Astronomers agree that planets are born in protoplanetary disks – rings of dust and gas that surround young, newborn stars. Although hundreds of such discs have been observed throughout the Universe, observations of planet birth and formation have proven difficult in these environments.

Now, astronomers at the Harvard and Smithsonian Center for Astrophysics have developed a new method to detect these newborn planets, and with it, they have discovered clear evidence of a small planet, similar to Neptune or Saturn, hiding in – a disk. The results are described in The Astrophysical Journal Letters.

“Direct detection of young planets is very difficult and so far has only been successful in one or two cases,” says Feng Long, a postdoctoral researcher at the Center for Astrophysics who led the new study. “Planets are always too faint for us to see because they are embedded in thick layers of gas and dust.”

Instead, scientists must hunt for clues to infer that a planet is developing beneath the dust.

New techniques to observe the birth of planets

“Over the past few years, we’ve seen many structures appear in discs that we think are caused by the presence of a planet, but could also be caused by something else,” says Long. “We need new techniques to look and argue that there is a planet out there.”

For his study, Long decided to re-examine a protoplanetary disk known as LkCa 15. Located 518 light-years away, the disk is in the sky in the constellation Taurus. Scientists previously reported evidence of planet formation in this disk using observations with the ALMA Observatory.

Long turned to new high-resolution ALMA data on LkCa 15, obtained mainly in 2019, and discovered two previously undetected faint features, he writes EurekAlert.

About 42 AU from the star — or 42 times Earth’s distance from the Sun — Long discovered a dusty ring with two separate, bright clumps of material orbiting inside it. The material was in the form of a small cluster and a larger arc and were separated by 120 degrees.

The new planet, about the size of Neptune or Saturn

Long examined the scenario with the help of computer models to find out what exactly caused the accumulation of material, and found that their size and location matched the pattern that indicated the presence of a planet.

The results show that the planet is about the size of Neptune or Saturn and is about one to three million years old (which is relatively young when it comes to planets).

Direct imaging of the tiny newborn planet may not be possible anytime soon due to technological constraints, but Long believes ALMA’s follow-up observations of LkCa 15 may provide additional evidence to support his planetary discovery.

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