The amount of material present in an astrolabe plays a crucial role in determining the potential size of a planet. Protoplanetary disks require sufficient amounts of primordial material to facilitate the formation of planets around newborn stars, however, a recently discovered exoplanet appears to defy this established theory and has scientists perplexed.
The growing list of planets that shouldn't exist now includes LHS 3154b, a Neptune-sized exoplanet that appears too large for its host star. LHS3154 is an "ultra-cool" dwarf star with a mass 9 times less than the sun. The planet itself is at least 13.2 times more massive than Earth. However, theoretical models have previously ruled out the possibility of such massive objects forming around low-mass stars.
The discovery of LHS3154b was made by a team of scientists led by Suvrath Mahadevan using the Habitable Zone Planet Explorer (HPF), an astronomical spectrograph developed at Pennsylvania State University. Mahadevan, a professor of astronomy and astrophysics and co-author of the Science paper, stressed that the new exoplanet highlights how "very limited" our understanding of the universe is.
HPF is explicitly designed to identify planets orbiting the coldest stars in the outer solar system. Detecting such planets is a considerable challenge because they must stay close to their host stars to maintain temperatures suitable for liquid water. Mahadevan explained that HPF can successfully detect planets in relatively close orbits around ultracool stars. Stars form from massive clouds of gas and dust. After a star is born, residual gas and dust begin to orbit the star and eventually form planets.
The researchers used computer simulations to confirm that the increased "planet-to-star mass ratio" determined by the HPF was not an expected result of a planetary system orbiting LHS 3154. The paper states that the existence of LHS3154b in this universe can be scientifically explained only if the mass of the protoplanetary disk is 10 times the mass of the host star.
The scientists noted that objects like LHS 3154b may be "extremely rare" based on ongoing surveys by the HPF and other instruments. Mahadevan said this discovery is a special test case for all existing theories of planet formation, which fits the purpose of the HPF.