A stellar association is a loose grouping of stars of similar spectral type and age that share a common motion. About 90 percent of all stars are thought to originate as members of associations. The TW Hydrae association (TWA) is a case in point: The group is made up of about thirty young stars, each thought to be roughly ten million years old. This is the youngest grouping of stars in the neighborhood of the Sun. You may recall 2M1207, which has turned up in these pages before, a brown dwarf member of the TWA that has a companion of planetary mass. Now we learn of another exotic find, a young, bright free-floating planet-like object. Jonathan Gagné (Carnegie Institution for Science) used the FIRE spectrograph on Carnegie's Baade 6.5-m telescope in Chile to measure the line-of-sight velocity of the object, known as 2MASS J1119-1137. This along with the sky motion of the object allowed researchers to make the definitive call that 2MASS J1119-1137 is indeed a member of the TW...

Back in 2014, astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) to produce high-resolution images of the planet-forming disk around the Sun-like star HL Tau, about 450 light years away in the constellation Taurus. The images were striking, showing bright and dark rings with gaps, suggesting a protoplanetary disk. Scientists believed the gaps in the disk were caused by planets sweeping out their orbits. All this was apparent confirmation of planet formation theories, but also a bit of a surprise given the age of the star, a scant million years, making this a young system indeed. Here is the ALMA image, along with the caption that ran with the original release of the story from NRAO. Image: The young star HL Tau and its protoplanetary disk. This image of planet formation reveals multiple rings and gaps that herald the presence of emerging planets as they sweep their orbits clear of dust and gas. Credit: ALMA (NRAO/ESO/NAOJ); C. Brogan, B. Saxton (NRAO/AUI/NSF)....

Kappa Ceti is a young star -- 400 to 600 million years old -- in the constellation Cetus (the Whale). It's a tremendously active place, its surface disfigured by starspots much larger and more numerous than we find on our more mature Sun. In fact, Kappa Ceti hurls enormous flares into nearby space, 'superflares' releasing 10 to 100 million times the energy of the largest flares we've ever observed on the Sun. What would be the fate of planets around a star like this? The question is directly relevant to our own system because Kappa Ceti is a G-class dwarf much like the Sun, giving us a look at what conditions would have been like when our own system was forming. The calculated age of the star, extrapolated from its spin, corresponds to the time when life first appeared on the Earth. Thus we're seeing a model of our distant past, one that makes it clear that a magnetic field is an essential for planetary habitability. The violent activity on the surface of Kappa Ceti is driving a...

David Kipping and colleagues have discovered what they describe as ‘the first validated transiting Jupiter analog,’ a planet orbiting the K-class dwarf KIC-3239945. Kepler-167e is about 90 percent the size of Jupiter and orbits its star at about twice the distance that the Earth orbits the Sun. Given the fact that the star is cooler than the Sun -- an orange rather than a yellow dwarf -- temperature estimates for the planet are in the 130 K range, only about 20 K warmer than Jupiter. The discovery is discussed on the Cool Worlds YouTube channel, an outreach project launched by the Cool Worlds Lab at Columbia University, and is the subject of a paper submitted to The Astrophysical Journal (citation below). Kepler-167e isn’t just another ‘hot Jupiter’, a class of worlds that is well populated. ‘Hot Jupiters’ occupy orbits extremely close to the parent star. Finding a true Jupiter analog -- i.e., a planet in a close to circular orbit in a position roughly analogous to Jupiter’s in our...

Keep your eye on a program called the Hubble Cloud Atlas. This is a collaboration between fourteen exoplanet researchers around the globe that is intent on creating images of exoplanets using the Hubble Space Telescope. But while we've been able to directly image a small number of planets before now, the Cloud Atlas project brings a new twist. The plan is to create time-resolved images that can tease out details about planetary atmospheres. The test case is the planet 2M1207b, about 160 light years out in the constellation Centaurus. Infrared imaging made it possible to directly observe this planet in April of 2004, a task accomplished by researchers from the European Southern Observatory using data from the Very Large Telescope at Paranal (Chile). What we know about this planet makes it a formidable -- and definitely uninhabitable -- object, one with a surface temperature in the 1700 K range. Image: The 2M1207 star system, showing the faint red object 2M1207b, a planet four times...

We learned on Wednesday that the Agency Program Management Council, which works under the aegis of NASA, has made the decision to proceed with the Wide Field Infrared Survey Telescope. WFIRST is the next step in major astrophysical observatories after the launch of the James Webb Space Telescope in 2018, an instrument that will work at near-infrared wavelengths to study dark matter and dark energy, with a significant exoplanet component. All these issues are relevant to what we do here at Centauri Dreams, but the exoplanet aspect of the mission, which includes a coronagraph to allow the close inspection of distant solar systems, is particularly interesting. Blocking the otherwise overwhelming glare of a host star (even at these wavelengths), the WFIRST coronagraph should help to reveal the planets around it, a crucial separation that will allow us to make spectrographic measurements of the chemical makeup of planetary atmospheres. Paul Hertz, director of NASA's astrophysics division...

We’re probing the atmospheres of exoplanets both from the Earth and from space. Transmission spectroscopy allows us to look at the spectra of starlight at various wavelengths as a transiting planet passes first in front of its host star, and then moves behind it. Now we have news of a successful detection of gases in the atmosphere of a super-Earth, using data from the Hubble Space Telescope. The team, made up of researchers at University College London and Catholic University of Leuven (Belgium) calls this a significant first. “This is a very exciting result because it’s the first time that we have been able to find the spectral fingerprints that show the gases present in the atmosphere of a super-Earth,” said Angelos Tsiaras, a PhD student at UCL, who developed the analysis technique along with colleagues Dr. Ingo Waldmann and Marco Rocchetto in UCL Physics & Astronomy. “Our analysis of 55 Cancri e’s atmosphere suggests that the planet has managed to cling on to a significant...

We’ve gone from discovering the presence of exoplanets to studying their atmospheres by analyzing the spectra produced when a planet transits in front of its star. We’re even in the early stages of deducing weather patterns on some distant worlds. Now we’re looking at probing the inside of planets to learn whether their internal structure is something like that of the Earth. The work is led by Li Zeng (Harvard-Smithsonian Center for Astrophysics), whose team developed a computer model based on the Preliminary Reference Earth Model (PREM), the standard model for the Earth’s interior. Developed by Adam Dziewonski and Don L. Anderson for the International Association of Geodesy, PREM attempts to model average Earth properties as a function of radius. Zeng adjusted the model for differing masses and compositions and applied the revised version to six known rocky exoplanets with well understood characteristics. The work shows that rocky worlds should have a nickel/iron core that houses...

Free floating planets -- planets without any star -- are exotic things, presumably thrown out of their original solar system by gravitational interactions with other worlds. But the line between such wanderers and bound planets isn’t always clear. A case in point is the object 2MASS J2126, found in an infrared sky survey and at one point considered to be part of a group of young stars known as the Tucana Horologium Association. If linked to this group, its age could be inferred and it was young and low enough in mass to be considered an independent planet. Now we learn otherwise, as a research team from the United Kingdom, Australia and the United States has determined that 2MASS J2126 is in an extraordinarily wide orbit around the star TYC 9486-927-1. Lead author Niall Deacon (University of Hertfordshire) has been focusing for several years on young stars with planetary companions in wide orbits. But this system has to come as a surprise. The young planet is about 1 trillion...

My essay Intensifying the Proxima Centauri Planet Hunt is now available on the European Southern Observatory's Pale Red Dot site. My intent was to give background on earlier searches for planets around the nearest star, leading up to today's efforts, which include the Pale Red Dot work using HARPS, the High Accuracy Radial velocity Planet Searcher spectrograph at La Silla, as well as David Kipping's ongoing transit searches with data from the Canadian MOST satellite (Microvariability & Oscillations of STars), and gravitational microlensing studies by Kailash Sahu (Space Telescope Science Institute). As it turned out, the choice of earlier Proxima planet hunts as a topic fit in where Alan Boss had left off. Boss (Carnegie Institution for Science) had led off the Pale Red Dot campaign's outreach effort with a piece on the overall background of exoplanetology (Pale Blue Dot, Pale Red Dot, Pale Green Dot). Whatever the color of the distant world, our tools are developing rapidly, and...

Knowing that the data from New Horizons continues to arrive gives me a warm feeling about the months ahead. Below we have the highest resolution color image of one of the two potential cryovolcanoes found on the surface during the Pluto flyby last summer. This is Wright Mons, some 150 kilometers across and 4 kilometers high. If this is indeed a volcano, none has been discovered in the outer system that can compare with it in size. Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute. The image is a composite drawn from New Horizons' Long Range Reconnaissance Imager (LORRI) on July 14, 2015. The range is approximately 48,000 kilometers, giving us features down to 450 meters across. JHU/APL has also incorporated color data from the Ralph/Multispectral Visible Imaging Camera (MVIC) taken about 20 minutes after the LORRI images were taken, from a range of 34,000 kilometers, and with a resolution of 650 meters per pixel. The scene on the...

A new observational campaign for Proxima Centauri, coordinated by Guillem Anglada-Escudé (Queen Mary University, London), is about to begin, an effort operating under the name Pale Red Dot. You'll recall Dr. Anglada-Escudé's name from his essay Doppler Worlds and M-Dwarf Planets, which ran here in the spring of last year, as well as from Centauri Dreams reports on his work on Gliese 667C, among other exoplanet projects. Pale Red Dot is a unique undertaking that brings the public into an ongoing campaign from the outset, one whose observations at the European Southern Observatory's La Silla Observatory begin today. The closest star to our Sun, Proxima Centauri was discovered just over 100 years ago by the Scottish astronomer Robert Innes. A search through the archives here will reveal numerous articles about the red dwarf and the previous attempts to find planets orbiting it. I'll point you to a round-up of exoplanet work on Proxima thus far next week, when my essay...

If they did nothing else for us, space missions might be worth the cost purely for their role in tuning up human ingenuity. Think of rescues like Galileo, where the Jupiter-bound mission lost the use of its high-gain antenna and experienced numerous data recorder issues, yet still managed to return priceless data. Mariner 10 overcame gyroscope problems by using its solar panels for attitude control, as controllers tapped into the momentum imparted by sunlight. Overcoming obstacles is part of the game, and teasing out additional science through extended missions taps into the same creativity. Now we have news of how successful yet another mission re-purposing has been through results obtained from K2, the Kepler 'Second Light' mission that grew out of problems with the critical reaction wheels aboard the spacecraft. It was in November of 2013 that K2 was proposed, with NASA approval in May of the following year. Kepler needed its reaction wheels to hold it steady, but like Mariner 10,...

Given this site’s predilections, it’s natural to think of Centauri A and B whenever the topic of planets around close binary stars comes up. But systems with somewhat similar configurations can produce equally interesting results. Take what we’re finding around the G-class star HD 7449, some 127 light years from our Sun. In 2011, a planet of roughly eight times Jupiter’s mass was found orbiting the star in an orbit so eccentric that it demanded explanation. A highly eccentric orbit can indicate another object in the system that is affecting the planet. Exactly what has now been determined. “The question was: is it a planet or a dwarf star?” says Timothy Rodigas (Carnegie Institution for Science), who led the work on the discovery. Rodigas’ team went to work using the Magellan adaptive optics system (MagAO) on the Magellan II (Clay) instrument at Las Campanas in Chile. MagAO allows sharp visible-light images to be acquired, with the instrument capable of resolving objects down to the...

At no more than 14 light years away, Wolf 1061 gains our attention with the discovery that this small red dwarf hosts three planets, in orbits of 4.9, 17.9 and 67.2 days respectively. Of particular interest is Wolf 1061c, which appears to be within the habitable zone, defined here as the region in which it would be possible for liquid water to exist on the surface, and potentially life. Wolf 1061c has a mass at least 4.3 times that of Earth, with inner planet Wolf 1061b coming in at 1.4 times that mass. Wolf 1061d is calculated to be at least 5.2 times Earth's mass. Image: The Wolf 1061 system, with the habitable zone depicted in green. Credit: University of New South Wales. One thing Wolf 1061 reminds us is that red dwarf stars are good targets for radial velocity studies. For one thing, such stars have low levels of luminosity, which means their habitable zones are small and planets within them are in close orbits. Such planets create a stronger, more detectable signature for...

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...