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Astronomers have discovered a small dwarf galaxy with more dark matter than we expected

Astronomers have discovered a small dwarf galaxy with more dark matter than we expected

A small ancient dwarf galaxy called Tucana II orbiting the Milky Way has a big secret. According to a new study of stars around the object, which are gravitally attached to it at great distances, the Dark matter The aura is much bigger than we thought.

In fact, it’s just so huge. Although Tucana II’s stellar mass is about 3,000 times the mass of the Sun, the dark matter corona weighs 10 million times the mass of the Sun. This is three to five times larger than previous estimates.

This indicates that the first galaxies in the universe could have been much larger than we know.

“Tucana II has a lot more mass than we thought, in order to connect these very distant stars,” Said astrophysicist Anrod Chitty of the Massachusetts Institute of Technology. “This means that the other remaining first galaxies would likely have these types of extended halos as well.”

The Milky Way has a stretch Full swarm Companion dwarf galaxies. These are small, faint clusters of stars that are very low in the mineral, which reveals that they are very old, because the minerals took a while to form in the hearts of the stars and spread through the universe.

Tucana II, located about 163,000 light years from Earth, is among the smallest. Based on the percentage of minerals in its stars, it is also among the oldest, as there are almost no minerals found. Chetti and his team were investigating these stars, hoping to find a group of older stars.

They took notes using the Australian National University SkyMapper A telescope and conducted the results through an algorithm that Kitty designed to pick out the mineral-poor stars. In addition to the stars in the core of Tucana II, the algorithm detected nine new stars, at very great distances.

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This was confirmed by data collected by the Gaia satellite – an ambitious project to map the Milky Way in three dimensions, including the movements of the stars. Those stars farther from the core of the dwarf galaxy were orbiting around, linked to gravity.

However, the previously estimated properties of the galaxy did not include enough mass to produce the kind of gravitational force that would keep those distant stars bound. Which means there’s a lump there that we couldn’t see or discover directly. Which, in turn, means dark matter.

We don’t know what dark matter is, but there is an invisible mass in the universe that is responsible for creating all the extra gravity, making galaxies spin faster, and bending space-time – and there’s a lot more of it than ordinary matter. This is dark matter, and we think glue is what binds the galaxies.

Without dark matter, galaxies would be moving further apart. Chiti said. “[Dark matter] A critical element in the formation of the galaxy and its cohesion together. “

Based on the stars’ positions and their motions, the team was able to update the dark matter mass estimate for Tucana II, eventually reaching a range of 10 million solar masses. This is the first evidence that super-bright dwarf galaxies can contain this much dark matter, and it raises many mysteries.

“This may also mean that the first galaxies formed in dark matter halos much larger than previously thought.” Said astrophysicist Anna Freibel From the Massachusetts Institute of Technology. “We thought that the first galaxies were smaller and weaker galaxies. But in reality they were probably many times larger than we thought, and not very small at all.”

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So where did all this dark matter come from? Evidence of this could be in the stars of the galaxy. When the team studied data from the Magellan Telescopes in Chile, they found that not all stars have the same mineral.

In fact, they have been starkly divided between two groups. The stars on the outskirts of Tucana 2 were three times less in mineral than the stars in the center, indicating two separate star groups. In the Milky Way, this could happen if a group of stars arrived from another location, such as colliding with another galaxy.

This is the first time that such a chemical difference between stars has been seen in an ancient galaxy, but the reasons for this are likely to be similar: Once upon a time, Tucana II was not a single galaxy, but rather two galaxies merging, and their dark matter combined halos.

“We may witness the first cannibal signature in the galaxy,” Freibel said. “A galaxy may have devoured one of its slightly smaller, more primitive neighbors, which then drove all of its stars out into the suburbs.”

However, the research has shown that the wide range of these small space galaxies can now be observed and distinguished, which means that other galaxies such as Tucana II can be recognized. There are even two candidates – ultra-clear dwarf galaxies Segue 1 and Bootes, each with one star a long distance from the galactic core.

The team plans to use their technology to find and study more of these stars and more of these galaxies.

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“There are likely to be many other systems, perhaps all of them, that these stars flash in their suburbs,” Freibel said.

The research has been published in Natural Astronomy.

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