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

Scientists may have discovered a way to detect elusive newborn planets hiding in the disks around young stars, and it’s based on the same gravitational phenomenon that keeps the James Webb Space Telescope at a stable position in deep space.

Researchers from the Harvard Center for Astrophysics have detected a likely 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 prominent signs – a clump and a crescent of material in a ring around the star, separated from each other by 120 degrees.

“This degree of separation does not occur by chance, it is mathematically significant,” said Feng Long, postdoctoral researcher at the Center for Astrophysics and lead author of a new study on the exoplanet, in a press release. The study was published Wednesday in Letters from the Astrophysical Journal.

The important context is that newborn planets are very difficult to discover, and not just because existing telescopes struggle to directly image relatively small, dim objects next to large, bright stars at a great distance.

“Direct detection of young planets is very difficult and has so far only been successful in one or two cases,” Dr Long said. “The planets are always too faint for us to see because they are embedded in thick layers of gas and dust.”

Instead, researchers like Dr Long are looking for signs of a planet in the disk of gas and dust that orbits young stars, known as the protoplanetary disk, from which planes form. .

For the current study, Dr. Long used data from the Atacama Large Millimeter/submillimeter Array (ALMA), an array of 66 radio telescopes in northern Chile, to examine in detail the structure of a protoplanetary disk known as the name LkCa 15. While studying an outer ring of matter orbiting the star at a distance 42 times that of Earth from the Sun, she noticed the strange cluster and arc of matter in their mathematically significant relationship.

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

When a massive object like a planet orbits another, like a star, their gravity cancels out at certain regions, called Lagrange 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 Earth, the first of these points, L1, exists about 1 million kilometers inside Earth’s orbit, between the Earth and the Sun, while the second, L2, exists a million miles away. kilometers directly behind the Earth from the Sun. The James Webb Space Telescope orbits Earth’s L2 point, ensuring the sensitive infrared telescope always has Earth at its back as both the telescope and the planet orbit the forming Sun.

A NASA illustration of Lagrange points relative to the Earth with respect to the Sun. These are areas where objects can remain in a stable position relative to the Earth.


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

The clump and arc of material that Dr Long found in protoplanetary disk LkCa 15 is also caught in what researchers believe are points L4 and L5 relative to a newborn planet, each at 60 degrees from the planet and 120 degrees apart.

When the researchers fed the information into a computer simulation, it also suggested conditions were right for a planet to be present, likely one between the size of Neptune and Jupiter and a relatively young one between one and three million years old. ‘years.

The planet alone is an exciting discovery for the research team, according to Dr Long, but she also hopes the technique of finding material captured in planetary Lagrangian points will spread into the field of exoplanetary science, even if it’s not the easiest technique. to implement.

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

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