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|Date: Wednesday 4 November 1998
Embargo: For immediate release
Today the UK Daily Telegraph newspaper has reported that a team of astronomers led by Hans Deeg from the Instituto de Astrofísica de Canarias has discovered evidence for a planet like ours with an orbit that allows the existence of life. Their observations were carried out at the Isaac Newton and Jacobus Kapteyn Telescopes, among others, and their findings have been published in the journal Astronomy and Astrophysics on 10 October. This is an extract from Robert Matthews' article:
"In the past three years, astronomers have made a steady stream of claims for supposed new planets orbiting other stars; the first was made in December 1995 by astronomers in Switzerland, and the count currently stands at about a dozen. Yet until now, all these claims have been for nothing more exciting than giant balls of gas so huge that their gravity makes their parent stars perceptibly "wobble".
But Dr Hans Deeg of the Astrophysics Institute at Tenerife and colleagues may now have bagged the big prize: evidence for a truly Earth-like planet following an orbit that could allow the existence of life. Since 1994, Dr Deeg and his colleagues have been using a world wide network of telescopes to keep close watch on CM Draconis, a star system about 57 light years away.
Made up of two small, dim, reddish stars circling one another, CM Draconis would normally attract little attention. Yet those ho-hum charecteristics make CM Draconis the perfect target for a simple, yet powerful, way of detecting Earth-like planets.
Known as the transit method, it relies on the fact that a planet crossing -- or "transiting" -- the face of a star will blot out a small fraction of the star's light, and thus cause a sudden fall in its brightness. By watching out for these tiny but regular falls in the brightness of stars, astronomers think they can detect the existence of planets too small to produce any other tell-tale signs in their parent stars [...]
The fact that the stars are small is another plus, says Dr Deeg: "The two stars are also only about a quarter the diameter of the Sun, so the transit of even an Earth-sized planet across one of these small stars would cause a detectable brightness drop".
For the past four years, Dr Deeg and colleagues have been patiently studying CM Draconis with 10 telescopes around the world, looking for the tell-tale patterns of light changes that hint at the presence of a planet.
[...] After shifting through the first three years of data -- covering more than 600 hours of observations -- the Transits of Extrasolar Planets (TEP) team thinks it might have hit paydirt. The evidence published in the journal Astronomy and Astrophysics takes the form of six small but definite dips in the light coming from the CM Draconis system.
According to Dr Deeg, they are the type of dips expected from planets roughly the size of Earth. "We have essentially ruled out the presence of planets much larger than about 2.5 times larger than the Earth," he says. "What may have caused some of these six potential transit events are planets about 1.5 to 2.5 times the radius of the Earth".
The TEP team is analysing the data to see which of the transits provides the best evidence. "Then we will go back to the telescope and check if new transits occur at the times we'd predict," says Dr Deeg. "One needs to be careful before making announcements in this game." If the six events do hold up, they may do more than merely point to the existence of a planet similar to the Earth in size: its orbit is likely to lie at the right distance from the central stars to give it a similar temperature range as well. "Our detection method is sensitive to the whole distance range of the habitable zone around CM Draconis, " says Dr Deeg [...]"
The Isaac Newton Group of telescopes (ING) consists of the 4.2m William Herschel Telescope, the 2.5m Isaac Newton Telescope and the 1.0m Jacobus Kapteyn Telescope. The ING is owned and operated jointly by the UK's Particle Physics and Astronomy Research Council (PPARC) and the Netherlands' Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO). The telescopes are located in the Spanish Observatorio del Roque de Los Muchachos on La Palma which belongs to the Instituto de Astrofísica de Canarias (IAC).
Javier Méndez Alvarez