It’s rare that 3 million years old would be considered young, but that’s the case for a recently discovered exoplanet. The study of planets outside our solar system, called exoplanets, has exploded in the last decade with more than 5,000 confirmed discoveries to date. But most of those are older, fully mature planets comparable in age to the Earth, which is around 4.5 billion years old.
Recently, though, astronomers using NASA’s Transiting Exoplanet Survey Satellite (TESS) found a planetary baby, which is the youngest transiting planet discovered so far. It is called transiting because it was spotted when it passed in front of its host star, in an event called a transit, which astronomers can spot by looking for dips in brightness from the star.
“To our knowledge, this makes IRAS 04125+2902 b the youngest transiting planet discovered so far by a factor of about three,” the authors wrote in their paper in the journal Nature describing the finding.
Previous researchers have discovered young exoplanets that are between 10 million and 40 million years old, but not younger than that — in part because planets this young can still be forming from the disk of matter around their stars, called the protoplanetary disk, or because this disk is so dense with dust and gas that it hides the baby planets from view. In this case, there was something funny about the disk of matter around star IRAS 04125+2902 that enabled the scientists to see the exoplanet — the disk was skewed, being at an odd angle compared to the orbital plane of the star.
The young planet is very close to its star, with a year there lasting just under nine Earth days, but it is big with a radius more than 10 times that of Earth. That size means it could be on its way to becoming a type of planet called a super-Earth or a sub-Neptune, types which we don’t see in our solar system but are common beyond it.
The planet is also relatively nearby, at around 520 light-years away from Earth. That makes it a great place to study how planets form, the researchers write, and suggest that using a tool like the James Webb Space Telescope could help uncover more about this unusual star and its planet: “Given its close proximity to Earth [160 parsecs, or 520 light-years] and rare configuration, the system is a powerful environment for understanding early formation and migration.”
