by Paul Gilster | Dec 13, 2012 | Outer Solar System |
One of the wonderful things about daily writing is that I so often wind up in places I wouldn’t have anticipated. Today’s topic includes the discovery of a long river valley on Titan that some are comparing to the Nile, for reasons we’ll examine below. But the thought of rivers on objects near Saturn invariably brought up the memory of a Frank R. Paul illustration, one that ran as the cover of the first issue of Hugo Gernsback’s Amazing Stories in April of 1926. The bizarre image shows sailing ships atop pillars of ice, a party of skaters, and an enormous ringed Saturn.
Is this Titan? The answer is no. The illustration is drawn from the lead story in the magazine, Gernsback’s serialized reprint of Jules Verne’s Off on a Comet, first published in French in 1877 under the title Hector Servadac. A huge comet has grazed the Earth and carried off the main characters, who must learn how to survive the rigors of a long journey through the Solar System, much of the time exploring their frozen new world on skates. I’ll spare you the plot details, but after a perilous fly-by of Jupiter they swing into Saturn’s realm:
…this remarkable ring-system is a remnant of the nebula from which Saturn was himself developed, and which, from some unknown cause, has become solidified. If at any time it should disperse, it would either fall into fragments upon the surface of Saturn, or the fragments, mutually coalescing, would form additional satellites to circle round the planet in its path.
To any observer stationed on the planet, between the extremes of lat. 45 degrees on either side of the equator, these wonderful rings would present various strange phenomena. Sometimes they would appear as an illuminated arch, with the shadow of Saturn passing over it like the hour-hand over a dial; at other times they would be like a semi-aureole of light. Very often, too, for periods of several years, daily eclipses of the sun must occur through the interposition of this triple ring.
If only Verne had been around to see Cassini’s images! Verne’s cometary voyagers can study the heavens with a certain detachment because the comet they are on, called Gallia, turns out to be circling back around toward the Earth, and they believe they will have the prospect of getting home. Off on a Comet is a lively tale. It would be interesting to see what Brian Stableford, who has translated so many early French tales of science fiction into English, would do with the text. Gernsback used a 1911 edition edited and I assume translated by Charles Horne, a New York-based college professor.
On to Titan
Jules Verne had no trouble concocting plots — in addition to his short stories, poems and plays (not to mention numerous essays), he wrote 54 novels in the series called Voyages Extraordinaires between 1863 and 1905. Here among much else are the familiar touchstones From the Earth to the Moon (1865), Journey to the Center of the Earth (1864) and Twenty Thousand Leagues under the Sea (1869). We can only wonder what a Verne armed with Cassini’s latest imagery might have come up with. Take a look, for example, at the river system in the photo below. No skating here, but a boat might work.
It goes without saying that we’ve never seen a river so vast anywhere beyond our own planet, and it does bear a certain resemblance to the Nile, with which it is being compared. What Richard Burton and John Hanning Speke might have given to have had a similar aerial view of the Nile, the search for whose headwaters brought them so much grief and personal animosity. This ‘Nile’ stretches for more than 400 kilometers from its origins to a large sea, its dark surface suggestive of liquid hydrocarbons along the entire length of this high-resolution radar image.
We’re looking at Titan’s north polar region, with a river valley flowing into Ligeia Mare, a sea larger than Lake Superior on Earth. We should actually consider this river a mini-Nile, given that its namesake runs for fully 6700 kilometers, but acknowledging its unique significance (thus far) in our exploration of Titan, the comparison still seems justified. In any case, the river has much to tell us about Titan if we can learn how to read it. Thus Jani Radebaugh, a Cassini radar team associate at Brigham Young University:
“Though there are some short, local meanders, the relative straightness of the river valley suggests it follows the trace of at least one fault, similar to other large rivers running into the southern margin of this same Titan sea. Such faults – fractures in Titan’s bedrock — may not imply plate tectonics, like on Earth, but still lead to the opening of basins and perhaps to the formation of the giant seas themselves.”
Image: Cassini’s view of a vast river system on Saturn’s moon Titan. It is the first time images from space have revealed a river system so vast and in such high resolution anywhere other than Earth. The image was acquired on Sept. 26, 2012, on Cassini’s 87th close flyby of Titan. The river valley crosses Titan’s north polar region and runs into Ligeia Mare, one of the three great seas in the high northern latitudes of Saturn’s moon Titan. It stretches more than 200 miles (400 kilometers). Credit: NASA/JPL-Caltech/ASI.
One day we may have a floating probe on Titan that can trace the course of such a river, working its way out into a dim sea under a sky whose dense cloud would doubtless screen the ringed Saturn from view. What a journey that would be. Even without the garish Frank Paul colors or the wild Vernian imagination, think of human instruments sending back data from a methane sea. Two proposals — Titan Lake In-situ Sampling Propelled Explorer (TALISE) and Titan Mare Explorer (TiME) show us what we might do with near-term technology to make this a reality.
by Paul Gilster | Dec 12, 2012 | Exoplanetary Science |
Finding a way to extend the classical habitable zone, where liquid water can exist on the surface of a planet, is a project of obvious astrobiological significance. Now a team of astronomers and geologists from Ohio State University is making the case that their sample of eight stars shows evidence for just such an extension. The stars in question, drawn from a dataset created by the High Accuracy Radial Velocity Planet Searcher spectrometer at the European Southern Observatory in Chile, were selected because they match up well with the Sun in terms of size, age and composition. Seven of the eight, however, show signs of much more thorium than found in our star.
It’s an interesting result, as seen in this Ohio State news release. The slow radioactive decay of elements like thorium, potassium and uranium, all found in the Earth’s mantle, helps to heat the planet. These are elements present at planetary formation and, according to Ohio State’s Wendy Panero, they are involved in producing enough heat to drive plate tectonics, which some believe to be a factor in maintaining our planet’s oceans. All this is in addition to the sources of heat convection found in the Earth’s core, which play a comparable role in crustal movement.
The work was presented last week at the American Geophysical Union meeting in San Francisco by Cayman Unterborn, a graduate student at Ohio State who is working under Panero. Unterborn’s thesis: More thorium in a stellar interior indicates that the interior of planets found around the star would be warmer than the Earth. He notes that one of the stars in the HARPS survey contains 2.5 times more thorium than the Sun. Unterborn’s calculations show that any terrestrial planets forming around that star would generate as much as 25 percent more heat than the Earth, providing a long-lasting driver for plate tectonics. The warmer planet would have a habitable zone farther from its star as well, supported by the additional internal heat.
Image: An artist’s impression of the ‘super-Earth’ HD 85512 b. Is it possible that a planet like this is warmer internally than the Earth, allowing life to form over a wider habitable zone? Credit: ESO/M. Kornmesser.
The cautious Unterborn is aware that he’s looking at a small sample:
“If it turns out that these planets are warmer than we previously thought, then we can effectively increase the size of the habitable zone around these stars by pushing the habitable zone farther from the host star, and consider more of those planets hospitable to microbial life. At this point, all we can say for sure is that there is some natural variation in the amount of radioactive elements inside stars like ours. With only nine samples including the sun, we can’t say much about the full extent of that variation throughout the galaxy. But from what we know about planet formation, we do know that the planets around those stars probably exhibit the same variation, which has implications for the possibility of life.”
The Ohio State researcher notes that thorium is more energetic and has a longer half-life than uranium. Planets rich in the element would tend to remain hot longer than the Earth, which gets most of the heat of its radioactive decay from uranium. As to why we wind up on the short end of the stick when it comes to thorium, Unterborn believes it harks back to the exploding stars that seeded local space with heavy elements long before our planet formed:
“It all starts with supernovae. The elements created in a supernova determine the materials that are available for new stars and planets to form. The solar twins we studied are scattered around the galaxy, so they all formed from different supernovae. It just so happens that they had more thorium available when they formed than we did.”
These results are clearly preliminary, and Jennifer Johnson (Ohio State), a co-author of the study, points to the need to expand its scope. One way to do that is to analyze noise in the HARPS data, something that is now on Unterborn’s to-do list, after which the team plans to expand the search to additional Sun-like stars. If there are indeed large numbers of stars whose basic composition creates planets that generate more internal heat than the Earth, then we need to consider the implications for how we analyze habitable zones and their longevity.
by Paul Gilster | Dec 11, 2012 | Culture and Society |
Patrick Moore, the legendary figure of British astronomy who died recently at his home in West Sussex, was deeply familiar with Ptolemy. The latter, a 2nd Century AD mathematician and astronomer, was the author of the Almagest, an astronomical treatise that presented the universe as a set of nested spheres and assumed a geocentric cosmos. Moore’s comprehensive knowledge of astronomy’s history would naturally have included the Almagest and probably Ptolemy’s astrological musings as well, but a different Ptolemy was a figure even more important to him, a cat of that name who was with him when he died. The author of 2012’s Miaow!: Cats Really are Nicer Than People! never hid his love for his feline friends.
I admire a man who, when faced with the reality that further treatments are unproductive, simply announces that he wants to go home. And go home he did, to the town of Selsey and the house called Farthings, where he died among family and friends. Moore was a man of fierce views and simple integrity whose generosity was uncommon. In a career in which he hosted the BBC show ‘The Sky at Night’ for an unprecedented 55 years, he inspired countless young people to explore the heavens. Brian May, the guitarist who published a book on astronomy with Moore, noted the latter’s devotion to his audience in a remembrance published in The Guardian.
In his private life Patrick was astoundingly giving. His dedication to young aspiring astronomers was legendary. He replied to every letter, responded to questions, helped students with gifts of equipment and the most precious gift of all – his time. He personally tutored some he thought particularly promising, and sponsored others through higher education; he gave away any income he made to the point where he had no security himself except that which his friends supplied.
‘The Sky at Night’ first appeared in 1957, and it is a remarkable fact that in the years since, Moore missed only a single episode, felled by a salmonella-laden egg in 2004. He could have gone to Cambridge and pursued an academic career, but when World War II came he lied about his age and joined Bomber Command, where he became a navigator. He called himself a ‘reluctant bachelor,’ and said that he felt the same about his fiancée Lorna in 2012 as he did in 1940, not long before she was killed by a German bomb. Love ran deep. He would never marry but would go on to parlay his extensive learning and air of eccentricity into the work of a lifetime.
The gifted amateur used a 12-inch reflector, specializing in lunar observations of a quality so high that he was chosen to be the first outside the Soviet bloc to see the results of the Luna 3 probe, showing images from the craft on the air. Moore was dealing with live TV in those days, and not all his plans worked out, as when technical problems compromised his coverage of Luna 4 transmissions, and at times his attempts to get a live telescopic view of a celestial object were ruined by cloud cover. None of this mattered and some of the glitches, such as his swallowing a fly that buzzed into his mouth, only added to the eccentric charm and reputation of the presenter. Many will remember Moore’s on-air work during the Apollo missions, which extended to later reporting on both Pioneer and Voyager. His Wikipedia article has more.
Much is being said in remembrance of Moore all over the Internet — see this obituary in The Telegraph, for example, in addition to the BBC article by Brian May that I linked to above. Moore the television presenter is remembered just as fondly as Moore the author. He began his work with Guide to the Moon in 1953 and continued for over 60 titles, much of the time working on the same 1908 Woodstock typewriter.
This morning I’ve been thumbing through the pages of his 1984 book Travellers in Space and Time, an illustrated journey through the cosmos that takes us as far as Andromeda, but I’m also thinking of titles that were older still, like The Picture History of Astronomy (1964) and Watchers of the Stars (1974). Books like these and Moore’s practical tomes on amateur astronomy brought celestial matters down to Earth, igniting enthusiasm and stoking the fires of young careers. This grand, ebullient man with the trademark monocle was indispensable, impossible to replace. “There will never be another Patrick Moore. But we were lucky enough to get one,” wrote May in his tribute. Do note that May has also set up a Patrick Moore website where members of the public he spoke to with such passion can leave their remembrances.
by Paul Gilster | Dec 10, 2012 | Culture and Society |
If Kansas may not be the first place that comes to mind when you think about interstellar matters, be aware that its state motto is ‘Ad Astra Per Aspera’ — to the stars through difficulties. That’s a familiar phrase for anyone who has pondered the human future in space, appearing in countless science fiction stories and often invoked by those with a poetical streak. It turns out that the Kansas motto was not, however, the work of some percipient 19th Century Robert Forward figure, but of one John Ingalls, a lawyer, scholar and statesman who introduced the motto as far back as 1861. And while its roots were in the coming Civil War, the story of Ingalls’ motto is so entertaining that it merits inclusion here, as reported by biographer G. H. Meixell:
“I was secretary of the Kansas state senate at its first session after our admission in 1861. A joint committee was appointed to present a design for the great seal of the state and I suggested a sketch embracing a single star rising from the clouds at the base of a field, with the constellation (representing the number of states then in the Union) above, accompanied by the motto, “Ad astra per aspera.” If you will examine the seal as it now exists you will see that my idea was adopted, but in addition thereto the committee incorporated a mountain scene, a river view, a herd of buffalo chased by Indians on horseback, a log cabin with a settler plowing in the foreground, together with a number of other incongruous, allegorical and metaphorical augmentations which destroyed the beauty and simplicity of my design.”
It was ever thus, and not just for politicians with an artistic bent. Any writer can tell stories about botched copy edits that would make even Ingalls shake his head in disbelief.
Space advocate Steve Durst was well aware of the history embedded in Ingalls’ motto, but also taken with the idea of Kansas in a more astronomical context. After numerous trips to the state, he would go on to found an organization called Ad Astra Kansas, focusing on high-tech and space research but with a wider charter that includes getting the word out about interstellar matters through education. The idea grew out of two other projects likewise affiliated with Durst’s Space Age Publishing Company: The International Lunar Observatory Association and an international series of public presentations called the Galaxy Forum. Durst says he has always been looking for “something broad that would be inspirational, directional, iconic, symbolic,” and in promoting the concept of interstellar flight, he has surely found it.
Image: Publisher and space activist Steve Durst, standing in front of the “Ad Astra Per Aspera” stained-glass artwork at the Kansas Cosmosphere and Space Center in Hutchinson just before Galaxy Forum Kansas on September 22, 2012.
Ad Astra Kansas came to my attention when I flew to San Jose last July to speak at a Galaxy Forum on the 4th and meet the energetic Durst, along with marketing editor Michelle Gonella. The organization is now a decade old, having begun its Ad Astra Kansas News in 2001, a publication that continues today under the editorship of Jeanette Steinert. The first Ad Astra Kansas Day was held in 2003, inaugurating a series of such meetings in various Kansas venues with an emphasis on business and education as space development continues. One of these is the Kansas Cosmosphere, a world-class aerospace facility in Hutchinson that seems to exemplify the anomalous nature of the enterprise. Here is a quiet farming community of some 42,000 people that boasts a major venue showcasing space exploration from the V-2 to Apollo.
What else could be created here? Durst talks about an interstellar research and development initiative, perhaps created as an archive or, long-term, a research center with an interstellar focus. Meanwhile, the organization continues to play a midwestern role in the Galaxy Forum program that began in Silicon Valley. Operating from his headquarters in Hawaii, home to ILOA, and an office in California, Durst, Phil Merrell, and Joseph Sulla of the ILOA Galaxy Forum program in Hawaii have, along with Gonella, expanded the forums around the world. They began July 4, 1984, as discussions of lunar exploration but by 2008 the focus had turned to the galaxy, with sessions as far afield as Canada, Beijing, Singapore and Japan. 2011 saw eleven Galaxy Forums from Shanghai to Bangalore, Hawaii and New York, bringing speakers and the general public together to discuss space and the human future in the broadest possible context.
My focus last July in San Jose’s Galaxy Forum was on the question of nearby targets for deep space missions, ‘nearby’ being defined as objects between the inner edge of the Kuiper Belt all the way to the Alpha Centauri stars. It was a good session, held at the city’s Tech Museum on July 4. Jon Lomberg had flown in from Hawaii and Seth Shostak was on hand from the SETI Institute. Durst’s hope is to provoke what he calls ‘galaxy consciousness,’ a way of looking at the future that leverages near-term projects like the lunar observatory but points beyond:
“We are at the start not just of new century but a new millennium. The Galaxy Forum is premised as much as anything on the fact that this is a new domain of learning for us, for all of humanity. Ninety years ago, before Hubble’s findings, we didn’t know there were galaxies or that we were part of one. Even today we have the sense that all those stars we see on a clear night comprise the universe, but that’s not true — it’s just a small patch of our own galaxy that we see. Professionals understand that, but in general educational practice from high school and early college down, there isn’t an awareness that between the finiteness of the Solar System and the infiniteness of the cosmos there is this larger knowable domain of the galaxy to explore.”
That’s a confounding fact but true — I still find myself having to explain the difference between ‘interplanetary’ and ‘interstellar’ at the oddest moments. Thus the idea of ‘galaxy consciousness’ is a praiseworthy target, but one that will require more than a generation of work. The idea grew out of Durst’s earlier work with the International Lunar Observatory Association, which itself emphasizes that its mission is “to expand human understanding of the cosmos through observation from our Moon.” The original ILOA mission was conceived as deployment of a 2-meter dish observatory near the lunar south pole, for observations both of the local environment as well as deep space as a way of educating people about the Solar System’s context in the cosmos. But ILOA is also working on a Google X-Prize entrant with the goal of placing a 10-cm optical telescope on the team’s lunar lander scheduled for 2014.
And in September 2012, ILOA signed a memo of understanding with the National Astronomical Observatories of the Chinese Academy of Sciences allowing ILOA scientists to conduct observations with the UV telescope set to fly on the Chang’e-3 lunar lander in 2013. With Galaxy Forums set to expand to South America and possibly Antarctica by 2014, ILOA is part observer, part educator, with the goal of having a voice in the changing philosophical perception of our planet’s place in the galaxy. Meanwhile, Ad Astra Kansas is a reminder that deep space begins close to home, in the students whose careers may be launched by education that opens minds to the cosmos. Who knew in 1861 that John Ingalls’ state motto would have that kind of reach?
by Paul Gilster | Dec 7, 2012 | Exoplanetary Science |
Do planets form easily around brown dwarf stars? Are they actually common? We’re getting a glimpse of the possibilities in new work at the Atacama Large Millimeter/submillimeter Array (ALMA), where a brown dwarf known as ISO-Oph 102 (also called Rho-Oph 102) is under investigation. In most respects it seems like a fairly run-of-the-mill brown dwarf, about 60 times the mass of Jupiter and thus unable to ignite hydrogen fusion. It’s also tiny, at 0.06 times the mass of the Sun, a dim object in the constellation of Ophiuchus.
The work suggests that in the outer regions of a dusty disk surrounding Rho-Oph 102 there exist the same kind of millimeter-sized solid dust grains found around the disks of young stars. That’s intriguing because astronomers have thought that earlier finer grains would not be able to grow into these larger particles in the cold, sparse disks assumed to be around brown dwarfs. Those that did form were thought to disappear quickly toward the inner disk, where they would be undetectable. The fact that these larger grains are here has interesting implications, according to CalTech’s Luca Ricci, who led the international team performing the study:
“We were completely surprised to find millimetre-sized grains in this thin little disc. Solid grains of that size shouldn’t be able to form in the cold outer regions of a disc around a brown dwarf, but it appears that they do. We can’t be sure if a whole rocky planet could develop there, or already has, but we’re seeing the first steps, so we’re going to have to change our assumptions about conditions required for solids to grow.”
Image: This wide-field view shows the star-forming region Rho Ophiuchi in the constellation of Ophiuchus (The Serpent Bearer), as seen in visible light. This view was created from images forming part of the Digitized Sky Survey 2. Credit: ESO/Digitized Sky Survey 2/Davide De Martin.
The disks around brown dwarfs may thus be more similar to those around young stars than we had realized, suggesting that rocky planets may not be uncommon here. We do have a few brown dwarf planets — 2M1207b, MOA-2007-BLG-192Lb and 2MASS J044144 — already in the book, one of them relatively small at 3.3 Earth masses. And a study by Andrey Andreeschchev and John Scalo (University of Texas) has indicated that terrestrial-mass planets should form around these objects as long as there is enough disk material to work with.
Image: Rocky planets are thought to form through the random collision and sticking together of what are initially microscopic particles in the disc of material around a star. These tiny grains, known as cosmic dust, are similar to very fine soot or sand. Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have for the first time found that the outer region of a dusty disc encircling a brown dwarf — a star-like object, but one too small to shine brightly like a star — also contains millimetre-sized solid grains like those found in denser discs around newborn stars. Credit: ALMA (ESO/NAOJ/NRAO)/M. Kornmesser (ESO).
The ALMA work also found carbon monoxide around the brown dwarf, its first detection in a brown dwarf disk. All this is promising stuff if we want to construct exotic scenarios about what may happen around these dim objects. Lacking the mass to fire hydrogen fusion, a brown dwarf is nonetheless going to emit heat because of its slow contraction due to gravity. Any brown dwarf with terrestrial planets around it is going to be doing a slow fade as it gives up gravitational potential energy. That means that if there is a habitable zone there, it gradually moves inward.
I’ve quoted him on this before, but Centauri Dreams reader Andy Tribick may not mind if I put this comment of his out there again. He’s talking about life around brown dwarfs:
It’d be interesting to come up with some scenarios for evolution on such a planet whose star decreases in luminosity as it ages (as opposed to more conventional stars that brighten as they age) – perhaps life might begin in the cloud layers of an initially Venus-like planet, moving to the surface as the atmosphere cools and the oceans rain out of the atmosphere, and finally moving to a more Europa-like state with the oceans frozen under an ice layer.
The 2004 study by Andreeshchev and Scalo I referred to above concluded that a brown dwarf with the mass of 0.07 solar masses, not all that far off Rho-Oph 102’s 0.06, could produce a habitability duration of a billion years, presumably long enough to get basic life functioning. And because the two scientists are talking about a classic habitable zone definition involving liquid water on the surface, you can see that Andy Tribick’s idea would extend the duration of possible habitability at both ends. Andreeshchev and Scalo themselves can extend habitability out to a surprising four billion years depending on how far they push the Roche limit, which governs how close a planet can be to its host star before it’s torn apart by tidal forces.
So maybe there’s a case for astrobiology around brown dwarfs, objects about which we still have much to learn. Just how common are they? While some scientists have suggested that brown dwarfs might be as common as the M-dwarfs that make up as much as 80 percent of the stars in the Milky Way, the results from WISE — the Wide-field Infrared Survey Explorer — turn up one brown dwarf for every six stars. That’s still a significant number of objects, and it includes 33 brown dwarfs known to be within 26 light years of the Sun, but the idea of interstellar targets closer than Alpha Centauri, at least stellar targets, is evidently fading from view.
But back to Luca Ricci and team and their work with ALMA. The great news embedded in the story is that ALMA is only partially up to strength. This array of radio telescopes in Chile’s Atacama desert operates at millimeter wavelengths and is intended to consist of 66 instruments when complete, but Ricci’s team worked with just a quarter of the final complement of antennas. In terms of observing planetary system formation, ALMA is already proving its worth, and a completed ALMA installation should be able to give us a close look at Rho-Oph 102:
“We will soon be able to not only detect the presence of small particles in discs, but to map how they are spread across the circumstellar disc and how they interact with the gas that we’ve also detected in the disc,” Ricci said. “This will help us better understand how planets come to be.”
The paper is Ricci et al., “ALMA observations of rho-Oph 102: grain growth and molecular gas in the disk around a young Brown Dwarf,” accepted at the Astrophysical Journal (abstract). The Andreeshchev and Scalo paper is “Habitability of Brown Dwarf Planets,” Bioastronomy 2002: Life Among the Stars. IAU Symposium, Vol. 213, 2004 (full-text).
