The Milky Way is full of heavyweights

The Galaxy appears to have an excess of very massive stars. The find could mean we can expect to see more gravitational waves in future.


Large stars, many times the mass of the Sun, appear blue in colour
Credit: NASA


The latest study of heavyweight stars has shown that our Galaxy may have an excess of high mass stars.

The finding is causing astronomers to rethink many assumptions about the Milky Way, such as its chemical make-up and how many gravitational waves we might expect to see.

A study led by researchers from the University of Oxford used images taken with ESO’s Very Large Telescope to examine the star formation region 30 Doradus.

They observed over 1,000 massive stars, 250 of which were found to have masses between 15 to 200 times that of the Sun.

The measurements found many more high mass stars than expected.

“In fact, our results suggest that most of the stellar mass is actually no longer in low-mass stars, but a significant fraction is in high-mass stars,” says Chris Evans, Principal Investigator for the VLT-FLAMES Tarantula Survey which the study was part of.


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The team were aiming to accurately measure the initial mass function– a measure of the distribution of stellar masses within a particular population.

However, in most places in the Universe, high mass stars are relatively rare, with stars over 10 solar masses making up just 1 per cent of the stellar population.

This rarity makes measuring their precise number difficult.

30 Doradus, however, is the largest star-forming region found locally and hosts the largest number of massive stars ever found, allowing the team to make thorough observations.

After studying the region, the researchers found that the IMF was much more weighted to the massive end than previously thought.

The find could have implications for our understanding of how these stars influence their surroundings.

During their lives the produce massive amounts of radiation and strong stellar winds which effect the surrounding space, a process known as feedback.

Then at the end of their life they explode in a supernova, seeding the Universe with the heavy elements needed to form planets.

“To quantatively understand all these feedback mechanisms, and hence the role of massive stars in the Universe, we need to know how many of these behemoths are born,” says Phillip Podsiadlowski, from the University of Oxford.

The find could change our view of the cosmos, as more larger stars mean more supernova, which could alter the chemical balance of the Universe.

“Also, the formation rate of black holes might be increased by 180 per cent, directly translating into a corresponding increase of binary black hole mergers that have recently been detected via their gravitational wave signals,” says Fabian Schneider from the University of Oxford.


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