Another discovery thanks to transits. The atmosphere of the exoplanet HD 209458b has been found to contain water vapor. And while that's not unexpected, the effectiveness of the transit method in making the find underlines how significant are the occasions when a planet passes in front of its star as seen from Earth. Studying the infrared spectrum, as Travis Barman did at Lowell Observatory, shows the apparent signature of water vapor absorption when compared to the visible spectrum. But don't expect an ocean world here. The planet involved orbits its star every three and a half days; HD 209458b is, in fact, a 'hot Jupiter,' its upper atmosphere heated to temperatures as high as 10,000 degrees K. The planet is doubtless losing thousands of tons of material every second as it vents gases into the incendiary environment so near its primary. Nonetheless, finding water vapor does provide confirmation of theories that suggest almost all extrasolar planets have water vapor in their...

Years ago I wrote a story called 'Rembrandt's Eye,' using as background a planet whose foliage was predominantly red. The story, which ran in a short-lived semi-pro magazine called Just Pulp, came back to mind when the news from Caltech arrived. Researchers at the Virtual Planetary Laboratory there now believe that Earth-type worlds may have foliage that is largely yellow, orange or, as in the case of my planet, red. The green of Earth's plant life is anything but a universal standard. This interesting conclusion emerges from computer models designed to provide pointers for the future search for plant life on exoplanets. After all, astronomers will need to know what they might see in the spectra we'll one day be able to harvest from space-borne observatories. Ponder everything that's involved, from the color of the main sequence primary star to the aquatic habitats of aqueous plants. The search involves the way photosynthesis might occur under varying conditions, with the filtering...

Since we've recently been discussing astrometry, the discipline that measures star distances and movements, now would be a good time to look at two significant projects that go beyond optical methods to use radio astrometry in planet hunting. The Radio Interferometric Planet Search (RIPL) will draw on the Very Long Baseline Array, ten dish antennae spanning more than 5000 miles, and the 100-meter Green Bank telescope in West Virginia. The target: 29 active low-mass stars to be examined in a three-year planet hunt. The targets are significant because they're a kind of star that's currently out of reach for radial velocity techniques. All are M dwarfs that are active, meaning they display 'starspots' (analogous to sunspots), flares or other activity in their chromospheres. The more active a faint star like this, the more likely that radial velocity measurements will be distorted with a 'jitter' that disturbs the precision of the measurement. RIPL ought to be able to sort out the...

A Neptune-class planet has been discovered around the nearby red dwarf GJ 674, and it's an intriguing one. Using the HARPS spectrograph on the European Southern Observatory's 3.6 meter telescope at La Silla (Chile), the discovery team determined that the new planet was 0.039 AU from its parent star, yielding a temperature of some 450 degrees K. With a minimum mass estimate of about 11 times the mass of Earth, it completes an orbit every 4.69 days. Whether GJ 674 b is largely gaseous or rocky is unknown, although further observations of its orbital eccentricity may yield clues. We're not down to Earth-mass planets yet, but this is an interesting find. This is the second-closest known planetary system (after Epsilon Eridani). GJ 674 is less than 15 light years away and it's one of the brightest M dwarfs in our field of view. That makes the transit situation interesting, as Greg Laughlin noted in this systemic post: At first glance, such an effort might appear to be hampered by the fact...