A world in the making revealed 518 light-years away with a new method


Astronomers from the Harvard and Smithsonian Center for Astrophysics have developed a new way to detect newborn planets, with evidence of a world like Neptune or Saturn lurking in a disk.

The results are described in The Astrophysical Journal Letters.

“Direct detection of young planets is very challenging and has only been successful in one or two cases so far,” says Feng Long, a postdoctoral fellow in 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 look for clues to infer that a planet is developing beneath the dust.

“In recent years, we’ve seen a lot of structures appear in the disks that we think are caused by the presence of a planet, but could also be caused by something else,” says Long. it’s a statement. “We need new techniques to look at and support that there is a planet there.”

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

Long delved into the new high-resolution ALMA data on LkCa 15, obtained mainly in 2019, and discovered two faint features that had not previously been detected.

About 42 astronomical units from the star, or 42 times the distance between Earth and the Sun, Long discovered a dusty ring with two separate, bright clumps of material orbiting within it. The material took the form of a small pool and a larger arc, and they were 120 degrees apart.

Long examined the scenario with computer models to find out what was causing the accumulation of material and found that its size and location matched the model for the presence of a planet.

“This arc and group are about 120 degrees apart,” she says. “That degree of separation doesn’t just happen, it matters mathematically.”

Positions in space known as Lagrange pointswhere two moving bodies, such as an orbiting star and planet, produce enhanced regions of attraction around themselves where matter can accumulate.

“We’re seeing that this material is not just free-floating, it’s stable and has a preference for where it wants to be based on the physics and objects involved,” Long explains.

In this case, the arc and the mass of material detected by Long are located at the Lagrange points L4 and L5. Hidden at 60 degrees between them is a small planet that causes dust to accumulate at points L4 and L5.

The results show that the planet is about the size of Neptune or Saturn, and between one and three million years old. That’s relatively young when it comes to planets.

Direct imaging of the tiny newborn planet may not be possible any time soon due to technological limitations, but Long believes further observations of LkCa 15 with ALMA they may provide additional evidence to support their planetary discovery.

He also hopes that his new approach to detecting planets, with material that preferentially accumulates at Lagrange points, be used in the future by astronomers.

“I hope this method can be widely adopted in the future,” he says. “The only caveat is that this requires very deep data as the signal is weak.”

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