NASA-funded astronomers have found two planets orbiting sun-like stars in a crowded cluster of stars, thus revealing that planets are found even in dense stellar environments.

The starry-skied planets discovered for the first time are two so-called hot Jupiters, which are massive gas-giant orbs that are boiling hot because they orbit closely around their parent stars.

The hot Jupiters orbs circle a different sun-like star in the Beehive Cluster, a collection of around 1, 000 stars that appear to be swarming around a common centre. 

"We are detecting more and more planets that can thrive in diverse and extreme environments like these nearby clusters," said Mario R. Perez, the NASA astrophysics program scientist in the Origins of Solar Systems Program. "Our galaxy contains more than 1,000 of these open clusters, which potentially can present the physical conditions for harboring many more of these giant planets." 

The newly discovered planets are known as Pr0201b and Pr0211b. The name ends with "b" because it is a standard naming convention for planets. 

"These are the first 'b's' in the Beehive," said Sam Quinn, a graduate student in astronomy at Georgia State University in Atlanta and the lead author of the paper describing the results, which was published in the Astrophysical Journal Letters. 

Quinn and his team along in association with David Latham at the Harvard-Smithsonian Center for Astrophysics spotted the planet with the help of 1.5-metre Tillinghast telescope at an Observatory in Arizona to calculate the slight gravitational wobble the orbiting planets induce upon their host stars.

"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." 

The discovery has left astronomers mystified as they believed that gaseous planets can't form close to their star because they would evaporate. Most theorists also believed that the planets form farther from their stars before migrating inward. 

"The relatively young age of the Beehive cluster makes these planets among the youngest known," said Russel White, the principal investigator on the NASA Origins of Solar Systems grant that funded this study. "And that's important because it sets a constraint on how quickly giant planets migrate inward. And knowing how quickly they migrate is the first step to figuring out how they migrate."