According to the “RT” website, the new study showed that our Milky Way galaxy is getting more massive as it devours 12 star systems orbiting around it.
Astronomers mapped these so-called “star streams” using the Anglo-Australian Telescope (AAT) in New South Wales, Australia.
The properties of stellar currents reveal the presence of dark matter, the mysterious form of matter in the unobservable universe.
“Imagine a Christmas tree, on a dark night, we see the Christmas lights, but we don’t see the tree they are wrapped around,” said Professor Geriant F Lewis of the University of Sydney, a co-author of the study.
“But the shape of the lights reveals the shape of the tree. It’s the same with stellar currents, their orbits revealing dark matter.”
“Currents form when small star systems, dwarf galaxies and globular clusters fall into our much larger Milky Way and are torn apart by our gravity,” Professor Lewis continued.
Dark matter makes up about 27% of the universe, and it is invisible because it does not reflect light. It can’t be seen directly with telescopes, but astronomers know it’s there because of the effects of gravity on the matter we can see.
Stellar currents could also reveal that the Milky Way has grown steadily over billions of years by slicing up and consuming smaller star systems.
“We see these currents being disrupted by the gravity of the Milky Way, and they eventually became part of the Milky Way,” said lead study author Professor Ting Li from the University of Toronto in Canada.
This study gives us a quick glimpse into the feeding habits of the Milky Way, such as the types of smaller star systems that it “eats”. And as our galaxy gets older, it gets fatter.
Lee and her team measured the velocities of the stars using the Anglo-Australian Telescope (AAT), a 4-meter optical telescope at Siding Spring Observatory in New South Wales, northwest of the state capital Sydney.
They used the Doppler shift of light to see how fast individual stars were moving. The Doppler effect describes when motion changes the frequency of a sound wave based on the direction in which its source is moving, but it occurs for light in addition to sound.
In addition to measuring their speeds, astronomers can use these observations to calculate the chemical compositions of stars and show their date of birth.
Professor Lewis said: “The first stars in the universe consisted of pure hydrogen and helium, because they were the only elements that originated in the Big Bang.”
As these stars grow, nuclear reactions in their cores produce heavier elements, and when they die, supernovae pollute the next generation with these heavier elements.
The size of the galaxy determines how rich its stars are in chemical elements. In a galaxy as large as the Milky Way, there are a lot of stars that go through their lives, and their size means they can hold their heavier elements, while a dwarf galaxy has a quieter life and can easily lose its elements when a star explodes.
Therefore, the level of chemical contamination tells you the size of the object that formed the current. “In our observations, we focus on measuring the amount of calcium (because it is easy to notice) which can tell us about general contamination but we can look for other elements as well,” the scientists explain.
In the future, the team plans to produce more measurements of stellar currents in the Milky Way.
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