Then, about 10 billion years ago, that growing galaxy ran into a smaller neighbor. Containing maybe 30 percent as many stars as the Milky Way, the dwarf galaxy ended up being consumed by its larger opponent. The merger flung those ancient, red stars from the galactic disk into the halo, where they still exist today; we can even see some of these stellar elders from Earth with a backyard telescope.
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But will they invade your privacy? The amount of Beryllium, one of the lightest elements, increased with time and serves as a sort of "cosmic clock," according to the team, led by Luca Pasquini of the European Southern Observatory.
The stars were found to be roughly The researchers added to that an interval of about million years they say it took for previous generations of stars in the Milky Way to form, explode, and seed the fledgling galaxy with the goods necessary to forge the types of stars found in NGC Previously, three methods had been used to arrive at similar age estimates with varying degrees of precision.
According to NASA:. They found that parts of the disk, for example, appeared impossibly ancient. The Gaia satellite has revolutionized our understanding of the Milky Way since its launch in December Things are changing rapidly everywhere. Fortunately, the smaller stars from this early stock are also slow to burn, so many are still shining. After decades of surveys, researchers had assembled a catalog of 42 such ancients, known as ultra metal-poor stars to astronomers, any atom bulkier than helium qualifies as metallic.
According to the standard story of the Milky Way, these stars should be swarming throughout the halo, the first part of the galaxy to form. By contrast, stars in the disk — which was thought to have taken perhaps an additional billion years to spin itself flat — should be contaminated with heaver elements such as carbon and oxygen.
In late , Sestito set out to study how this metal-poor swarm moves by writing code to analyze the upcoming Gaia results. Perhaps their spherical paths could offer some clues as to how the halo came to be, he thought. He found that most were streaming through the halo, as predicted. Follow-up research confirmed that the stars really are long-term residents of the disk, and not just tourists passing through.
From two recent surveys, Sestito and colleagues amassed a library of roughly 5, metal-poor stars. A few hundred of them appear to be permanent denizens of the disk.
Another group sifted through about stars identified by another survey, finding that about 1 in 10 of these stars lie flat in circular, sunlike orbits. And a third research group found stars of various metallicities and therefore various ages moving in flat disk orbits. How did these anachronisms get there? Sestito speculated that perhaps pockets of pristine gas managed to dodge all the metals expelled from supernovas for eons, then collapsed to form stars that looked deceptively old.
Or the disk may have started taking shape when the halo did, nearly 1 billion years ahead of schedule. To see which was more probable, he connected with Tobias Buck , a researcher at the Leibniz Institute for Astrophysics in Potsdam, Germany, who specializes in crafting digital galaxy simulations.
Past efforts had generally produced halos first and disks second, as expected. But these were relatively low-resolution efforts. In these digital simulations, a Milky Way—like galaxy forms and evolves over The numbers are pretty astounding.
NASA estimates the galaxy at , light-years across. Since one light year is about 9. Our galaxy is part of a collection known as the Local Group. Because some of these galaxies are prominent in our sky, the names tend to be familiar.
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