Pluto & Charon

By Codex Regius

On 14 July 2015, the New Horizons spacecraft passed through the system of the former ninth planet, Pluto. This book gives a preliminary overview of the results that had been obtained from data sent by New Horizons to Earth till spring 2016. Dr Rainer Riemann, astrophysicist of the University of Heidelberg, Germany, has added a preface to this volume.

• Language: English
• Publisher: XinXii
• Release date: Oct 8, 2016
• ISBN: 9783961420032

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References

Preface

In this book its two authors have managed to present the intriguing results of New Horizons’ Pluto flyby in a mode that non-professionals will understand, without waiving appropriate scientific accuracy.

Pluto was discovered by Clyde Tombaugh in 1930 and stayed the only known large object in the outer solar system for more than 60 years. Then, since the 1990s, improved CCD technology helped track down more than a thousand other objects in the ‘Kuiper Belt’. The size of some of them came close to Pluto, and Eris, photographed in 2003 but escaping notice till 2005, threatened even to replace it as the biggest object in the Kuiper Belt. The result was a re-definition of the term ‘planet’ by the general assembly of the International Astronomical Union, held in Prague in summer 2006. Pluto is no longer called a planet since. From the perspective of celestial mechanics, this decision may be reasonable and logical because Pluto does something that a decent planet should not do: It crosses the orbit of another planet. The large planet Neptune has forced small Pluto and several hundred, recently discovered, smaller bodies called plutinos into a 3:2 orbital resonance by its gravitational force that avoids any collisions with Neptune.

Fortunately, half a year had already passed since the launch of the New Horizons spacecraft when the new definition of the term ‘planet’ was voted about. If Pluto had not been a planet at that time any more, some overzealous US-senators might have simply cancelled its construction to add the money saved to their military budget. (This was what had indeed happened to the Dawn spacecraft for some months.) In such a case, the wonderful close-ups of this amazing world at the very edge of the solar system would have escaped us.

With the findings of New Horizons in mind, said new definition should be reconsidered. I am sure that the voting would have had a different result if we had already known back then what New Horizons has revealed to us about Pluto. The new definition is based on celestial mechanics only and does not take Pluto’s peculiarities into account that it has from the planetologist’s point of view. It has more characteristics of a regular planet than the twice as large inner planet Mercury: While Mercury is a grey orb whose surface has primarily been shaped by impacts, New Horizons has shown us Pluto as a body with a distinctive geology of its own from far away already. There are diverse types of terrain present: mountainous areas alternate with smooth plains of nitrogen glaciers in which water icebergs are drifting about, driven to the edges of convection cells by up-welling heat; their dark summits peak out like islands.

Unlike airless Mercury, Pluto does have an atmosphere that does not simply become more tenuous from inside out, but it is many-layered in the very meaning of the word: images of Pluto‘s rim reveal several banks of haze at different levels above ground. There must be some kind of weather as well. As Pluto heads on to those parts of its orbit that are remote from the sun, a part of its atmosphere will freeze out and precipitate on its surface, only to thaw again when it is back to perihelion - 200 years later. And one of the images, scientists believe, even seems to depict a cloud bank.

Moreover, Pluto has a complex satellite system comprised of five moons, and their periods resonate with each other and they are almost exact multiples of the revolutional period of the biggest moon, Charon. Compare this to the fact that Mercury and Venus have no moons at all, our Earth, one, Mars, two small ones, and among the minor planets there are only systems with up to two moons known.

Even though Pluto may not be elevated to planet status again, our solar system and the eight planets that are officially left will presumably not represent the complete image yet. During the last few years, six lesser bodies have been discovered far away whose perihelions (their points of closest approach to the sun) are located far beyond Neptune and the Kuiper Belt. And their orbits are close together in space, which may perhaps not be explained by chance alone. These objects measure less than 1,000 km in diameter, and therefore, they are certainly not proper planets. But they cannot have developed out there, in empty space. Something larger must have taken them so far out from the sun, like Neptune has set the plutinos and other objects of the Kuiper Belt on their courses.

Mike Brown, he who has initiated Pluto’s demolition by discovering almost Pluto-sized Eris, supposes that a planet may be lurking out there that has about 10 times the mass of the Earth. Such a behemoth would certainly fit the new criteria for ‘proper’ planets, and Mike Brown has already assigned the unofficial name Planet Nine to it. Based on the data of those six farthest bodies, an approximate orbit of this still hypothetical planet can be also computed. According to these values, it travels around the sun 700 times as far out as Earth and 30 times as far out as Neptune, spending about 20,000 years on one revolution. But at which point of its orbit it might be at the moment, that cannot be computed.

That this planet has not been discovered yet should not struck anyone by surprise. Since the brightness of a body decreases by the fourth power of its distance from the sun, even an object as large as Neptune would be a million times dimmer than that. Mike Brown is rather confident, however, that his Planet Nine will be detected within the next 5 to 10 years by improved sky survey programmes. Once it has been located, a spacecraft will certainly be sent to this planet, and the two authors behind the Codex Regius label are no doubt already standing ready to publish the results of this flyby in a book. If NASA should take recent plans of a laser-powered interstellar miniature probe serious, this might even happen within our lifetime.

We have waited long enough for the Pluto flyby.

But … it has been worth waiting, that you will see on the following pages!

Dr Rainer Riemann

Heidelberg, in June 2016

Primary events of nine and a half years of spaceflight 2006 - 19 January Launch

28 January Course correction

30 January Course correction

09 March Course correction

07 April Crossed the orbit of Mars

11-13 June New Horizons observes planetoid 2002 JF56 (lated named ‘APL’) 21 September First images of Pluto (using LORRI)

2007 - 28 February Passing Jupiter/gravity assist 27 June New Horizons‘ first hibernation begins 25 September Course correction

September-November Annual Checkout Operation (ACO) 1

2008 - 08 June Crossed the orbit of Saturn

July-August Annual Checkout Operation (ACO) 2

2009 - July-August Annual Checkout Operation (ACO) 3

29 December New Horizons has crossed half the distance to Pluto

2010 - May-July Annual Checkout Operation (ACO) 4

30 June Course correction

16 October New Horizons has spent half the time of flight to Pluto

2011 - 18 March Crossed the orbit of Uranus

May-July Annual Checkout Operation (ACO) 5

02 December New Horizons is closet to Pluto than any other man-made object

2012 - May-July Annual Checkout Operation (ACO) 6

2013 - May-August Annual Checkout Operation (ACO) 7

2014 - June-August Annual Checkout Operation (ACO) 8; first optical navigation control (OpNav 1) 15 July Course correction

25 August Crossed the orbit of Neptune

06 December Final awakening from hibernation

2015 - 08 January Approach phase 1 commences, distance: 225 mio. km.

25 January OpNav 2 commences

10 March Course correction

04 April Approach phase 2 commences, distance: 121 mio. km.

05 April 100 days left to fly-by (P-100).

09 April First colour image of the Pluto system May-June New Horizons resolves Pluto better than Hubble 18 June IR scanning of the Pluto system commences 24 June Final complete scanning of the Pluto system by LORRI. Approach phase 3 commences, distance: 26 mio. km.

13 July Fly-by commences - Distance: 1.2 mio. km. Final data transmission: ‘The Planet with a Heart’

14 July Closest approach to Pluto

15 July Telemetry data received, 0:53 UT. Science data from 09:50 UT. End of fly-by at 1.2 mio. km.

Nine years of approach

Who would have thought that New Horizons was approaching a world that more resembled the droll imaginations of a pulp-SF author than the expectations of serious observers? Not so long ago, someone had tersely written about this planet:

‘There are hardly any reliable data and detailed pictures of the dwarf planet Pluto available so far. It is simply too small and too far away. Till now, astronomers can only guess on even values as basic as its density.... But beyond that, guesswork and assumptions prevail, based on those few data that are known about the conditions in the outer solar system. Is Pluto’s inside differentiated by layers or is it uniform? May there even be liquid water beneath its surface, a kind of ocean, like on Jupiter’s moon Europa? All these questions are still unanswered.’ (Podbregar, 2015)

What the spacecraft saw instead were wadis delved by a substance that we are used to breathe rather than to drink - frozen lakes and an entire ocean basin that look as fresh as if they offered themselves for skating - water assuming functions that are attributed to basalt on our own planet-wandering mountains that move across the surface and accumulate at obstacles - volcanic calderas that have never released hot magma but substances that we would exploit as refrigerants. And a blue sky with layers of haze and clouds that strikes us as looking more earth-like than that of Mars.

Nothing of this had yet been seen when New Horizons, after nine years of hibernation, opened its eyes and turned them to Pluto again.

New Horizons is on a journey to a new class of planets we’ve never seen, in a place we’ve never been before. For decades we thought Pluto was this odd little body on the planetary outskirts; now we know it’s really a gateway to an entire region of new worlds in the Kuiper Belt, and New Horizons is going to provide the first close-up look at them.

Hal Weaver, project scientist for New Horizons

At the garden door (6 Dec 2014 - 10 Mar 2015)

New Horizons awakens

Four milliard kilometres away from Earth and still twice as far from Pluto as Earth is from the Sun, New Horizons finally awoke from its state of rest. Since its launch on 19 January 2006 and its brief swing-by at Jupiter in February 2007, it had spent 1,873 days - about two thirds of its flight time - in hibernation.

Science-fiction readers may feel reminded of astronauts lying in freezers to prevent them from ageing during a long space mission. And this comparison is in fact not entirely inappropriate. During its 18 hibernation phases of the last 7 years that had extended over periods from 36 to 202 days, New Horizons had been nearly dead, with most of its systems switched off. Like in the case of our fictional space travellers, ageing and wearing of components was to a certain extent held back in this manner, power reserves conserved and the risk of system failures reduced. There was not much going to happen on this voyage, anyway. The pathways into space are empty, long and, above all, boring.

The spacecraft draws its power supply from a radionuclide battery. When all its instruments are active, it consumes less energy than two 100-watt light bulbs.

Only the on-board flight computer controlled the functionality of its systems and send a weekly readiness signal to Earth. Predefined programme sequences woke New Horizons two or three times a year to check essential systems, to calibrate the instruments, to collect measured data, to test functions that would be needed during the flyby and to carry out any required course corrections. Then the spacecraft was returned into hibernation mode again, unless something thrilling was going to happen, like the gravity assist by Jupiter that made New Horizons the fastest spacecraft ever.

New Horizons’ LORRI camera shot this frame of the gaseous planet Neptune from a distance of 26 AU (approx. 4 milliard km) on 10 July 2014, 25 years on the day precise after Voyager 2 had passed it. Neptune was at that time farther away from New Horizons than Pluto.

Many times the question had been asked what the mission crew on Earth had actually been doing all that time. Mission Operations Manager Alice Bowman used to affirm that she did not know ‘a single New Horizons operations person who was ever