New Planets Are Like Bees In A Hive.
Astronomers have discovered two gas giant planets orbiting stars in the Beehive cluster, a collection of about 1,000 tightly packed stars. Image credit: NASA/JPL-Caltech
When it comes to a swarm of stars, almost all amateur astronomers are familiar with M44 – the “Beehive”. It’s a well known and observed object.Now we have even more reason to take a look at this magnificent stellar collection. For the first time, NASA-funded astronomers have observed planets orbiting sun-like stars in this familiar cluster. This is the best evidence so far that planets are able to evolve in a dense stellar neighborhood. While they aren’t conducive to life, can you image the night skies?!
The two newly discovered planets are “hot Jupiters” – massive and extremely hot – locked in a tight orbit around their parent stars. Each one circles a different sun-like star in the Beehive, a loose galactic star cluster consisting of about a thousand individual members. Each of these stars were born about the same time from the same cloud of material and share the same basic chemical composition. Rather than spread out through space, this group stayed loosely bound by mutual gravitational attraction.
“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.”
This image of the Beehive star cluster points out the location of its first known planets, Pr0201b and Pr0211b, or, as astronomers call them, the first 'b's' in the Beehive. Image copyright: Stuart Heggie
To put a smile into the situation, 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,” 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.
According tot he news release, 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. The team used the telescope to measure the slight gravitational wobble the orbiting planets induce upon their host stars. Past studies had turned up two planets around massive stars in cluster, but this is the first time planets have been observed around stars similar to the Sun.
“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.”
Now that we know they are there, we have even more questions – burning ones like why do hot Jupiters orbit so close to their stars? One of the most common theories is they first evolved further away and then moved inward due to an eccentric orbit. “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.”
Why the “b’s” in the Beehive? The astronomers suspect the planets formed in M44 because it is a metal-rich cluster. Its members have more heavy elements, like iron, than our Sun. According to White, “Searches for planets around nearby stars suggest that these metals act like a ‘planet fertilizer,’ leading to an abundant crop of gas-giant planets. Our results suggest this may be true in clusters as well.”
Original Story Source: JPL/NASA News Release.
