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Space Mission Eddington Seeks Out Quaking Stars And Earthlike Planets

January 08, 2002

Members of the media are invited to attend the meeting. No pre-registration is required, but it would be helpful if advance notice of attendance is given to the RAS press officer, Peter Bond, or to one of the organisers. There may be opportunities for interviews during the morning registration period and the lunch session.

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Scientists from more than 40 European laboratories, including eight in the UK, are currently working to develop an ambitious European Space Agency mission named Eddington.

There are two main goals for Eddington. One is to discover and study Earth-like planets around distant stars. The other is to measure small internal vibrations of stars to determine their internal structure.

Peering beneath the scorching hot surfaces of stars would seem impossible, but scientists have discovered that these giant balls of gas vibrate as shock waves pass through them. Although oscillating stars have been observed from the ground, very much smaller variations can be detected from space. Using a technique known as asteroseismology, astronomers will be able to use these vibrations to find out about the interiors of stars.

"It`s just like the technique geologists use on Earth ," explained Professor Ian Roxburgh (QM-UL), one of the organisers of the RAS meeting. "By studying seismic (earthquake) waves, they are able to find out about the Earth`s internal structure."

"In the case of Eddington, we spend several months measuring as accurately as possible the light outputs of certain stars," he said. "These long time sequences can be used to reveal the internal oscillations of the stars and tell us what they are like inside."

"These studies will help us to understand the evolution of stars (including our Sun) and galaxies, as well as improve our methods of measuring ages and stellar distances," he added.

At present, more than 70 extrasolar planets are known, but most of these are larger than Jupiter, the king of our Solar System, and hundreds of times bigger than the Earth. The challenge for the future is to discover small, Earth-like, rocky planets that may be able to support life.

Using a wide-field photometer, consisting of a 1.2 metre diameter telescope with a CCD camera, Eddington will search for the small amount of dimming observed when a planet passes in front of a star. By studying approximately 500,000 stars, this could result in the discovery of perhaps 20,000 planets - of which 100 or so would be expected to be Earth-like worlds located in the temperate, habitable zones around their stars.

"We can calculate the orbital period of the planet, and so determine its orbital distance, by measuring the time interval between each transit," explained Professor Roxburgh.

"The depth of the eclipse - the amount of dimming - tells us how much of the star has been covered and so indicates the size of the unseen planet," he added. "Since we known the properties of the star, we can also calculate whether the planet lies in the so-called `Habitable zone` - neither too hot nor too cold for life."

Eddington is not the only spacecraft with a mission to seek out Earth-like planets. NASA`s recently announced Kepler observatory will also be using the transit method to detect planets crossing the line-of-sight between the planet`s parent star and the observer. Dr. William Borucki of NASA`s Ames Research Center, principal investigator for Kepler, will be describing this exciting mission at the RAS meeting.

Members of the media interested in extra solar planets may also wish to attend the RAS Monthly (Ordinary) Meeting which begins at 16.00 in the Scientific Societies Lecture Theatre, when Dr. Jane Greaves of the UK Astronomy Technology Centre in Edinburgh will be presenting a paper entitled "Disks and planets around nearby stars".

Royal Astronomical Society (RAS)