Are Solar Systems like ours commonplace? One way of answering this is to look at the role of planets like Jupiter, which may have helped to determine the habitability of the inner planets. But worlds like Jupiter in orbits around 5 AU do not appear to be the norm, as Andrew LePage points out in this discussion of a new exoplanet find. LePage, publisher of an essential site on exoplanet detection (www.DrewExMachina.com) is also a Senior Project Scientist at Visidyne, Inc. in Boston. Today he shows us what we know and just how much we still need to clarify about the occurence of planets like Jupiter and their role in system habitability. By Andrew J. LePage A couple of decades ago, astronomers thought they had planetary systems figured out: they consisted of a more or less orderly set of worlds orbiting in the same plane with small rocky worlds close in and much larger, volatile-rich planets orbiting farther out beyond the "snow line" where plentiful water freezes into solid ice. Along...

I can only wonder what Miguel de Cervantes Saavedra would have thought of the idea that a distant star would one day be named for him. I wonder, too, what the Spanish novelist (1547-1616) would have made of the idea that planets circled other stars, and that planets around the star named for him would have names taken from his most famous work, Don Quixote. Maybe the great character of the book's title, obsessed with tales of chivalry, would have been unhinged enough to take things like other solar systems in stride. We have the NameExoWorlds contest to thank for these speculations. The contest, organized by the International Astronomical Union (IAU) gave the public the opportunity to choose the names of selected stars and planets. The star named for Cervantes is mu Arae (HD 160691), a G-class star about fifty light years out in the constellation Ara (the Altar). Here we've found three gas giant planets comparable to Jupiter as well as a 'super-Earth.' And frankly, as a reader who...

Planets that transit across their star as seen from Earth allow us to use transmission spectroscopy to study their atmospheres. The idea is straightforward: Even though we can't see the planet at optical wavelengths, we can examine the starlight that travels through its outer atmosphere during the transit. Each atmosphere leaves its own signature, and the atmospheres of some of the 'hot Jupiters' thus far studied have raised questions. Why do some of these worlds have less water than our models of their atmospheres would predict? Is this an indication that such planets formed in protoplanetary disks that were depleted of water? A new study brings us some answers by going to work on eight hot Jupiters (WASP-6b, WASP-12b, WASP-17b, WASP-19b, WASP-31b, WASP-39b, HAT-P-1b and HAT-P-12b) using the Hubble Space Telescope. The worlds chosen here offer a wide range of temperature, surface gravity, mass and radii. All eight were observed at optical wavelengths using Hubble's Space Telescope...

If you were trying to identify the kind of star that should produce Earth-like planets, you’d think the task would be straightforward. Our theories of planet formation focus on a circumstellar disk around a young star out of which planets form, and we’ve already gathered evidence that gas giant worlds are more likely to form around stars that are rich in iron. Since rocky planets are rich in iron and silicon, doesn’t this mean their stars should be rich in metallic elements? New work out of the Carnegie Institution for Science suggests that the answer is surprisingly complex. As presented by Johanna Teske at the Extreme Solar Systems III meeting in Hawaii, the team’s work has revealed that smaller planets do not require high iron content in their parent stars. In fact, looking at the abundance of 19 different elements in seven stars orbited by at least one rocky planet (these are drawn from the Kepler catalog), the team finds that rocky worlds do not preferentially form around stars...

Oh to be in Hawaii for the Extreme Solar Systems III conference rather than simply following events on Twitter! The exoplanet community's choice of venues for these gatherings is hard to beat, the first of them, in 2007, having occurred on Santorini, a storied island in the Aegean Sea southeast of the Greek mainland, with a 2011 follow-up in Jackson Hole, WY. If you haven't been following events on Twitter (#ExSS3), you can at least check the full program with abstracts online, where you'll see quite a few familiar names. Alexandre Santerne's session at ExSS3 is one I wish I could have sat in on yesterday. Leading an international team, Santerne (Instituto de Astrofísica e Ciências do Espaço, Portugal) has gone to work on Kepler detections of gas giants. You would think that planets of this size would be fairly straightforward detections, but it turns out that this is not the case. In fact, Santerne and team find that half of the giant exoplanet candidates are false positives. To be...

A quick follow-up on our most recent discussion of KIC 8462852 (and thanks to all for the continuing high level of discussion in the comments) because today’s topic touches on a bit of the same ground. Centauri Dreams regular Harry Ray was first to notice a paper from Eva Bodman and Alice Quillen (University of Rochester) titled “KIC 8462852: Transit of a Large Comet Family.” From the paper: ...if the comet family model is correct, there is likely a planetary companion forming sungrazers. Since the comets are still tightly clustered within each dip, a disruption event likely occurred recently within orbit, like tidal disruption by the star. This comet family model does not explain the large dip observed around day 800 and treats it as unrelated to the ones starting at day 1500. The flux changes too smoothly and too slowly to be easily explained with a simple comet family model. I’ve only had the chance to glance at this work so far, but it’s heartening to see another paper analyzing...

Learning that our own Solar System has a configuration that is only one of many possible in the universe leads to a certain intellectual exhilaration. We can, for example, begin to ponder the problems of space travel and even interstellar missions within a new context. Are there planetary configurations that would produce a more serious incentive for interplanetary travel than others? What would happen if there were not one but two habitable planets in the same system, or perhaps orbiting different stars of a close binary pair like Centauri A and B? My guess is that having a clearly habitable world -- one whose continents could be made out through ground-based telescopes, and whose vegetation patterns would be obvious -- as a near neighbor would produce a culture anxious to master spaceflight. Imagine the funding for manned interplanetary missions if we had a second green and blue world that was as reachable as Mars, one that obviously possessed life and perhaps even a civilization....

Just a few days ago we looked at evidence that Kepler-438b, thought in some circles to be a possibly habitable world, is likely kept out of that category by flare activity and coronal mass ejections from the parent star. These may well have stripped the planet’s atmosphere entirely (see A Kepler-438b Caveat - and a Digression). Now we have another important study, this one out of the Harvard-Smithsonian Center for Astrophysics, taking a deep look at the red dwarf TVLM 513–46546 and finding flare activity far stronger than anything our Sun produces. Led by the CfA’s Peter Williams, the team behind this work used data from the Atacama Large Millimeter/submillimeter Array (ALMA), examining the star at a frequency of 95 GHz. Flares have never before been detected from a red dwarf at frequencies as high as this. Moreover, although TVLM 513 is just one-tenth as massive as Sol, the detected emissions are fully 10,000 times brighter than what our star produces. The four-hour observation...

Centauri Dreams continues to follow the fortunes of the Gemini Planet Imager with great interest, and I thank Horatio Trobinson for a recent note reminding me of the latest news from researchers at the Gemini South installation in Chile. The project organized as the Gemini Planet Imager Exoplanet Survey is a three-year effort designed to do not radial velocity or transit studies but actual imaging of young Jupiters and debris disks around nearby stars. Operating at near-infrared wavelengths, the GPI itself uses adaptive optics, a coronagraph, a calibration interferometer and an integral field spectrograph in its high-contrast imaging work. Launched in late 2014, the GPIES survey has studied 160 targets out of a projected 600 in a series of observing runs, all the while battling unexpectedly bad weather in Chile. Despite all this, project leader Bruce Macintosh (Stanford University), the man behind the construction of GPI, has been able to announce the discovery of the young 'Jupiter'...

Given my abiding interest in red dwarf stars and the planets that circle them, I always keep an eye on what's happening with the MEarth project. Two arrays of robotically controlled telescopes are involved in MEarth (pronounced 'mirth'), one at the Fred Lawrence Whipple Observatory on Mt. Hopkins (AZ), the other a cluster of eight at the Cerro Tololo Inter-American Observatory in Chile. Both these arrays are controlled from MEarth's offices in Cambridge (MA). MEarth is all about observing nearby M-dwarfs in the hunt for Earth-class planets. My fascination in these stars is simply a result of the numbers. We've learned that M-dwarfs comprise as much as 80 percent of the stars in the Milky Way. Earth is not, in other words, orbiting the most common type of star out there. We also know that M-dwarfs host planets. If we learn that conditions on such worlds can support life, then we've dramatically expanded the search space for astrobiology. The prospect of a living world, probably...

Finding a habitable world around any one of the three Alpha Centauri stars would be huge. If the closest of all stellar systems offered a blue and green target with an atmosphere showing biosignatures, interest in finding a way to get there would be intense. Draw in the general public and there is a good chance that funding levels for exoplanet research as well as the myriad issues involving deep space technologies would increase. Alpha Centauri planets are a big deal. The problem is, we have yet to confirm one. Proxima Centauri continues to be under scrutiny, but the best we can do at this point is rule out certain configurations. It appears unlikely, as per the work of Michael Endl (UT-Austin) and Martin Kürster (Max-Planck-Institut für Astronomie), that any planet of Neptune mass or above exists within 1 AU of the star. Moreover, no 'super-Earths' have been detected in orbits with a period of less than 100 days. This doesn't rule out planets around Proxima, but if they are there,...

An old friend used to chide me about the space program, asking good-naturedly enough why it mattered to travel nine years to get to a place like Pluto (this was not long after the New Horizons launch). 'Just another rock,' he would say. 'Why go all that way to look at just another rock?' Although we had many disagreements, Abe was one of the shrewdest people I've ever known. I had met him when he was in his sunset years, but in his prime he had run a large financial operation, been the subject of a story on the front page of the Wall Street Journal and had made a serious fortune in real estate speculation. So what about this 'just another rock' meme? Abe died a few years back but I think about him in relation to things like yesterday's story on Charon. The point is, it's not just another rock. It's this particular rock. And maybe it's not a rock at all; maybe it's a ball of icy slush. And maybe, as we've learned, it's a seriously interesting thing that surpasses expectation. Each...

Useful synergies continue to emerge among our instruments as we ponder the future of exoplanet studies. Consider the European Space Agency’s PLATO mission (PLAnetary Transits and Oscillations of stars). Operating from the L2 Lagrangian point, PLATO will use 34 telescopes and cameras on a field of view that includes a million stars, using transit photometry, as Kepler did, to find planetary signatures. Working at optical wavelengths, PLATO will look for nearby Earth-sized and ‘super-Earth’ planets in the habitable zone of their stars. This mission is scheduled to be launched in 2024, an interesting date because it’s also the year that the European Extremely Large Telescope (E-ELT) is scheduled to see first light. Huge new installations like these, although ground-based, are so powerful that they should be able, with the help of adaptive optics, to study planetary atmospheres on the PLATO-discovered planets. Thus we get the best of both worlds, with repairable and upgradable ground...

With almost 2000 exoplanets now confirmed, not to mention candidates in the thousands, it's amazing to recall that it was just twenty years ago that the first planet orbiting a main sequence star beyond the Solar System was found. Continued work on the world revealed that 51 Pegasi b is about half as massive as Jupiter, though 50 percent larger. Orbiting its star in roughly four days, the planet is some fifty light years from Earth. Thus we began to learn not just that exoplanets were out there, but that their environments could be truly extreme -- remember that it was just in 1992 that planets were found around the pulsar PSR 1257+12. Without any evidence other than my imagination, I grew up believing that most stars should have planets, and just assumed that their stellar systems were more or less like our own. There should be a few planets too close to their star for life to exist, and several gas giants out at the outskirts of the system, and somewhere in between there should be...

The European Southern Observatory's SPHERE instrument is turning up interesting things around the star AU Microscopii. Surrounded by a large dusty disk, the star is young enough to raise the interest of those studying how planets form. What has turned up are structures that Anthony Boccaletti (Observatoire de Paris) describes as 'arch-like, or wave-like,' a structure that his research team has never seen before. The issue is addressed in a new paper in Nature, which discusses five wave-like arches at different distances from the star. Fortunately, AU Mic is a well studied star, with abundant Hubble imagery taken in 2010 and 2011 available for comparison. The results of that comparison are striking: The features do indeed show up on the Hubble imagery, but they show distinct change with time, meaning they are in rapid motion. "We reprocessed images from the Hubble data and ended up with enough information to track the movement of these strange features over a four-year period,"...

If we had a space-based instrument fully capable of analyzing an exoplanet's atmosphere in place right now, where would we find our best targets? The goal, of course, is to pluck out the signature of biological activity, which means we're looking at planets in the habitable zone of their stars, that region where liquid water can exist on the surface. Right now there aren't many planets that fit the bill, but the day is coming when there will be hundreds, then thousands. How we optimize our search time and choose the targets with the most likely pay-off is a major issue. Which is where a new metric called the 'habitability index for transiting planets' comes into play. Developed by Rory Barnes and Victoria Meadows (University of Washington), working with research assistant Nicole Evans, the index is an attempt to prioritize the selection process, looking at those exoplanets that should be at the top of our list. Says Barnes: "Basically, we've devised a way to take all the...

Learning that there is flowing water on Mars encourages the belief that human missions there will have useful resources, perhaps in the form of underground aquifers that can be drawn upon not just as a survival essential but also to produce interplanetary necessities like rocket fuel. What yesterday's NASA announcement cannot tell us, of course, is whether there is life on Mars today, though if the detected water is indeed flowing up from beneath the surface, it seems a plausible conjecture that some form of bacterial life may exist below ground, a life perhaps dating back billions of years. I've speculated in these pages that we may in fact identify life around other stars — through studies of exoplanet atmospheres — before we find it elsewhere in our Solar System, given the length of time we have to wait before return missions to places like Enceladus and Europa can be mounted. Perhaps the Mars news can help us accelerate that schedule, at least where the Red Planet is...

Given the scale of our own Solar System, the system circling the star Beta Pictoris can’t help but give us pause. Imagine not only the orbiting clouds of gas, dust and debris that we would expect around a young star (8-20 million years old) with a solar system in formation, but also a gas giant planet some ten to twelve times the mass of Jupiter, in an orbit something like Saturn’s. Now factor in this: The disk in question, if translated into our own system’s terms, would extend from about the orbit of Neptune to almost 2000 AU. Now we have a view of Beta Pictoris b as it moves through a small slice (one and a half years) of a 22 year orbital period. The work of Maxwell Millar-Blanchaer (a doctoral candidate at the University of Toronto) and colleagues, the imagery appears in a paper published yesterday by The Astrophysical Journal. Millar-Blanchaer used observations from the Gemini Planet Imager on the Gemini South telescope in Chile to image Beta Pictoris b, the work being part of...

Extending missions beyond their initial goals is much on my mind as we consider the future of New Horizons and its possible flyby past a Kuiper Belt Object. But this morning I'm also reminded of EPOXI, which has given us views of the Earth that help us study what a terrestrial world looks like from a distance, characterizing our own planet as if it were an exoplanet. You'll recall that EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) is a follow-on to another successful mission, the Deep Impact journey to comet Tempel 1. As is clear from its acronym, EPOXI combined two extended missions, one following up the Tempel 1 studies with a visit to comet Hartley 2 (this followed an unsuccessful plan to make a flyby past comet 85P/Boethin, which proved to be too faint for accurate orbital calculations). The extrasolar component of EPOXI was called EPOCh (Extrasolar Planet Observation and Characterization), using the craft's high resolution telescope to make...

Yesterday's article on supernovae 'triggers' for star and planet formation shed some light on how a shock wave moving through a cloud of gas and dust could not only cause the collapse and contraction of a proto-star but also impart angular momentum to an infant solar system. Today's essay focuses on a somewhat later phase of system formation. Specifically, how is it that gas giants like Jupiter and Saturn can form in the first place, given core accretion models that have 'trigger' problems of their own? Here's the issue: To create a gas giant, you need plenty of hydrogen and helium, material in which a solar nebula would be rich. But we're learning a lot about how planetary systems evolve, and the emerging reality is that the gas disks from which planets are made usually last a comparatively brief time, somewhere on the order of one to ten million years. That would imply that the gas giants had to accumulate their atmospheres within this timeframe. But how? Jupiter's atmosphere is...