Only recently has the idea of habitable planets around red dwarf stars taken hold. But it's a fascinating one, especially if you take a look at the potential window for life to develop on such worlds. M-class red dwarfs live anywhere from 50 billion up to several trillion years, a vast stretch compared with our own Sun's projected ten billion years. And with 75 percent of main sequence stars thought to be red dwarfs, the hunt for life can be expanded enormously if we add red dwarfs to the mix. But getting a stable environment for that life to develop is another matter, for planets in the habitable zone around such stars would be close enough to their primaries to be tidally locked, with one side always in sunlight, the other in darkness. The thought of a frozen dark side and a scalded day side isn't pretty. It wasn't until the late 1990s that models of heat transport within the atmosphere developed that could even out these stark extremes. Now it looks as though habitable worlds...

The news from AU Microscopii couldn't be more interesting, but I'm late getting to it simply because the recent American Astronomical Society meeting left us with so many good things to talk about (wish I could have been there!). But we'll be examining this red dwarf, 33 light years away in the constellation Microscopium (the Microscope) for a long time because it's so useful for study. It's close enough for the Hubble Space Telescope to image it with excellent resolution, and we know from such studies that the star is encircled by a debris disk. Check the image below, where you can see that the disk is nearly edge on as seen from Earth. Image: The dust and debris disk surrounding the star AU Microscopii, as imaged by the Hubble Space Telescope. The lines indicate the polarization of starlight reflected from the disk, which reveals the porosity or fluffiness of the dust grains. The disk is about 120 astronomical units (AU) across, where one AU is equivalent to the distance between...

For some 'hot Jupiters,' at least, changes in the weather aren't much of an issue. In a new study presented at the American Astronomical Society meeting in Seattle, three Jupiter-class planets orbiting within five million miles of their host stars were found to have remarkably similar temperatures globally, even though they're tidally locked. You would expect that a planet with one side turned perpetually toward its star would show considerable temperature variation between the day and night sides, but that does not appear to be the case. "We can't say for sure that we've ruled out significant day-night temperature differences, but it seems unlikely there is a very big contrast based on our measurements and what we know about these systems," said Eric Agol (University of Washington). Agol is lead scientist for the project, which used the Spitzer Space Telescope to measure infrared light from the three systems at eight different positions in their orbits. The study showed no infrared...