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Millions of Stars Are Forming in Small nearby Galaxy


Image credit: Turner et al. Cloud D is the brightest part of this radio wave image, lit up by 7,000 O type stars. The white spots are star clusters and the blue background is a Hubble image of NGC 5253

Recently scientists have observed a dwarf galaxy in the process of forming stars with an unusual rate in regard to its size. The supernebula in the galaxy seems to be regarded as a throwback to a time when huge star clusters were created, which could enable us to have a rare insight into the past of our own galaxy.

It is known that stars form within nebulae, while giant nebulae could generate a huge number of stars at once. But, what Professor Jean Turner of UCLA discovered recently was quite different from anything we have observed previously, because it had produced a cluster with the weight that was a million times heavier than the mass of the sun.

As Turner said, after looking for the gas cloud forming the supernebula as well as its star cluster for some years, his team has finally detected it.

Cloud D is kind of supernebula incorporating a cluster with brightness of a billion times similar to the sun. Located at the galaxy NGC 5253 with just 10.9 million light-years away, that is extremely close to us in terms of galactic standards, its luminosity should be expected to be easily observed. However, owing to the fact that the dust of the nebula hides the visible light the stars generate, Turner could identify find only by application of the submillimeter radio detectors.

Talking of his discovery, Turner said that they were seeing the dust created by the stars. In normal conditions, when looking at a star cluster, the stars would have dispersed all their gas and dust long time ago. However in this case of the cluster, they had seen the dust.

Apart from its size, the thing that allows Cloud D to become unusual is its efficiency to create stars. More than half the mass of Cloud D has become stars so far and it still keeps doing so as expected. Generally, gas clouds in the Milky Way would have a tenth of such efficiency.

However, it was not always like this. It is evident with the example of globular clusters that as early as ten billion years ago the nebulae around the Milky Way were pretty more efficient in regard to forming stars. By careful examination of Cloud D, scientists could have an opportunity to see the way in which this process occurred. In addition, it is a good chance to observe it at the very beginning. The cluster forming from Cloud D is three million years with the predicted lifespan of into a billion years.

On contrary, those less efficient clouds would meet their destiny by losing most of their gas to the galactic disk or bulge. So some astronomers were doubtful that it could be possible for such efficiency remains in the modern universe. In Turner’s opinion, high efficiency was the result from the force-feeding of star formation by a streamer of gas falling into the galaxy.

While there are two supernovae within NGC 5253 for the past 120 years, which is rare concerning a small galaxy, Turner and her colleagues have not found any evidence that there was a supernova within Cloud D. This was amazing because the huge O type stars, to which Cloud D belonged, would burn out and explode very rapidly.

In the end, a large amount of supernovae would disperse Cloud D into interstellar space, including most of the heavier elements generated by the huge stars during the short period of their lifespan.