Image: Anglo-Australian Obervatory
Using a new high-precision system on the four-meter Anglo-Australian Telescope (AAT), an international team of scientists has identified three more planets orbiting stars within 150 light-years from Earth. They are the first planets discovered by this Southern-based search, which complements the Northern surveys run by Geoffrey Marcy, Paul Butler and Michael Mayor. Although three planets isn't much compared to the 46 that have been found in the North over the past 5 years, Chris Tinney, team leader at the AAT, says many more candidates are probably in the pipeline. "In three years you can catch only the short-period planets," he explains. "To pick up ones with longer obits you hav to observe for a few more years."
The new objects do indeed have relatively short years. The tiniest, which is slightly smaller than Jupiter, whizzes around its star in a neck-breaking three Earth days. The middle-sized planet, weighing in at 1.26 Jupiter masses or more, circles the star epsilon Reticulum in Net within 426 days. (Despite its Earth-like years, the new planet is probably a gas giant like Jupiter.) And the biggest of the trio--another gas giant that is at least 1.86 Jupiter masses--takes 743 days to cruise around its star, mu Ara in the constellation of Ara. Like planets found in the Northern searches, these three made themselves known by the effect they have on their parent star: The mass of the planet tugs on the star, making it wobble and shifting its light in a telltale way.