Steinn Sigurðsson (Pennsylvania State) has been reporting from the Greek island of Santorini, where he is attending the Extreme Solar Systems conference. I want to send you at once to Steinn's Dynamics of Cats weblog, where updates are being filed and will presumably continue through today, the conference's last day. It sounds like a terrific gathering filled with the energizing news of discoveries, its theme being, in addition to finding Earth-like planets, the study of exoplanets in tricky places like dense star clusters, near giant stars and orbiting pulsars. That last is fitting enough, given that the first extrasolar planets of Earth-like mass were discovered 15 years ago around the pulsar PSR 1257+12; in fact, the conference meets on the occasion of that anniversary and celebrates as well the sixtieth birthday of Alex Wolszczan, the discoverer of those worlds. All of that and beauteous Santorini too, though as Steinn reports, the heat has been the worst since 1916, as per...

Speaking of bio-signatures, as we did at the end of yesterday's post on planetary atmospheres, take note of the Virtual Planet Laboratory, a working group at the Jet Propulsion Laboratory that is trying to figure out what life's markers might look like across a wide range of biological types. The most obvious signature for life itself is the presence of unusual combinations of things. A world without life shouldn't, for example, give us strong signatures in both methane and oxygen simultaneously. We looked at this subject in an April post, but a recent news release prompts me to put it back into play. The work is highly theoretical, proceeding as it does with no current examples of extrasolar planetary spectra from terrestrial-class worlds to look at. But we can begin with photosynthesis and its variants, as discussed here by Robert Blankenship (Washington University, St. Louis), a member of the group of researchers: "When you consider another world you've got to find that life there...

Where does the Solar System keep its water? Beyond Mars, the trend seems to favor more and more water content the farther out we go. Thus Jupiter, which is considered depleted in water, is eclipsed in these terms by Saturn, though that planet has less water than other volatiles. Move on to Uranus and Neptune and you get into serious water enrichment. "The farther out you go in the solar system, the more water you find," says Bruce Fegley (Washington University, St. Louis). Fegley's work, discussed at the Chicago meeting of the American Chemical Society last March, points to a compelling theory about the outer planets: From Jupiter to Neptune, these are worlds whose atmospheres are 'primary,' drawn directly from the solar nebula as the planets of our Solar System were forming. Just as the Sun is rich in hydrogen and helium, Jupiter likewise shows large amounts of hydrogen and helium, though less carbon, nitrogen and oxygen than the other gas giants. Observations of methane, hydrogen...

Watching the motion of the stars they orbit has been how most of the planets beyond our Sun have thus far been discovered. Such radial-velocity methods are getting more precise all the time, but a likely planet around the nearby star Fomalhaut comes out of an entirely different line of research. Alice Quillen (University of Rochester) is an expert on stellar disks and the planets that help to shape them. And she has learned to predict a planet's size and position from her studies. In the case of Fomalhaut, Quillen worked with Hubble Space Telescope imagery showing the star's surroundings in greater detail than ever before. The Hubble images took advantage of a coronagraph to mask the light of the star to bring out detail in the dimmer ring, confirming what astronomers had previously noted -- Fomalhaut is off-center within its ring. Image: Hubble's view of Fomalhaut's dust ring. Credit: University of Rochester/STScI. Quillen's models examine ring/planet interactions for young stars,...

My younger son Alec can be forgiven a certain amount of confusion over the term 'Planet X.' Back in the 1980s, I told him all about the marvelous Edgar G. Ulmer film The Man from Planet X, a favorite since my own childhood. Ulmer was a gifted director who is rarely talked about today (see his 1945 film Detour for a glimpse of just how gifted). And 1951's The Man from Planet X was compelling in a way that few B movies of the era achieved, with an alien whose spooky presence has stuck with me ever since I first saw him on an old black-and-white set. But then Alec encountered a different 'Planet X' in an astronomy class, learning that some astronomers had searched for a planet beyond Pluto, although at that point with notable lack of success. Planet X was supposed to account for various orbital oddities exhibited by Pluto and become emblematic of a fabulous, unknown place at the very edge of the system that was the ultimate catch for the next Clyde Tombaugh. I didn't think it existed...

Buy a commercial telescope today, equip it with a CCD detector, and you're arming yourself to enter the exoplanet hunt. A CCD, or charge-coupled device, is a sensor that proves far more efficient than photographic film at capturing incoming light. It wasn't so long ago that such tools were available only at large observatories, but no more. Today's amateur can observe a planetary transit, sensing the slight dimming that the planet causes to the starlight as seen from Earth. The trick is knowing when and where to look, and on that score, the Transitsearch network, often working with the American Association of Variable Star Observers, offers ephemeris and transit search results for stars thought to be candidates for such detections. For those new to the term, an ephermeris (pl. ephemerides) is a table plotting the position of celestial bodies. Look to Transitsearch for an example. Greg Laughlin (UC Santa Cruz) noted this morning on the systemic site that he was overhauling the look...