Detecting the minimum mass of the galaxy

By analyzing light from small, faint galaxies orbiting the galaxy Milkey Way, researchers at the University of California Irvine believe they have found the minimum mass of galaxies in the universe: 10 times more. million times the mass of the Sun.

The mass may be considered to be the smallest 'building block' of the invisible, mysterious material that we still call dark matter. Stars formed in this building block clump together to become galaxies.

Scientists have so far only learned a little about the properties of dark matter, although it accounts for 5/6 of all matter in the universe.

Louis Strigari, the lead author of the study and a member of the Department of Physics and Astronomy at the University of California Irvine, said: 'Understanding the minimum mass of the galaxy, we can get deep knowledge. chromaticity on the properties of dark matter. It plays an essential role in understanding the universe and the process of life formation. '

The results of the study are published in the August issue of Nature.

Dark matter controls the development of structures in the universe. Without it, galaxies like the Milky Way will not exist. Scientists have known how the gravitational pull of dark matter absorbs normal matter, causing galaxies to form. There is also a suspicion that small galaxies join together over time to form larger galaxies, such as the Milky Way.

Galaxies of the smallest mass were discovered, called dwarf galaxies , varying in brightness: from 100 times the brightness of the sun to 10 million times. At least 22 of the dwarf galaxies turn around the Milky Way. Scientists studied 18 of them based on data obtained from Chile's Keck telescope and Magellan telescope in Chile with the goal of calculating their mass. When analyzing stars 'light in each galaxy, they determined the speed of the stars' movement. Thanks to that speed, they calculated the mass of each galaxy.

Scientists predict that the galactic mass will change, the brightest galaxy is the heaviest and the faintest galaxy is the lightest. But surprisingly, all dwarf galaxies have the same mass: 10 million times the mass of the Sun.

The defense galaxies studied by the University of California Irvine are about 500,000 light-years away from the Milky Way.(Photo: J. Bullock / M. Geha / R. Powell; Image courtesy of University of California - Irvine)

Manoj Kaplinghat, co-author of the study and assistant professor of physics and astronomy at the University of California Irvine, explained the result by an analogy in which humans act as dark matter. . He said: 'Assuming you are an alien flying over Earth, you will find urban areas because of the concentrated lights at night. Based on the brightness of the light, you surmise that more people live in Los Angeles than Mumbai but the truth is not like that. What we just discovered is quite similar to the fact that all capitals, although there are almost alien-visible areas at night, have a population of about 10 million people. '

Because dwarf galaxies are mostly dark matter, the ratio of dark matter to ordinary matter is about 10,000: 1. The galaxy's minimum mass detection reveals a fundamental characteristic of dark matter. James Bullock - co-author of the study and director of the Center for Cosmology at the University of California Irvine - said: 'We are excited because these galaxies are practically unobservable, but they contain a lot of gigantic material. This helps us better understand the element that makes up dark matter. It also tells us some things about the way galaxies form in the universe. '

According to scientists, dark matter clusters may exist without a single star. The only dark matter clusters they have discovered to date are clusters that are illuminated by stars.

Scientists hope to understand the microscopic properties of dark matter when the Large Hadron Collider in Switzerland comes into operation later this year. This is the device that accelerates two lines of received particle rays in a circle in the opposite direction, then shoves them together to recreate the conditions after the Big Bang explosion. With this method, scientists hope to create dark matter for the first time in the laboratory.

This international project is attended by physicists from the University of California Irvine. In collaboration with the galaxy study is Joshua Simon of the California Institute of Technology, Marla Geha of Yale University, Beth Willman of the Harvard-Smithsonian Center for Astrophysics, and Matthew Walker of Cambridge University.

The research was funded by the National Science Foundation. Gary McCue also supports the Center for Cosmology, University of California Irvine to conduct research.