Star formation theories challenged by new telescope discovery

[Judi Lynn]

Star formation theories challenged by new telescope discovery
Reuters
Nov 21, 2014

SANTIAGO – Theories about how massive stars are born could be revised after astronomers in Chile found evidence that the dust and gas surrounding a young star could survive bombardment by the star’s own radiation.

The Atacama Large Millimeter/submillimeter Array (ALMA) observed a young star in the constellation of Scorpius that has a mass about 15 times greater than that of the sun.

A star forms from a collapsing gas cloud. The nascent star attracts more gas and dust due to gravity, gradually creating a spinning “accretion disk” from which planets can be formed. Some of that material is fired off in supersonic jets of gas.

Particularly high mass stars, though, emit ultraviolet radiation in their birth that many astronomers have thought until now would destroy the disk and jets and impede the star’s formation.

More:
http://www.japantimes.co.jp/news/2014/11/21/world/science-health-world/star-formation-theories-challenged-by-new-telescope-discovery/#.VG7uQ2dxnIV

[Igel]

1. How so?

What's counteracting the radiation pressure to clear out the dust?

Does radiation pressure add up to enough to counter Poynting-Robertson? Seems unlikely.

Magnetic field strength?

Don't like pop sci much of the time. Often the writers more interested in saying, "Ha! Ha! The experts are wrong so they're no smarter than we are!" than actually saying anything that actually informs.

[DreamGypsy]

2. Here's the original ALMA press release - Chilean astronomers using ALMA discover new clues...

... about massive star formation: http://www.almaobservatory.org/en/press-room/press-releases/773-chilean-astronomers-using-alma-discover-new-clues-about-massive-star-formation

(a much more satisfying title)

Massive stars emit a large amount of ultraviolet radiation that destroys the molecules and dust surrounding the star and creates ionized gas, which in turn impedes the star's growth process. This is why previous theories have suggested that the model of a small star forming from a protoplanetary gas and dust disk isn’t applicable to high mass stars. According to the study published today, dust and molecular gas can survive the destructive effects of ultraviolet radiation that accompanies the birth of a massive star.

The young star that was studied, G345.4938+01.4677, is located in the Scorpius constellation and has a mass 15 times greater than the Sun. This is where scientists made at least three important discoveries. "The first thing we detected is a supersonic stream emerging from the star forming inside the ionized gas region. This suggests that the accretion disk and gas stream are strong enough to survive despite the damage caused by ultraviolet light," explained Andrés Guzmán, the study’s principal researcher and a postdoctoral fellow at the University of Chile.

ALMA's cutting-edge technology enable astronomers to get, for the first time, evidence of the effect of electric fields on the emission of lines of hydrogen. "The detection of this so called Stark effect was possible due to the high density of gas around this star and ALMA's extraordinary sensitivity," said Guido Garay, Director of the Astronomy Department at the University of Chile and a co-author of the study.

"Thanks to the sensitivity and high angular resolution of ALMA we could for the first time detect a rotating disk around a massive star and effects of electric fields on the hydrogen line emission from a jet from the same star", added Lars Nyman, Head of Science Operations at the JAO ALMA Observatory and co-author of the study.

Fig. 2: Image in the infrared spectrum near G345.4938+01.4677 obtained by the VVV project using the VISTA telescope at Cerro Paranal Observatory. In the lower left corner is a close-up of the central area, showing the cavity created by the jet stream. In the center of the image the young high mass star appears as a small and weak red spot.


The research results were published in The Astrophysical Journal.