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There Might Be More Big Stars In The Universe Than We Thought

New Hubble infrared view of the Tarantula Nebula

Detailed image of the Tarantula Nebula from Hubble. NASA/ESA/E. Sabbi (STScI)

It is suggested from some latest observations that the number of large stars have been underestimated and in fact these form in starburst events. If this discovery is more than just an exception to the rule, there could come some consequences for many astronomical theories.

According to a report released from the journal of Science, an international team of astronomers has studied the stars within 30 Doradus, also called the Tarantula Nebula, a starburst region in the Large Magellanic Cloud. The group was able to characterize the properties of 452 stars in 30 Doradus and, out of all of them, 247 were heavier than 15 times our Sun. There are nearly 25 to 50 more massive stars than theoretical predictions, known as the initial mass function (IMF), would expect.

The IMF is the description of the distribution of masses for any population of stars when it took shape. It’s an empirical distribution. The mass of stars have the final say over their evolution and way in which they’re going to end their life. For instance, more massive stars mean more supernovae, which leads to more black holes and neutron stars. It also has impact on the evolution of the stars’ host galaxies as a whole, the IMF would be very useful for providing statistics, because there are  over 100 billion stars in galaxies.

Nevertheless, this doesn’t mean that the IMF is perfect. Since it was proposed by Edwin Salpeteral in 1955 , the IMF has been tweaked to better characterize the low-mass end of star mass distribution. It is found out that there are a lot more small stars than previous prediction, and the latest research shows that some tweaking might be necessary for certain environments, even at the high end of mass distribution.

The study has put forward some questions to be answered by  more observation, such as whether the excess of massive stars is linked with advantageous conditions in the gas clouds, or whether it is common during starburst events, and if there are other mechanisms at work.

The quite interesting thing is the existence of some of the most massive stars ever observed, with some being over 200 times massive than the mass of the Sun. The scientists estimate that bigger stars might still exist in the core of the nebular, which was not resolved.

The Tarantula Nebula is the most active and largest (over 600 light-years) starburst region in the local group of galaxies. Supernova 1987A, the closest supernova observed since the invention of the telescope, occurred on the outskirts of this nebula.

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