Astronomers find Saturn-like baby planet hidden in dust
Astronomers have always found it challenging to observe planetary birth and development in protoplanetary discs. Maybe not anymore. A group of astronomers at the Center for Astrophysics | Harvard & Smithsonian (CfA) have found a novel method to find these elusive newborns. As a bonus, they also found "smoking gun" evidence of a small Neptune or Saturn-like planet lurking in one such disc.
Why does this story matter?
Observing the development of a young planet in the protoplanetary disc will tell us a lot about the process that leads to planet formation. However, this has always proved to be a challenge. The new method devised by astronomers gives us a chance to understand the presence of a young planet without direct observation. This could prove to be a watershed moment for astronomy.
Directly looking at protoplanetary discs is challenging
The protoplanetary discs where planets take shape are bands of gas and dust. These thick layers of gas and dust prevent astronomers from observing planet births as the emerging light is rather faint. "Directly detecting young planets is very challenging and has so far only been successful in one or two cases," said Feng Long, who led the project.
Astronomers have to look for clues to infer planetary birth
Since looking at young planets directly is not an option, astronomers have to look for clues to understand whether a planet is developing beneath the thick band of gas and dust. However, at times, finding the clues of planetary presence can be difficult. "We need new techniques to look at and support that a planet is there," says Long.
What did the new study find?
For the new study, Long revisited LkCa 15, a protoplanetary disc located 518 light years away in the Taurus constellation. Observations by the ALMA observatory previously have shown evidence of planetary formation in the disc. She used that data and found a dusty ring with two clusters of material circling within it at a distance of around 42 astronomical units.
The build-up of material indicated the presence of a planet
The material Long found appeared as a small clump and a larger arc that were separated by 120 degrees. It is this degree of separation that turned out to be vital. With the help of computer models, she examined the data to find out what is causing the build-up of material. She understood that their size and location matched the presence of a planet.
How did Long understand the presence of a planet?
Long's discovery is based on Lagrange points. Lagrange points are points of equilibrium for small objects under the influence of two massive orbiting bodies. In this case, the arc and clump of material detected are located at L4 and L5 Lagrange points. Hidden between them at 60 degrees is a small planet causing the accumulation of dust at L4 and L5.
The planet is 1-3 million years old
Based on the findings, the planet is roughly the size of Neptune or Saturn. It is one-three million years old, which is young when it comes to planets. However, locating planets in protoplanetary discs using this method will be hard, considering the technological constraints.
