Astronomers have caught a massive star in the act of formation, proving that massive stars form in a similar way to smaller stars, although with more sparks. They form when clumpy disks of material fall onto the newborn stars, generating bright flares.
The discovery, made by an international team and published in Nature Physics, focused on protostar S255IR NIRS, located 6,000 light-years from Earth and believed to have about 20 times the mass of the Sun. The researchers witnessed an explosive outburst within an accretion disk, confirming what simulations have recently suggested.
"These outbursts, which are several orders of magnitude larger than their lower mass siblings, can release about as much energy as our Sun delivers in over 100,000 years," said lead author Dr. Alessio Caratti o Garatti of the Dublin Institute for Advanced Studies in a statement. "Surprisingly, fireworks are observed not just at the end of the lives of massive stars, as supernovae, but also at their birth!"
The observation of the outburst was possible thanks to the Gemini Observatory, the European Southern Observatory (ESO), Calar Alto, and SOFIA. The data indicate a gas clump about twice as heavy as Jupiter was accelerated at supersonic speed and then ingested by the star.
Stars form from large clouds of gas and dust. As the center of it collapses into a protostar, some of the leftover gas flattens out into a disk where planets might eventually form. In the case of massive stars, the disk should be quickly dissipated by the strong light of the newborn star. However, it appears that in some cases, the disk becomes clumpy and those clumps fall onto the central object, making it even more massive.
"How accretion disks can survive around these massive stars is still a mystery, but the Gemini spectroscopic observations show the same fingerprints we see in lower mass stars," added Caratti o Garatti. "Probably the accretion bursts reduce the radiation pressure of the central source and allow the star to form, but we still have a lot of explaining to do in order to account for these observations."
There are still several unknowns regarding how stars form, but hopefully observations like this will help shine a literal light on this fascinating subject.