Where exactly do ‘hot Jupiters’ come from? I usually see explanations involving planetary migration for Jupiter-class objects with tight orbital periods of 10 days or less, the thinking being that such planets are too close to their host stars to have accumulated a Jovian-style gaseous envelope there. Migration explains their placement, with gas giants forming much further out in their planetary systems and then migrating disruptively inward to become hot Jupiters. Does the scenario work? Consider the hot Jupiter WASP-47b, which has two low-mass planets nearby in its system. WASP-47b is a problem because a migrating gas giant should have produced profound gravitational issues for small worlds in the inner system, likely ejecting them entirely. A new paper from Chelsea Huang and Yanqin Wu (University of Toronto), working with Amaury Triaud (University of Cambridge), tries to explain the dilemma posed by WASP-47b. The answer turns out to be that, according to Kepler data used by the...

Small red stars are drawing increased attention as we continue to discover interesting planets around them. The past two days we've looked at the four worlds around K2-72, a red dwarf about 225 light years out in the constellation Aquarius. That two of these worlds have at least the potential for liquid water on the surface makes the system a prime target for further study. Now we return to another recently discussed system of note, TRAPPIST-1. Designated 2MASS J23062928-0502285, this ultracool dwarf is also in Aquarius, though at forty light years, much the closer target. As with K2-72, we have multiple planets here (three), and also like the K2 discovery, TRAPPIST-1 orbits a star small and dim enough to make planet detection easier -- a transiting world presents a clear signature and the study of planetary atmospheres is possible through what is known as transmission spectroscopy, wherein light from the star that has passed through the planet's atmosphere is analyzed. Today we have...

Is the K2-72 system, discussed yesterday as part of a recent exoplanet announcement from Ian Crossfield and colleagues, as intriguing as it looks? Ravi Kopparapu has some thoughts on the matter. Dr. Kopparapu's work on exoplanet habitability is well known to Centauri Dreams readers -- he offered an overview in these pages called How Common Are Potential Habitable Worlds in Our Galaxy?, which ran in 2014. An assistant research scientist at NASA GSFC and the University of Maryland, Dr. Kopparapu began his exoplanet career with James Kasting at Penn State following work on the LIGO collaboration enroute to his PhD from Louisiana State. Analyzing habitable zone possibilities around different kind of stars, as well as modeling and characterizing exoplanet atmospheres, plays a major role in his research interests. I was pleased to receive the following note on the recently announced K2-72 system and want to run his thoughts today given the interest this unusual system has already begun to...

Today’s announcement of the confirmation of over 100 planets using K2 data reminds me of how much has gone into making K2 a success. You’ll recall that K2 emerged when the Kepler spacecraft lost function in two of its four reaction wheels. Three of these were needed for pointing accuracy, but ingenious pointing techniques and software updates have made K2 into a potent project of its own. The latest announcements demonstrate that certain benefits emerged from the changed mission parameters, especially in the ability of K2 to move away from the original field of view (toward Cygnus and Lyra) and focus on targets in the ecliptic plane. What we gain from that change is that working in the ecliptic allows more chances for observation from ground-based observatories in both northern and southern hemispheres as they perform the needed exoplanet follow-up. But there are other factors that make K2 potent. With all targets being chosen by the entire scientific community (not limited to the...

A team led by Lucas Cieza (Universidad Diego Portales, Santiago, Chile) has produced the first image directly showing the water snowline in a protoplanetary disk, using the Atacama Large Millimeter/submillimeter Array (ALMA). It's fascinating to actually see a mechanism we've long discussed in these pages when analyzing exoplanetary systems (or for that matter, our own). We have a young star called V883 Orionis to thank for the possibility. It's an FU Orionis star of the kind we recently looked at in FU Orionis: Implications of Sudden Brightening for Planet Formation. And here, too, the implications are rich. FU Orionis stars are young, pre-main sequence objects that can produce extreme changes in magnitude and spectral type. The eponymous FU Orionis itself, 1500 light years away in the constellation Orion, underwent an event in 1936 that took it from a visual magnitude of 16.5 to 9.6. In the case of V883 Orionis, a similar outburst in temperature and luminosity has heated the...

A brown dwarf as a 'quieter' version of Jupiter? That's more or less the picture offered in a new paper on WISE 0855 from Andrew Skemer (UC-Santa Cruz) and colleagues. Here we're working in the Solar System's close neighborhood -- WISE 0855 is a scant 7.2 light years from Earth -- and we're observing an object that is the coldest known outside of the Solar System. That makes the observational task difficult, but it has yielded rich results in the discovery of clouds of water or water ice. We learn that WISE 0855 is about five times the mass of Jupiter, with a temperature in the range of 250 K (-23 Celsius). This is the nearest known object of planetary mass, but it is too faint to characterize with conventional spectroscopy -- separating light into its component wavelengths -- in the optical or near infrared. But it turns out the object can be studied through thermal emissions from deep in its atmosphere in the range of 5 µm (a range frequently used to study Jupiter's own deep...

Into the annals of oddball orbits now comes HD 131399Ab, a planet whose wide orbit inside a triple-star system is unlike anything we've yet seen. 320 light years from Earth in the constellation Centaurus, this is a gas giant of about four Jupiter masses that was discovered through direct imaging. The discovery was made with the European Southern Observatory's Very Large Telescope in Chile using the SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) instrument, which exploits differential imaging to screen stellar light from planetary signatures. HD 131399Ab is the first exoplanet discovered by SPHERE, which incorporates adaptive optics, a coronagraph and, with its differential imaging features, distinguishes a planet by the polarization of reflected light. Stars emit unpolarized light -- here the electromagnetic waves oscillate randomly, and in different directions, as explained in this ESO news release. But light reflected from a planetary surface is partially polarized,...

If our Solar System had a ‘hot Jupiter’ that migrated inward after Mars, Earth and Venus had formed, would any of the terrestrial planets have survived? It’s a question worth pondering given how many hot Jupiters we’ve turned up, raising the question of how these planets form in the first place. One possibility is formation in situ, close to the parent star. But there is also an argument for migration, with planets forming in cooler regions further out in the system and migrating inward as a result of interactions with the protoplanetary disk or other planets. Perhaps the planet known as K2-33b can help us with some of this. It is no more than 11 million years old, in an orbit that creates a transit every 5.4 days. With follow-up observations by the MEarth arrays on Mount Hopkins (AZ) and at the Cerro Tololo Inter-American Observatory in Chile, researchers led by Andrew Mann (University of Texas at Austin) have been able to determine that K2-33b is a Neptune-class world some five...

I would like to thank the many Centauri Dreams readers who contributed to the successful Kickstarter campaign to fund a year's worth of study of KIC 8462852. As I write, there is less than an hour to go, but we have already gone well over the needed $100,000 mark. Congratulations to Tabitha Boyajian, and thanks for all the work she and her colleagues have put into this effort. Now we have a year of observations ahead using the Las Cumbres Observatory Global Telescope Network. The long-term observations will be crucial because we don't know what to expect in terms of sudden dimming in this star's light curve. What a pleasure it is to write for this audience. Readers here have played a large role in pushing this project over the top, and we'll follow the work on KIC 8462852 closely in coming days. Meanwhile, have a look at Penn State's Jason Wright discussing 'Tabby's Star.' [youtube jjh0oK7ZyfM 500 416] Speaking of Unusual Stars… If KIC 8462852 is a star that some believe is...

Given everything we're learning about planets around other suns, it's frustrating that we have so little information about the chemical composition of the rocky planets we've found thus far. Now we have a new study, announced at the San Diego meeting of the American Astronomical Society, that offers data on a 'planet-like body' whose surface layers are being consumed by the white dwarf SDSSJ1043+0855. Although it's been known for some time that the star has been devouring rocky material orbiting around it, the new work offers a striking view of the accretion process and the composition of what was once a differentiated body. At least, that's the best interpretation of the data taken from the Keck Observatory's HIRES spectrometer (installed on the 10-meter Keck I instrument) and the Hubble Space Telescope. White dwarf stars are the remains of stars like the Sun -- this one was once a few times the Sun's mass -- that have gone through their red giant phase and expelled all their outer...

Before getting into today's subject, the discovery of an interesting long-period circumbinary planet, I want to make another pitch for Centauri Dreams readers to support the Kickstarter campaign for Tabby's Star. I've written often about this mysterious star whose light curves are anomalous and demand further study. Trying to find out what's happening around KIC 8462852 means acquiring more data, and the Kickstarter campaign would provide an entire year of observations using the Las Cumbres Observatory Global Telescope Network. We're now down to 48 hours and of the $100,000 needed, about three-fourths has been raised. Coming down the homestretch, the remaining $24,000 should be achievable, but it looks to be a dramatic finish. If you haven't been following the KIC 8462852 story, you can check the archives here, or for a quick overview, see my article A Kickstarter Campaign for KIC 8462852. Whatever you can do to help would be hugely appreciated as we try to learn as much as possible...

In late 2015, an international team led by David Sing (University of Exeter, UK) studied ten 'hot Jupiters' to try to figure out why some of these planets have less water in their atmospheres than expected from earlier modeling. Sing and company were working with transmission spectroscopy, possible when a planet transits its star and starlight is filtered by the planet's atmosphere. The team used data from the Hubble instrument as well as the Spitzer Space Telescope, covering wavelengths ranging from the optical into the infrared. A cloudy planet appears larger in visible light than in infrared, the difference in radius at the two wavelengths being used to show whether the atmosphere is cloudy or clear. The result, published in Nature, concluded that there was a correlation between hazy and cloudy atmospheres and scant detection of water. In other words, clouds were simply hiding the expected water vapor, and dry hot Jupiters were ruled out. It's an important finding because dry hot...

The first generation of stars in the universe began to shine in an era when chemical elements like carbon and oxygen were not available. It was the explosion of these early stars in supernovae that began the process of enrichment, with heavier elements fused in their cores now spreading into the cosmos. Lower-mass stars and planetary systems began to appear as heavier elements could form the needed dust grains to build planetary cores. Avi Loeb (Harvard-Smithsonian Center for Astrophysics) and grad student Natalie Mashian have been looking at a particular class of ancient stars called carbon-enhanced metal-poor (CEMP) stars. Here the level of iron is about one hundred-thousandth as high as our Sun, a clear marker that these stars formed before heavy elements were widely distributed. These stars are interesting because despite their lack of iron and other heavy elements in comparison to the Sun, they are rich in carbon, an excess that leads to the possibility of planets forming around...

So often planets described as ‘potentially habitable’ turn out to be over-rated -- we look deeper into their composition and characteristics only to find that the likelihood of liquid water on the surface is slim. How to make more accurate calls on the matter of habitability? One way may be to combine orbital and atmospheric models, adjusting each with the known parameters of the planet in question. A new study does just that for the interesting world Kepler-62f. About 1200 light years from Earth in the direction of the constellation Lyra, Kepler-62f has a radius 40 percent larger than Earth’s, which puts it well below the 1.6 RE demarcation line that is increasingly thought to define the difference between Earth-like worlds and planets that are more like Neptune. We’re probably looking at a rocky planet here. It’s also a planet that orbits its K-class primary at a distance that could place it in the outer regions of the habitable zone (as defined, again, by the presence of liquid...

I suppose the most famous fictional depiction of the Sun as it swells to red giant stage is in H. G. Wells’ The Time Machine, in a passage where the time traveler takes his device by greater and greater jumps into the remote future. This is heady stuff: I moved on a hundred years, and there was the same red sun–a little larger, a little duller–the same dying sea, the same chill air, and the same crowd of earthy crustacea creeping in and out among the green weed and the red rocks. And in the westward sky, I saw a curved pale line like a vast new moon. ‘So I travelled, stopping ever and again, in great strides of a thousand years or more, drawn on by the mystery of the earth’s fate, watching with a strange fascination the sun grow larger and duller in the westward sky, and the life of the old earth ebb away. At last, more than thirty million years hence, the huge red-hot dome of the sun had come to obscure nearly a tenth part of the darkling heavens. Wells would have had no real idea...

What’s a movie director supposed to do about gravity? In The Martian, we see Matt Damon moving about on Mars with a gait more or less similar to what he would use on Earth, despite Mars’ 0.38g. Harrison Ford changes worlds but never strides in The Force Awakens. About the gravitational challenges of 1953’s Cat Women of the Moon, the less said the better. Even so, we can chalk all these problems up to the fact that both top directors and their B-film counterparts are forced to film at the bottom of a gravity well, so a certain suspension of disbelief is at least understandable. But assuming that gravity invariably increases as planets get bigger can be misleading, as Fernando J. Ballesteros (Universitat de València) and Bartolo Luque (Universidad Politécnica de Madrid) demonstrate in a new paper in Astrobiology. We learn that some larger worlds in our own Solar System have gravity not all that different from the Earth. In fact, the surface gravities for Venus, Uranus, Neptune and...

If you look into the software that made possible yesterday's exoplanet results, you'll find that VESPA (Validation of Exoplanet Signals using a Probabilistic Algorithm) is freely available online. The work of Princeton's Timothy Morton, who spoke at the announcement news conference, VESPA is all about calculating the probabilities of false positives for signals that look like transiting planets. Transits, of course, are what the Kepler space telescope has been about, catching the slight stellar dimming as a planet crosses across the face of a star. The numbers quickly get mind-boggling because while Natalie Batalha (NASA Ames), joined by Morton, NASA's Paul Hertz and Kepler/K2 mission manager Charlie Sobeck (a colleague of Batalha at Ames) could point to 1284 newly confirmed exoplanets, they represent only a fraction of what must be in the Kepler field of view. Out of its over 150,000 stars, Kepler can only see the planets that transit their host stars, making this a problem of...

About forty light years from Earth in the constellation Aquarius is the star designated 2MASS J23062928-0502285, which as of today qualifies as perhaps the most interesting ultracool dwarf we've yet found. What we learn in a new paper in Nature is that the star, also known as TRAPPIST-1 after the European Southern Observatory's TRAPPIST telescope at La Silla, is orbited by three planets that are roughly the size of the Earth. We may have a world of astrobiological interest -- and conceivably several -- orbiting this tiny, faint star. Image: Comparison between the Sun and the ultracool dwarf star TRAPPIST-1. Credit: ESO. If we untangle the TRAPPIST acronym, we find that it refers not to an order of monks (famous for their beers) but to the TRAnsiting Planets and PlanetesImals Small Telescope, a 60 cm robotic instrument that is operated from a control room in Liège, Belgium. TRAPPIST homes in on sixty nearby dwarf stars at infrared wavelengths to search for planets. Michaël...

The star YLW 16B, about 400 light years from the Earth, has roughly the same mass as the Sun. But unlike the Sun, a mature 4.6 billion year old star, YLW 16B is a scant million years old, a variable of the class known as T Tauri stars. Whereas our star is relatively stable in terms of radiation emission, the younger star shows readily detectable changes in radiation, a fact that astronomers have now used in combining data from the Spitzer space telescope with four ground-based instruments to learn more about the dimensions of its protoplanetary disk. Image: This illustration shows a star surrounded by a protoplanetary disk. Material from the thick disk flows along the star's magnetic field lines and is deposited onto the star's surface. When material hits the star, it lights up brightly. Credit: NASA/JPL-Caltech. The method is called photo reverberation, and it takes advantage of the fact that when the star brightens as material from the turbulent disk falls onto its surface, some of...

At Palo Alto's superb Amber India, I was thinking about Alpha Centauri. There are several Amber India locations in the Bay area, but the Palo Alto restaurant dishes up, among other delights, a spicy scallop appetizer that is searingly hot and brilliantly spiced. Greg and Jim Benford were at the table, Claudio Maccone and my son Miles. It was the night before Breakthrough Discuss convened. And while the topics roamed over many aspects of spaceflight, it was that star system right here in our solar neighborhood that preoccupied me. How lucky could we be to have not one but two stars this close and so similar to our own? Centauri A is a G-class star, Centauri B a K, and if we hit the jackpot, we could conceivably find planets orbiting both. Then there is Proxima Centauri, an M-dwarf that is the closest star of all to the Solar System. The presence of so many astronomers on the Breakthrough Discuss roster made it clear we'd get the latest on the hunt for planets here, a vital factor as...