The rare 'baby' planet is just 5 to 10 million years old.
Nearly 500 light-years from Earth, in the Scorpio constellation, lies the youngest fully-formed exoplanet ever detected by astronomers. The newfound planet, K2-33b, is still pretty young — just 5 to 10 million years old — and if we compared it to our solar system, it most resembles Neptune, although one major difference is that it orbits its host star every 5 days — compared to Neptune’s 60,190.
Astronomers discovered K2-33b using NASA’s Kepler Space Telescope, or K2, as well as the W.M. Keck Observatory on Mauna Kea, Hawaii. How planets form, especially in their early years, is still a fairly mysterious process, so finding a planetary system during its infant stage is a pretty big deal.
"The newborn planet will help us better understand how planets form, which is important for understanding the processes that led to the formation of Earth," said co-author of the paper, Erik Petigura of Caltech, in a NASA news release.
K2-33b’s star is only surrounded by a thin veil of planetary debris of dust and gas — called the protoplanetary disk — which is a sign that the planet-formating phase is coming to an end.
"Initially, this material may obscure any forming planets, but after a few million years, the dust starts to dissipate," said co-author Anne Marie Cody of NASA's Ames Research Center in California's Silicon Valley. "It is during this time window that we can begin to detect the signatures of youthful planets with K2."
In other words, there may be more planets than just K2-33b!
Astronomers also noticed something very strange about K2-33b: it orbits very close to its star — nearly 10 times closer than Mercury is to the sun. As you can imagine, that makes it hot. But how massive planets like K2-33b end up in these small orbits is a process astronomers are still trying to understand.
Previous studies suggested it takes hundreds of millions of years to migrate from a distant orbit into a close one, but K2-33b isn’t old enough for that. So how did the planet get where it is?
There are two main ideas: it could have traveled there by a process called disk migration, which only takes hundreds or thousands of years; or the planet could have formed “in situ” — right in place.
"It is extremely rare to find a planet at this stage of its infancy, and gives us a unique opportunity to try and understand more about how all planets form and develop, including Earth," explained Dr. Sasha Hinkley of the University of Exeter, one of the researchers behind the discovery, in a press release.
Trevor David of Caltech in Pasadena, lead author of the study published online in the scientific journal Nature, concluded, "The question we are answering is: Did those planets take a long time to get into those hot orbits, or could they have been there from a very early stage? We are saying, at least in this one case, that they can indeed be there at a very early stage."