December 9, 2021

Beyond Going Long

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The Milky Way may lose a number of satellite galaxies

The area around the Milky Way is not empty. It is full of dwarf galaxies – small, faint, low-mass, each containing about 1,000 stars.

This is not strange. From our observations of other large galaxies, we know that dwarf galaxies often cluster nearby and can be caught in the gravitational field of a larger object.

Select astronomers to date About 60 small galaxies Within 1.4 million light-years of the Milky Way, though more is likely hidden in the dark. Most of them seem to get confused like the fruit flying around a banana.

However, according to a new analysis of data from the Gaia satellite, most of these galaxies are actually relatively new to the region — and too new to orbit the Milky Way, at least not yet, the researchers say.

“We came to the conclusion that due to their disproportionately high energies and angular momentum, most dwarfs cannot be long-lived satellites, and if they can be linked to the Milky Way, they are on the first path, 2 billion less than a year ago,” the scientists write. in the new paper It was led by astrophysicist François Hammer of the Paris Observatory in France.

Dwarf galaxies in the region around the Milky Way. (ESA/Gaia/DPAC, CC BY-SA 3.0)

The Gaia mission is an ongoing project to map the Milky Way with the greatest accuracy yet, including the 3D locations, speeds, and velocities of stars and objects (in and out of bits).

Using measurements of these properties, Hammer and colleagues used data from Gaia’s first third publication to calculate the motions of 40 dwarf galaxies outside the Milky Way. Then they used parameters such as the 3D velocity of each galaxy to calculate its orbital energy and angular velocityAnd

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The results were really interesting – because they showed that most dwarf galaxies that are satellites of the Milky Way move much faster than known objects orbiting the Milky Way, such as Gaia-Enceladus and Dwarves Sagittarius. Spherical galaxy.

The Milky Way has dismantled other galaxies repeatedly throughout its long history. Gaia-Enceladus, also known as Gaia Sausage, was absorbed about 9 billion years ago. Its traces are found in a group of stars orbiting around relatively low energies.

The dwarf globular galaxy Sagittarius is currently being disrupted by tidal forces and is merging into the Milky Way, a process that began about 4 to 5 billion years ago. These stars rotate slightly faster than the stars of Gaia-Enceladus.

Dwarf galaxies move more aggressively. The team concluded that this means that these dwarf galaxies may not be close enough to the Milky Way because their gravitational field slows down the Milky Way.

Scientists say this discovery could change our understanding of the interactions between regular galaxies and the properties of dwarf galaxies and dwarf galaxies.

It is possible that some dwarf galaxies are trapped in the Milky Way’s orbit (but it is not possible to determine which ones), but how long these galaxies will last is an open question.

“The Milky Way is a big galaxy, so its tidal force is simply enormous, and it’s probably very easy to destroy a dwarf galaxy after a passing or two pass,” Hummer explainsAnd

If a dwarf galaxy can survive longer than expected in dwarf Milky Way galaxies, something must connect it, such as higher concentrations. dark matterAn invisible glue that binds the universe.

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The possibility that dwarf galaxies contain astonishing amounts of dark matter has been strongly suggested. The speed of their starsthat can’t be explained Just having ordinary matterAnd

The new results indicate that there is no need to include dark matter in our models of these galaxies; Future research could examine whether they are currently subject to tidal perturbations with a broader set of parameters.

It is also worth noting that the researchers’ results do not differ from paper from 2006 found it The speed of the Large and Small Magellanic Clouds Based on the data of the Hubble Space Telescope, there was a lot more than was previously thought, which indicates that these galaxies are not satellites. It seems that this assumption Since it was abandoned At least, according to some researchers.

However, we don’t know much about the Milky Way and the things around it, and there’s no doubt that Gaia is changing our understanding of our little corner of the universe.

“Thanks to Gaia, it is now clear that the history of the Milky Way is a much bigger story than astronomers previously understood.” This astrophysicist Timo Prusik claims this European Space Agency.

“We hope that by examining these exciting clues, we will be able to uncover fascinating chapters from our galaxy’s past.”

The search was published in Astrophysical JournalAnd