An abnormal abundance of massive stars in the Tarantula Nebula

The Tarantula Nebula (Image X-ray: NASA/CXC/PSU/L.Townsley et al.; Optical: NASA/STScI; Infrared: NASA/JPL/PSU/L.Townsley et al.)
The Tarantula Nebula (Image X-ray: NASA/CXC/PSU/L.Townsley et al.; Optical: NASA/STScI; Infrared: NASA/JPL/PSU/L.Townsley et al.)

An article published in the journal “Science” describes the really out-of-the-ordinary amount of massive stars discovered in the Tarantula Nebula, a region of the Great Magellanic Cloud, one of the Milky Way’s satellite dwarfs galaxies. A team of researchers participating in the VLT-FLAMES Tarantula Survey (VFTS) used ESO’s Very Large Telescope to observe nearly 1,000 massive stars in that region concluding that there’s a much higher amount than expected by the models with various important astronomical implications.

The VFTS survey uses the FLAMES (Fibre Large Array Multi Element Spectrograph) instrument mounted on the VLT telescope to study the Tarantula Nebula, also known as 30 Doradus or with the initials NGC 2070 and C 103. It’s a starburst region, which means that is characterized by an extraordinary star formation. It’s the largest region of that type in the group of galaxies of which the Milky Way is part, therefore it’s the object of particular attention.

The purpose of the survey is not only to make a census of the young stars in the Tarantula Nebula but also to better understand the influences of the most massive ones on the surrounding area. These stars emit enormous amounts of radiation even in the ultraviolet frequencies and intense stellar winds that can have effects in the region.

These massive stars consume their hydrogen very quickly and then explode into supernovae after a few million years, generating further effects in the short term but also in the long run because they generate heavy chemical elements. Their short life makes their study more difficult compared to smaller stars, which consume their hydrogen slowly so they live very long and exist in great abundance.

For these reasons, the Tarantula Nebula is an excellent object of study of starburst regions and gives us an idea of ​​what can happen in galaxies that are distant and therefore much more difficult to observe in detail. During the VFTS survey, the researchers studied the characteristics – temperature, brightness and others – of 452 massive stars among the almost 1,000 observed. Many of these stars are really massive surpassing the 15 solar masses.

The results of this study show that there are more stars bigger than 30 solar masses than expected from star-formation models. This means that in the Tarantula Nebula there are more radiation than normal and there will be more supernovae than normal which will leave more neutron stars and above all black holes.

The Tarantula Nebula area is relatively small in astronomical terms, being a few hundred light years across. The consequence is that in a few million years the likelihood of mergers between the new neutron stars and black holes will also increase.

The study of the Tarantula Nebula indicates that those massive stars formed in a relatively short period, a few million years. Understanding what happened would provide new information on the mechanisms that trigger intense star formation in certain areas of space.

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