ALMA Scan Reveals Embryonic Star Formation
July 10, 2013

New Observations Give Peek Into Massive Star Formation

[ Watch the Video: Zooming in on the Birth of a Monster Star ]

Lee Rannals for - Your Universe Online

Astronomers used ESO's Atacama Large Millimeter/submillimeter array (ALMA) to gain one of the best views yet of a star in the process of forming.

The embryonic monster star sits inside Spitzer Dark Cloud (SDC) 335.579-0.292 right now, which contains over 500 times the mass of the Sun. Astronomers say the cloud will be giving birth to a very brilliant star with up to 100 times the mass of the Sun. The brightest stars in the galaxy form within cool and dark clouds, but the processes are both shrouded in dust and a mystery.

The team used ALMA to perform a microwave prenatal scan to get a clearer look at the formation of the star. There are two theories on how massive stars like this begin to form. One is that the parental dark cloud fragments create several small cores that collapse on their own and eventually form stars. The other says the entire cloud begins to collapse inwards, with material racing towards the cloud's center to form one or more massive stars.

This new observation supports the theory of global collapse for the formation of massive stars, rather than fragmentation.

"The ALMA observations reveal the spectacular details of the motions of the filamentary network of dust and gas, and show that a huge amount of gas is flowing into a central compact region," said team member, Ana Duarte Cabral from the Laboratoire d'Astrophysique de Bordeaux, France.

Scientists first spotted SDC335.579-0.292 as a dramatic environment of dark, dense filaments of gas and dust through observations with NASA's Spitzer Space Telescope and the European Space Agency's (ESA) Herschel Space Observatory. The team used ALMA to look at the forming star in detail, observing the amount of dust and the motion of the gas moving around within the dark cloud.

"The remarkable observations from ALMA allowed us to get the first really in-depth look at what was going on within this cloud," says Nicolas Peretto of CEA/AIM Paris-Saclay, France. "We wanted to see how monster stars form and grow, and we certainly achieved our aim! One of the sources we have found is an absolute giant - the largest protostellar core ever spotted in the Milky Way."

The star's core has over 500 times the mass of our Sun swirling around within it, and the ALMA observations show that much more material is still flowing inwards and increasing the mass still further. This material will eventually collapse to form the giant star.

"Even though we already believed that the region was a good candidate for being a massive star-forming cloud, we were not expecting to find such a massive embryonic star at its center," says Peretto. "This object is expected to form a star that is up to 100 times more massive than the Sun. Only about one in ten thousand of all the stars in the Milky Way reach that kind of mass!"

Gary Fuller from the University of Manchester, UK said that not only are these stars rare, but their birth is extremely rapid, so finding such a massive object is a "spectacular result."

This research was presented in a paper entitled "Global collapse of molecular clouds as a formation mechanism for the most massive stars" and is scheduled to appear in Astronomy & Astrophysics.