Elusive newborn planets can create telltale signs with their gravity, scientists say

Elusive newborn planets can create telltale signs with their gravity, scientists say

Artistic illustration of a small Saturn-like planet discovered in the LkCa 15 system, about 518 light-years from Earth (M.Weiss / Center for Astrophysics | Harvard & Smithsonian)

Artistic illustration of a small Saturn-like planet discovered in the LkCa 15 system, about 518 light-years from Earth (M.Weiss / Center for Astrophysics | Harvard & Smithsonian)

Scientists may have discovered a way to detect elusive newborn planets hidden in the disks around young stars, and it relies on the same gravitational phenomenon that allows the James Webb Space Telescope to remain in a stable position in deep space.

Researchers at Harvard’s Center for Astrophysics have detected a probable newborn exoplanet the size of Saturn around a star 518 light-years away in the constellation Taurus, as seen from Earth. Importantly, the key to the discovery was two important signs: a lump and a crescent of material in a ring around the star, separated from each other by 120 degrees.

“That degree of separation doesn’t just happen, it’s mathematically important,” Feng Long, a postdoctoral fellow at the Center for Astrophysics and lead author of a new exoplanet study, said in a press release. The study was published Wednesday in The letters of the astrophysical diary.

The important background is that newborn planets are very difficult to discover, and not simply because existing telescopes have a hard time viewing such small and faint objects directly alongside large bright stars at great distances.

“Detecting young planets directly is very challenging and has only been successful in one or two cases so far,” said Dr. Long. “The planets are always too faint to be seen because they are embedded in thick layers of gas and dust.”

Instead, researchers like Dr. Long look for signs of a planet in the disk of gas and dust orbiting young stars, known as the protoplanetary disk, from which planes are formed.

For the present study, Dr. Long used data from the Atacama Large Millimeter / submillimeter Array (ALMA), a network of 66 radio telescopes in northern Chile to examine in detail the structure of a protoplanetary disk known as LkCa 15. While studying an outer ring of material orbiting the star at a distance 42 times greater than Earth’s from the Sun, he noted the strange cluster and arc of material in their mathematically meaningful relationship.

“We’re seeing that this material isn’t just free-floating,” said Dr. Long. “It’s stable and has a preference where it wants to be placed based on the physics and objects involved.”

When a massive object such as a planet orbits another, such as a star, their gravity vanishes in certain regions, known as Lagrangian points, relative to the planet. Objects entering one of these points can remain in a relatively stable position relative to a planet, orbiting the point rather than the planet.

For the Earth, the first of these points, L1, exists approximately 1 million miles inside Earth’s orbit, between the Earth and the Sun, while the second, L2, exists one million miles directly behind the Earth. relative to the Sun. The James Webb Space Telescope orbits Earth’s L2 point, ensuring that the sensitive infrared telescope always has the Earth behind it as the telescope and planet both orbit the forming Sun.

A NASA illustration of the Lagrangian points relative to the Earth in relation to the Sun. These are areas where objects can remain in a stable position relative to the Earth.  (NASA)

A NASA illustration of the Lagrangian points relative to the Earth in relation to the Sun. These are areas where objects can remain in a stable position relative to the Earth. (NASA)

Jupiter, meanwhile, hosts two asteroid swarms, the Trojan asteroids, at its points L4 and L5, which are 60 degrees ahead, and behind Jupiter along the planet’s orbital path.

The lump and arc of material that Dr. Long found in the protoplanetary disk LkCa 15 are similarly captured in what the researchers believe are points L4 and L5 relative to a newborn planet, each 60 degrees away from the planet. and 120 degrees from each other.

When the researchers put the information into a computer simulation, they also suggested that the conditions were right for the presence of a planet, probably one the size of Neptune and Jupiter and a relatively young one of three million years.

The planet alone is an exciting discovery for the research team, according to Dr. Long, but it also hopes that the technique of searching for material captured in planetary Lagrangian points will catch on in the field of exoplanetary science, even if it is not the technique. simpler to implement.

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

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