Astronomy Buff

Hubble Detects Extrasolar Planet Atmosphere Blowing in the Solar Wind

by Tony on February 1st, 2007

Some 150 light years away, in the constellation Pegasus, a planet orbits so close to its star that the upper layers of the atmosphere is streaming outward like a comet flying by the Sun. The star is informally known as Osiris, and the planet is fondly known as HD 209458b.

This planet is special in the sense that it was the first transiting extrasolar planet discovered, which means its orbit causes the planet to pass between our line of sight and the disk of the star. We know the planet is there because the star dims just a bit every time it passes in front of it.

Each pass in front of the star takes about three hours and the star dims by about 1.7%. It takes the star about 3.5 days make one orbit (that’s its year folks).

By using spectroscopes pointed at the star while the planet transits, astronomers can measure the chemicals that make up its atmosphere, and infer things like its temperature.

A new study using archival observations made in 2003 with Hubble’s Space Telescope Imaging Spectrograph by David Charbonneau of the Harvard-Smithsonian Center for Astrophysics, a team led by Gilda Ballester, has found that this planet has an upper atmosphere that is hotter than the Sun (from this press release):

“The layer we studied is actually a transition zone where the temperature skyrockets from about 1,340 degrees Fahrenheit (1,000 Kelvin) to about 25,540 degrees (15,000 Kelvin), which is hotter than the Sun,” said Gilda Ballester of the University of Arizona in Tucson, leader of the research team. “With this detection we see the details of how a planet loses its atmosphere.”

This planet is unlike anything in our solar system. It is larger than Jupiter and orbits very close to Osiris, if this planet were in our solar system, it would be inside the orbit of Mercury. Its atmosphere is structured like a layer cake, and the solar wind from the star is blowing material off of the upper layers at the rate of 10,000 tons per second.

The Spitzer Space Telescope, an orbiting infrared observatory, also provided data for this study.

See, I told you the future is in the infrared…

Here’s the press release from HubbleSite

Here another good article from Space.com.

Technorati Tags: extrasolar planets, hubble space telescope, telescopes

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POSTED IN: general astronomy, stars