Hungry young star seen munching down on a ‘space hamburger’ for the first time

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When a star is born, it needs a healthy diet of gas and dust to grow up into a big, powerful star like our Sun. Now, for the first time, scientists have directly observed a protostar going through this early “feeding” process. The discovery, published today in Science Advances, settles an old debate about exactly what happens when a new star is born.

Using high-powered radio telescopes, researchers recorded a so-called accretion disk forming around a star named IRAS 05413-0104. These rotating disks are made of up of interstellar matter, including iron and silicate, and feed the star’s core, causing it to grow in size. In the case of this particular newborn star, the disk even looked like a hamburger, according to the study.

“There’s a dark lane in the middle where it’s colder, and brighter features on the top and bottom where the matter is being heated by the center of the star,” Chin-Fei Lee, a researcher at Taiwan’s national Institute of Astronomy and Astrophysics and lead author of the study, tells The Verge. “I think this is very exciting science. It’s never been seen before.”

Accretion disks like this have been glimpsed around older, bigger stars in the past, says Lee, but never on such a small protostar. The star has a mass of between a fifth and a third of the Sun, and is just 40,000 years old, while our own Sun has been around for some 4.5 billion years.

IRAS 05413-0104’s accretion disk also settles an old debate in the science of star formation. Up until now, astrophysicists weren’t sure whether or not these disks even formed around very young stars. Computer simulations suggested that the magnetic fields in the protostar’s core might be too intense, stopping the disk from spinning and gathering matter. Now we know this isn’t the case, although the exact interaction of the magnetic field and the accretion disk has yet to be fully mapped out.



The figure a) shows a zoomed out view of the star, with two gaseous jets ejected from its top and bottom. Figure b) shows a close-up of the accretion disk, and c) a model of the same. The darker color is because the gas is colder; the brighter regions are hotter.
Image: ALMA (ESO/NAOJ/NRAO)/Lee et al.

The researchers used a group of radio telescopes in Chile known as ALMA (or the Atacama Large Millimeter/submillimeter Array) to find the disk. ALMA is the most expensive ground-based telescope in the world, and became fully operational in mid-2013 after costing $1.4 billion to build.

Gilles Chabrier, an astrophysicist at the University of Exeter who researches star formations and did not take part in the study, praised the paper and said the discovery was “just the tip of the iceberg.” “Before ALMA the resolution was too crude to probe these early interstellar discs,” Chabrier tells The Verge. “I think very soon we are going to find a lot of these.”

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