What are the chances that we'll find habitable planets around Alpha Centauri A and B? Centauri Dreams has long kept an eye on the work of Greg Laughlin (UC-Santa Cruz) and colleagues, who have been working on the Alpha Centauri question with ever more interesting results. Following their work on Greg's systemic site has been fascinating, and for those who would like to be quickly brought up to speed, it's useful to know that Laughlin has made their recent paper summarizing these findings available online. Anyone serious about the study of these closest stars to Earth will want to download and read these promising results. Laughlin's group simulated the formation of planetary systems around Centauri B, beginning with a disk populated with 400 to 900 lunar-mass protoplanets, then following its development over 200 million years. To say the results are encouraging would be an understatement. All the simulations lead to multiple-planet systems, with at least one planet of Earth mass or...

Centauri Dreams has long championed Webster Cash's innovative New Worlds mission concepts, which would use a 'starshade' to block the light of distant stars to reveal their planetary systems. Cash envisions using multiple spacecraft for this assignment, one the starshade itself, the other a telescope that would make the needed observations. After a series of ups and downs, New Worlds now receives new life in the form of a $1 million award from NASA to study the starshade's possibilities. Remember that we're still at an early research level when it comes to funding of this kind -- the actual observatory, a design Cash calls New Worlds Observer -- would cost an estimated $3.3 billion to design and build. Other mission concepts are still in play (fully nineteen observatory concepts have been chosen for further study), so the road ahead is by no means clear as we look toward space missions that can identify Earth-like planets around other stars. But Cash's designs are well vetted, and...

What exactly is that dark material spread so widely over Saturn's various moons? From Hyperion to Iapetus, Dione and Phoebe, we find a black substance coating a wide range of objects, suggesting that whatever the stuff may be, there must be a common mechanism for moving it from one moon to another. A series of papers on Saturn's moons appears in the February issue of Icarus, where these interactions are now under study. Just what the material is remains a mystery. But Roger Clark (US Geological Survey) notes that as the Cassini data build, we're beginning to track down some of its components, including bound water and, possibly, ammonia. Studying Dione, Clark's team noted the fine-grained nature of the dark material there. Its distribution and composition indicate the dark material is not native to the moon, and indeed, the same signature appears not only among other moons but also in Saturn's F-ring. From the abstract to the study by Clarke and colleagues: Multiple lines of evidence...

About two weeks ago we looked at the work of Michael Meyer (University of Arizona), whose team examined over 300 Sun-like stars (spectral types F5-K3) at mid-range infrared wavelengths. A wavelength of 24 microns detects warm dust, material at temperatures likely to be found between 1 and 5 AU from the parent star. The headline that day was Meyer's contention that many if not most such stars produce terrestrial planets. Now Meyer is presenting these findings at the annual meeting of the American Association for the Advancement of Science, doubtless putting the exoplanet hunt back in the daily papers, at least for a day. Bear in mind that in using the term 'terrestrial' we're talking about small, rocky worlds like the inner planets of our Solar System. That could include worlds like our own, of course, but could also include hellish places like Mercury and Venus and their analogues around other stars. Nonetheless, it's exciting to think that the chances of rocky planet formation are...

Finding solar system analogs is tricky business, as we saw yesterday when examining the discovery of Jupiter and Saturn-class worlds around a distant star. That find, I notice, is getting some attention in the popular media as an indication that our Solar System may not be unique. But take a look at the gas giant recently found around HD 154345 if you want to see an even closer analog to our own system. HD 154345b is a single world, to be sure, but it orbits a G8 dwarf much more like the Sun than the diminutive star examined yesterday, and it's a close match for Jupiter not only in size but orbital position. The planet's minimum mass is 0.95 Jupiter's, and its 9.2 year circular orbit carries it around its star at a distance of some 4.2 AU. Sound familiar? What's happening around HD 154345 is more or less what a distant astronomer using our current technologies would see if observing our Solar System. Rather than using microlensing, the discovery team here put radial velocity...

We always have to watch our preconceptions, an early one in the exoplanet game being that solar systems around other stars would look pretty much like our own. Then we started the whole exoplanet discovery binge by finding planets around a pulsar, of all things, and went on to the terrifically odd world of 'hot Jupiters,' whose existence had not been predicted by most theorists. Now we've gotten used to the idea that solar systems come in huge variety, but finding one that looks more or less like ours would still be comforting, and would make it seem more likely that there are other 'Earths' out there, perhaps teeming with life. Today and tomorrow we look at two such finds, noting the resemblance to what we have around Sol and pondering the implications for the broader planet search. First up is not a single but a double planetary find, two worlds that inhabit a place much like that of Jupiter and Saturn in our Solar System. Not only is this an intriguing discovery in itself, but...

We have a long way to go in the study of circumstellar disks, especially around smaller stars. Given the difficulty of making such observations, work at the Subaru Telescope has focused on stars more massive than the Sun in hopes of studying the more apparent structure of the disks around such stars. But FN Tauri is an exception. The young star is a tenth of the Sun's mass, its disk seven times lighter than the lowest mass disk previously imaged, which was around the star TW Hydrae. The hope is to extend our knowledge of planetary formation more broadly across stellar types to learn what kind of worlds they form and where. The team of Japanese researchers performing this work used the Coronagraphic Imager with Adaptive Optics (CIAO) at the Subaru Telescope. What they've learned about FN Tauri is that the thick, roughly circular disk, with a radius of 260 AU, is relatively featureless at this point in the star's evolution (FN Tauri is thought to be a mere 100,000 years old). Thus far...

When you have assets in space, the thing to do is redeploy them as needed. That creates what's called an 'extended mission,' and the latest spacecraft to get one is Deep Impact, the vehicle whose impactor made such a splash when it was driven into comet Tempel 1 in the summer of 2005. That July 4 explosion was memorable enough, but under the name EPOXI the doughty craft leaves its vaporized impactor behind and moves on to two other missions, one of which has direct extrasolar applications. For one of EPOXI's twin goals is to observe five nearby stars known to have transiting exoplanets. Observations began on January 22. The 'hot Jupiters' around the five stars have been confirmed previously, but EPOXI's mission is to see whether any of these transiting gas giants is accompanied by other worlds in the same stellar system. Perhaps the most intriguing aspect of the investigation is summed up by Drake Deming (NASA GSFC): "We're on the hunt for planets down to the size of Earth, orbiting...