Birth of planets: new observations shed light on this little known phenomenon

Researchers at the University of Michigan may have discovered a protoplanet in June 2022, a phenomenon that astronomers are still struggling to observe.

"It is the beginning of a new era", Jean-François Gonzalez, researcher at the Astrophysical Research Center of Lyon and specialist of protoplanetary disks, is enthusiastic. The specialist reacts to Sciences et Avenir after the discovery of two protoplanets, as these stars in the making are called (in the context of research work in which he did not participate). "It is difficult to find them because most of the time young planets are hidden in dust disks" explains Jean-François Gonzalez. The observed number of planets in formation can be counted on the fingers of one hand.

Researchers from the University of Michigan have found this candidate protoplanet, around a very young star (V1295 Aql); their results will be published in the Astronomical Journal. Earlier the same year, in April 2022, astronomers detected another "baby planet", named AB Aurigae b, thanks to the Hubble and Subaru telescopes (Japan).

Observe the environment of the stars

The protoplanets are formed thanks to the accretion of dust and gas present around a star, this environment around the star is then called proto-planetary disk. After several million years of evolution, these protoplanets become planets.

To increase the chances of detecting these planetary embryos, the University of Michigan researchers increased the size of the observed sample and chose an unusual detection technique: polarimetry, which allows to observe objects by contrast with polarized light. Moreover, they preferred to observe the indices left by the planets rather than the planets themselves. These famous clues are the grooves and holes in the large rings composed of dust grains that form around stars. But these features only betray stars of less than 3 solar masses. "For more massive stars, the structures are quite different, rather spiral. Researchers are developing theories on different modes of formation" says Jean-François Gonzalez.

A common process

The astronomers were then able to image 44 targets with 80% of them surrounded by dust. Images that inform researchers about the dynamics in the accretion disks. They were also able to discover circumstances that seem unfavorable to the birth of planets: binary stars would form planets less often than single stars. A brown dwarf near a star could also be a brake on planetary formation.

Don't panic though, the planet formation process "is quite common and robust in space" says Jean-François Gonzalez. If future observations confirm that the object detected by the University of Michigan researchers is a protoplanet, it would be one of the few known exoplanets around a massive star.