Starry starry starry night: Star count may triple

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Van Dokkum agreed, saying, “Frankly, it’s a big pain.”

Ellis said the new study does make sense. Its biggest weakness might be the assumption that the chemical composition of dwarf stars is the same in elliptical galaxies as in the Milky Way. That might be wrong, Ellis said. If it is, it would mean there are only five times more red dwarf stars in elliptical galaxies than previously thought, instead of 10 or 20, van Dokkum said.

Slightly closer to home, at least in our own galaxy, another study also published in Nature looks at a single red dwarf star in a way that is a step forward in astronomers’ search for life beyond Earth. A team led by a Harvard scientist was able to home in on the atmosphere of a planet circling that star, using the European Southern Observatory’s Very Large Telescope in Chile.

The planet lives up to the word alien. The team reports that this giant planet’s atmosphere is either dense with sizzling water vapor like a souped-up steam bath, or it is full of hazy, choking hydrogen and helium clouds with a slightly blue tint. The latter is more likely, say the researchers and others not involved in the study.

While scientists have been able to figure out the atmosphere of gas giants the size of Jupiter or bigger, this is a first for the type of planet called a super Earth _ something with a mass 2 to 10 times Earth’s. The planet is more comparable to Neptune and circles a star about 42 light years from Earth. A light year is nearly 6 trillion miles.

The planet is nowhere near livable _ it’s about 440 degrees (about 225 degrees Celsius). “You wouldn’t want to be there. It would be unpleasant,” said study co-author Eliza Kempton of the University of California Santa Clara.

But describing its atmosphere is a big step toward understanding potentially habitable planets outside our solar system, said study chief author Jacob Bean at the Harvard Smithsonian Center for Astrophysics.

Bean and Kempton looked at the light spectrum signature from the large planet as it passed in front of the dwarf star, and the result led to two possible conclusions: steam bath or haze.

The steam bath is the more interesting possibility because water is key to life, said outside scientist Alan Boss of the Carnegie Institution of Washington.

But an upcoming and still unpublished study by Kempton and Bryce Croll at the University of Toronto points more toward a hydrogen-helium atmosphere, several astronomers said.

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Online:

Nature: http://www.nature.com/nature

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