Giant Planet Discovery Disrupts Solar System Models

Penn State researchers have uncovered a planet significantly larger than its ultracool host star, challenging previous beliefs about planet formation. Published in Science, their findings showcase a planet more than 13 times Earth’s mass orbiting a star nine times less massive than our sun. This discovery contradicts existing theories on small star planet formation, highlighting the first instance of a high-mass planet encircling an ultra-low-mass star.

Giant planet discovery disrupts solar system models: our cosmic understanding

Suvrath Mahadevan, the Verne M. Willaman Professor of Astronomy and Astrophysics at Penn State and a paper co-author, emphasized the discovery’s profound implications for our cosmic understanding. He highlighted that the planet’s existence challenges conventional knowledge, as the low-mass star where it orbits wouldn’t typically support such a heavy planet.

Mahadevan clarified the conventional process: stars form from gas and dust clouds, leaving behind disks around newborn stars that could potentially evolve into planets. However, in the case of the low-mass star LHS 3154, the expected mass in its planet-forming disk doesn’t align with the observed massive planet, prompting a reevaluation of planetary and stellar formation theories.

The team spotted this massive planet, dubbed LHS 3154b, using an astronomical tool called the Habitable Zone Planet Finder (HPF), developed at Penn State. This specialized instrument aims to detect planets orbiting cooler stars outside our solar system that might sustain liquid water, crucial for supporting life.

Giant planet discovery disrupts solar system models: planets around stars

Mahadevan explained that while finding such planets around stars like our sun is challenging, the detectability increases around ultracool stars due to their lower temperatures. Planets capable of hosting liquid water can orbit much closer to these stars compared to Earth’s distance from the sun. This proximity, combined with the ultracool star’s low mass, causes detectable shifts in the star’s light, indicating the presence of an orbiting planet.

He used an analogy, likening the star to a campfire: just as one must get closer to a cooling fire to stay warm, planets near colder stars need proximity for warmth. This proximity allows subtle changes in the star’s light spectrum, indicating the gravitational tug of an orbiting planet.

Located at the McDonald Observatory’s Hobby-Eberly Telescope in Texas, the HPF delivers some of the most precise infrared signal measurements from nearby stars.

Guðmundur Stefánsson, lead author and NASA Sagan Fellow in Astrophysics at Princeton University, noted the significance of the HPF’s role in discovering uncharted planets around low-mass stars. The instrument, developed from scratch, has been instrumental in uncovering new findings about this intriguing group of planets orbiting nearby stars.

New planets

While the HPF has previously confirmed new planets, the discovery of LHS 3154b surpassed all expectations. According to Megan Delamer, a Penn State astronomy graduate student and paper co-author, current theories struggle to explain the observations regarding the massive planet’s formation around star LHS 3154. The inferred heavy planetary core challenges existing models, suggesting a greater amount of solid material in the planet-forming disk than anticipated.

“This discovery is a litmus test for prevailing planet formation theories,” highlighted Mahadevan. “HPF was designed precisely for this purpose: to unravel the planetary formation process around the most prevalent stars in our galaxy and uncover these planets.”

The paper also includes contributions from various Penn State authors, including Eric Ford, Brianna Zawadzki, Fred Hearty, Andrea Lin, Lawrence Ramsey, and Jason Wright. Additionally, it involves researchers from Princeton University, the University of Leiden, the University of California, Irvine, the University of California, the Carnegie Institution for Science, Carleton College, The University of Texas at Austin, The University of Arizona, the University of Colorado, the California Institute of Technology’s Jet Propulsion Laboratory, Johns Hopkins University, Australia’s Macquarie University, and the Hobby-Eberly Telescope at UT Austin.

The study received funding from several sources, including the Center for Exoplanets and Habitable Worlds at Penn State, the Pennsylvania Space Grant Consortium, the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), and the Heising-Simons Foundation.

Read the original article on sciencedaily.

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