If the weather on Uranus, examined here yesterday, isn't exotic enough for your taste, consider the situation on Jupiter-class worlds around other stars. A 'hot Jupiter' orbiting extremely close to its star spawns weather like nothing we've ever experienced, as modeled by computer simulations coming out of the University of Arizona. And while we can't actually image these objects yet, we can certainly deduce a great deal about them from observations made during the times they transit their star. On that score, well-studied HD 189733b is an early example of pushing the envelope. Located 63 light years from Earth, this transiting planet orbits once every 2.2 days, scooting along a mere three million miles from its primary. Spitzer Space Telescope data culling variations in starlight during the frequent planetary transits have allowed us to peg daytime temperatures on worlds like these, usually in a range somewhere between 2000 and 3000 degrees Fahrenheit (1300 and 1900 degrees Kelvin)....

How tides affect habitability has become a sub-genre within exoplanetary studies, a theme pushed hard by the gifted trio of Brian Jackson, Rory Barnes and Richard Greenberg (University of Arizona). You may want to browse through earlier Centauri Dreams entries on their work, especially this fascinating take on habitability around M dwarfs, in which the authors consider the possibility that Gliese 581 c was once a relatively benign place, but is now in an orbit that renders life impossible. Orbital evolution is the broad issue, sustained complex life demanding planets with low eccentricities. And orbital evolution can take a lot of time to operate. Now I see that Brian Jackson has presented new work on tides and habitability at the 40th annual meeting of the Division of Planetary Sciences in Ithaca, NY. Here we push into interesting questions about planets already inside a habitable zone that are nonetheless too hellish to support life, and planets outside that zone that seem too cold...

Computer simulations are showing us how to detect the signature of Earth-like planets -- indeed, planets nearly as small as Mars -- around other stars. That interesting news comes out of NASA's Goddard Space Flight Center, where a supercomputer named Thunderbird has been put to work studying dusty disks around stars similar to the Sun. Varying the size of the dust particles along with the mass and orbital distance of the planet, the team led by Christopher Stark (University of Maryland) ran 120 different simulations. "It isn't widely appreciated that planetary systems -- including our own -- contain lots of dust," Stark says. "We're going to put that dust to work for us." Indeed. Useful and observable things happen as dust responds to the forces acting upon it. For one thing, starlight can exert a drag that causes dust particles to move closer to the parent star. More to the point, particles spiraling inward can become involved in orbital resonances with planets in the system. A...

At first glance, the object called COROT-exo-3b doesn't seem all that interesting. True, planets that orbit remarkably close to their stars were a surprise when first detected, but we've since found enough of them to know that a gas giant in a four-day orbit, which is about how long this object takes to circle its star, is not a great rarity. We've also learned that radial velocity methods are going to detect large, close objects more quickly than planets that orbit farther from their primary. Why is COROT-exo-3b making news? Then you look a little more closely at the new find. For one thing, the COROT mission depends not upon radial velocity measurements but planetary transits. More significantly, COROT-exo-3b is roughly the size of Jupiter but is fully twenty times as massive. Orbiting an F-class dwarf with metallicity values much like the Sun, the object opens up a new perspective, for we've found planets twelve times as massive as Jupiter and stars seventy times as massive, but...

When Worlds Collide, the 1932 novel of planetary catastrophe, presented the most extreme extinction event imaginable. A pair of wandering planets enters the Solar System, one on collision course with the Earth, the other destined to be captured into orbit around the Sun. The doughty crew of an escaping rocket, on their way to a new life on the captured world, can only watch in horror as the Earth is destroyed. Now we learn about a 'when worlds collide' scenario that seems to have involved two mature, Earth-sized planets in a distant Solar System. The system in question is BD+20 307, originally thought to be a single star with a massive, warm dust disk, but now known to be a close binary orbiting the common center of mass every 3.42 days. Both stars are similar to the Sun in mass, temperature and size. Moreover, the system seems to have an age comparable to our own Sun, and the sheer amount of dust at roughly Venus to Earth distance is quite interesting. We would expect the dust...