Stars are heavier than we thought before

(ORDO NEWS) — A group of astrophysicists at the University of Copenhagen have come up with important results regarding star populations outside the Milky Way.

This result could change our understanding of a wide range of astronomical phenomena, including the formation of black holes, supernovae, and how galaxies die.

For as long as humans have explored the skies, what stars look like in distant galaxies has remained a mystery. In a study published today in The Astrophysical Journal, a team of scientists from the Niels Bohr Institute at the University of Copenhagen is questioning previous ideas about stars outside our own galaxy.

Since 1955, it has been thought that the composition of stars in other galaxies in the universe is similar to that of hundreds of billions of stars in our own a mixture of massive, medium-mass, and low-mass stars.

But using observations of 140,000 galaxies across the universe and a wide range of refined models, the team tested whether the same distribution of stars as in the Milky Way applies elsewhere.

The answer is no. Stars in distant galaxies tend to be more massive than those in our “local neighborhood”. This discovery has a big impact on what we think we know about the universe.

“The mass of stars tells us a lot, as astronomers. If you change the mass, you also change the number of supernovae and black holes that emerge from massive stars.

In essence, our result means that we will have to rethink a lot of what we once thought because distant galaxies look very different than our own,” says Albert Sneppen, a PhD student at the Niels Bohr Institute and first author of the study.

Light from 140,000 galaxies analyzed

Researchers have assumed that the size and mass of stars in other galaxies are similar to our own for more than fifty years, for the simple reason that they could not observe them through a telescope as they could the stars of our own galaxy.

Distant galaxies are billions of light years away. As a result, only light from their most powerful stars reaches Earth.

This has been a headache for researchers around the world for years, as they have never been able to accurately determine how stars are distributed in other galaxies, and this uncertainty has led them to believe that they are distributed in the same way as the stars in our own Milky Way.

“We have only been able to see the tip of the iceberg and have known for a long time that expecting other galaxies to be similar to our own was not a good guess. However, no one has yet been able to prove that different populations of stars form in other galaxies.

This study allowed us to make it is this that could open the door to a deeper understanding of the formation and evolution of galaxies,” says Associate Professor Charles Steinhardt, co-author of the study.

For the study, the scientists analyzed light from 140,000 galaxies using the COSMOS catalog, a large international database of more than a million observations of light from other galaxies.

These galaxies are distributed from the nearest to the farthest corners of the universe, from which light traveled a full twelve billion years before becoming observable on Earth.

Massive galaxies die first

According to the researchers, the new discovery will have a wide range of consequences. For example, it is still not resolved why galaxies die and stop forming new stars. The new result suggests that this can be explained by a simple trend.

“Now that we can better decipher the mass of stars, we can see a new pattern: the least massive galaxies continue to form stars, while the more massive galaxies stop producing new stars. This suggests a surprisingly universal trend in the death of galaxies,” Snappen concludes.

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