Researchers at Penn State University have discovered LHS 3154b, an unusually massive planet orbiting an ultra-cold dwarf star. The discovery contradicts current theory and prompts a re-evaluation of how stars and planets form.
The discovery of a planet too large for the sun calls into question what we previously understood about planets and their formation in the solar system, according to researchers at Penn State University.
In a paper published in the same journal on November 30th, science, researchers report the discovery of a planet more than 13 times the mass of Earth orbiting the “ultracool” star LHS 3154, which itself has a mass nine times less than that of the Sun. The mass ratio between the newly discovered planet and its host star is more than 100 times higher than that between the Earth and the Sun.
This video is an artistic representation of the newly discovered star system LHS 3154. This system contains planets that are much more massive relative to the Sun than current models predict.Credit: Abigail Hope Minnich
challenge current theory
The discovery reveals that the most massive planet known is in a close orbit around an ultracool dwarf star, the least massive and coldest star in the universe. The discovery goes against current theory predicting planet formation around small stars, and suggests that such a high-mass planet orbiting such a low-mass star has only been discovered. It’s my first time.
“This discovery really drives home how much we don’t know about the universe,” said Subrath Mahadevan, the Vern M. Willaman Professor of Astronomy and Astrophysics at Penn State University and co-author of the paper. Told. “You wouldn’t expect such a massive planet to exist around such a low-mass star.”
formation of stars and planets
He explained that stars form from large clouds of gas and dust. After a star forms, the gas and dust remain as a disk of matter that orbits the newborn star and may eventually grow into a planet.
“The planet-forming disk around 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.”
Penn State researchers Subrath Mahadevan and Megan Delamar describe the discovery of a giant planet orbiting a small star.Credit: Penn State University
Detection using HPF
Researchers discovered the oversized planet, named LHS 3154b, using an astronomical spectrometer built at Pennsylvania State University by a team of scientists led by Mahadevan. The instrument, called the Habitable Zone Planet Finder (HPF), is designed to detect planets orbiting the coolest stars outside our solar system, with their surfaces containing liquid water, a key ingredient for life. may exist.
Detection of planets around ultracool stars
Detecting such planets around stars like the Sun is extremely difficult, but the low temperatures of ultracold stars mean that planets that can have liquid water on their surfaces are relatively rare compared to Earth or the Sun. That means it is much closer to the star. Mahadevan explained that the shorter distances between these planets and their stars, combined with the low mass of the ultracool stars, provide a detectable signal that signals the planet’s presence.
“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.”
Importance of HPF
The HPF, installed on the Hobby-Eberly Telescope at McDonald Observatory in Texas, provides the most accurate measurements to date of infrared signals from nearby stars.
“Our discoveries with HPF were particularly special because HPF is a new instrument that we designed, developed and built from scratch with the purpose of studying the unknown planetary population around the lowest mass stars. That’s why,” says Guðmundur Stefansson. NASA Sagan Fellow in Astrophysics princeton university He was the first author on the paper, helped develop HPF, and worked on the research as a graduate student at Penn State. “Now we are reaping the benefits and learning new and unexpected aspects of this exciting group of planets orbiting some of our closest stars.”
This equipment already provides important information. Discovery and confirmation Stefansson explained that the discovery of planet LHS 3154b exceeded all expectations.
Reconsidering planet formation theory
“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 very exciting.” said Megan Delamar, a Penn State astronomy graduate student and co-author of the paper. paper. “Current theories of planet formation have difficulty explaining what we’re seeing.”
In the case of the giant planet discovered orbiting the star LHS 3154, the team’s measurements inferred that the massive planet’s core contained a larger amount of solid material in the planet-forming disk than current models predict. Delamar explained. This discovery also makes sense because the dust mass and dust-to-gas ratio in the disk surrounding a star like LHS 3154 (when the star is young and newly formed) must be 10 times higher, so this It also casts doubt on our understanding. It was larger than anything observed to form a planet as massive as the one the research team discovered.
“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.”
Reference: “A Neptune-mass exoplanet Near-orbits around very low-mass stars challenge formation models” Guðmundur Stefánsson, Suvrath Mahadevan, Yamila Miguel, Paul Robertson, Megan Delamer, Shubham Kananodia, Caleb I. Cañas, Joshua N. Winn, Joe P. Ninan, Ryan C. Terryn, Ray Holcomb, Eric B. Ford, Brianna Zawadzki, Brendan P. Bowler, Chad F. Bender, William D. Cochran, Scott Didamus, Michael Endle, Connor Frederick, Samuel Halverson, Fred Harty, Gary J. Hill, Andrea SJ Lin, Andrew J. Metcalf, Andrew Monson, Lawrence Ramsey, Arpita Roy, Christian Schwab, Jason T. Wright, Gregory Zeiman, November 30, 2023 Day, science.
DOI: 10.1126/science.abo0233
Other Penn State authors on the paper are Eric Ford, Brianna Zawadzki, Fred Harty, Andrea Lin, Lawrence Ramsey and Jason Wright. Other authors of the paper are Joshua Winn of Princeton University, Yamila Miguel of Leiden University, Paul Robertson of the University of California, Irvine, Ray Holcomb of the University of California, and Shubham Kanodia of the University of California. Carnegie Institute for ScienceCaleb Cañas of NASA Goddard Space Flight Center, Joe Ninan of India’s Tata Institute of Fundamental Research, Ryan Therian of Carleton University, Brendan Bowler, William Cochran, Michael Endle, and Gary Hill of the University of Texas at Austin; Chad Bender of the University of Arizona, Scott Didames, Connor Fredrick, and Andrew Metcalfe of the University of Colorado, Samuel Halverson of the Jet Propulsion Laboratory of California Institute of Technology, Andrew Monson of the University of Arizona, Arpita Roy of Johns Hopkins University, Australia – Christian Schwab of Macquarie University and Gregory Zeiman of the Hobby-Eberly Telescope at the University of Texas at Austin.
This research received funding from the Penn State Center for Exoplanets and Habitable Worlds, the Pennsylvania Space Grant Consortium, the National Aeronautics and Space Administration, the National Science Foundation, and the Heising-Simons Foundation.