Does one size fit all when it comes to star formation?

It is widely known (among astrophysicists at least!) that disks of accumulated matter are an essential component in the formation of low mass stars. These disks form when a rotating cloud of dust and gas collapses and, after formation, they direct material from the cloud onto a protostar at the centre. This protostar keeps accreting more and more material until it reaches a temperature high enough for it to fuse hydrogen. At this point it starts its life on the main sequence – the longest stage in the evolution of a star, and the one that our own Sun is currently at.

This all works fine for stars with less than about ten times the mass of the Sun, but above that limit our knowledge of the formation of stars gets a little hazy. In the above process, the protostar is constantly emitting light and therefore exerting pressure outwards. This radiation pressure works against the gravity that is causing more material to be added to the protostar. It is believed that no stars with a mass higher than about ten solar masses could form by the above method, as the radiation pressure from higher mass star would become more powerful than gravity and halt the formation. For this reason, it has been suggested that high mass stars form when two smaller stars merge, and not through the formation of disks like their less massive counterparts.

However, researchers working on the Very Large Telescope Interferometer at the European Southern Observatory have found evidence of a disk of material around a young star about twenty times as massive as the Sun. The star IRAS 13481-6124 is in the constellation Centaurus and it about ten thousand light years away from us.

Below you can see a video of IRAS 13481-6124 and its disk:

Kraus et al detected two bow shocks, caused by the interaction between an outflow of gas and dust from the star and the interstellar medium. The existence of this outflow is evidence for a disk around the star, as jets of material are a common feature of accretion disks around protostars.

This disk surrounding IRAS 13481-6124 is very hot and compact, and is very similar to disks observed around low mass stars, suggesting that the formation of high mass stars may not be so different after all.

Kraus, S., Hofmann, K., Menten, K., Schertl, D., Weigelt, G., Wyrowski, F., Meilland, A., Perraut, K., Petrov, R., Robbe-Dubois, S., Schilke, P., & Testi, L. (2010). A hot compact dust disk around a massive young stellar object Nature, 466 (7304), 339-342 DOI: 10.1038/nature09174


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