Hazy red sunset on extrasolar planet

December 11, 2007
Hazy red sunset on extrasolar planet
An artist's impression of the extrasolar planet HD 189733b seen here with its parent star looming behind. The planet is slightly larger than our own Solar System's Jupiter. Its atmosphere is a scorching eight hundred degrees Celsius. Astronomers have found that the sunset on HD 189733b would look similar to a hazy red sunset on Earth. Credit: ESA, NASA and Frederic Pont (Geneva University Observatory)

A team of astronomers have used the NASA/ESA Hubble Space Telescope to detect, for the first time, strong evidence of hazes in the atmosphere of a planet orbiting a distant star. The discovery comes after extensive observations made recently with Hubble’s Advanced Camera for Surveys (ACS).

The team, led by Frédéric Pont from the Geneva University Observatory in Switzerland, used Hubble’s ACS to make the first detection of hazes in the atmosphere of the giant planet. "One of the long-term goals of studying extrasolar planets is to measure the atmosphere of an Earth-like planet, this present result is a step in this direction" says Pont. "HD 189733b is the first extrasolar planet for which we are piecing together a complete idea of what it really looks like."

The new observations were made as the extrasolar planet, dubbed HD 189733b, passed in front of its parent star in a transit. As the light from the star passes through the atmosphere around the limb of the giant extrasolar planet, the gases in the atmosphere stamp their unique signature on the starlight from HD 189733.

The planet itself, orbiting close to its parent star, is a ‘hot-Jupiter’ type of gas giant slightly larger than Jupiter. The proximity to its star results in an atmospheric temperature of roughly seven hundred degrees Celsius. Measurements of the way light varies as the planet passes in front of its parent star indicates that HD 189733b has neither Earth-sized moons nor any discernable Saturn-like ring system.

Hubble’s ACS camera, coupled with a grism (a kind of cross between a prism and a diffraction grating) allowed the astronomers to make extremely accurate measurements of the spectrum of HD 189733b, allowing conclusions to be drawn about the composition of the planet’s atmosphere. The exquisite level of precision needed to make this observation can only, at the moment, be achieved from space. The combination of a large planet and relatively small parent star – only 76% of the diameter of our Sun – contributes to the success of this delicate experiment.

Where the scientists had expected to see the fingerprints of sodium, potassium and water there were none. This finding, combined with the distinct shape of the planet’s spectrum, infers that high level hazes (with an altitude range of roughly 1000 km) are present. So the atmosphere on HD 189733b would look very similar to a gorgeous red sunset over Athens! Venus and Saturn’s moon Titan, in our own Solar System, are also covered with haze. According to the scientists the haze probably consists of tiny particles (less than 1/1000 mm in size) of condensates of iron, silicates and aluminium oxide dust (the compound on Earth which the mineral sapphire is made of).

As part of the observations of HD 189733, the teams of astronomers also needed to accurately account for the variations in the star’s brightness during the set of observations. ‘Starspots’ like those seen on our own Sun may cover several percent of the star and are thought to be about 1000 degrees Celsius cooler than the rest of HD 189733’s surface. It was found that there is a starspot on the star’s surface which is over 80,000 km across.

Source: Hubble Information Centre

Explore further: Exoplanets 101: Looking for life beyond our Solar System

Related Stories

Iron found in fossils suggests supernova role in mass dying

August 22, 2016

Outer space touches us in so many ways. Meteors from ancient asteroid collisions and dust spalled from comets slam into our atmosphere every day, most of it unseen. Cosmic rays ionize the atoms in our upper air, while the ...

Jupiter's great red spot heats planet's upper atmosphere

July 27, 2016

Researchers from Boston University's (BU) Center for Space Physics report today in Nature that Jupiter's Great Red Spot may provide the mysterious source of energy required to heat the planet's upper atmosphere to the unusually ...

Two pairs of planets perform in the August twilight

August 17, 2016

Step outside as the stars come out, look southwest, and you'll see an eye-catching pattern. For the next few days (August 17–22, 2016), bright orange Mars shines to the right of Saturn and the reddish star Antares. The ...

Recommended for you

NASA team probes peculiar age-defying star

August 29, 2016

For years, astronomers have puzzled over a massive star lodged deep in the Milky Way that shows conflicting signs of being extremely old and extremely young.

Milky way had a blowout bash six million years ago

August 29, 2016

The center of the Milky Way galaxy is currently a quiet place where a supermassive black hole slumbers, only occasionally slurping small sips of hydrogen gas. But it wasn't always this way. A new study shows that 6 million ...

NASA's Juno successfully completes Jupiter flyby

August 29, 2016

NASA's Juno mission successfully executed its first of 36 orbital flybys of Jupiter today. The time of closest approach with the gas-giant world was 6:44 a.m. PDT (9:44 a.m. EDT, 13:44 UTC) when Juno passed about 2,600 miles ...

Hubble spots an irregular island in a sea of space

August 29, 2016

This image, courtesy of the NASA/ESA Hubble Space Telescope's Advanced Camera for Surveys (ACS), captures the glow of distant stars within NGC 5264, a dwarf galaxy located just over 15 million light-years away in the constellation ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.