Scientists working with data from the Atacama Large Millimeter/ submillimeter Array (ALMA) have come across the most massive stellar embryo ever discovered in the Milky

Way. It’s a real monster of a baby star, growing in a cosmic womb 500 times the mass of our own Sun.

The unbelievable part is that it’s still growing, sucking up material in its environment with its powerful gravity and adding to a blooming protostellar core that may eventually form several newborn stars.

This core is found 11,000 light years away in a region of space known as the Spitzer Dark Cloud or SDC. It’s shrouded by dense dust and gas, so has been difficult to observe with much accuracy until a Cardiff-based team led by French scientist Nicolas

Peretto recently studied it.

“The remarkable observations from

ALMA allowed us to get the first really in-depth look at what was going on within this cloud,” said Peretto. “We wanted to see how monster stars form and grow. One of the sources we have found is an absolute giant – the largest protostellar core ever spotted in the

Milky Way. Even though we already believed that the region was a good candidate for being a massive starforming cloud, we were not expecting to find such a massive embryonic star at its centre.”

By analysing the data from the

European Southern Observatory’s

Chilean telescope, the team were able the estimate that the SDC protostar should go on to form a particularly brilliant star of around 100 solar masses, of which there are only around 10 to 40 million in the galaxy.

That might sound like a lot, but that’s only one that reaches this kind of mass for every 10,000 stars in the

Milky Way.

Stars of this mass are all formed in similarly cool and dark clouds to the

SDC, but there are two main, current theories as to how they are born: one is that the cloud fragments to form several cores that eventually create smaller stars. The other is that the entire cloud collapses as a single entity towards the centre, forming one or two stars with gigantic masses.

“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 Ana Duarte Cabral from the Laboratoire d’Astrophysique de

Bordeaux, in France.

These observations provide strong support for the more dramatic, cloudcollapse theory and were made using only a quarter of ALMA’s full array of antennae, which bodes well for future research into star formation.

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