Massive stars more abundant in nearby galaxy: study

Astronomers have revealed an 'astonishing' overabundance of massive stars - with masses over ten times that of the Sun - in a neighbouring galaxy.
The discovery, made in the gigantic star-forming region 30 Doradus in the Large Magellanic Cloud galaxy, has 'far- reaching' consequences for our understanding of how stars transformed the pristine universe into the one we live in today, researchers said.
"We were astonished when we realised that 30 Doradus has formed many more massive stars than expected," said Fabian Schneider from the University of Oxford in the UK.
The team used ESO's Very Large Telescope to observe nearly 1,000 massive stars in 30 Doradus, a gigantic stellar nursery also known as the Tarantula nebula.

The researchers used detailed analyses of about 250 stars with masses between 15 and 200 times the mass of our Sun to determine the distribution of massive stars born in 30 Doradus - the so-called initial mass function (IMF).
Massive stars are particularly important for astronomers because of their enormous influence on their surroundings (known as their 'feedback').

They can explode in spectacular supernovae at the end of their lives, forming some of the most exotic objects in the universe - neutron stars and black holes.
"We have not only been surprised by the sheer number of massive stars, but also that their IMF is densely sampled up to 200 solar masses," said Hugues Sana from the University of Leuven in Belgium.

"Until recently, the existence of stars up to 200 solar masses was highly disputed, and the study shows that a maximum birth mass of stars of 200-300 solar masses appears likely," said Sana, co-author of the study published in the journal Science.
In most parts of the universe studied by astronomers to date, stars become rarer the more massive they are.
The IMF predicts that most stellar mass is in low-mass stars and that less than one per cent of all stars are born with masses in excess of ten times that of the Sun.
Measuring the proportion of massive stars is extremely difficult - primarily because of their scarcity - and there are only a handful of places in the local universe where this can be done.

The team turned to 30 Doradus, the biggest local star- forming region, which hosts some of the most massive stars ever found, and determined the masses of massive stars with unique observational, theoretical and statistical tools.
This large sample allowed the scientists to derive the most accurate high-mass segment of the IMF to date, and to show that massive stars are much more abundant than previously thought.