Centauri Dreams
Imagining and Planning Interstellar Exploration
Hydrothermal Activity in the ‘Broken Heart’ of Enceladus
Enceladus has been a magnet for investigation since 2005, when the Cassini spacecraft began to reveal the unusual activity at the moon’s south pole, where we subsequently learned that geysers of water ice and vapor laden with salts and organic materials were spraying into space from deeply fractured terrain. Subsequent studies have homed in on what is now believed to be a 10-kilometer deep ocean beneath an ice shell 30 to 40 kilometers thick.
Now we learn that evidence for hydrothermal activity — water reacting with a rocky crust in a process that warms and saturates it with minerals — has been found on Enceladus, drawing on a four-year analysis of Cassini data. The new paper, published in Nature, is one of two just out that paint a gripping picture of active processes on the moon. It uses computer simulations and laboratory experiments to make sense out of Cassini’s early detection of silicon-rich rock particles flung into space by Enceladus’ geysers.
Researchers working on data from Cassini’s cosmic dust analyzer instrument believe the particles are grains of silica, found in sand and quartz on Earth, but it was the consistent size of the grains (6 to 9 nanometers) that helped them pin down the process responsible. Lead author Sean Hsu (University of Colorado at Boulder) and Cassini scientist Frank Postberg (Heidelberg University) collaborated with colleagues at the University of Tokyo, whose laboratory work explained the conditions needed to form silica grains of the same size as those detected by Cassini. The environment to produce them is thought to exist on the seafloor of Enceladus.
Image: This cutaway view of Saturn’s moon Enceladus is an artist’s rendering that depicts possible hydrothermal activity that may be taking place on and under the seafloor of the moon’s subsurface ocean, based on recently published results from NASA’s Cassini mission. Credit: NASA/JPL.
The process outlined in the paper works like this: Water should infuse the core of Enceladus, where gravity measurements by Cassini have already indicated the rock is porous. Water warmed in the interior, laden with dissolved minerals, interacts with colder water as it moves upward toward the geyser regions at the south poles, with silica crystallizing along the way. We learn something about conditions inside Enceladus here, for temperatures of at least 90 degrees Celsius would be required for the silica grains to be produced. A relatively quick transit is implied (no more than several years), accounting for the uniform size of the grains.
The hydrothermal activity displayed here is not dissimilar to what we find on Earth when silica-rich super-saturated water experiences a significant drop in temperature, and scientists are already talking about the possible astrobiological implications. John Grunsfeld, associate administrator of NASA’s Science Mission Directorate in Washington, puts it this way:
“These findings add to the possibility that Enceladus, which contains a subsurface ocean and displays remarkable geologic activity, could contain environments suitable for living organisms. The locations in our solar system where extreme environments occur in which life might exist may bring us closer to answering the question: are we alone in the Universe.”
Geophysical Research Letters is the source of the second paper, which looks at methane in the plumes emanating from Enceladus’ south pole, suggesting that it too is the likely result of hydrothermal activity. The French and American scientists involved in this work have discovered that clathrates forming under high pressure in the moon’s ocean could trap methane molecules inside water ice, an efficient process for depleting oceanic methane.
The hydrothermal explanation for the abundance of methane in the plume is that hydrothermal processes cause the ocean to become super-saturated with methane, so that the methane is being produced faster than it can be converted into clathrates. This solution fits well with the hydrothermal activity suggested by the grains of silica described in the Nature paper. Another possibility is that the clathrates release their methane as they are forced up into the plumes. Both of these processes may be occurring on Enceladus, but the work on silica grains gives weight to the hydrothermal explanation.
Image: This illustration depicts potential origins of methane found in the plume of gas and ice particles that sprays from Enceladus, based on research by scientists working with the Cassini Ion and Neutral Mass Spectrometer. Credit: NASA/JPL.
In a Scientific American essay called First Active Hydrothermal System Found Beyond Earth, Lee Billings points to the significance of these two papers in relation to astrobiology:
One of the leading theories for the origin of life on Earth postulates that it began in hydrothermal vents at the bottom of the ocean, where seawater percolating through hot rocks created energy- and nutrient-rich environments favoring the formation of the first cells. Today, Earth’s active hydrothermal vents are seafloor oases, harboring ecosystems that flourish in the darkness, isolated from the surface world. Find someplace else beyond Earth where hot rock and water intermingle, and even if it’s far from the sun life might flourish there, too. Such systems may have been common early in the solar system’s history, when rocky planets and icy moons were still relatively hot and wet from their initial formation. But until now scientists had no evidence of ongoing hydrothermal activity anywhere beyond Earth.
Hydrothermal activity within Enceladus tells us that there is a heat source here beyond radioactive materials at the core, probably the result of the moon’s orbit around Saturn and the heat generated by the resulting interactions. Billings points to another possible process: serpentinization, in which chemical reactions between water and rock generate heat, all occurring in a fractured, porous core. He adds: “Enceladus’s sizzling core may actually be a bit like a broken heart, kept alive by tidal forces continually pumping seawater through its fractured veins.” That passage alone should make you want to read all of Billings’ essay.
The papers are Hsu et al., “Ongoing hydrothermal activities within Enceladus,” Nature 519 (12 March 2015), 207-210 (abstract), and Bouquet et al., “Possible evidence for a methane source in Enceladus’ ocean,” Geophysical Research Letters, published online 11 March 2015 (abstract). This NASA news release is helpful.
Mission Updates: New Horizons, Hayabusa 2
While we wait for the Dawn spacecraft to come back around the lit side of Ceres as it continues a long period of orbital adjustment, let’s check in on two other spacecraft with the potential for a big science return. New Horizons performed a 93-second thruster burn on March 10 that was the farthest burn from Earth of any spacecraft in history. We’re now in the approach phase to Pluto/Charon and this was the first maneuver of that phase, designed to slow the spacecraft by a mere 1.14 meters per second. The New Horizons team describes this as ‘a tap on the brakes’ considering that the probe is moving at 14.5 kilometers per second.
As this New Horizons news update informs us, yesterday’s burn delayed arrival time at Pluto/Charon by 14 minutes, 30 seconds as the spacecraft’s course was adjusted. New Horizons is now 149 million kilometers from Pluto — in other words, 1 astronomical unit, or AU, meaning the spacecraft is the same distance from its target as the Earth is from the Sun. It takes a radio signal 4 hours, 28 minutes to reach us from New Horizons’ current position.
Image: This image shows New Horizons’ current position along its full planned trajectory. The green segment of the line shows where New Horizons has traveled since launch; the red indicates the spacecraft’s future path. Positions of stars with magnitude 12 or brighter are shown from this perspective, which is above the Sun and “north” of Earth’s orbit. Credit: New Horizons / JHU/APL.
Emily Lakdawalla has an excellent overview of the upcoming Pluto/Charon encounter, from which this note about data transmission:
Data will arrive on Earth in a series of downlinks. Downlink sessions can last as long as about 8 hours, but are usually somewhat shorter. Whenever New Horizons is downlinking data, it can’t take new photos, so the downlinks get shorter and less frequent as the spacecraft gets close to the time of the flyby, when it concentrates on collecting as much data as possible. Because data downlinks are slow, there will be much less data downlinked than New Horizons has stored on board. After data is downlinked, it must be processed before posting online. How long that will take is not yet known.
Near-Earth Asteroid Sample Return
Meanwhile, Japan’s Hayabusa 2 has just completed its initial checkout and evaluation, a process that has been ongoing since the spacecraft’s launch on December 3 of last year. Following on the original Hayabusa (MUSES-C) mission to the near-Earth asteroid 25143 Itokawa, Hayabusa 2 is likewise designed around a sample return, with arrival at the target asteroid 1999 JU3 in July of 2018. A year and a half of operations near the asteroid are to follow, with departure in December of 2019 and a return to Earth in December of 2020.
Like the Dawn spacecraft, Hayabusa 2 is powered by ion engines, which continue to prove their worth in precision maneuvering around such small objects. The sample collection procedure revolves around the Small Carry-on Impactor (SCI) that the spacecraft will deploy from a distance of 500 meters along with a camera. The SCI contains a 4.5 kilogram charge and a copper projectile that will strike the asteroid at 2 km/s. The camera will observe the explosion while Hayabusa 2 moves behind the asteroid. The plan is to take sub-surface samples from the resulting 1-meter crater from an asteroid known to be rich in carbon compounds.
1999 JU3 is an Apollo asteroid, one of a group of near-Earth objects that always bear watching because they have semi-major axes larger than Earth’s but perihelion distances less than Earth’s aphelion (the Chelyabinsk impactor, which struck the southern Urals with such spectacular effect in February of 2013, is believed to have been an Apollo-class asteroid). 1999 JU3 is also considered a more primordial asteroid than Itokawa. By taking samples from below the surface, researchers target materials less affected by solar radiation and exposure to space, thus offering a clearer view of the object’s chemical evolution.
Image: Relative locations of Hayabusa 2, Earth, Sun and 1999 JU3 as of March 3, 2015. Red grid shows plane of the ecliptic. Credit: JAXA.
According to JAXA, the Japanese space agency, Hayabusa 2 will burn its ion engines about 400 hours in March as it prepares for an eventual Earth flyby late this year, with a second period of engine operation in June. JAXA reports that the spacecraft is in good health and now moving to the cruise phase of the mission. With upgraded communications, navigation and attitude control systems and a small lander called MASCOT ( (Mobile Asteroid Surface Scout)) built by the German Aerospace Center in cooperation with the French space agency CNES, Hayabusa 2 should tell us much about the composition of this class of near-Earth asteroids, a population we’ll eventually investigate with human crews as we deepen our knowledge of nearby space.
The Fermi Question: No Paradox At All
We’ve talked often enough about the so-called ‘Fermi paradox’ in these pages, but Gregory Benford recently passed along a new paper from Robert H. Gray making the case that there is in fact no paradox, and that Fermi’s intentions have been misunderstood. It’s an interesting point, because as it turns out, Fermi himself never published anything on the subject of interstellar travel or the consequences if it proved possible. The famous lunch conversation at Los Alamos in 1950 when he asked ‘Where is everybody’ (or perhaps ‘Where are they’) has often been seen as a venue for Fermi to express his doubts about the existence of any extraterrestrial civilization, and the ‘Fermi Paradox’ has become a common trope of interstellar studies.
Robert Gray (Gray Consulting, Chicago) believes this is a misunderstanding, and sorts through the aftermath of that particular event. It would be another 27 years before the term ‘Fermi paradox’ even appeared in print, inserted into a JBIS paper by D. G. Stephenson. This followed upon Michael Hart’s 1975 discussion, which Gray sums up as ‘they are not here; therefore they do not exist,’ an argument Hart used to question the wisdom of pursuing SETI. Frank Tipler’s subsequent paper (1980) took us into the realm of artificial intelligence, claiming that self-replicating probes could use even current spacecraft speeds to colonize the galaxy in less than 300 million years. Tipler concluded that we were probably the only intelligent species in the universe since we had not encountered evidence for the existence of such probes.
Maybe we should leave Fermi’s name out of this, writes Gray:
Using Fermi’s name for the so-called Fermi paradox is clearly mistaken because (1) it misrepresents Fermi’s views, which were skeptical about interstellar travel but not about the possible existence of extraterrestrials, and (2) its central idea ”they are not here; therefore they do not exist” was first published by Hart. Priority of publication and accuracy suggests using a name like Hart-Tipler argument instead of ‘Fermi paradox.’
Image: Enrico Fermi (1901-1954), whose famous question may have been misunderstood by subsequent writers.
I notice that as it currently stands, the Wikipedia entry for Fermi Paradox describes it as “…sometimes referred to as the Fermi-Hart paradox,” but Gray can turn to no less an eminence than Iosif Shklovsky, Russian astronomer and co-author, with Carl Sagan, of Intelligent Life in the Universe (Holden Day, 1966), who preferred the term ‘Hart Paradox,’ while Stephen Webb opined we might try ”Tsiolkovsky-Fermi-
Viewing-Hart paradox” in his book Where Is Everybody (Copernicus, 2002). David Viewing had argued in 1975 that extraterrestrial civilizations might well exist despite the factors that Hart noted, meaning we should actively search for evidence of them.
Gray even falls back on Konstantin Tsiolkovsky, who wondered about questions like these in the 1930s. But is there any paradox here? Gray thinks not, for a paradox implies a statement that is self-contradictory, the nature of the contradiction suggesting that something is wrong:
The Hart-Tipler argument takes the seemingly obvious fact they are not here as evidence that a premise ”technological extraterrestrials exist” must be false, because if they did exist, the colonization argument leads to the conclusion they are here, which seems absurd. This is a reductio ad absurdum argument, not a paradox, although like a paradox it depends on every statement being true—yet the argument consists of many speculations which are not known to be true.
Good point. Consider which statements we cannot know, starting with the assumption that interstellar flight is feasible, although most of us here believe that if we can envision it with our current level of technology, then it is at least a rational assumption. In fact, the original Project Daedalus was conceived in part as a way of showing that if we could, at levels of scientific development not far ahead of our own, design a starship, then surely other civilizations of much longer duration than ours would have found better ways to make these things happen.
As for the other implicit assumptions, the unknown nature seems clear enough. Would the galaxy indeed fill, as per Tipler, with self-reproducing probes in the kind of timeframes he imagined? Would this ‘colonization’ take a form we could understand or detect (Gray doesn’t get into this question, though it seems pertinent). Would any presence from another star system be likely to persist over millions or even billions of years? Clearly we have no answers here, and have no way of knowing whether we ever will. Assuming that each of these positions is therefore true and that Earth would be a visited world is thus a questionable stance.
According to three of those who were there (Emil Konopinski, Edward Teller, and Herbert York, all quoted in the Gray paper), Fermi’s point was not that extraterrestrial civilizations did not exist, but that interstellar travel that might bring them here was infeasible. As Gray sees it, the true ‘they are not here; therefore they do not exist’ argument should be credited to Michael Hart and Frank Tipler. The question may not be purely theoretical, for it turns out that this Hart-Tipler argument became one of the reasons given for canceling NASA’s SETI program in 1981, being cited by William Proxmire, who referenced Tipler’s work. Gray asks whether continued use of it in this way may perpetuate low funding levels in SETI. And this is worth quoting:
The literature on searches (Tarter, 1995) indicates that only a small fraction of the radio spectrum has been searched—0.3 GHz in surveys covering much of the sky (Leigh and Horowitz, 2000) using transit observations, and 2 GHz in targeted searches of 800 stars (Backus et al., 2004)—out of a terrestrial microwave window from 1 to 10 GHz, a free-space window up to 60 GHz (Oliver and Billingham, 1971), and much more electromagnetic spectrum beyond, including optical. Few searches would have detected low-duty-cycle signals anticipated by some (Benford et al., 2010; Gray, 2011), because both radio and optical surveys typically observe positions for only minutes. An incomplete search for signals cannot be used as evidence of complete absence of technological extraterrestrials.
The paper is Gray, “The Fermi Paradox Is Neither Fermi’s Nor a Paradox,” Astrobiology Volume 15, Number 3 (2015). Abstract available.
Searching for Exoplanet Rings
Not long ago we looked at the discovery of what appears to be a disk orbiting the huge gas giant J1407b (see Enormous Ring System Hints of Exomoons). The example of Saturn is one thing that makes us wonder whether rings might exist around exoplanets, but of course in our own Solar System we also have Jupiter, Uranus and Neptune as hosts of ring systems of different sizes. In the case of J1407b, we’re not strictly sure that the object is a planet. If it’s actually a brown dwarf, we might be observing a protoplanetary disk in a young system.
I’m not surprised when it comes to looking for ring systems around exoplanets that David Kipping (Harvard-Smithsonian Center for Astrophysics) should be in the mix. Working with Jorge Zuluaga (University of Antioquia) and two of their students, Kipping is co-author of a paper discussing how we might identify what are now being called ‘exorings.’ As illustrated in the figure below, an exoplanet’s transit signature is a key, taking advantage of the fact that a planet with a ring system will produce a longer, deeper transit than the same planet without any rings.
Image: Schematic representation of the transit of a ringed planet in front of its star. When compared with the light curve of an non-ringed analogue (dashed line) the transit of a ringed planet is deeper (the relative flux diminishes by a larger fraction) and longer. Credit: Jorge Zuluaga/David Kipping.
The trick here is to separate the effect of a larger planet seen in transit from a smaller world with a ring system. The paper explains that in transit studies, objects that appear larger than expected are often classed as false positives, a category that the authors think merits a careful look in case what is being rejected is actually a planet with a ring system. From the paper:
The transits of a Saturn-like ringed-planet are up to ?3 times deeper than that expected for a spherical non-ringed one. These deep transits will be interpreted as produced by a planet ?1.7 times larger. Additionally, if independent estimations of its mass were also available, the density of the planet will be underestimated by a factor of ?5. Thus, instead of measuring Saturn’s density ?0.7 g/cm3 , this planet would seem to have an anomalously low density of ?0.14 g/cm3 . Even under more realistic orientations (cosiR ? 0.2) the observed radius will be ?20% larger and the estimated density almost a half of the real one.
It is conceivable, then, that some ‘false-positive’ transits conceal a population of planets with rings.
An effect based on asterodensity profiling that the authors call the ‘photo-ring’ effect also comes into play. Here we examine the transit depth and its duration. The first is related to the size of the star, while the second depends on orbital velocity and the mass of the star. Out of this information we can estimate the star’s density, a result that can be compared with independent density calculations from methods like asteroseismology or the transits of other planetary companions to see if the results coincide. A discrepancy may be telling: The presence of rings around the transiting world, the authors argue, leads to an underestimation of stellar density.
Interestingly, the two effects we seek (anomalous transit depths and photo-ring effect) are complementary with respect to the orientation of the ring plane. For large inclinations and obliquities (face-on rings), the effect on transit depths is significant whilst the photo-ring effect is negligible. Alternatively, if rings have relatively low obliquities (edge-on rings), then the photo-ring effect will be considerable but the depth anomaly small.
Image: Magnitude of the so-called Photo-ring effect predicted by Zuluaga, Kipping et al., at different projected inclinations and tilts (small “saturns”). Credit: Jorge Zuluaga/David Kipping.
The strategies that emerge from this study are thus complementary. We can look for already confirmed transiting planets that appear to have anomalously low densities for further study. We can also reinvestigate our catalog of false-positives due to anomalously large transit depths to see if any of these could mask a ringed planet’s signature. Finally, we can search for transit signals that show the ‘photo-ring’ effect, looking for discrepancies in density calculations.
None of this implies that studying transit lightcurves itself does not remain significant:
We stress that the method presented here is complementary to the methods developed to discover exorings through detailed light curve modelling (Barnes & Fortney 2004; Ohta et al. 2009; Tusnski & Valio 2011). As explained earlier, the role of these methods will be very important once a suitable list of potential exoring candidates [is] found. It is, however, also important to note the great value of light curve models developed under the guiding principle of computational efficiency (semianalytical formulae, efficient numerical procedures, etc.), such as the basic models presented here.
We thus have a relatively straightforward technique for surveying our transiting planet catalogs for ringed-planet candidates, looking for that subset that can be subjected to more detailed lightcurve analysis. The paper is Zuluaga et al., “A Novel Method for Identifying Exoplanetary Rings,” accepted for publication at Astrophysical Journal Letters (preprint).
Dawn Orbits Ceres
I spent the morning working on an interesting paper about detecting ‘exorings’ — ring systems like Saturn’s around exoplanets — while switching back and forth to Twitter and various Web sources to follow events as the Dawn spacecraft became gravitationally captured by Ceres. I have problems with so-called ‘multi-tasking,’ which at least in my case means I do two things at once, performing each task less effectively than if I were tackling them separately. Fortunately, I have all weekend to tune up the exorings story, and I put it temporarily aside to work on Dawn’s historic arrival.
Congratulations to the entire Dawn team on the continuance of this splendid mission. We have much to look forward to as observations proceed and the orbit stabilizes. Similarly, we have the almost immediate prospect of following New Horizons in to Pluto/Charon, another case of a previously blurry object taking on breathtaking resolution as the days pass. The bounty of 2015 then opens into an uncertain future when it comes to exploring the outer system, but we can hope that the New Horizons extended mission will happen as anticipated and investigate a Kuiper Belt Object. We can also hope that the European Space Agency proceeds with its Jupiter Icy Moons Explorer without what would have been the NASA side of the mission.
Regarding Dawn, remember that the benefits of ion propulsion have never been more obvious thanks to this mission. The first spacecraft to reach orbit around a dwarf planet (at approximately 1239 UTC today), Dawn is also the first spacecraft to orbit more than one target, having explored the asteroid Vesta from 2011 to 2012 before moving on to its current location. That gives us quality data time at the two most massive asteroids in the main belt that stretches between Mars and Jupiter.
The just released image above was taken on March 1, before orbital insertion and before Dawn swung behind Ceres. The view is just a teaser for the scenery we’re going to be looking at as the spacecraft begins its orbital investigations. It took seven and a half years to get here (and 4.9 billion kilometers along the route), but we now have a healthy spacecraft at its target. This image was taken about 48,000 kilometers out, at a Sun-Ceres-spacecraft angle (phase angle) of 123 degrees. The image scale here is 2.9 kilometers per pixel. We’ll get new imagery in April as Dawn moves back around the near side of Ceres with respect to the Sun.
Planet in a Quadruple Star System
Planets in multiple star systems intrigue us particularly when we try to imagine the view from the surface. Call it the ‘Tatooine Effect,’ made to order for visual effects specialists and cinematographers. But planets like these also raise interesting issues. Lewis Roberts (JPL) and colleagues have just published a new study of the 30 Ari system, demonstrating that it is a quadruple star system with a gas giant of about four times the mass of Jupiter in a 335 day orbit around its primary star.
We already knew about the planet in the 30 Ari system. What’s new is the discovery of the additional star. At 23 AU from the planet, the newly discovered fourth star would seem to be a factor in the orbital dynamics of the gas giant, but just what effects it has remain to be studied. The paper, which also reports the detection of a stellar companion to the exoplanet host system HD 2638, notes that 30 Ari is the second quadruple system known to host an exoplanet. And interestingly, both HD 2638 BC and 30 Ari BC have projected separations of less than 30 AU, so that the stellar companions may play a key role in the evolution of the exoplanets’ orbits.
Image: A gas giant orbiting a binary star. How planets interact with their primary and other stars in multiple-star systems like these is a question that will demand orbital computations over a long span of observation. Credit: NASA, E. Schwamb.
According to this news release from the University of Hawaii’s Institute for Astronomy, the view from the surface of the 30 Ari planet (or, let’s say, a moon around it) would involve the primary star and two other stars bright enough to be visible in daylight. One of the bright ‘stars’ would actually be a binary system if examined in a telescope. The other known planet in a quadruple system is Ph1b in a system designated KIC 4862625, from which a different view would emerge. Ph1b is on a circumbinary orbit, a giant planet of between 20 and 55 Earth masses orbiting an eclipsing binary made up of a G- and an M-class dwarf, with a second binary star at a distance of 1000 AU.
While quadruple star systems are somewhat unusual (Andrei Tokovinin of the Cerro Tololo Inter-American Observatory in Chile.estimates that about four percent of solar-type stars are in quadruple configurations), the scant number of planets we’ve found in such systems may be the result of how we observe. The Roberts paper, published in The Astronomical Journal makes the point, and notes the inherent observational difficulties:
Known close visual binaries are traditionally excluded from radial-velocity (RV) exoplanet programs because the presence of a visual companion degrades the RV precision. This intrinsic bias complicates statistical inferences about exoplanets in binaries. Moreover, a faint visual companion that is itself a close spectroscopic binary pair can produce periodic low-amplitude RV modulation in the combined light that can be mistaken for an exoplanet. False positive exoplanet detections caused by unrecognized hierarchical multiplicity of their hosts may reach 1-2% (Tokovinin 2014b) of the total exoplanet sample. This is yet another reason to observe exo-hosts with high angular resolution and deep dynamical range.
But despite their difficulties, the fact that exoplanets and the stars they orbit have a common origin means that the more we learn about the multiple star system in question, the more we learn about the exoplanet as well. Just what effects do multiple stars in their various configurations have on the planets around them? One possibility is that gravitational nudges from these nearby stars may affect the protoplanetary disk, producing massive planets on eccentric orbits as the disk is disrupted. To learn more, we need to increase the number of observed binary systems, especially those where the binary separation is small.
Thus far the pattern that has emerged is that the frequency of exoplanets among single stars is roughly the same as that around the components of wide binaries, the latter defined as those having a semimajor axis greater than 100 AU. The evidence suggests that wider binaries have little impact on exoplanet orbital dynamics. But when we get to binaries with separations of less than 100 AU, we find fewer exoplanets but in general more massive ones. No planet has yet been detected in a stellar binary with a separation of less than 10 AU. It’s worth keeping in mind that Centauri A and B, our nearest neighbors, close to within 11 AU at their closest approach.
Looking around for fictional descriptions of multiple star systems as viewed from one of their planets, I come back to a book I mentioned not long after this site began, Stanton A. Coblentz’s Under the Triple Suns (Fantasy Press, 1955). Here’s what Coblentz imagined some sixty years ago, a bit of fun to end this post:
The red sun glowed high in the copper heavens. It was as wide as a dozen moons, and of the color and brightness of smoldering embers; and it did not end sharply as a disk should, but terminated in a nebulous crimson fringe. It shed its rays like a dying fire over a great sweep of wooded, partly hilly country, terminated in the distance by saw-toothed mountains, and marked at closer range by the loop of a cascading river and the oval of a lake, and by a cluster of shimmering beehive structures that billowed and fluttered in the breeze.
After a time, above the serrate edges of the far-off ranges, a white illumination began to spread; and the mist-banks about the peaks, ruddy before, took on a sheet-like glare as a globe that seemed of a hand’s width slowly swam into sight. Although much smaller than the red sun, it dominated the scene by its intense hot flame.
The white orb was about fifteen degrees above the horizon when another light began to emerge. Of an almost unbearable brilliance, it looked not much larger than a silver dollar; but its companions seemed almost pale beside its terrible sea-blue incandescence. Evidently the blue sun and the white belonged together, like the earth and the moon; and the three luminaries, along with a Saturn-like ringed fourth that had no fire of its own but glowed red, white or blue according to the influence of the moment, circled with a gradual movement from west to east.
The paper is Roberts et al., “Know the Star, Know the Planet. III. Discovery of Late-Type Companions to Two Exoplanet Host Stars,” The Astronomical Journal Vol. 149, No. 4 (2015), 118 (abstract / preprint).
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