The stars are more massive than we thought

A team of astrophysicists from the University of Copenhagen has achieved a great result regarding the population of stars beyond the Milky Way. The result may change our understanding of a wide range of astronomical phenomena, including the formation of black holes, supernovae and why galaxies die.

Since humans have studied the sky, it remains a mystery what stars look like in distant galaxies. In a study published today in The Astrophysical Journala team of researchers from the Niels Bohr Institute at the University of Copenhagen is putting an end to previous knowledge about stars beyond our own galaxy.

Since 1955, the composition of stars in other galaxies in the universe has been assumed to correspond to the composition of the hundreds of billions of stars in our own – a mixture of massive, medium-sized and low-mass stars. But using observations of 140,000 galaxies across the universe and a wide range of advanced models, the team tested whether the same apparent star distribution in the Milky Way applies elsewhere. The answer is no. Stars in distant galaxies are generally more massive than those in our “local neighborhood”. The discovery has a huge impact on what we think we know about the universe.

“The mass of stars tells us a lot about astronomers. If you change the mass, you also change the number of supernovae and black holes that emerge from massive stars. As such, our result means we will have to revise many things. we once assumed because distant galaxies look very different from ours, ”says Albert Sneppen, a graduate student at the Niels Bohr Institute and first author of the study.

Analysis of light from 140,000 galaxies

The scientists assumed that the size and weight of the stars in other galaxies were similar to ours for more than fifty years, for the simple reason that they were not able to observe them through a telescope as they could with the stars in our own galaxy. .

Distant galaxies are billions of light-years away. As a result, only the light from their most powerful stars reaches Earth. This has puzzled scientists around the world for years, as they have never been able to accurately clarify the distribution of stars in other galaxies, an uncertainty that has led them to believe that they were distributed, just like the stars in our Milky Way.

“We were only able to see the tip of the iceberg, and we have long known that it was not a very good guess to expect other galaxies to look like ours. However, no one has ever been able to prove that “This galaxy forms different star populations. This study allowed us to do just that, which could open the door to a deeper understanding of how galaxies form and evolve,” said Associate Professor Charles Steinhardt, co-author of the study.

In the study, the researchers analyzed light from 140,000 galaxies using the COSMOS Catalog, a large international database of more than one million light observations from other galaxies. These galaxies are distributed from the nearest to the farthest of the universe, from which light has traveled twelve billion years before it can be observed on Earth.

Massive galaxies die first

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

“Now that we are better able to decode the mass of the stars, we can see a new pattern; smaller massive galaxies continue to form stars, while more massive galaxies stop giving birth to new stars. This indicates a remarkable universal tendency in the death of galaxies, ”concludes Albert Sneppen.

The research was conducted at the Cosmic Dawn Center (DAWN), an international center for basic astronomy research supported by the Danish National Research Foundation. DAWN is a collaboration between the Niels Bohr Institute at the University of Copenhagen and DTU Space at the Technical University of Denmark.

The center is dedicated to understanding when and how the first galaxies, stars and black holes formed and evolved in the early universe, through observations using the largest telescopes as well as theoretical work and simulations.

About the study

  • The empirical function used to describe the mass distribution of a population of stars is known as the IMF – Initial Mass Function. It covers a distribution of low-mass, medium-mass and massive stars that astronomers have observed across the Milky Way. Historically, scientists have worked on the assumption that the IMF is universal and also applies to other galaxies in the universe.
  • In their analysis of the galaxies, the researchers looked at the amount of light emitted by galaxies at different wavelengths. Large massive stars are bluish, while small low-mass stars are more yellow or red. This means that by comparing the distribution of blue and red colors in a galaxy, one can measure the distribution of large and small stars.
  • Scientists looked more closely at 140,000 galaxies scattered across the universe over the last 12 billion years of the universe’s history.
  • The results show that stars in distant galaxies are generally more massive than those in our local neighborhoods, and that the farther away scientists look, the more massive the average stars become.

Leave a Comment