Astronomers have identified a young planetary system where the disk is warped, offering a clear view of a planet that is just three million years old.
Planet-forming disks are a natural outcome of angular momentum conservation as molecular clouds collapse to form stars. During this collapse, the clouds begin to spin faster, eventually flattening into a disk shape. These "protoplanetary disks" are thought to form planets over roughly 10 million years, after which the disk material dissipates, leaving behind a mature planetary system.
Because of these prohibitive timescales, astronomers cannot follow a single planet through multiple developmental stages. To understand how planets are born and grow to their adult state, astronomers have to combine the planets' life story from snapshots of multiple planetary systems, each observed at a different age. For systems younger than a few million years, astronomers can typically only observe the protoplanetary disk because it often obscures the planets and can't be detected. Conversely, most of the fully formed exoplanets astronomers detect are in systems that are billions of years old and in which the disk is long gone.
The discovery, "A giant planet transiting a 3Myr protostar with a misaligned disk," was published in the most recent edition of Nature and featured on the NASA Discovery page. Led by Madyson Barber and Andrew Mann from the University of North Carolina, with assistance from University of New Mexico Department of Physics & Astronomy Associate Professor Diana Dragomir, the research has unveiled a rare example of a young, massive planet orbiting the star IRAS 04125+2902.
This system resides in the Taurus-Auriga Molecular Cloud, a stellar nursery home to hundreds of newly-formed stars. This three million-year-old infant planet is the youngest transiting planet detected to date, roughly equivalent to a 10-day-old newborn on human timescales. The host star retains its protoplanetary disk, distinguishing it from other known planetary systems.
"This planet is unique because, while it is just three million years old and the disk within which it formed is still present, that disk is misaligned with the orbit of the planet, allowing us an unexpected peek at this "toddler" planet itself," explained UNM Department of Physics & Astronomy Associate Professor Diana Dragomir, who is a co-author on the paper. "This rare gem of a system will undoubtedly be studied with many kinds of telescopes to answer questions about what planets are like at this very young age."
Previously, systems like this were thought to be nearly impossible to detect. By three million years, it was uncertain if planets had developed to a detectable degree. For context, Earth took 10-20 million years to form, though gas giants such as this newborn planet are believed to form much faster.
Additionally, if the disk and planet were aligned, the disk would obstruct astronomers' view. Indeed, it is generally expected that planets will align with the disk from which they formed. However, in this case, the inner portion of the disk is depleted, and the outer disk is tilted relative to both the planet and its host star.
This discovery challenges current theories of planet formation timescales and the relationship between planets and their parent disks. It also offers a unique opportunity to study a planet shortly after its formation.
The University of New Mexico helped support this research.
