Tuesday, September 20, 2022

Elusive newborn planets can make telltale signs with their gravity

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Scientists may have discovered a way to spot elusive newborn planets hiding in the discs around young stars, and it’s based on the same gravitational phenomenon that allows the James Webb Space Telescope to stay in a stable position in space.

Researchers at the Harvard Center for Astrophysics have spotted a likely newborn Saturn-sized exoplanet around a star 518 light-years distant in the constellation of Taurus, as seen from Earth. Importantly, key to the discovery were two important signs – a blob and a crescent of material in a ring around the star, separated by 120 degrees.

“This level of separation doesn’t just happen — it’s mathematically important,” Feng Long, a postdoctoral researcher at the Center for Astrophysics and lead author of a new study on the exoplanet, said in a press statement. The study was published in Wednesday The Letters of the Astrophysical Journal.

The important background is that newborn planets are very difficult to detect, and not just because existing telescopes have a hard time imaging such relatively small and faint objects next to large bright stars at great distances.

“Direct detection of young planets is a major challenge and has only been successful in one or two cases so far,” said Dr. Long. “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 for signs of the presence of a planet in the disk of gas and dust orbiting young stars known as the protoplanetary disk from which plans are formed.

For the current study, Dr. Long data from the Atacama Large Millimeter/submillimeter Array (ALMA), a network of 66 radio telescopes in northern Chile, to take a detailed look at the structure of a protoplanetary disk known as LkCa 15 Outer ring of material containing the star in a Orbiting at a distance 42 times Earth’s orbits the Sun, she noticed the strange accumulation and arc of material in their mathematically significant relationship.

“We see that this material doesn’t just float around freely,” said Dr. Long. “It’s stable and has a preference for where it wants to be based on the physics and the objects involved.”

When one massive object like a planet orbits another like a star, its gravity cancels out relative to the planet at certain regions known as Lagrange points. 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 such point, L1, exists about 1 million miles within Earth’s orbit between the Earth and the Sun, while the second, L2, exists a 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 Earth’s back as the telescope and planet both orbit the Sun in formation.

Jupiter, on the other hand, hosts two swarms of asteroids, the Trojan asteroids, at its L4 and L5 points, which sit 60 degrees in front of and behind Jupiter along the planet’s orbit.

The lump and the sheet of materials that Dr. Long found in the protoplanetary disk LkCa 15 are also trapped in points L4 and L5, which the researchers believe are newborn planets, each 60 degrees from the planet and 120 degrees apart.

When the researchers fed the information into a computer simulation, it also suggested that the conditions were right for the existence of a planet, likely one between the sizes of Neptune and Jupiter and a relatively young age of one to three million years.

The planet alone, according to Dr. Long made an exciting discovery for the research team, but she also hopes the technique of searching for material trapped in planetary Lagrange points will gain traction in the field of exoplanet science, even if it’s not the easiest technique to implement.

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

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