Saturday, October 30, 2010


New Book Carousels

Check out the new amazon book carousels recommending books by subject area at the bottom of this blog :-)

Thursday, October 14, 2010


Glise 581g - first 'earth-like' exoplanet?

Original Blog Post

Nasa scientist and Nobel laureate in physics John Mather's recent comment about 'Earth-like' planets was rather timely. Mather said: 'We know there are earth-like planets out there, but what we don't know is whether any of them are capable of supporting life.' Well, Nasa have announced that: "If confirmed, [Gliese 581g] would be the most Earth-like exoplanet yet discovered and the first strong case for a potentially habitable one."

Thus far we have an unconfirmed report that Gliese 581g might be rocky (since it may be too small to be a gas giant - although the mass given is a minimum figure) and that it seems to be in the right 'goldilocks' temperature zone for liquid water - that's if there is any water there and if the atmosphere is of the right composition!

Of course, the phrase 'Earth-like' is being used with some lattitude here: the gravity on Gliese 581g is higher than on earth (because its about three to four times the size of Earth). Moreover, the planet is 'tidally locked', meaning it doesn't rotate (i.e. no seasons). This probably means that there's only a narrow 'twilight zone' of the planet that's even potentially habitable; assuming, of course, that the atmosphere (if it even has one) hasn't frozen out over time to the night side of the planet!

At most (it's hard to extrapolate here), this discovery may indicate that rocky planets in the habitable zone of stars aren't all that rare; but consider this interesting passage from The Hiffington Post article on the discovery:

'Vogt and Butler ran some calculations, with giant fudge factors built in, and figured that as much as one out of five to 10 stars in the universe have planets that are Earth-sized and in the habitable zone. With an estimated 200 billion stars in the Milky Way galaxy, that means maybe 40 billion planets that have the potential for life, Vogt said. However, Ohio State University's Scott Gaudi cautioned that is too speculative about how common these planets are.'

There's more to habitability - let alone the origin of life - than a chunk of rock at the right temperature!

Scientists have expressed caution about the overblown claim made by Steven S. Vogt that "the chances of life on this planet are 100 percent”:

"'Until we know more about this planet and the origin of life itself, any claim of certain habitation is idiotic and does not serve science,' said Dr. Stuart Clark, author and astronomy journalist... 'As cool as it is, please realize that right now all we really know about it is its orbit and estimated mass. That’s it.' said Lee Billings, editor at Seed Magazine. 'In other words, barring observational evidence that may still be a generation away, Gliese 581g is "Earth-like" only in terms of mass/orbit.'” - Universe Today

"nobody really knows what is going on on Gliese 581g, said Sara Seager, a planetary astronomer at the Massachusetts Institute of Technology. “If it was all carbon dioxide, like Venus, it would be pretty hot,” she said, adding that she would give the planet a 90 percent chance of holding water. That, she pointed out, is faint praise in scientific circles. “Sounds high, but would you fly on a plane that only had an 8 or 9 chance out of 10 of making it?” she asked. “Everyone is so primed to say here’s the next place we’re going to find life,” Dr. Seager said, “but this isn’t a good planet for follow-up.” - New York Times

Update (Oct 14th)

According to a New Scientist report, 'First life-friendly exoplanet may not exist'!

A second research group using more data than the first have failed to find any trace of Glise581g (although they do confirm the existence of the other planets in the system that were previously known about):

'We easily recover the four previously announced planets, "b", "c", "d", and "e". However, we do not see any evidence for a fifth planet in an orbit of 37 days," says Francesco Pepe of the Geneva Observatory in Switzerland... The discrepancy has raised some questions about the discovery. "The Geneva team's report at this meeting has certainly raised doubts," says astronomer Ray Jayawardhana at the University of Toronto in Canada...' - New Scientist

Wednesday, October 06, 2010


Peter S. Williams - Updated Speaker's Page

My newly updated Damaris Trust speaker's page is now live,
giving info about me, my publications and suggested topics for talks, etc.

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