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Thursday, June 07, 2007


No transits for Gliese 581

The news has been officially released at the the annual meeting of the Canadian Astronomical Society at the Royal Military College in Kingston, Ontario. Gliese 581 is a nice stable star, but no transits were detected by MOST. This wasn't really surprising, as there was only between a 1 in 20 and 1 in 50 chance of a transit. Quoting from the press release:

The MOST results ... rule out dips in the starlight down to a level of about 0.1%
that would be caused by a transiting planet roughly the size of the
Earth. That doesn't mean there's no planet, just that from Earth, we
don't see its orbit nearly edge-on. But it does mean we can't directly
measure the size of the planet Gliese 581c, to test models of its
structure. That's the disappointing news.

The encouraging news is that the star itself seems remarkably stable
over the six weeks it was monitored by MOST. The brightness of the star
changed by only a few tenths of a percent over that time. This level of
stability means that this red dwarf star provides a stable source of
light, hence heat, to the surface of planet Gliese 581c. "The climate
there should not be a wild rollercoaster ride that would make it
difficult for life to get a foothold," notes MOST Mission Scientist Dr.
Jaymie Matthews, a professor in the Department of Physics & Astronomy
at the University of British Columbia. "It also suggests the star is
quite old, and settled in its ways, so that the planets around it have
been around for billions of years. We know it took about three and a
half billion years for life on Earth to reach the level of complexity
that we call human, so it's more encouraging for the prospects of
complex life on any planet around Gliese 581 if it's been around for
at least as long."
So, the results while disappointing in that we miss out on finding more about Gliese 581c (or d), but we know a lot of interesting information about the system. I'll blog some of my ideas about this later on. Centauri Dreams also has some good discussion of this report.

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