How many stars of this type live in other galaxies? It seems like a simple question, but it’s notoriously difficult to pin down because astronomers have such a hard time estimating stellar populations in distant galaxies.
Now a team of astronomers has completed a census of more than 140,000 galaxies and discovered that distant galaxies tend to have heavier stars.
Even though astronomers don’t have a complete census of all the hundreds of billions of stars in the Milky Way galaxy, they’ve sampled enough of them to get a pretty good idea of the population.
We know, roughly, how many small dwarf stars there are, how many medium Sun-like stars there are, and how many giant stars there are.
But repeating this exercise for other galaxies is extremely difficult. Most galaxies are simply too distant to identify and measure the individual stars within them.
We only see their brightest and heaviest stars, and have to guess the populations of the smaller ones.
Typically, astronomers just assume that the demography of a distant galaxy roughly matches what we see in the Milky Way, because on average galaxies shouldn’t look so different from each other.
Recently, a team of astronomers used the COSMOS catalog to study 140,000 individual galaxies, developing techniques to estimate the population of stars in each.
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 future fate of heavier galaxies
“We were only able to see the tip of the iceberg, and we’ve known for a long time that expecting other galaxies to look like ours wasn’t a particularly good guess to make. has never been able to prove that other galaxies form different populations of stars. This study allowed us to do just that, which could open the door to a deeper understanding of the formation and evolution of stars. galaxies,” says Associate Professor Charles Steinhardt, co-author of the study.
The team found that, on average, galaxies farther away tended to have larger stars than the Milky Way. On the other hand, the nearby galaxies were relatively similar to ours.
“The mass of stars tells astronomers a lot. 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 that we will have to revise many things .we once assumed, because distant galaxies look very different from our own,” says Albert Sneppen, graduate student at the Niels Bohr Institute and first author of the study.
This work has several important implications.
For one thing, astronomers can no longer assume a uniform population of stars when looking at distant galaxies, which represent the youngest galaxies to appear in the universe. It also forces us to rethink how galaxies evolve over billions of years.
“Now that we are better able to decode the mass of stars, we can see a new pattern; less massive galaxies continue to form stars, while more massive galaxies stop giving birth to new stars. This suggests a remarkably universal trend in the death of stars and galaxies,” Sneppen concludes.
This article was originally published by Universe Today. Read the original article.