Astronomers have discovered a fast-forming exoplanet around a young star, challenging existing theories about the pace of planetary formation. The planet, formed in just 3 million years, orbits a future orange dwarf star and weighs 10 to 20 times the mass of Earth, making it one of the youngest such bodies observed outside our solar system.
This discovery, located within the Milky Way galaxy about 520 light-years from Earth, suggests that planets can form much quicker. For perspective, Earth took 10 to 20 million years to form. The star, less hot and less massive than our sun, retains about 70% of its mass and shines at half its luminosity.
Madyson Barber, a graduate student at the University of North Carolina at Chapel Hill and lead author of the study published in Nature, highlighted this finding. “This discovery confirms that planets can form within 3 million years, a timeframe not previously confirmed,” Barber explained. UNC astrophysicist Andrew Mann, a study co-author, emphasized the unknowns in planetary formation timescales, especially for giant planets requiring substantial gas from their protoplanetary disks.
The planet, IRAS 04125+2902 b or TIDYE-1b, completes an orbit around its star every 8.8 days at a proximity, similar to the distance between Mercury and the sun in our solar system. Its size and density fall between Earth and Neptune, with a diameter about 11 times greater than Earth’s.
Researchers believe the planet initially formed further from its star before migrating inward, challenging the theory that large planets cannot quickly form close to their stars due to rapid disk dissipation.
NASA’s Transiting Exoplanet Survey Satellite (TESS) detected the planet using the transit method, which involves observing dips in starlight when a planet crosses in front of its host star from Earth’s viewpoint. Madyson Barber, the study’s lead author, remarked, “This is the youngest-known transiting planet and matches the youngest planets discovered.”
Astronomers typically use this method to detect less massive planets, as they often directly image more massive ones. The early detection of this planet overturns previous beliefs that young transiting planets were undetectable due to obstructive protoplanetary disks. Barber explained that a warped outer disk allowed a clear view, enabling this significant observation.
