1st alien planets found around sun-like stars in cluster

Washington - NASA-funded astronomers have spotted planets orbiting sun-like stars in a crowded cluster of stars for the first time.

The findings offer the best evidence yet that planets can sprout up in dense stellar environments. Although the newfound planets are not habitable, their skies would be starrier than what we see from Earth.

The starry-skied planets are two so-called hot Jupiters, which are massive, gaseous orbs that are boiling hot because they orbit tightly around their parent stars.

Each hot Jupiter circles a different sun-like star in the Beehive Cluster, also called the Praesepe, a collection of roughly 1,000 stars that appear to be swarming around a common centre.

The Beehive is an open cluster, or a grouping of stars born at about the same time and out of the same giant cloud of material. As such, the stars share a similar chemical composition. Unlike the majority of stars, which spread out shortly after birth, these young stars remain loosely bound together by mutual gravitational attraction.

“We are detecting more and more planets that can thrive in diverse and extreme environments like these nearby clusters,” Mario R. Perez, the NASA astrophysics program scientist in the Origins of Solar Systems Program, said.

“Our galaxy contains more than 1,000 of these open clusters, which potentially can present the physical conditions for harbouring many more of these giant planets,” Perez said.

The two new Beehive planets are called Pr0201b and Pr0211b. The star’s name followed by a “b” is the standard naming convention for planets.

“These are the first ‘b’s’ in the Beehive,” Sam Quinn, lead author of the study, said.

Quinn and his team, in collaboration with David Latham at the Harvard-Smithsonian Center for Astrophysics, discovered the planets by using the 1.5-meter Tillinghast telescope at the Smithsonian Astrophysical Observatory's Fred Lawrence Whipple Observatory in Arizona to measure the slight gravitational wobble the orbiting planets induce upon their host stars.

Previous searches of clusters had turned up two planets around massive stars but none had been found around stars like our sun until now.

“This has been a big puzzle for planet hunters,” Quinn said.

“We know that most stars form in clustered environments like the Orion nebula, so unless this dense environment inhibits planet formation, at least some sun-like stars in open clusters should have planets. Now, we finally know they are indeed there,” he added.