inactivity, punctuated by relatively short spells of intense activity when encountering Earth, Mars, and several asteroids. Ensuring that the spacecraft survived the hazards of travelling through deep space for more than ten years has been one of the major challenges of the Rosetta mission, and has been hugely successful to date.

To that end, Rosetta was placed in hibernation between June 8th 2011 and January 20th 2014 in order to limit consumption of power and fuel. During that lengthy hibernation, the spacecraft rotated once each minute while facing the Sun for solar power; with the only electrical systems kept running being the radio receivers and command decoders. On January 20th 2014, a “wake-up” command was sent to Rosetta. ESA scientists were hugely relieved that the dormant spacecraft received the command and awoke from its hibernation in excellent health and ready to take on all challenges ahead of it.

August 2014 Rendezvous with Comet 67P/Churyumov-Gerasimenko
Since its reawakening in January, Rosetta has been steadily approaching the comet. For the past 90 days or so, it has been moving at only about 2 metres per second with respect to the comet. As you read this, the space probe is imaging the comet, allowing ESA scientists and engineers to determine the comet’s size, shape and orientation and rotation; allowing for Rosetta to complete its orbital insertion, which takes place on Wednesday August 6th 2014.

Using its approximately 1.7 Tonnes of propellant, the space probe’s propellant system and 24 thrusters recently manoeuvred the probe into an orbit just ahead of the comet, with the final orbit about the comet to be established on August 6th.

Rosetta will then start its science program, using eleven different instruments to photograph and map the comet to great precision, determine its internal structure and monitor any gas and dust emanating from the surface.

November Landing on Comet 67P/Churyumov-Gerasimenko
Once the comet has been mapped, five potential landing sites will be identified. Once ESA scientists have determined the best one, they will plan for a November landing. At that time Rosetta will move to within 1 kilometre of the comet, and release the lander Philae, which will set gently down on the comet at walking pace.

Once secure on the surface, it will anchor itself to the comet (because the comet’s gravity is too small to securely hold the lander on the surface) and proceed to conduct a series of sophisticated experiments, including drilling into the comet’s surface and placing surface materials into the body of the lander where their makeup can be determined to atomic and molecular levels.

Journey towards and away from the Sun
Comet 67P/CG is known as a Jupiter-class comet, meaning that its orbit is affected by the strong gravity of the giant planet Jupiter. Indeed Jupiter changed the orbit of 67P/CG in 1959, so that now the comet travels on an elliptical orbit that brings it to within 185 million kilometres of the Sun at closest approach (perihelion) and out to over 850 million kilometres at its furthest (aphelion).

Over the next 16 months and during the next perihelion on August 13th 2015, both Rosetta and Philae will monitor, image and measure all that happens on and around the comet as it draws nearer to the Sun. As already indicated, because 67P/CG will not travel too close to the Sun, so it is not expected to become as chaotic as comets which venture much closer to the Sun. Nevertheless, there will be plenty of activity, and as of June 2014, Rosetta has already begun to see small quantities of water emanating from the comet, and such activity will but increase greatly over the next year or so, providing both probes with an unprecedented opportunity to examine the makeup, composition and interaction of the comet as it orbits about the Sun.

Rosetta and Philae: Science Objectives and Instruments
Rosetta and Philae are charges with carrying out the following tasks:
• Detailed imaging and mapping of the comet
• Determination of the internal structure of the comet
• Determination of the material makeup, including elemental, isotopic and molecular details, of the comet’s volatile materials, dust and other materials and any organic materials expected to be present in the comet
• Image, monitor and measure the release of all materials, volatile or otherwise, from the comet as it reaches its closest point to the Sun in August 2015; and observe how these materials interact with the Sun’s solar wind and magnetic field

So how will Rosetta and Philae do all of that? The Rosetta orbiter contains no less than 11 scientific instruments including cameras for imaging the comet, a thermal camera to determine its material makeup, a type of radar know as radio-sounding that can penetrate the comet and determine its interior makeup, a mass-spectrometer and dust analyser to analyse materials emanating from the comet and plasma and magnetic field analysers for monitoring the interaction of the comet’s materials with the Sun’s solar wind and magnetic field.

Philae’s science package of 10 instruments is arguably more sophisticated; and includes an Alpha Proton X-Ray Spectrometer (as on the Mars Rovers) to determine the elemental makeup of the surface, a drill to drill into the surface and place samples into its body where a suite of instruments will determine the molecular makeup of the materials, including organic materials, and even determine the isotopic nature of the elements (critical for determining whether comets were the primeval source of all of Earth’s water). Radio-sounding and acoustic instruments will measure the internal structure of the comet, while high resolution cameras will image its surface.

Both the orbiter and the lander will conduct a suite of hard-science experiments typical of modern analytical laboratories. The instruments on board both Rosetta and Philae are more sophisticated than those on the Mars Exploration Rovers Spirit and Opportunity, and on a par with most of the instruments on the Mars Science Laboratory Curiosity; constituting one of the most sophisticated space science missions ever conducted.

Comets and Origins
Comets are tiny icy worlds usually only single kilometres in diameter. They are remnants of formation of the Solar System 4.6 billion years ago. As the Sun formed, countless trillions of tonnes of volatile materials such as water, carbon dioxide, ammonia and methane, as well as organic materials to the complexity of nucleic acids and amino acids that make up DNA ad proteins in life as we know it, were synthesized in the proto-planetary disk surrounding the Sun.

As the planets like Earth and Mars formed, the lighter elements and synthesized volatile materials moved further out from the Sun, contributing to the formation of the gas giant planets Jupiter, Saturn, Uranus and Neptune; but with the left over volatiles forming a vast swarm of perhaps a trillion comets, most of which reside in the Oort Cloud far out in the Solar System between 0.1 and 1 Light Year distance (one-hundred-billion to one-thousand-billion kilometres out – by comparison Pluto resides at approximately six-billion kilometres from the Sun.)

What is so crucial about comets is that they retain a record of the actual synthesis of both volatile materials such as water and carbon dioxide, and of organic molecules to the complexity of genetic nucleotides and amino acids known to be important to life as we know it, in the region of the Sun before the Earth itself had formed.

Hence “67P CG” represents one of a vast family of objects that are potentially older than the Earth, retaining a pristine record of complex chemistry occurring about the Sun relevant to the formation of life on Earth before and when the Earth was taking form. For this reason, comets are seen as very important in our search for the origin of the Solar System, of Earth and its oceans and of life itself.

Rosetta Mission – Relevance and Value to Science & Society
Given that we still have very little idea as to how life originated, studying such primeval evidence as retained in comets constitutes one of the most important endeavours in science. The Rosetta mission is arguably as important as the Mars exploration programme in search of evidence of origins on Mars, and perhaps The Hubble Space Telescope and the CERN Large Hadron Collider, both of which are currently revolutionising our understanding of the nature, origin and fate of the Universe itself.

Among the questions regarding the origin of life we must answer are:
• What is the origin of Earth oceans? In particular, is the water making up our oceans indigenous to our planet, or did it arrive from a mass bombardment of comets, asteroids and meteorites known to have occurred billions of years ago?
• Where did the basic organic materials for life originate – from organic synthesis on our planet, or from organic materials within comets and meteorites manufactured in the vicinity of the Sun before and during Earth formation?

The Rosetta mission may go some way toward answering both of these fundamental questions, among others.

And so we can see why this mission is named Rosetta. As with the Rosetta stone which allowed modern society to decipher the hieroglyphics of ancient Egypt – the Rosetta mission to 67P/CG may provide the cipher to enable us to better read the cosmic book of life – to see better the connection between the origin of life on Earth and its connection to the origin of the Solar System; and to link the origin of life on Earth to a deeper insight into the cosmic abundance of life.

This opportunity has been afforded to us through the technological and scientific endeavour of our ancestors and current generation of scientists alike, and we have taken that opportunity. To not do so would be a dereliction of duty to ourselves, to society, to our place in the great unfolding human story and to future generations who will need the insights we glean from this mission to make new and ever more enlightened decisions and undertake new endeavours to better understand who we are, where we have come from and what our cosmic fate can be.

I recommend that you follow the Rosetta mission over the next 16 months or so via the following links. In the Documents section of this blog (see Menu at top of Blog) you will also find a downloadable PDF document titled “TPS_ESA_Rosetta” containing this blog in a more bullet-point format, as well as containing greater detail on both the Rosetta Orbiter and Philae Lander and their science instruments, as well as a set of images including source URSs to hi-res versions, and required credits should you use any of the images.

Web (ESA):

Rosetta on Twitter:

Rosetta on Facebook:

Rosetta Blog:

Rosetta on Youtube:


1. Rosetta Space-probe and Philae Comet Lander:


Caption: In November 12014, Rosetta (upper) will set the Philae lander (lower) onto the surface of comet 67P / Churyumov-Gerasimenko as it closely approaches and then circles the Sun

Hi-Res Source:

Credit: ESA–J. Huart

2. Illustration of the size of comet 67P/ Churyumov-Gerasimenko

Caption: Illustration showing the relative size of comet 67P / Churyumov-Gerasimenko to well known features on Earth. Though huge on a human scale, comet “67P” is a small celestial body and possesses only a very weak gravity.

Hi Res Source:

Credit: ESA

3. Comet images on August 1st 2014 67P / Churyumov-Gerasimenko


Caption: On 1st of August, Rosetta took this image of comet 67P / Churyumov-Gerasimenko, revealing it to be a double lobed, peanut shaped object.

Hi-Res Source:

Credit: ESA

The Summer Solstice 2014 and The Summer Night Sky

It’s been some time since I’ve blogged! I had hoped to blog a tad more regularly, but it’s becoming clear to me that it’ll take longer to get up to speed with regular blogging (with worthwhile content!).

So I’m still in a phase of extensive research and literature surveying for intended blogs on the future of Mars exploration, the changing landscape of space exploration and related sociological issue. When all of that is complete it will hopefully lead to some insightful blogs as there are many changes taking place right now in how space exploration is being planned and pursued, and on how people in general perceive it – and with MANY outstanding and issues too. Watch this space!

In the mean time, what a perfect opportunity to write a little about the summer solstice and the summer night sky from Ireland. As you may have heard on the RTE Radio 1 Marian Finucane Show on Sunday 22nd June, we chatted about the summer solstice, so I thought I’d post some details on the solstice from an astronomical point of view, and talk a little about what constellations are in the night sky over Ireland. A little rushed, but here goes:

Key Points:

– Moment / time each year when Sun reaches highest point in the sky
– When (2014): 11.51am on June 21st
– Height above the horizon from Ireland (Altitude): 60.5 degrees above the horizon
– For all points on Earth, including Ireland, the Sun reaches a different height in the sky for each and every day. In mid winter it reaches only about 13.5 degrees above the horizon (called the winter solstice), shortening our days; while in mid summer it reaches an altitude of 60.5 degrees (summer solstice), lengthening our days. Mid point between those extremes – at the spring equinox (March) and autumnal equinox (September) the Sun reaches an interim height (about 37 degrees) and we get approximately equal length days and nights
– Cause: Earth’s axis is tilted by 23.5 degrees, it is spinning and it is orbiting the Sun. So in summer Earth is tilted toward the Sun and we see it higher in the sky, in winter we’re tilted away from the Sun and we see it lower in the sky, and for every other day of the year the Sun reaches a height at noon between those extremes.
– To help visualize this, concentrate first on the extremes. So in summer we’re tilted 23.5 degrees towards the Sun meaning that when it rises into the sky it reaches a great height. Conversely in December we’re tilted 23.5 degrees away from the Sun so we see it correspondingly lower in the sky. On the equinoxes we’re neither tilted away nor toward the Sun so it reaches an interim height – and we get 12 hours day and night. Of course the Earth is always tilted at 23.5 degrees – that doesn’t change through the year; what we’re interested in here is the orientation of that tilt with respect to the Sun, and at the equinoxes the Earth is tilted at 23.5 degrees for sure, only neither towards nor away from the Sun.
– Each place on the Earth experiences the same affect but to differing amounts depending on its latitude on the globe; so every location in the northern hemisphere sees the Sun at its highest point in their sky on June 21st.
– To work out the maximum angle of the Sun above the horizon on the summer solstice at your latitude:
(90 degrees – your Latitude) + 23.5 degrees (that equals 60.5 degrees for Ireland)
– To work out the maximum angle of the Sun above the horizon at your latitude during the winter solstice:
(90 degrees – your Latitude) – 23.5 degrees (approximately 13.5 degrees for Ireland)

– The Earth orbits the Sun once a year and so the Sun appears to traverse the sky once a year (from west to east)
– We don’t see the Sun actually move from west to east throughout the year, rather we see it at about the same position at the same time each day, with the background stars (from our line of sight) changing accordingly throughout the year. To visualize this, imagine asking a friend to stand still while you walk around them keeping your eyes firmly fixed on them at all times. As you circle your friend they will stay in the centre of your field of view. However, what you see behind them will continuously change as you circle them. It’s like this for the Earth circling the Sun. We see the Sun at approximately the same place in the sky at the same time each day, but the stars or constellations behind the Sun change as the year passes by.
– So as Earth orbits Sun it appears to move in relation to the background stars. Ancient civilisations organised groups of stars in the sky into patterns called constellations; and the Sun passes through one constellation per month. Hence the 12 constellations it passes through are called the constellations of the zodiac, and are named: Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn and Aquarius. The path around the sky through the zodiac that the Sun appears to travel is called the ecliptic.
– But the tilt of the Earth has a significant effect on the Sun’s apparent yearly motion about the sky in a vertical sense (as in: higher in summer and lower in winter), and is the cause of us having longer days in summer and shorter days in winter.
– Because the Earths axis is tilted by 23.5 degrees the Sun moves around the sky once a year on a path that is tilted at an angle of 23.5 degrees to the celestial equator (the extension of the Earth’s equator into the sky that divides the sky into north and south). So the Sun’s yearly path is a great circle in the sky (called the ecliptic) that intersects the celestial equator at an angle of 23.5 degrees and so the Sun appears to travel from south to north and back again in a cyclical manner over its yearly path. The Sun is below the celestial equator for 6 months and so appears in southern part of the sky, and is above the equator for 6 months and appears in the northern sky. It is this south-to-north (and back again) apparent movement of the Sun in the sky over the course of a year that gives us longer and shorter days; where (for us in the north) the Sun reaches its furthest point north in the sky in summer, appearing higher in the sky and giving us longer days, while it reaches its furthers point south in winter and hence appears lower in the sky, giving us shorter day.
– The point when it traverses south to north – where the ecliptic intersects the celestial equator – is called spring equinox and gives us 12 hours of day and night (approximately). This is also called the First Point of Aries because when ancient civilisations discovered this phenomenon, the Sun appeared in the constellation of Aries as it travelled from south to north.
– Also, at the time of such celestial discovery about 2000 years ago, in mid-summer the Sun resided in the constellation of Cancer and also directly over head at a latitude of 23.5 degrees north of Earth’s equator. This is why that latitude is called the Tropic of Cancer. Similarly at mid winter in the north (mid summer in the south) the Sun resided in the constellation of Capricorn and also appeared directly overhead at a latitude of 23.5 degrees south of Earth’s equator and why that latitude is called the Tropic of Capricorn. Precession of the Earth’s axis over a 26,000 year period means that although Earth’s tilt remains about about 23 degrees, it’s orientation changes (think of a spinning top rapidly rotating at a tilt but the orientation of the tilt changing over time). As a result of this precession the constellation the Sun appears in at the equinoxes and solstices changes over time (by about 1 degree in the sky every 72 years) so that today the Sun no longer appears in Aries at the spring equinox but instead now appears in the constellation of Pisces; and similarly no longer appears in Cancer at the summer solstice and instead has moved into the constellation of Gemini at that time of the year.

Finally, Earth’s precession also means that, were it not for regular corrections we make to our calendar, mid-summer in the northern hemisphere would occur in December in about 13,000 years from now. To ensure we retain our existing calendar with mid-summer always in June, we add fractions of a second to our clocks every few years, nudging the calendar back into place to counteract the Earth’s precession.

The Summer Constellations

Of course, while we can’t directly see which constellation the Sun is in at any given moment (because that constellation is behind the Sun in the day time), as the Sun moves from constellation to constellation, it correspondingly affects which constellations we see at the night. In particular, those constellations on the far side of the sky to the Sun at any given moment will appear in the middle of the night.

This is why we see different constellations in the night sky during different times of the year. For example, the constellations of Taurus is visible in the southern sky in winter, but during the summer it is not visible at night because the Sun is actually in the constellation of Taurus so it is in the sky during the day.

So this gives us a lovely opportunity to ask what constellations are in the summer sky around the time of the summer solstice and though July? Though of course the skies are less dark than in winter (because the days are longer and the Sun does not set so far below the horizon at our latitude), the summer night sky from Ireland is nothing less than spectacular.

Firstly, traversing the sky from northeast towards southwest you see the faint white band of the Milky Way galaxy itself, of which we are a part. The Milky Way is a galaxy of perhaps 200 billion stars, each like our Sun, and the band of light is the combined starlight of all 200 billion of those stars.

The main feature of our summer skies is called the “Summer Triangle” made up of the three brightest stars you can see as you look overhead and south: the brilliant blue-white star Vega (in the constellation Lyra) almost directly over head at midnight through July, Deneb the strong white star in the magnificent constellation of Cygnus the Swan (also known as the Northern Cross) and the white-yellow star Altair furthest south in the constellation of Aquila. Altair is of particular note because, at just 16 light years distance, it is one of our closest cosmic neighbours (and is the star to which the gallant crew travelled in the iconic 1950’s film “Forbidden Planet”).

The constellation of Cygnus the Swan is also of particular interest. To find it, look for a large cross or crucifix outline of seven stars almost directly over head during July, of which the brightest star is Deneb. Cygnus lies within the rich star fields of the Milky Way, and viewing this constellation through binoculars is nothing short of spectacular, where you will witness countless thousands of stars to rival any Star Wars movie scene.

The Kepler exoplanet finder space probe, which has discovered about 2000 planets around other stars, concentrated its efforts exclusively within Cygnus, so it is surely intriguing to know, as you look through your binoculars at the stars within the constellation, that many of them possess families of planets.

Finally in the summer night sky we cannot ignore the giant ‘W’ of the sky: Cassiopeia. Though Cassiopeia is visible in the sky all year round from Ireland, it is particularly splendid in summer in the northeast region of the sky. Identifying it for the first time is hugely satisfying, and again observing it through binoculars is nothing short of spectacular. A particular treat through binoculars is the magnificent double star cluster in the constellation of Perseus, the next door constellation to Cassiopeia. and you can find the double cluster easily using Cassiopeia as a guide – from the left most star of Cassiopeia find the 2nd and 3rd stars of the great ‘W’ – then extend their line downwards for about twice their separation and you arrive at the fabulous double cluster in Perseus. Each of the clusters comprises more than 300 blue-white giant stars and are perhaps only 12 to 13 million years old – a blink of the eye in cosmological terms and when compared to our Sun’s 4,500 million year age!

I urge each and every one of you to come to know the motion of the Sun, Moon, Planets and stars in our sky. Read about it, learn how people of old figured out such motions. Convince yourself of Earth’s movement about the Sun and how it affects the seasons, length of day, how high the sun can reach in the sky and what constellations you can see at each time of the year. There is no doubt that gaining such insight delivers a great sense of connection and ‘place’ in the greater natural scheme.

Likewise, I strongly advise you to come to know the night sky at various times of the year. There is nothing more enthralling than identifying the constellations for yourself. The first time you see a constellation pattern in the sky is a very exciting moment; and without trying to be over the top about it, a quite personal moment. For me, that moment occurred when I was about 10 or 11. I had read about the constellation of Orion from a beautiful little book called the “Observers Book of Astronomy” my Patrick Moore, and set out on winter evenings to see it for myself. I spent no less than three winters looking for it, but to no avail. I just could not find it. For the first couple of winters I looked and looked. What kept drawing my attention, however, was three stars in a straight line that would appear in the autumn sky to the southeast , and fade in spring to the southwest. I found those stars fascinating, but for love nor money I could not find Orion. I read about it more and more, but nothing could reveal it to me.

And then, on the third winter, while looking at those intriguing three star, Orion presented itself to me in a moment of pure revelation. I looked at the three stars and realised in a moment of joy and exhilaration that they were actually at the centre of Orion! There was Orion, magnificent – HUGE – surrounding those three stars (the belt of Orion!) in the sky, dominating a much, much larger part of the southern sky than I had expected – in front of me all the time. My mistake over the previous years had been a lacking of perception of the size of the constellations in the sky. I had thought they were tiny, and that I would have to track them down with fine precision within a small part the sky! Nothing could have prepared me for the sheer size and scale of the the constellations in the sky and how readily visible they are to the unaided eye; and so I could not see Orion even on the most glorious of dark, crisp nights. I will never forget that night and that moment of personal discovery; and I urge each and every one of you to similarly explore the sky – most especially with your naked eye and at most with a pair of binoculars – but first and foremost with your eyes only (and a good night sky guide), to discover the constellations for yourself.

And be sure to look into the summer night sky on some calm cloudless evening – either with the naked eye to discover the constellations for yourself or with a pair of binoculars to witness the splendor of the heavens just beyond the perception of the naked eye. Find out a little of the mythology of each constellation you identify, learn what stars, nebulae and star clusters are in it, read a little of the astrophysics that describes the processes underlying the formation, evolution and fate of the stars and indeed the Milky Way itself. Finally, perhaps explore the magnificent and unique Hubble Space Telescope image archive on-line to witness visual details not visible from the ground and indeed to learn more about the powerful cosmological processes that drive the workings of the Universe itself. Make such a quest your own. From looking into the night sky to learning about the underlying cosmological forces at play, there is much you can do to enhance your sense and understanding of nature on the grandest scheme. You do not need to be a scientist or astronomer to do this, and each and every one of us has an entitlement to such a sense of connection and ownership of the universe within which we live.

Happy observing and learning!

TPS Ireland talks about Mars in Feb. and March (2014)

I’m delighted to say that I’ve been invited to give two talks through February and March as TPS Ireland representative, which anyone can attend. I’ll deliver the same talk on both occasions. It’s titled “Exploring Mars, Discovering Earth” which was the theme for The United Nations Space Week 2013, run in October 2013; and for which Mars geomorphologist Professor Mary Bourke at Trinity College Dublin ran a fabulous week of public events related to Mars.

The talk in Feb. and March will be an updated version of the talk I gave last October. So while I’ll talk about the basis for Mars exploration and discuss the latest missions and mission findings, I’ll also mention some arising issues such as newly announced robotic missions to Mars by both ESA and NASA; and if time permits, offer some context on recently proposed human missions to Mars such as “Inspiration Mars” and “Mars One”, looking at their merits and concerns.

I plan to write blogs on all of those issues in the coming months, and am as we speak drafting a blog on the basis of, and reasoning behind, current robotic Mars exploration. I hope to post that blog by mid February.

In the mean time, if you feel inclined, please do attend one of the upcoming talks. They are aimed at the general public, are rich in astounding Mars images (some in 3D) and video animations, and will also present the very latest findings from the MER Opportunity and MSL Curiosity rovers. The details are as follows:

Talk 1: Presented by Kevin Nolan of The Planetary Society to The Irish Skeptics Society, on Wednesday 26th February, at 8pm in the Davenport Hotel, Merrion Square. All are welcome.

Talk 2: Presented by Kevin Nolan of The Planetary Society to The Irish Astronomical Society, on Monday 31st March, at 8pm in Ely House, 8 Ely Place, Dublin 2. All welcome, free event.

Mars Exploration Rover Opportunity 10th Anniversary – 25th January

On January 25th 2014 the Mars Exploration Rover “Opportunity” celebrates ten years operations on the surface of Mars. This blog provides a little insight into that remarkable ten year (and continuing) mission. If you click on the Documents section you can find a PDF document I’ve put together for download providing an overview of Mars Exploration and the Opportunity mission. In future blogs I’ll provide some insight into the reasoning for Mars exploration and the current program for Mars exploration being pursued by NASA and ESA in particular. For now, it is surely appropriate to reflect on the remarkable MER Opportunity rover.

The Mars Exploration Rovers (MER) Spirit and Opportunity both landed on Mars in January 2004. Their mission was straight forward – to investigate whether their respective landing locations once retained large bodies of standing water on Mars billions of years ago. Verification of past surface water would strengthen the case for Mar being similar to Earth in its early history, and perhaps of life-related activity occurring on the planet. Since Mars still retains a planet-wide record of its early planetary activity, any such discovery would present an unprecedented opportunity for humanity to further explore and examine conditions similar to those that gave rise to life on Earth (conditions long since gone from our world).

While within just months of landing on the surface Spirit had verified that the 100km wide crater it landed in was indeed a vast lake in its early history, Opportunity’s landing was nothing short of remarkable. It scored a ‘cosmic hole in one’ by inadvertently landing within a tiny 22m wide crater upon a vast flat plain called Meridiani Planum, suspected to have been a sea on Mars billions of years ago. Nothing could have prepared scientists for what they were about to witness, starting from the first images sent back to Earth by Opportunity: images of the exposed walls of the tiny shallow crater revealing water-based sedimentary layered structure and even salt deposits on the surface of the crater; immediately and unequivocally verifying that Meridiani Planum had indeed been a sea on Mars billions of years ago.

Although MER Spirit and Opportunity were chartered to carry out a 90-day primary mission (with extensions expected), nobody had expected that, 10 year later and 40 kilometres down range, MER Opportunity would still be operational. Not only has Opportunity survived four sub -100oC Martian winters, but it also managed to survive a 3-year, 20-km trek across the vast sandy plains of Mars to reach a huge 22km-wide crater called Endeavour, which it arrived at in September 2011. To add poignancy to Opportunity’s mission, NASA revealed to the World in September 2011 (in honour of the tenth anniversary of the 9-11 Twin Towers attacks) that a small piece of aluminium making up the robotic arm of Opportunity originated from the shattered aluminium body of one of the World Trade Centre Twin Towers.

Today, Opportunity is still going strong. It has been reprogrammed from Earth to be an autonomous artificial–intelligent “thinking machine” capable of planning excursion and scientific investigations on its own and without instruction from Earth. Although showing signs of wear and tear, it celebrates 10 years of roving across the surface of Mars on January 25th 2014, after which it will embark on among its most important scientific investigation – a several kilometre excursion south along the rim of Endeavour crater to a site found from orbit to retain clay materials – materials that formed billions of years ago in a non-acidic water environment, and materials which on Earth are seen as potentially important to the origin of life here. The years ahead for Opportunity may turn out to be its most productive of all; contributing to one of the most extraordinary feats of exploration every undertaken by humanity.

For the rest of this blog, lets take a look at some overview facts, and some images, related to Mars exploration; and to the achievements of Opportunity:

Mars Exploration:

o Mars is a rocky planet half the diameter of the Earth and although dormant today, it retained oceans, seas, lakes, rivers and an atmosphere in its early history

o Since Mars retains a planet wide record of that early activity similar to Earth, it offers a significant opportunity to explore the origin of life itself, and to determine if life arose there.

o NASA and ESA have therefore been engaged in a hugely successful 5-phased, multi-decadal robotic program of Mars exploration since 1997, and continuing today…

Some Mars Exploration Highlights:

o Mars Global Surveyor Orbiter (1997 – 2005): Verified ancient water systems from orbit

o Mars Odyssey Orbiter (2001 – Present): Finds vast reservoirs of water-ice on Mars today

o Mars Exploration Rovers Spirit and Opportunity (2004 – Present): Unequivocal verification of ancient seas and lakes on Mars. Opportunity has driven 40km across Mars to the present day

o Mars Phoenix Lander (2008): Direct contact with water-ice just centimetres below the surface

o Mars Science Laboratory (2012 – Present): Verified that its landing site, Gale Crater, was habitable in Mars’ past

Opportunity’s – Ten Year Journey across Mars

Among the most extraordinary and exhilarating aspects of Opportunity’s mission is the journey it has embarked on over the past ten years, and continuing to this day:

• January 25th 2004: Eagle Crater: Opportunity arrived on Mars on Meridiani Planum – a dried ancient sea bed near Mars’ equator. It landed in a small crater called Eagle Crater, approximately 22m across and showing both water-based sedimentary layering and precipitated sea salt on the surface all around the rover. An extraordinary happenstance.
• April 20th 2004: Endurance Crater: After about 80 days, on April 20th 2004, Opportunity arrived at a football-stadium sized crater called Endurance Crater, at about 800m distance from its landing site. There, it discovered sedimentary rocks created by water deposition, and verified that the region had been inundated by water from two different seas at two different eras in Mars’ ancient past.
• January 2005 – September 2006: Opportunity travels over 7km to a 700m wide crater called Victoria Crater. On route it becomes lodged in a tiny sand-dune (subsequently called “Purgatory Dune” and requiring NASA to spend 6 weeks to dislodge the rover). On route to Victoria crater Opportunity finds further extensive evidence that entire regions was once a sea. As the rover arrived at Victoria crater it was photographed from Mars orbit by the newly arrived Mars Reconnaissance Orbiter which can image objects from orbit as small as 30cm on the surface.
• August 2008 – September 2011: Journey to Endeavour Crater. The decision was taken in August 2008 to send Opportunity on an epic 20km trek to a 22km wide crater called Endeavour Crater. For 3 years the rover drove relentlessly across the Martian landscape and arrived at Endeavour Crater in August 2011. This is now regarded as among the most epic voyages of exploration every engaged by humanity. On route the rover photographed a meteorite that was then given the name “Oileán Ruaidh” – named after the island off the coast of Donegal of that name and bearing a very similar shape!
• September 2011 – Present Day. Since late 2011, Opportunity has been exploring the rim of Endeavour Crater because the rim material is composed of materials from Mars’ earliest history over 4 billion years ago. It may yet make some of its most important discoveries at this location, including the examination of clay materials that only arise as a result of water that is neither acidic nor alkaline but instead is of neutral pH. Clay materials are seen as important to natural processes potentially leading to the origin of life.
• Present-day – the future: Opportunity has traveled over 40 km across the Martian surface and will continue its voyage of discovery for the foreseeable future.

Opportunity – Milestones, Discoveries & Achievements

• Launch: July 7, 2003
• Launch Vehicle: Delta II H
• Arrival: Jan. 25. 2004 UTC
• Landing Site: Meridiani Planum
• Mission Duration: Still roving!
• Odometry: 24 miles (40 km)
• Images Returned: 187,000
• Verified that Meridiani Planum was an ancient sea. Verified that at two different times in Mars’ past a sea resided there; for a minimum of several hundred thousand years (and likely millions of years) in each era.
• Unequivocal evidence (for the first time) of surface water on another world. This also suggested that Mars possessed a dense atmosphere about as dense as Earth’s atmosphere today. Although the water activity at that location was probably not conducive to life as we know it, water is seen as a crucial ingredient to the origin, inner-workings and development of life as we know it.
• Opportunity will shortly analyse surface clay materials – suggesting water from yet another era and this time much more conducive to life as we know it. Clay materials are seen as important in aiding the polymerization of organic and genetic materials.

Images (with captions, hi-res source links and credits)

1. Mars Exploration Rover:


Caption: Artist Impression of MER Opportunity on Mars. The Mast Stereo Camera and Robotic Arm are seen clearly.



Credit: Courtesy NASA/JPL-Caltech

2. Festoon Cross Bedding: Evidence of Past Running Water on the Surface of Mars

Caption: This image shows distinctive centimetre-sized “festoons.” They imply the presence of small, sinuous sand ripples that form in water, and are the preserved remnants of tiny underwater sand dunes formed long ago by waves in shallow water on the surface of Mars.



Credit: Courtesy NASA/JPL-Caltech

3. Opportunity’s Journey 2004 – 2014


Image showing MER Opportunity’s epic journey across the Martian surface. Opportunity was not designed to travel such vast distances, but so well built is the rover that to date it has traveled almost 40km – the furthest any machine has traversed any world beyond Earth. Opportunity shows no signs of stopping, and may have several more years of operational life left.



Credit: Courtesy NASA/JPL-Caltech

4. Opportunity Current Location

Opportunity’s location in January 2014: Murray Ridge is on a part of the rim of Endeavour Crater called Solander Point. Murray Ridge is named in honour of Bruce Murray, former head of the Mars Viking Mission, Director of JPL and co-founder of The Planetary Society, who passed away on August 29th 2013. This image was taken on the 3,496th Martian day (Sol) with Opportunity’s near-infra red camera. Each colour represents a different mineral; enabling scientists to decipher Mars’ ancient surface activity because different minerals form under different temperatures, pressure and humidity. Despite the remarkable statistics regarding Opportunity’s journey, it is the scientific data that Opportunity returns to Earth relentlessly that is most valuable of all, allowing us to understand Mars’ early history and favourability for life-origins related processes; a challenge still in its infancy.



Credit: Courtesy NASA/JPL-Caltech


Welcome to my new blog. My name is Kevin Nolan. I’m the Coordinator to Ireland for The Planetary Society and the author of the book “Mars, A Cosmic Stepping Stone” (Springer/Copernicus, NY, 2008).

This blog aims to provide current affairs, analysis and (hopefully) objective insight into aspects of space exploration and astronomy; with particular focus on Mars, Mars exploration, Life in The Universe and our ever-changing perspective of our place in the Universe. There will be healthy doses of science-and-society, space-policy and other sociological aspects to space exploration.

As a science communicator, I have a particular interest in communicating the relevance of science to those not interested in science as a subject, but who are interested in the relevance, value and impact of science on our lives, on society and upon the future.

Thanks for visiting this blog, and I look forward to regular posts (aiming for about one new post every two weeks for the time being and eventually one a week when I find my feet) on the important topics of the moment. It will be an interesting learning experience for me, and hopefully provide some worthwhile information and insight to you; and perhaps prod some interesting comments too.

…and of course – I will be providing details of ALL Planetary Society Ireland events here too!