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The artist’s illustration depicts a potential view of a planet heading toward a low-mass host star. The planet, named LHS 3154b, likely has a Neptune-like composition.
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Astronomers are casting doubt on theories of planet formation after discovering an exoplanet that technically doesn’t exist.
The planet is about the same mass as Neptune, more than 13 times more massive than Earth, and was detected orbiting an ultra-cool M dwarf star called LHS 3154, which is nine times smaller than the Sun. . M-type dwarfs are the smallest and coolest type of star.
The planet, called LHS 3154b, moves closely around its star, making one orbit every 3.7 Earth days, making it the most massive known planet in a close orbit around one of the coldest low-mass stars in the universe. According to the latest report.The study was published Thursday in the journal science. It upends the way scientists understand the formation of planetary systems.
pennsylvania state university
This diagram compares the sizes of the Sun and Earth with the smaller, cooler star LHS 3154 and its orbiting planet, LHS 3154b.
“This discovery really drives home how little we know about the universe,” said study co-author Subrath Mahadevan, the Vern M. Willaman Professor of Astronomy and Astrophysics at Penn State. he said in a statement. “You wouldn’t expect such a massive planet to exist around such a low-mass star.”
a star is born Arising from large clouds of gas and dust, the remaining material forms a disk around the star, after which planets are born. The amount of material present in the disk around a star determines the mass of planets that form around the star. The material of the disk largely depends on the mass of the star.
For example, small M dwarfs are the most common throughout the Milky Way, and they usually have small rocky planets orbiting them, rather than gas giants.
“The planet-forming disk around the low-mass star LHS 3154 is not expected to have enough solid mass to form this planet,” Mahadevan said. “But it already exists, so now we need to reconsider our understanding of how planets and stars form.”
The planet orbits a star about 51 light-years from the Sun and was discovered using the Habitable Zone Planet Finder (HPF) on the Hobby-Eberly Telescope at McDonald Observatory in Texas.
A team of scientists led by Mahadevan built an HPF designed to detect planets orbiting within the habitable zones of small, cold stars. The habitable zone is where a planet is just the right distance from a star that is warm enough to have liquid water on its surface and possibly support life.
The lower surface temperatures of small stars mean that planets can orbit more closely and still maintain fragile elements such as water on their surfaces. And when a planet orbits closely around a star, the gravitational pull between both bodies creates a noticeable wobble, which HPF can detect in infrared light.
“Think of the star like a campfire. The colder the fire, the closer you need to get to it to stay warm,” Mahadevan said. “The same goes for planets. If the star is cooler, the planet needs to be moved closer to its star to make it warm enough for liquid water to exist. If the planet has an orbit close enough to its ultracool star, If so, we can detect it by looking at the very subtle changes in a star’s spectrum, or the color of its light, as it is pulled by an orbiting planet.”
Study co-author and astronomy graduate student Megan Delamar said that based on modeling and analysis, the research team believes the planet has a heavy core and is too close to the star to exist in a planet-forming disk. He believes more solid material will be needed than is possible. at Pennsylvania State University.
The researchers estimate that the amount of dust in the disk would need to be at least 10 times greater than what is typically seen in disks around low-mass stars.
“Our current theories about planet formation have difficulty explaining what we’re seeing,” Delamar said in a statement. “Based on current survey work with HPF and other instruments, objects like the one we discovered are likely to be very rare, so detecting it is really exciting.”
Several giant planets have been discovered orbiting low-mass stars. Planet GJ 3512 b discovered in 2019but their orbital period is much longer, and the planets do not orbit the star as closely.
“What we discovered provides an extreme test case for all existing theories of planet formation,” Mahadevan said. “This is exactly what we built his HPF for: discovering how the most common stars in the galaxy form planets, and finding those planets.”