Life in the Universe

Detection of Terrestrial Planet Candidate in a Temperate Orbit about Proxima Centauri

Summary
Proxima Centauri is the closest star to our Solar System. At 4.24 light years distant, it is the closest of a triple star system called the Alpha Centauri system comprising of two Sun-like stars at a distance of 4.38 light years, and Proxima Centauri, a red dwarf star residing about two trillion kilometres or a little under 0.2 light years closer to us, and in orbit of its two companions. In our night sky they are located in the southern hemisphere constellation of Centaurus.

Given the detection in recent years of thousands of planets around other stars, called exoplanets, there has been a major aspiration to detect a planet around any of the three stars of the Alpha Centauri system. To this end, the European Southern Observatory (ESO), the largest astronomical institution in the world, set a science (and science-outreach) project in motion in January 2016 called PaleRedDot – a specific search for the existence of a planet exhibiting potential Earth-like characteristics around Proxima Centauri; and on August 24th 2016 the PaleRedDot consortium of scientists from the UK, Spain, Chile, the US and other countries published findings in the journal Nature that strongly indicates the presence of an Earth-sized planet orbiting Proxima Centauri. PaleRedDot has achieved success – within just months of its initiation!

What is intriguing about this discovery is that the planet, currently designated Proxima B, is similar in size to the Earth at around 1.3 Earth masses, and also resides at a distance of 7.4 million kilometres from its cool red parent star within what is called its habitable zone – the region about the star that could allow any water on an orbiting planet to exist in liquid state. These characteristics make Proxima B a candidate terrestrial or candidate Earth-like planet.

While details of the planet’s make up and surface conditions are currently unknown and none of the new evidence suggests any actual terrestrial characteristics, such is the rapid development of telescopes and analysis techniques that it is likely only a matter of a years before we gain sound insight into many of Proxima B’s characteristics, including whether any of its potential for terrestrial-like behaviour has been realised.

And so this discovery marks the beginning of an intensive period of endeavour and discovery, heralds a new era in exoplanetary science given the proximity of the planet, that will surely lead to significant new insights into Proxima B in particular and planets and solar systems in general.

With highly innovative technical proposals emerging for long range robotic exploration of the outer Solar System and beyond, the discovery of Proxima B also offers a new and unprecedented planetary target at our closest stellar neighbour, and will act as a major sign post toward the stars in the coming decades. We have our first confirmed planetary exploration destination beyond our own Solar System!

This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image between the planet and Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.

This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image between the planet and Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Credit: ESO/M. Kornmesser

Background

The Sun and Stars
Our Sun provides virtually all energy in our Solar System and Earth could not have given rise to or sustained life as we know it without its presence. At just one hundred and fifty million kilometres distance, the Sun is a very close neighbour indeed.

All of the stars in the night sky are also suns, some much larger and hotter than ours such as the brilliant blue-white star Rigel in the constellation of Orion; with many others smaller and redder in colour and shining more dimly than our Sun. Such dim stars are called red dwarfs.

By contrast our Sun is an in-between star – yellow in colour – and with a diameter of one million kilometres is unremarkable in size, mass and brightness when compared to the most massive stars like Rigel.

Of the 400 billion of stars in our Milk Way galaxy, the vast majority (75%) are red dwarfs, while just 4% are like our Sun. Still, that’s approximately 16 billion Sun-like stars in just our galaxy.

The distances between the stars are truly vast. While we measure the distances between the planets of our Solar System in tens or hundreds of million of kilometres, stellar distances are typically many trillions of kilometres. Such distances are truly gargantuan and so the light year has been adopted to indicate the distances between the stars, where one light year is the distance travelled by a ray of light in one year – 10 trillion kilometres (well, 9.6 trillion km).

Our Milky Way galaxy, containing upwards of 400 billion stars, is a flattened disk extending more than one hundred thousand light years, and with a central bulge more than twenty thousand light years in thickness.

Exoplanets
In the quest to fully understand our Milky Way galaxy and the Universe in general – and our place in the greater scheme – we have always wondered whether the far off stars are accompanied by planetary systems. But with such vast distances to contend with, evidence of planets around other stars, called exoplanets, has been beyond our detection capabilities until quite recently.

Over the past twenty years however, telescopes, detectors, computers and analytical techniques have improved so radically that we have been able to detect planets around many stars. And so today the detection of exoplanets is one of the most active fields of science, involving the World’s great telescopes such as the European Southern Observatory located in Chile, and space probes such as NASA’s Kepler Exoplanet Detector and the Hubble Space Telescope. As of the time of writing, approximately 3500 exoplanets have been confirmed, with new planets being discovered on a near daily basis.

Such has been the transformation of the detection and study of exoplanets that by now we have even achieved the first tentative census of planets in the entire Milky Way galaxy; and the numbers are staggering.

For example, we are confident that almost every star in the galaxy has at least one planet, so that makes for a minimum of four hundred billion planets, and the full count is likely to run into the trillions. It is estimated that there may be upwards of 30 billion Earth-sized planets in the Milky Way (note – ‘sized’ not ‘like’) and intriguingly we suspect that of the 16 billion Sun-like stars in the Milky Way, one in five of those has an Earth-sized planet residing in its habitable zone. That makes for about 3 billion stars like our Sun each with a planet the size of the Earth residing in its habitable zone, in just our Milky Way galaxy alone.

Exoplanet Detection
Detecting exoplanets is an extraordinarily challenging business even today. In most cases, our largest telescopes are still not powerful enough to actually see planets around other stars directly; and so we have had to develop sophisticated techniques to indirectly detect the existence of exoplanets.

Of the many techniques available, two stand out for now. The first is called the Transit Method. Here, we monitor a star’s brightness over a prolonged period of time, and if a planet happens to be orbiting the star along our line of sight, we should see the star temporarily dim in brightness as the planet passes in front of the star. The Kepler space probe has detected all of its exoplanets using this method, but as powerful as this techniques is, it only works if the alignment is right – and it’s only right for a few percent of all stars visible form Earth.

The second method is called the Doppler or Radial Velocity method. Here, we monitor changes in the spectrum or detailed colour of the star as it wobbles, where the wobble is caused by a nearby orbiting object such as planet. As the star wobbles toward us we see it more blue, and as it moves away from us we see it more red. The changes in colour are minute, but they are detectable, especially stellar wobbles caused by large Jupiter-sized planets orbiting their parent star.

Earth-like Planets and the search for Life in the Universe
Of course one of the fundamental quests for humanity is the two-pronged question of the origin of life on Earth and the cosmic abundance of life. With so many astounding advances in science, answers to those questions have remained frustratingly elusive.

But with the development of exoplanet detection we can begin to open new avenues of investigation, most especially in the search for planets like our own that might harbour life.

And so the search for both Earth-sized and Earth-like planets has become a hot pursuits in science today. While planets of Earth size may reside anywhere in a given solar system from the scorching inner regions to the frozen outskirts; Earth-like or potentially Earth-like suggests a planet of similar mass and make-up to Earth residing in a particular region of its solar system called the habitable zone – a relatively narrow zone around the star where liquid water may exist on the planet’s surface. Such a constraint renders the detection of such planets incredibly challenging, and as already indicated, so new are even our best detection techniques that the best we can hope for today is the detection of potential or candidate Earth-like planets, with actual confirmations of any present Earth-like characteristics being some years off. Nevertheless, significant progress is been made of late, and currently, of the 3,500 known exoplanets, about 600 are known to be Earth-sized, with approximately 40 of those being candidate Earth-like planets.

So while the search for candidate Earth-like planets is making ground-breaking progress, detailed examinations of the currently known potential Earth-liked planets remains firmly beyond our capabilities for now.

Red Dwarfs
But lets not forget about those 75%, or upwards of 300 billion red dwarf stars in our galaxy. While they are smaller, cooler and dimmer than the Sun, they are enormous in number, and each can of course possess a habitable zone, however close to the parent star that might be. And so of late there has been renewed interest in investigating red dwarfs too in the search for Earth-like planets. And while as indicated we have already detected about 40 potentially Earth-like planets, including red dwarfs in our search opens up one significant avenue of investigation – our closest stellar neighbour Proxima Centauri.

Alpha Centauri System and Proxima Centauri
The three closest stars to us – the gravitationally bound Alpha Centauri system – resides at a modest distance (on stellar scales) of just over 4 light years. While that’s still 40 trillion kilometres and currently too far to reach by space probe (the New Horizons space probe which took 10 years to travel to Pluto would take over 60,000 years to reach Alpha Centauri); nevertheless the three stars of the Alpha Centauri system are close enough that, if they contain exoplanets, we could determine the characteristics of those planets using our best current and near-future planned Earth-based observation techniques; and that would be a major break-through in exoplanet studies.

Of the three stars in the system, Alpha Centauri A and B are both very similar in age, size, mass and colour to our Sun. Nevertheless, given that they orbit each other at a distance equal to the distance of our Sun to the planet Saturn, Alpha Centauri A and B constitute a wholly different kind of system to our own. We can already tell there are no Jupiter-sized planets orbiting those stars for example, and while tentative evidence exists for an Earth-sized planet orbiting Alpha Centauri B, there is much debate on the interpretation of the available evidence.

Proxima Centauri on the other hand orbits both Alpha Centauri A and B at a distance of about 2 trillion kilometres, and indeed currently resides about two trillion kilometres closer to us than its stellar companions. It is a lot smaller than its far off stellar companions – a little larger than the planet Jupiter, but having accumulated more than 125 times the mass of Jupiter during its formation it was too massive to remain as a planet and became a red dwarf star, albeit with a luminosity far fainter than its companions or our Sun (about 0.0017 the Sun’s luminosity).

This picture combines a view of the southern skies over the ESO 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower-right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope. Proxima Centauri is the closest star to the Solar System and is orbited by the planet Proxima b, which was discovered using the HARPS instrument on the ESO 3.6-metre telescope.

This picture combines a view of the southern skies over the ESO 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower-right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope. Proxima Centauri is the closest star to the Solar System and is orbited by the planet Proxima b, which was discovered using the HARPS instrument on the ESO 3.6-metre telescope. Credit: Y. Beletsky (LCO)/ESO/ESA/NASA/M. Zamani

PaleRedDot
With a pressing desire to detect any planet close by and a potential Earth-like planet in particular, the European Southern Observatory decided in January 2016 to initiate a project to see if we could detect any Earth-sized planets orbiting Proxima Centauri. The project was given the apt title PaleRedDot, a play on the famous “Pale Blue Dot” phrase coined by Carl Sagan upon seeing an image of the Earth as a tiny pale blue dot in a Voyager 1 photograph taken in 1990.

PaleRedDot set itself the challenging task of identifying whether there are any small planets orbiting Proxima Centauri using the Doppler method. This is challenging because the Doppler method is best suited to detecting Jupiter sized planets rather than Earth-sized planets which only causes a minute wobble of their parent star. But given the closeness of Proxima Centauri, it was deemed worth the attempt.

And so the ESO consortium, lead by astronomer Guillem Andlada-Escude of Queen Mary University UK, initiated their search in January 2016, accompanied with a high profile science-outreach campaign allowing anyone to look in online at the project and see its progress. And to the amazement of all, the data gathered in just ninety days from January to March 2016 was sufficient to confidently identify the existence of at least one planet orbiting Proxima Centauri.

Pale Red Dot was an international search for an Earth-like exoplanet around the closest star to us, Proxima Centauri. It used HARPS, attached to ESO’s 3.6-metre telescope at La Silla Observatory, as well as other telescopes around the world.  It was one of the few outreach campaigns allowing the general public to witness the scientific process of data acquisition in modern observatories. The public could see how teams of astronomers with different specialities work together to collect, analyse and interpret data, which ultimately confirmed the presence of an Earth-like planet orbiting our nearest neighbour. The outreach campaign consisted of blog posts and social media updates on the Pale Red Dot Twitter account and using the hashtag #PaleRedDot. For more information visit the Pale Red Dot website: http://www.palereddot.org

Pale Red Dot was an international search for an Earth-like exoplanet around the closest star to us, Proxima Centauri. It used HARPS, attached to ESO’s 3.6-metre telescope at La Silla Observatory, as well as other telescopes around the world. It was one of the few outreach campaigns allowing the general public to witness the scientific process of data acquisition in modern observatories. The public could see how teams of astronomers with different specialities work together to collect, analyse and interpret data, which ultimately confirmed the presence of an Earth-like planet orbiting our nearest neighbour. The outreach campaign consisted of blog posts and social media updates on the Pale Red Dot Twitter account and using the hashtag #PaleRedDot. For more information visit the Pale Red Dot website: http://www.palereddot.org Credit: ESO/Pale Red Dot

Proxima B
Most extraordinary of all is that the planet, designated Proxima B, has been found to have a mass at least 1.3 Earth masses, making it likely Earth-sized; while its orbit about Proxima Centauri is a close orbit of just 7.4 million kilometres distance. Given the star’s cool atmospheric temperature of 3000K, this sets Proxima B within the star’s habitable zone, making it a potential or candidate Earth-like planet.

While such a close orbit may sound somewhat bizarre, it is worth remembering that Proxima Centauri is just 1.3 times the diameter of the planet Jupiter; where Jupiter’s outermost Galilean moon Callisto (itself about the size of the planet Mercury) orbits Jupiter at a distance of just two million kilometres. So Proxima B’s orbit of 7.4 million kilometres distance may be small by Earth-Sun standards, but for the Proxima Centauri system, it is just fine.

This PaleRedDot project has been an overwhelming success, and its discovery of a candidate Earth-like planet orbiting our closest stellar is truly significant.

This infographic compares the orbit of the planet around Proxima Centauri (Proxima b) with the same region of the Solar System. Proxima Centauri is smaller and cooler than the Sun and the planet orbits much closer to its star than Mercury. As a result it lies well within the habitable zone, where liquid water can exist on the planet’s surface.

This infographic compares the orbit of the planet around Proxima Centauri (Proxima b) with the same region of the Solar System. Proxima Centauri is smaller and cooler than the Sun and the planet orbits much closer to its star than Mercury. As a result it lies well within the habitable zone, where liquid water can exist on the planet’s surface. Credit:ESO/M. Kornmesser/G. Coleman

This plot shows how the motion of Proxima Centauri towards and away from Earth is changing with time over the first half of 2016. Sometimes Proxima Centauri is approaching Earth at about 5 kilometres per hour — normal human walking pace — and at times receding at the same speed. This regular pattern of changing radial velocities repeats with a period of 11.2 days. Careful analysis of the resulting tiny Doppler shifts showed that they indicated the presence of a planet with a mass at least 1.3 times that of the Earth, orbiting about 7 million kilometres from Proxima Centauri — only 5% of the Earth-Sun distance.

This plot shows how the motion of Proxima Centauri towards and away from Earth is changing with time over the first half of 2016. Sometimes Proxima Centauri is approaching Earth at about 5 kilometres per hour — normal human walking pace — and at times receding at the same speed. This regular pattern of changing radial velocities repeats with a period of 11.2 days. Careful analysis of the resulting tiny Doppler shifts showed that they indicated the presence of a planet with a mass at least 1.3 times that of the Earth, orbiting about 7 million kilometres from Proxima Centauri — only 5% of the Earth-Sun distance. Credit: ESO/G. Anglada-Escudé

Proxima B and Habitability
While Proxima B resides in the habitable zone of Proxima Centauri, it must be made clear that the evidence accumulated to date provide absolutely no insight into the characteristics of Proxima B, other than that it’s a rocky planet at least 1.3 time the mass of the Earth residing in its parent star’s habitable zone. No information is currently forthcoming on the material make-up of its surface, whether is has an atmosphere, volatile systems including water, or on its actual habitability.

Indeed, there are some issues mitigating against clemency and stability that we are already aware of, such as that Proxima B’s rotation is likely tidally locked to its orbit (like the Moon which only shows one face to Earth at all times), and hence the dark side of Proxima B never receiving any direct sun light at all; as well as other issues associated with Proxima Centauri itself such as its very powerful magnetic field, the fact that it’s a flare star and associated disproportionately strong X-Ray emissions.

None of these can be claimed to be fatal to life supporting systems on Proxima B however – indeed the fact that it resides close to such an energetic star makes for a potentially very interesting environment because it will likely be a dynamic world in non-extreme ways (on a cosmic scale), and likely not dormant as with many of our Solar System’s large moons, for example.

Scientific Relevance
And so the discovery of a planet orbiting out next door neighbour will provide for opportunities to investigate a planet orbiting a different kind of star to our sun in unprecedented detail. When techniques improve, likely within just years, we will determine it’s material make up, atmospheric and other volatile material systems, interaction with parent star, presence of other planets and moons and other dynamisms on the planet and within its system.

Already the available data tentatively suggests a second planet in the system with an orbit somewhere between 80 and 600 days, though it must be restated that the evidence is tentative.

At a minimum we can be optimistic that Proxima B will be a very interesting and dynamic world, and if it happens to involve liquid water and other planetary volatile material systems, it may turn out to be of fundamental importance to our quest for origins and the cosmic abundance of life.

Sociological Relevance
By all measures, the importance of the discovery of a candidate Earth-like planet orbiting our closest stellar neighbour cannot be overstated.

As just described, if it turns out that Proxima B is Earth-like, it will provide significant new insights into the age old questions of origins and the cosmic abundance of life.

And in the context of our push to the far outer reaches of the Solar System with New Horizons to Pluto and into the Kuiper Belt, and the development of NASA’s Space Launch System (SLS) in 2018 which could deliver spacecraft to Pluto in just 3 years and will likely enable deep space missions to the Kuiper belt beyond Pluto; the discovery of Proxima B offers the coming generations of space explorers a major new destination to aim for.

It may seem far fetched to us today to contemplate sending a space probe there, but it is likely that in the next few decades new mechanisms to send small space craft to the nearest stars will begin to emerge. The discovery of Proxima B will contribute fundamentally to that push, because it offers a destination to aim for. What has been until now a notion of travelling to unknown destinations among the stars becomes a tangible mission to reach a specific planet in the Proxima Centauri system. There cannot be a closer target beyond our Solar system, and such tangibility will likely precipitate into a specific and targeted mission over the coming decades. We can be confident that all involved today in spawning projects to reach the nearest stars in the coming decades will be transfixed by this discovery.

As just two examples, currently in the US both NASA and DARPA are considering interstellar travel within the next 100 years; while Russian Entrepreneur Yuri Milner has donated no less than 100 million dollars to develop tiny space probe technology through an initiative called Breakthrough Stardust that could enable tiny robotic probes to travel to the Alpha Centauri or Proxima Centauri in just 20 years.

In a nutshell, we now have a destination planet orbiting our next door neighbour; and that will surely spur on innovation for the coming decades in space exploration.

Future Work
As ground-breaking as the discovery of Proxima B is, it represents only the very beginning in a new era of both exoplanetary studies and of interstellar space exploration. We could not ask for a better scenario in the study of candidate Earth-like planets; while the presence of this planet sets space exploration onto a whole new path beyond the Solar System.

And so many new astronomical studies of Proxima Centauri, and indeed of all our nearest stellar neighbours, are already ramping up. PaleRedDot will now aim at improving our understanding of the Proxima Centauri system and Proxima B, and will also continue into the future to study many near by stars.

More broadly, exciting new missions about to get under way such as the next generation space telescope (called the James Webb Space Telescope JWST), the new TESS Exoplanet Finder both due to launch in 2018, as well as the development of ESO EELT – a gigantic telescope to see first light in 2024, among many other projects; all mean that Proxima B will come under intense scrutiny in the next few years, and will surely give up its secrets as to its characteristics and whether it is, or is not, Earth-like.

The discovery of Proxima B heralds a new era in exoplanet studies and space exploration, and is likely to become a very important, and very familiar world to us in the coming decades.

This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.

This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Credit: ESO/José Francisco ( http://josefrancisco.org )

Acknowledgment: thanks to Will Goodbody, Science and Technology Correspondent, RTE, for laying the groundwork for this blog.

Follow Proxima B, PaleRedDot and Exoplanet developments:

Pale Red Dot:
Web: https://palereddot.org
Twitter: @Pale_red_dot #PaleRedDot
Facebook http://www.facebook.com/PaleRedDot

European Southern Observatory
News https://www.eso.org/public/news/eso1629/
ESO Press Conference:
https://eso.adobeconnect.com/_a848728127/p3l3qqhq6un/?launcher=false&fcsContent=true&pbMode=normal

Research Paper in Nature:
http://www.eso.org/public/archives/releases/sciencepapers/eso1629/eso1629a.pdf

Exoplanets:
http://exoplanets.org

Breakthrough Initiatives
http://www.breakthroughinitiatives.org

NASA / DARPA One Hundred Year Starship
http://100yss.org

JWST
http://www.jwst.nasa.gov

TESS
https://tess.gsfc.nasa.gov/index.html

EELT
https://www.eso.org/sci/facilities/eelt/

GAIA
http://sci.esa.int/gaia/

Advertisements

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.

Encounter_01_highRes
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.

Pluto_1
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

KBO_1110113Y_HST
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).
Credit: NASA/ESA/STSCI

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.

NHPlutoEncounterTrajectory_NomV8_Guo20150615
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

Facebook:
https://www.facebook.com/new.horizons1

Twitter:
https://twitter.com/NASAnewhorizons

Hashtag:
#PlutoFlyBy

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:

iOS
https://itunes.apple.com/us/app/new-horizons-nasa-voyage-to/id473217882?mt=8

Android
https://play.google.com/store/apps/details?id=com.simulationcurriculum.plutosafari&utm_content=buffer84669&utm_medium=social&utm_source=facebook.com&utm_campaign=buffer

Web:

New Horizons Home Web site
http://pluto.jhuapl.edu

Public Outreach Website:
http://www.seeplutonow.com

New Horizons Pluto Close Encounter Play Book:
http://pluto.jhuapl.edu/Mission/The-Path-to-Pluto/NH_Obs_Playbook_LORRI-MVIC.pdf

NASA New Horizons Web site
http://www.nasa.gov/mission_pages/newhorizons/main/index.html

Interview with Clyde Tombaugh
http://www.achievement.org/autodoc/page/tom0int-1

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).

tom0-001
Figure 1: Clyde Tombaugh (1906 – 1997)

Pluto_discovery_plates
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”)

Introduction
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):
http://www.esa.int/Our_Activities/Space_Science/Rosetta

Rosetta on Twitter:
@ESA_Rosetta

Rosetta on Facebook:
https://www.facebook.com/RosettaMission

Rosetta Blog:
http://blogs.esa.int/rosetta/

Rosetta on Youtube:

Images:

1. Rosetta Space-probe and Philae Comet Lander:

Rosetta_and_Philae_at_comet_node_full_image_2

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: http://www.esa.int/spaceinimages/Images/2013/12/Rosetta_and_Philae_at_comet6

Credit: ESA–J. Huart

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

How_big_is_Rosetta_s_comet_node_full_image_2
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: http://www.esa.int/spaceinimages/Images/2014/07/How_big_is_Rosetta_s_comet

Credit: ESA

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

Comet_from_1000_km_node_full_image_2

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

Hello!

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!