by Astronomers have discovered a giant extrasolar planet, or “exoplanet,” orbiting an ultrasolar dwarf star that is far too small to host such a world, challenging scientists’ models of how planets and planetary systems are born.
The planet in question, named LHS 3154 b, is 13 times as massive Worldmeaning it has a mass similar to the solar system’s ice giants Neptunebut it closely orbits a tiny dwarf star, which is nine times less massive than the sun.
This means the ratio of the Neptune-like world to its parent star — LHS 3154, located around 51 light year away – it is 100 times greater than the mass ratio between the Earth and the sun, which researchers did not think was possible. This is the first time that a planet with such a large mass has been discovered around one of the smallest stars in the universe.
“This discovery really drives home the point of how little we know about it the universe” research co-author and Penn Verne State University M. Willaman Professor of Astronomy and AstrophysicsSuvrath Maadevan, said in a statement. “We wouldn’t expect such a massive planet around such a low star.”
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Challenging how the stars and planets were born
Stars are formed when huge clouds of gas and dust gather into dense patches that grow until they eventually collapse under their own gravity. This leaves an infant star surrounded by a disk of leftover material called a “protoplanetary disk.”
As the name suggests, it is from the remaining disk of material that scientists believe planets will eventually form. The amount of material left over from star formation sets a limit to how large these potential planets can be.
The team concluded that LHS 3154 b has such a heavy planetary core that the planet-forming disk from which it originated would have to retain a lot of solid material. In short, it would be that there would be more material than what current models predict is possible, research coauthor and astronomy explained Penn State graduate student Megan Delamer.
Therefore, this particular discovery exoplanet also raises questions about the formation of the stars. This is because the dust-to-mass and dust-to-gas ratios of the original protoplanetary disk of LHS 3154 would have had to be ten times higher than predicted to give birth to a Neptune-like world. huge with LHS 3154 b. .
“The planet-forming disk around the low-mass star LHS 3154 is not expected to have enough solid mass to form this planet,” explained Mahadevan. “But it’s out there, so now we have to reexamine our understanding of how planets and stars form.”
The Habitable Zone Planet Finder is exceeding expectations
Mahadevan and colleagues detected the exoplanet LHS 3154 b using the Habitable Belt Planet Finder (HPF), an astronomical spectrograph at the Hobby-Eberly Telescope at the McDonald Observatory in Texas. HPF is designed to detect exoplanets orbiting some of the coolest stars in the The Milky Way.
The particular focus of the instrument, which Mahadevan actually helped build alongside a team, is on the planets that are neither too close nor too far from their stars to host liquid water, life’s primary necessity. The planets that sit in the so-called would be habitable zone around their stars.
Such planets are not easy to see, in part because the habitable zone of cool stars is much closer to those stars than the zone in our Solar system, for example. This means that these worlds are often obscured by light from their relatively small parent stars.
Furthermore, these planets are expected to be small themselves, making them more difficult to detect.
“Think of it like the star is a campfire. The cooler the fire gets, the closer you get to that fire to stay warm,” Mahadevan said. “The same is true for planets. If the star is cooler, a planet will have to be closer to that star if it is hot enough to have liquid water.
“If a planet has an orbit that is close enough to its ultrasound star, we can detect it by seeing a very noticeable change in the color of the star’s spectrum or light as it is pulled by an orbiting planet.”
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The detection of LHS 3154 b is important for the HPF as it demonstrates the instrument’s ability to deliver important exoplanet results, with a team member and NASA Sagan Fellow in Astrophysics at Princeton University saying that this result exceeds all expectations for the instrument.
“What we discovered provides a very large test case for all the theories of planet formation,” Mahadevan said. “This is exactly what we built HPF to do, to find out how to find the most common stars in our galaxy – and the planets.”
The team’s research was published on 30 November in the journal Science.
