29 November 1999
For immediate release
An undergraduate has been credited with the co-discovery of six new extrasolar planets around nearby stars.
A year ago, Kevin Apps became the first UK astronomer to be involved in the detection of a new planet. Since then Kevin, studying Physics with Astrophysics at the University of Sussex, has topped his achievement with the addition of several more planets.
His discovery was made in collaboration with world-famous 'planet hunters' Steven Vogt, Geoff Marcy and Paul Butler from the USA. Funding came from both NASA and the National Science Foundation.
The team deployed the massive Keck telescope in Hawaii, undertaking a survey that monitors approximately 500 nearby Sun-like stars for planets. Kevin, who has been an astronomy enthusiast since he was seven, was inspired to become involved in the project by a visit to the Keck telescope. "It's the world's largest telescope", said Kevin. "Very few professionals get to use it - only a dozen or so groups in the world."
He scrutinised the American astronomers' target list of stars to see which were potential planet-bearers and discovered that 30 of them were unworkable. Kevin was astonished when his offer to choose 30 replacement stars was accepted. His theory is that solar systems comparable to ours may be the most likely to harbour life, so he based his search around Sun-like stars. He selected 30 stars that were "dead ringers for the Sun" - having the same size, mass, temperature and luminosity - and sent details to the USA so that they could be monitored on the Keck telescope.
Planets around extrasolar stars cannot be seen directly, so astronomers find them with a technique that involves searching for a tell-tale "wobble" in the motion of a star. The wobble indicates a disturbance in the motion, which is caused by the gravitational pull of a large mass, i.e. the planet. The size and duration of the wobble determines the mass of the planet as well as the length of time it takes to orbit the star.
To his great surprise, one of the stars that Kevin had selected turned up a planet. The planet hunters were so impressed, they not only invited him to visit the Keck telescope for an observing run, but also asked him to weed out any more unsuitable stars from their target list and generate further targets for investigation. In January two of these revealed the existence of planets. And now, a year later, another of Kevin's original 30 stars has come up trumps for him, leading to the discovery of planet HD 222582.
The icing on Kevin's cake is that he has been credited with the co-discovery not only of this planet but also of five others. Vogt, Marcy and Butler asked him to investigate the properties of the 500 target stars and his work has won him a credit on the research team's paper, to be published in the Astrophysical Journal. Geoff Marcy is impressed with Kevin's contribution, commenting: "He shows a fierce interest in this research. It's great to have him as a colleague."
This new batch of six increases the number of extrasolar planets that astronomers have detected to a total of 28. Already the properties of these planets have defied expectations, upsetting existing theories about how planets form. Scientists are working on new telescopes that should tell them more about the planets detected to date and enable a more comprehensive search for other extrasolar planets.
Two of Kevin's planets show evidence of an additional, companion planet further out. Previously only one other system of multiple planets had been identified. It will take years of additional observations to work out the orbits of these companion planets, say the research team, but the evidence suggests that a fair number of multiple planet systems exist.
Further information about the planet search is available on the Web at www.physics.sfsu.edu/~gmarcy/planetsearch/planetsearch.html.
For further information, please contact Alison Field, Communications Officer, University of Sussex Tel: 01273 678888, Fax: 01273 678335, email: A.Field@sussex.ac.uk
Photographs of Kevin Apps are available