AN EXCESS OF EARTHS

Armagh Observatory, 28 January 1999

Astronomers have recently discovered about a dozen planets orbiting stars similar to the Sun. These planets are probably large Jupiter-like gas giants. The detection of smaller rocky planets like the Earth is still beyond the limits of the most sensitive telescopes.

Life as we know it, depends on water particularly, a breathable atmosphere, and a suitable climate. The Earth is the only known planet which has water in the liquid, solid and gaseous forms. An astronomer at Armagh Observatory, Dr John Chambers, is currently running computer programmes to find out how abundant Earth-like planets may be in the Universe.

The starting point for the programmes is the assumption that a planetary system is created from a disk of many tiny particles circling a star. Collisions between these particles result in the formation of fewer, larger bodies which orbit in certain zones around the star. These larger bodies eventually merge into a sole planet in each of these zones.

A planet is termed "habitable" if it has surface liquid water. The presence of liquid water depends on the planet's distance from its parent star. John Chambers' programme yielded a number of artificial planetary systems, all of which showed at least one habitable, or possibly habitable, planet. This work implies that there are numerous life-supporting worlds somewhere out there. An interesting result is that the planet Mars would probably be habitable if its atmosphere was thicker.

FOR FURTHER INFORMATION CONTACT John McFarland, tel.: 01861-522928 (work), or 01762-879549 (home).

Last Revised: 15th June 1999 WWW contact: webmaster@star.arm.ac.uk

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