Planet MOA-2007-BLG-192-L b might be similar to the size of the Earth

Tuesday, January 20, 2009


Wow, this was a pleasant surprise:

In June of 2008, astronomers announced the finding of one of the smallest exoplanets yet around a normal star other than the Sun. The planet – believed to be a rocky exo-world — was found through a microlensing event, and was estimated to be 3.3 times the size of Earth, orbiting a brown dwarf star. But new analysis suggests the star may be larger than first thought, making the planet smaller than the original estimates. Astronomers say the exoplanet, called MOA-2007-BLG-192-L b could weigh just 1.4 Earths - less than half the original estimate. Observations over the next few months should be able to test the prediction.
It turns out that the star might be a red dwarf instead of a brown dwarf, which is great news:
But more recent observations suggest the parent star is actually heavier than first thought - a type of star called a red dwarf, team member Jean-Philippe Beaulieu of the Paris Astrophysical Institute reported last week at a meeting of the Royal Astronomical Society in London.

That suggests the planet weighs just 1.4 Earths. In size terms, that makes it a near twin of our own planet, closer in mass than any known planet except Venus.
More detailed observations are due to be made in April or May, so we should know a bit more about this in a few months.

One particularly interesting article about red dwarves and their possibility for supporting life is from 2001 and can be seen here. One big advantage red dwarves have over much larger stars is that they take such a long time to exhaust their fuel, and even though planets close enough to them to have a warm climate would be tidally locked (always having the same face to the star like the Moon to us), the area in between day and night would be an interesting kind of belt neither too warm nor too hot, and there's nothing better for life than a continuously unchanging environment.

My favourite part of the article is the end:

Which leads to an intriguing thought. Any planets that circle red dwarfs may have given rise to astronomers as parochial as those on Earth. These alien observers may have concluded that only red dwarfs can support life, blessed as they are with stable planets where suns never set and seasons never disrupt the climate. Indeed, their SETI programs may ignore Sun-like stars altogether. After all, they might argue, any temperate planet orbiting such a star would lie so far out that it would rotate freely, subjecting life to a relentless cycle of light and dark. Any tilt of the axis would cause severe summers and winters, and changes in axial tilt might induce ice ages, with mighty glaciers smothering much of the globe. How on Earth could life possibly arise on such a hostile world?


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