by Paul Gilster | Feb 25, 2011 | Culture and Society
by Kelvin Long
Physicist and aerospace engineer Kelvin Long is the co-founder of Project Icarus, the interstellar design study that is a successor to Project Daedalus. Here he gives us a look at the history of the British Interplanetary Society, whose accomplishments and continuing efforts in the area of interstellar propulsion have energized the entire field. As well as being an active Tau Zero practitioner, Long is a fellow of the BIS and a member of the recently reconstituted BIS Technical Committee, and the Assistant Editor of the Journal of the British Interplanetary Society. More about the history of the BIS can be read in the BIS publication ‘Interplanetary’ written by the current President Bob Parkinson, which is now available from the society’s Web site.
The British Interplanetary Society (BIS) is a name synonymous with interstellar travel throughout its history. First formed by Philip E. Cleator in Liverpool in 1933, the organization’s headquarters were subsequently moved to London. The BIS is the oldest space organisation in the world still in its original form. In an age of competition, market forces and short term thinking, that’s a tradition to treasure. In 2013, the BIS will be eighty years old, conceivably the length of time it would take a future interstellar probe to reach the nearest star system. In that time, a World War has been fought, the Berlin Wall has fallen, man has walked upon the surface of the Moon and as these words are being written an interstellar precursor probe, New Horizons, is on its way to the furthest reaches of our solar system: The dwarf planet Pluto and beyond.
Although the BIS includes the word ‘British’ in its name, for much of its history roughly half of the membership has been international, with a strong contingent based in the United States. The Society has faced pressure over the years to change its name to ‘The British Interstellar Society’ or ‘The British Rocket Society’ or even ‘The International Rocket Society.’ The debate over the name throughout the years has really been a distraction from the society’s work and to its credit, the BIS has resisted this pressure, keeping to its principles and remaining focused on its goals of promoting and facilitating advancements in the field of astronautics – all geared towards a human presence in space. It has also continued to maintain a careful balance, addressing an audience that spans science fiction fans, popular science readers and professional physicists, all interacting and sharing ideas with each other, all space cadets at heart.
Many famous BIS members will be familiar to the readers of Centauri Dreams. Sir Arthur C Clarke played a fundamental role in the early days of the BIS and served as chairman on two separate occasions between 1946-1947 and again between 1951-1953. Arguably, the BIS gave him an important platform to share his ideas with like-minded people, not afraid to speculate outside of conventional thinking, but in a rigorous and scientific way. The American physicist Robert Forward was also a devoted member of the society and contributed many first rate papers to society publications. Physicists and writers who are members today include Greg Matloff, Eric Davies, Marc Millis, Claudio Maccone and our own Paul Gilster.
Those who live within commuting distance of the BIS HQ refer to it as “their spiritual home.” Perhaps it’s the Clarke connection, or perhaps nostalgia for the rapid developments in rocketry after the Second World War. The philosopher and science fiction writer Olaf Stapledon, famous for his twin accomplishments ‘Last & First Men’ and ‘Starmaker’, addressed the society in 1948, giving a lecture titled ‘Interplanetary Man’. One of the current long-time members is the science and science fiction writer Stephen Baxter, famous for his collaborations with Clarke as well as his own books, such as ‘Titan’ and ‘The Time Ships’, an authorised sequel to the H G Wells classic ‘The Time Machine’. Writers seem drawn to what the BIS has to offer.
An Early British Lunar Project
In 1938, the BIS Technical Committee, led by H. E. Ross and R. A. Smith, decided to undertake a pioneering scientific study – perhaps the first of its kind – to produce a conceptual design of a spacecraft that would carry a crew of three safely to the Moon. The mission would permit the crew to land for a stay of fourteen days, and provide for a safe return to the Earth with a final payload of half a ton. The object of the exercise was to demonstrate that, within the capabilities of propellants that could be specified (at least theoretically) at the time, such a mission was not merely possible but would be economically viable – insofar as the vehicle lift-off mass from the Earth would be no more than one thousand tons. The resulting conceptual design came to be known as the BIS Lunar Spaceship, and for all its flaws it is a classic, ground-breaking study, one that occupies a pioneering place in the history of astronautics.
Image: The BIS Lunar Spaceship landing on the Moon. Credit and copyright: R.A. Smith/JBIS. Smith and Bob Parkinson were responsible for a volume recounting the story of the BIS lunar design called The High Road to the Moon, now available on CD-ROM from the Society.
In 1919 the American physicist Robert Goddard, in his classic paper “A Method of Reaching Extreme Altitudes,” went a stage further than the step-rocket principle in suggesting a firing procedure that amounted to the continuous discarding of materials that are no longer required. In principle, this could result in a significant improvement in payload ratio. The BIS, in its design concept, adopted a cellular construction that conformed to Goddard’s suggestion. The spacecraft was divided into six layers of equal hexagonal cross-section; the six sections were made up of an array of tubes each consisting of a separate rocket motor. Each of the lowest 5 layers was made up of 168 motors, intended to impart sufficient velocity to achieve escape from the Earth’s gravitational field.
The remaining stage consisted of 45 medium motors and 1200 smaller tubes intended to land the remainder of the vessel on the surface of the Moon, allow for subsequent escape, and for reduction in velocity prior to entering Earth’s atmosphere. Perhaps the most important and lasting achievement of the Lunar Spaceship study came from its conclusions regarding landing and lift-off from the lunar surface. R.A. Smith developed the concept after the Second World War in an article entitled “Landing on an Airless World.” This article accurately depicted the procedure that would later be adopted with the Apollo Lunar Excursion Module.
The BIS Lunar Spaceship project at least proved the engineering feasibility of landing on the moon and by that act made the idea more credible. When the proposal came about in the early 1960s to actually make an attempt at the moon, it is quite possible that the work done by the BIS in the late 1930s and later had some role to play in the minds of those scientists advising the political leaders of the time, such as the German-born rocket engineer Wernher von Braun.
And On to the Stars
But moon rockets were not to be the only significant technical achievement from members of the BIS. Their achievements also include the 1970s Project Daedalus starship study. This volunteer engineering design study was conducted between 1973 and 1978 to demonstrate that interstellar travel is feasible in theory. The project addressed the Fermi Paradox, which was first postulated by the Italian physicist Enrico Fermi in the 1940s. This supposes that there has been plenty of time for intelligent civilizations to interact within our galaxy when one examines the age and number of stars, as well as the distances between them. Yet the fact that extra-terrestrial intelligence has never been observed leads to a logical paradox where our observations are inconsistent with our theoretical expectation. This paradox also seemed to reinforce the prevailing paradigm at the time that interstellar travel was impossible.
Project Daedalus was a bold way to examine the Fermi Paradox head on, using current or near-future technology, and gave a partial answer – interstellar travel is feasible. The basis of this belief was the demonstration of a credible engineering design just at the outset of the Space Age that could, in theory, cross interstellar distances. In the future, scientific advancement would lead to a refined and more efficient design.
Image: Project Daedalus, the massive starship conceived by members of the British Interplanetary Society, marked the first complete design study for an interstellar craft. Credit and copyright: Adrian Mann.
Project Daedalus had three goals. First, the spacecraft was to be designed using current or near-future technology. Second, the spacecraft must reach its destination within a working human lifetime and third, the spacecraft was to be be designed to allow for a variety of target stars. The final design solution was published in a special supplement of the Journal of the British Interplanetary Society in 1978. The two-stage engine configuration was powered by inertial confinement fusion using deuterium and helium-3 pellets. Electron beam diodes positioned around the base of the engine exhaust would impinge on the pellets and ignite them to produce large energy gain, at a rate of 250 detonations per second. This would continue for a boost phase lasting over 3.8 years, followed by a cruise phase lasting 46 years, travelling at over 12% of the speed of light until the 450-ton science probe would finally reach its destination, the Barnard’s Star system 5.9 light years away. This it would transit in a matter of days, for Daedalus was a flyby probe.
The Project Daedalus study was primarily led by Alan Bond, Tony Martin and Bob Parkinson. Even today the study distinguishes itself from all other similar projects as the most complete engineering study ever undertaken for an interstellar probe. Even if Daedalus is not the template for how our robotic ambassadors will someday reach the distant stars, at the very least it will be a crucial part of the journey for getting to that first launch. Rigorous engineering assessments are the only way to provide reliable information on what is possible today or in the near-future.
Both the BIS Lunar Spaceship and Project Daedalus starship study appeared in the 1980 television series Cosmos, produced by the astronomer Carl Sagan. Sagan had himself addressed the BIS in 1974 on the topic of ‘extraterrestrial intelligence’ at a packed meeting at the Royal Society of Arts. Project Daedalus has inspired many around the world, and this includes the recent successor design study Project Icarus, which is a joint initiative between the BIS and the Tau Zero Foundation, possibly a first for this type of collaboration. And although it is not interstellar in implication, I should also mention that the BIS has recently undertaken a study for a crewed station at the Martian geographic North Pole. Project Boreas was led by Charles Cockell and may yet be the basic template for a future science station on Mars.
The Growth of International Astronautics
The BIS played a fundamental role in the formation of the International Astronautical Federation (IAF), which helps to co-ordinate global space activity and astronautics. The IAF was formed in September 1951 at a conference of several European and American delegates in London. The IAF organizes the annual conference known as the International Astronautical Congress (IAC) to provide a forum for the exchange of experiences and ideas around astronautics, with the long-term goal of opening up space to all humankind. It promotes awareness of international space activities and fosters information exchange between different space programs.
The BIS is perhaps best known for its popular magazine Spaceflight and its technical publication Journal of the British Interplanetary Society (JBIS). First published in 1934, JBIS may be the oldest astronautical journal in the world. Its history has seen the publication of many groundbreaking papers, such as the first paper on interstellar travel by Les Shepherd in 1952 or the paper on a programme for achieving interstellar flight by Val Cleaver in 1954. A collection of seminal papers on atomic rockets was also published by Shepherd and Cleaver with others in 1948 and 1949. Even today JBIS is pushing the boundaries of visionary thinking, with a warp drive symposium organised in 2007 and the papers appearing in the journal in 2008. The BIS is always looking to that distant horizon for what’s next in astronautics and the future of man in space. JBIS is the forum for the publication of those ideas. It is open to submissions from anyone, provided the paper is scientifically accurate, well presented and contains a novel insight or discussion of a problem relating to the field of astronautics.
Like many organisations in difficult financial times, the BIS has been struggling in the last few years and only a handful of members are rallying around to maintain the continued legacy of an astronautical pillar. One of the ways that people can help the society is to join it. So why should people join? It’s an open and inclusive society for everyone from science fiction fans, students, industry professionals, academics and space enthusiasts. The BIS provides thought leadership on spaceflight and astronautics through its publications, innovative technical projects, symposia and events. It promotes and stimulates the latest research. The society also fosters debate and provides a global home for people interested in space to connect with each other. Its global membership includes some of the world’s leading thinkers on spaceflight. This unique heritage of the society is an amazing foundation of pioneering ideas which continues to push the boundaries of possibility, from both a technological, sociological and philosophical perspective.
With its rich history of ideas and creative thinkers, it is amazing to think that the BIS has never had government backing and indeed has not played a major role in informing British government policy throughout most of its history, despite the fact that members of the BIS possibly know more about astronautics than many other organisations in Europe. The BIS has not traditionally been a strong lobbyist organisation, although in recent times the society was involved in discussions to form the United Kingdom Space Agency and to get a British astronaut assigned to the European Space Agency team. But what really matters is the intellectual value in the ideas that the BIS facilitates and is bold enough to promote widespread thinking on. These ideas literally ‘make’ the future, by laying the seeds for what is feasible on that next horizon.
In 1932, Robert Goddard said: “How many more years I shall be able to work on the problem I do not know; I hope, as long as I live. There can be no thought of finishing, for ‘aiming at the stars’ both literally and figuratively, is a problem to occupy generations, so that no matter how much progress one makes, there is always the thrill of just beginning.” It is organisations like the BIS that enable the promise of solving this problem through successive generations of inspired pioneers, by facilitating the emergence of measured speculation with scientific objectivity, of real world engineering and thought provoking theories of physics. In order to continue, the society needs members to sustain the vision and keep the promise of a future for our species in space alive today. Join the society, and contribute towards that worthwhile goal. The society would welcome all people interested in the field of astronautics. The BIS needs members to sustain it if it is to continue to provide the service that this interstellar forum wants. This is your rallying cry – join the British Interplanetary Society today and help us to work towards the dream of a peaceful human presence in interplanetary and interstellar space in the decades ahead – ad astra.
A Short Bibliography
A.Bond & A.R.Martin et al., Project Daedalus Final Report, Special Supplement of JBIS, 1978.
A.C.Clarke, The Challenge of the Spaceship (Astronautics and its Impact Upon Human Society), JBIS 6, pp. 66-78, 1946.
A.V.Cleaver, A Programme for Achieving Interplanetary Flight, JBIS 13, pp.1-27, 1954.
C.S.Cockell (Ed), Project Boreas, A Station for the Martian Geographic North Pole, BIS Publication, 2006.
K.F.Long & R.Obousy et al., Project Icarus: Son of Daedalus – Flying Closer to Another Star, JBIS 62, pp.403-414, 2009.
H.E.Ross, The BIS Space-Ship, JBIS 5, pp.4-9, 1939.
L.R.Shepherd, Interstellar Flight, JBIS 11, pp.149-167, 1952.
by Paul Gilster | Feb 24, 2011 | Deep Sky Astronomy & Telescopes
We recently looked at protoplanetary disks around the stars AB Aur and LkCa 15, new studies using adaptive optics at the Subaru telescope on Mauna Kea. Today we learn about another interesting disk, this one around the young star T Chamaeleontis (T Cha), about 350 light years from Earth in the southern constellation called the Chamaeleon. The star is a scant seven million years old and, as was the case with the Subaru studies, we’ve gained evidence for planet formation within the disk. The latest work, performed with the European Southern Observatory’s Very Large Telescope, has delivered powerful evidence for a small companion. Brown dwarf or planet? At this point, we don’t know.
T Cha is a T Tauri star, meaning it is young, luminous and too cool for hydrogen fusion to operate. Instead, the star is powered by energy released as it contracts for the tens of millions of years it will take to reach the main sequence. The Very Large Telescope used adaptive optics technology and a technique called sparse aperture masking (SAM) to find the companion object. SAM is a type of interferometry that excels at isolating faint objects that are close to brighter ones. The object was searched for at wavelengths of 2.2 and 3.8 microns, but could only be found at the longer wavelength, indicating a planet or a cool, dust-shrouded brown dwarf.
Image: This artist’s impression shows the disk around the young star T Cha. Using ESO’s Very Large Telescope this disk has been found to be in two parts, a narrow ring close to the star and the remainder of the disk material much further out. A companion object, seen in the foreground, has been detected in the gap in the disk that may be either a brown dwarf or a large planet. The inner dust disk is lost in the glare of the star in this picture. Credit: ESO/L. Calçada.
The inner ring of the protoplanetary disk detected around T Chamaeleontis is a scant 20 million kilometers from the star, with the outer region of disk material located 1.1 billion kilometers out and beyond. The companion object is found in the gap between the two disks. Says Nuria Huélamo (Centro de Astrobiología, ESAC, Spain), lead author of one of the papers on this work, “For us the gap in the dust disc around T Cha was a smoking gun, and we asked ourselves: could we be witnessing a companion digging a gap inside its protoplanetary disc?”
The signature of the companion object turned out to be clear. It was close to the edge of the outer gap, and orbiting the star at about a billion kilometers, slightly more distant than Jupiter is within our own Solar System. The ESO offers a superb video showing the twin disks of T Chamaeleontis and the location of the star’s companion from a variety of perspectives. I wasn’t able to embed the video successfully here because of margin problems, but I do recommend you give it a look.
The papers are Olofsson et al. 2011, “Warm dust resolved in the cold disk around TCha with VLTI/AMBER,” Astronomy & Astrophysics Vol. 528, L6, published online 24 February, 2011 (abstract) and Huélamo et al. 2011, “A companion candidate in the gap of the T Cha transitional disk,” Astronomy & Astrophysics Vol. 528, L7, published online 24 February, 2011 (abstract).
by Paul Gilster | Feb 23, 2011 | Communications and Navigation
You would think that Internet pioneer Vint Cerf would be too busy with the upcoming transition from Internet Protocol version 4 to IPv6 — not to mention his other duties as Google’s Chief Internet Evangelist — to keep an eye on space communications. But the man behind the Net’s TCP/IP protocols never lets the human future off-planet get too far from his thoughts. These days the long hours he has already spent on developing a new methodology that lets us network not just Earth-based PCs but far-flung spacecraft have begun to pay off. 2011 should be a banner year for what many have already begun to call the InterPlanetary Internet.
At issue is a key problem with the way the Internet works. TCP/IP stands for Transmission Control Protocol/Internet Protocol, and it describes a method by which data are broken into small data envelopes and labeled for routing through the network. When they reach their destination, the packets are then reassembled. We know how the Net that grew out of these protocols transformed communications, but for TCP/IP to work well, it relies on the fast turnover of data. The key tools are ‘chatty,’ exchanging data over and over again to function.
The classic case is File Transfer Protocol, or FTP, which takes eight round trips — that’s eight cycles of data connection — before the requested file can make its trip, and as anyone who has worked with FTP (especially in the early days of the Net) knows, FTP servers will time out after a certain period of inactivity. But if you’re trying to network spacecraft, you can’t work under these conditions. At interplanetary distances, speed of light delays add up, and latency that could make an Earth-based connection hiccough can quickly grow to hours and days.
The new Bundle Protocol that the InterPlanetary Internet project under Cerf’s direction has come up with takes care of this problem, compensating for all these delays. It’s part of the larger concept of delay tolerant networking now being overseen by the Delay Tolerant Networking Research Group, which ultimately grew out of the Internet Society’s Interplanetary Internet group, with Cerf at the thick of things all along. In a recent interview in Network World, Cerf noted that the Bundle Protocol has gone beyond theory into actual space operations.
You’ll find the new method, for example, running aboard the International Space Station. And delay tolerant networking protocols have been uploaded to the EPOXI spacecraft, whose most recent claim to fame was its visit to Comet Hartley 2 — this is the same vehicle, then called Deep Impact, that drove an impactor into comet Tempel 1 back in 2005. The new protocols have already been tested with a light-delay time of approximately 80 light seconds, and much more is in the works. Here’s Cerf on what’s coming up:
…during 2011, our initiative is to “space qualify” the interplanetary protocols in order to standardize them and make them available to all the space-faring countries. If they chose to adopt them, then potentially every spacecraft launched from that time on will be interwoven from a communications point of view. But perhaps more important, when the spacecraft have finished their primary missions, if they are still functionally operable — they have power, computer, communications — they can become nodes in an interplanetary backbone. So what can happen over time, is that we can literally grow an interplanetary network that can support both man and robotic exploration.
Networking our space resources is a key element of a space-based infrastructure. Right now, most space exploration has involved point-to-point radio links. When you wanted to communicate with a distant spacecraft like Voyager 2, you had to dedicate expensive radio dishes to that specific task. A system in which we can store and forward data among spacecraft lets us maximize our communications, letting multiple missions forward their data to a central node on the interplanetary Net for subsequent transmission to Earth. As space testing of delay tolerant methods grows, the Bundle Protocol is also in action in various academic settings and in NASA laboratories. The building of an interplanetary network backbone has commenced.
by Paul Gilster | Feb 22, 2011 | Exoplanetary Science
If by any chance you missed Lee Billings’ recent work on BoingBoing, let me direct you to Cosmic Commodities: How Much is a New Planet Worth? Lee has been talking to planet hunter Greg Laughlin (UC-Santa Cruz) about the latter’s equation that quantifies the worth of a given planet. It’s an ingenious concept, one that accepts inputs like planetary mass, estimated temperature, type and brightness of the primary star, and generates a value in cash. Why do this? It’s a way to measure the potential of an exoplanet to be interesting. or in Laughlin’s terms, “a way for me to be able to quantify how excited I should be about any particular planet.”
Reasons to Go
You can follow the genial and long-running musings on planetary value on Laughlin’s systemic blog, but read Billings if you’re not already familiar with the equation, because his interview with Laughlin walks you through all the parameters step by step. One of the interesting things about the equation is that the brighter the star appears to you, the more valuable the planet. That makes basic sense because we use photons to study exoplanets, and the equation says it is easier to do this if we have more photons to work with. Here’s Laughlin on the matter:
Think of it this way: If we’re sitting here on Earth, our sun is extraordinarily bright in the sky. The brightness of the Sun thus makes that term enormous if we run this equation for the Earth. If we evaluate this equation for the Earth, we get an answer of about 5 quadrillion dollars. And that’s basically the value of all our infrastructure, accumulated through history.
Being there, in other words, is everything, and we can watch the equation change with proximity:
If, for instance, there is a planet orbiting in the habitable zone of Alpha Centauri B, part of the closest star system in the sky other than our Sun, that planet’s worth about $6 billion using this scale. But then if you voyage there, Alpha Centauri B appears brighter, and brighter, and brighter, until it is your Sun in your sky and you’re on the planet’s surface. So in going there you have this ability to intrinsically increase value. And that’s an exciting thing because it ultimately provides a profit motive for perhaps going out and making a go of it with these planets.
This is saying that something that is several billion dollars on Earth, could be, if you go there, a quadrillion-dollar payoff.
Image: Exoplanet hunter Greg Laughlin. Credit: UC-Santa Cruz.
Costs of an Imaging Mission
You might object that using dollars and cents to put a value on an exoplanet is an arbitrary way to assign value, but there’s a cunning logic here. What drew me to write this was the fact that if you take the $6 billion that Laughlin’s equation pegs for a planet in the habitable zone of Centauri B and look at it in terms of how you might study it, the $6 billion starts to resonate. If we did find out in the next few years that such a planet existed, we would doubtless want to examine it through a space-based direct imaging telescope, and it’s Laughlin’s guess that the public would be willing to spend well more than a million — and certainly far less than a trillion — dollars to mount such a mission.
In other words, $6 billion might not be so far off if you’re thinking of building a cutting-edge space telescope to study an extremely attractive planet in Centauri B’s habitable zone. It was through a recent post on systemic that I learned about the most ‘valuable’ of exoplanet candidates so far, the object called KOI 326.01, to which Laughlin’s equation assigns a value of $223,099.93. KOI means ‘Kepler Object of Interest,’ a reminder that we haven’t yet even confirmed its existence. It’s a candidate, in other words, but an interesting one because it appears to be a bit smaller than Earth and orbiting in the habitable zone of its star.
Generalizing from Kepler
Laughlin’s valuation formula is great fun to play with — Mars, for example, merits a paltry $14,000, for reasons you can explore in the Billings interview. But let’s back out to the bigger picture discussed recently by Kepler head William Borucki at the American Association for the Advancement of Science’s annual meeting in Washington. Based on Kepler results and extending them throughout the galaxy, we come up with close to 50 billion planets as the roughest of estimates, with at least 500 million of them in the habitable zone of their stars.
All this is still evolving, of course, because we know that stars can have more than one planet, and the Kepler telescope needs more time to identify planets that are, like the Earth, at a greater distance from their star. And even when we have a more or less complete list of planetary candidates, we still have to confirm the findings via techniques like transit timing. It’s interesting to see, too, that a Kepler-like instrument studying our system would probably detect only one planet because our system is not co-planar enough to make multiple detections likely.
So let’s see. Kepler is a $600 million mission, and KOI 326.01 leads all candidates with a perceived value of $223,099.93. What new worlds will Kepler find that can get those two figures a little closer to each other? Surely an Earth-mass planet in the habitable zone of a G-class star would raise the ante, but we have more data collection and analysis ahead before we can make any such calls. Meanwhile, Borucki told the AAAS that 10.5 percent of the stars in the Kepler sample should have Earth-sized planets. Add in the 7.3 percent that should have super-Earths and it’s clear we should expect interesting places to explore both near and far in the galaxy.
Near, of course, is better, which is why we need to move from a statistical sampling mission like Kepler to an active examination of stars close to our Sun. Both the PLATO mission (PLAnetary Transits and Oscillations of Stars) and TESS (Transiting Exoplanet Survey Satellite) point us in that direction, and the hope here is that the exciting Kepler results will give both missions further impetus. Meanwhile, we continue to await with interest the results of ongoing investigations of the Alpha Centauri stars, in the hopes that a planet there will hit Greg Laughlin’s jackpot.
by Paul Gilster | Feb 21, 2011 | Outer Solar System
Of all the interesting targets the WISE (Wide-Field Infrared Explorer) mission might find, I’ve focused primarily on two in Centauri Dreams: A small star, doubtless a brown dwarf, that might be found closer to us than the Alpha Centauri trio, and a large planet out in the Oort Cloud that might be disturbing cometary orbits. That latter scenario turned up again last March in Finding the Real Planet X, when we looked at various theories about large objects in the outer system, including the thinking of John Matese and Daniel Whitmire (University of Louisiana at Lafayette).
Parameters of a Perturber
Matese has studied the possibility of small stars near our Sun for two decades, but his view now, as revealed in a paper just published in Icarus, is that an object three to five times larger than Jupiter may be the perturber we’re looking for. Matese and Whitmire’s paper on the matter has been available as a preprint since April, but its publication in Icarus has caught the eye of the press, as in this story in The Independent. Think of all the time Percival Lowell devoted to finding a large ‘Planet X’ that wasn’t there (although the detection of Pluto did come out of the search), while a truly massive Planet X at a far greater distance may now turn up in WISE data.
And the Planet X we’re talking about is not ‘Nemesis’ — that would be the name for the small star once considered a possibility as a binary companion to the Sun. Matese and Whitmire prefer ‘Tyche,’ the good sister of Nemesis in mythology, as the name for the gas giant they hope to find in WISE’s data. We’ll have to wait a bit to find out, but not all that long. WISE, whose transmitter has now been turned off, has completed its principal and extended missions and is in hibernation as of early February. The first release, covering 57 percent of the data gathered, will be in April, with the full dataset becoming available in 2012. Matese and Whitmire have calculated that the object should have a temperature of roughly 200 Kelvin, and WISE should be able to see it.
Tyche sounds like a gas giant, according to Whitmire, but even assuming it to be so, we won’t know if it qualifies as a ‘ninth planet’ of our system until the International Astronomical Union considers the matter. After all, we live in a world where Pluto lost its status due to reconsideration of small icy worlds, and it may be that a massive gaseous world out in the Oort Cloud at 15,000 AU would raise questions about its origin. Is it likely that such a planet would have formed around another star, and if so, shouldn’t there be a new, separate designation?
The Planet and the Tides
We’ll see what happens when and if Tyche is discovered. Beyond the possibility of a new planet, the paper on this work becomes absorbing in its study of the effects of the galactic tide (drawing objects toward the center of the galaxy) in pulling comets out of the Oort Cloud. In their analysis of earlier work on the matter, the authors conclude, “…the data are of sufficiently high quality to unambiguously demonstrate the dominance of the galactic tide in making comets discernable at the present epoch.” Where Tyche fits into that picture is that a certain percentage of long-period comets evidently enter the Solar System at an angle that the galactic tide theory cannot explain, offering evidence of perturbation by our unseen companion.
From the paper (here I’m quoting the preprint, as I don’t yet have the Icarus paper. Be aware that this section may have been amended in the final draft):
We have described how the dynamics of a dominant galactic tidal interaction, weakly aided by an impulsive perturbation, predicts specific properties for observed distributions of the galactic orbital elements of outer Oort cloud comets. These subtle predictions have been found to be manifest in high-quality observational data at statistically significant levels, suggesting that the observed OOC comet population contains an ? 20% impulsively produced excess. The extent of the enhanced arc is inconsistent with a weak stellar impulse, but is consistent with a Jovian mass solar companion orbiting in the OOC.
Not only that, but such a body would have roiled the system enough to produce some of the stranger things we’ve found recently:
A putative companion with these properties may also be capable of producing detached Kuiper Belt objects such as Sedna and has been given the name Tyche. Tyche could have significantly depleted the inner Oort cloud over the solar system lifetime requiring a corresponding increase in the inferred primordial Oort cloud population. A substantive difficulty with the Tyche conjecture is the absence of a corresponding excess in the presumed IOC daughter population.
In other words, the Tyche work can explain the behavior of comets from the outer Oort Cloud, but it has trouble with the inner Oort (IOC). Even as we go to work on the dynamics of cometary motion in that region, we should know soon whether this analysis is purely theoretical or has planetary implications. The Independent says Matese and Whitmire think WISE will find Tyche in short order, quoting the latter: “If it does, John and I will be doing cartwheels. And that’s not easy at our age.”
The paper is Matese and Whitmire, “Persistent evidence of a jovian mass solar companion in the Oort cloud,” Icarus Vol. 211, Issue 2, pp. 926-938 (abstract / preprint).