Some 163,000 lightsyears of the Milky Way is a much smaller and much older galaxy: Toucan II, so named because of the constellation of tropical birds in which it sits. Sitting on the periphery of the gravitational pull of our galaxy, Tucana II offers researchers the opportunity to understand the composition of the first galactic structures in the universe.
Now, a team of astronomers has done it found evidence of an extended halo of dark matter around the galaxy. His research was published today in the journal Nature Astronomy.
“We know [dark matter] it’s because for galaxies to stay connected, there has to be more matter than we can visibly see, from the light of the stars, ”said Anirudh Chiti, an astronomer at the Massachusetts Institute of Technology., in a phone call. “This led to the hypothesis of existing dark matter as an ingredient that holds galaxies together; without it, the galaxies we know, or at least the things that are on its outskirts, would only collapse.
A halo of dark matter is a gravitational region matter linked to space. (The halo of dark matter in the Milky Way it extends far beyond the flying that constitutes the visible things of our galaxy). The team found that the gravitational limits of Toucan II range from three to three five times more massive than previously thought, showing that even some of the oldest galaxies will have halos of dark matter.
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Toucan II turns out to be the most chemically primitive galaxy we know today, meaning that some of its stars have a very low metal content (the heaviest elements in the universe occurred later). The team realized that Toucan II had the halo of dark matter when observations of stars in this region of the sky revealed that the stars were moving in tandem.
“If you just look at the region of the sky where the galaxy exists, you don’t really see any clustering or overdensity of stars,” Chiti said. who is main author of the recent article, dit. “Just when you look at their speeds and you realize it’s a group of stars moving at the same speed, you realize there’s a galaxy out there.”
As study co-author Anna Frebel, also an MIT astronomer, said in a university press release, the apex of the Tucana II movement resembles “bath water flowing down the drain.” Interestingly, some of the galaxy’s peripheral stars are older than the stars closest to the galactic center. The team hypothesizes that Tucana II may be the result of a previous galactic fusion, a cosmic shock that saw one primitive galaxy being consumed by another, resulting in stars of different origins in the same galaxy.
Whether or not this theory of the origin of Toucan II is fulfilled, there will surely be a similar collision in its future.. Because it is within the gravitational field of the Milky Way, much more massive, eventually the relatively small galaxy will be swallowed up by ours.
Although astronomers know how to detect halos of dark matter, they still do not know exactly what dark matter is. In addition to finding their halos around galaxies, researchers are also looking for the identity of dark matter. mysterious neutron star signals and in the form of tiny and theoretical black holes.