Hazy red sunset on extrasolar planet

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

Related stories:

Venus Express searching for life – on Earth
(PhysOrg.com) -- Scientists using ESA’s Venus Express are trying to observe whether Earth is habitable. Silly, you might think, when we know that Earth is richly stocked with life. In fact, far from being a pointless exercise, Venus Express is paving the way for an exciting new era in astronomy.
Meteorite experiment deals blow to 'bugs from space' theory
A novel experiment has dealt a setback to a theory that life on Earth was kickstarted by bacteria that hitched a ride on space rocks.
First picture of likely planet around sun-like star unveiled
(PhysOrg.com) -- University of Toronto astronomers have unveiled what is likely the first picture of a planet around a star similar to the sun.
Physicists Rule Out the Production of Dangerous Black Holes at the LHC
(PhysOrg.com) -- On August 8, the world's largest particle accelerator, the Large Hadron Collider near Geneva, Switzerland, began the process of slowly throttling to full power. When its proton beams are circling at full speed and collisions begin, scientists from around the world will finally be able to start collecting data.
Living with a Star
What if you woke up one morning and found your whole planet had been swallowed by the atmosphere of a star?
August brings the Perseid meteors and a cluster of planets
(PhysOrg.com) -- The annual Perseid meteor shower will peak before dawn on Aug. 12. This year the Perseids will be competing with the nearly full moon at first, but after the moon sets there will be many bright streaks in the sky.
A new era in search for 'sister Earths'?
Research presented at a recent astronomical conference is being hailed as ushering in a new era in the search for Earth-like planets by showing that they are more numerous than previously thought and that scientists can now analyze their atmospheres for elements that might be conducive to life.
Hubble Instruments Slated for On-Orbit 'Surgery'
When astronauts visit the Hubble Space Telescope in October 2008 for its final servicing mission, they will be facing a task that has no precedence – performing on-orbit ‘surgery’ on two ailing science instruments that reside inside the telescope – the Space Telescope Imaging Spectrograph (STIS) and the Advanced Camera for Surveys (ACS).

News discussion:

Space & Earth science news