Tuesday, August 31, 2010

New Paper: M Dwarfs in the Mid-Infrared

I've submitted a paper to the Astronomical Journal called M Dwarfs in the Mid-Infrared AKARI/IRC Sky Survey.

AKARI is a Japanese satellite that took pictures of most of the sky at wavelengths of 9 and 18 microns. For comparison, visible light is around 0.5 micron.

I found that about a thousand nearby -- that means within about 70 lightyears -- late-K and M dwarfs were detected. These are stars that around about half the mass of the Sun. For the most part, the brightnesses at 9 microns, where AKARI detected most of the them, are exactly what astrophysicists predicted backed on the brightnesses measured at 2 microns in the 2MASS Survey.

However, I do find a few of the M dwarfs are about 30% brighter than they should be. This may just be random error -- that is, we expect some measurements to be off just by poor luck. On the other hand, if the excess is real, it's very interesting.

One explanation for such an excess is that the M dwarf is surrounded by dust grains that about 300-500K. How would you get grains -- small particles -- around an M dwarf? The grains could be debris form collisions between asteroids. If this is the case, these M dwarfs have Super-Asteroid Belts much more massive and denser than our Solar System's. Also, the asteroids would be near the "habitable zone" where liquid water can exist on planets. Obviously, it's difficult to imagine life existing on asteroids that are constantly colliding with each other, but it's an exciting possibility.

Unfortunately, we really need independent measurements of the mid-infrared brightnesses before we can believe there really are excesses. The Spitzer Space Telescope no longer can make these measurements, because it ran out of coolant as scheduled last year, but perhaps the SOFIA observatory can. I'm looking forward to it, whether I or someone else make the measurements

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