The Milky Way may have lost a whole group of satellite galaxies


The space around the Milky Way is not vacant. It’s teeming with dwarf galaxies — small, faint, and low in mass, with only about 1,000 stars each.

It is not unusual. We know from our observations of other large galaxies that dwarf galaxies often cluster nearby and can be caught in the gravitational field of a larger object.

Select astronomers to date Approximately 60 small galaxies Within 1.4 million light-years of the Milky Way, although there are likely many hiding places in the dark. Most of them seem to be hanging around, like fruit flies around a banana.

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

“We conclude that due to their high energies and unparalleled angular moments, most dwarfs cannot be long-lived satellites, and if they can be associated with the Milky Way, they are in the first place. Corridor, that is, they fell less than two billion years ago,” the researchers write in a new way ورق It was led by astrophysicist François Hammer of the Paris Observatory in France.

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

The Gaia mission is an ongoing project to map the Milky Way in the highest resolution yet, including the 3D locations, motions, and velocities of stars and objects inside (and to some extent outward).

Using measurements of these properties, Hammer and colleagues used data from Gaia’s 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 momentum.

The results were really interesting — they showed that most dwarf galaxies thought to be Milky Way moons move much faster than known objects orbiting the Milky Way, such as the stars Gaia Enceladus and the Sagittarius dwarf. Spherical galaxy.

The Milky Way has disassembled other galaxies repeatedly in its long history. Gaia-Enceladus, also known as Gaia sausage, was classified about 9 billion years ago. Its traces remain in a group of stars orbiting around relatively low energies.

The dwarf globular galaxy in Sagittarius is currently being perturbed by tidal forces (gravity) and is merging into the Milky Way, a process that began about 4 to 5 billion years ago. These stars travel 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 have been close to the Milky Way long enough to slow down the massive galaxy’s gravitational field.

The researchers say this discovery could change our understanding of the interactions between regular and dwarf galaxies, as well as the properties of dwarf galaxies.

It is possible that some dwarf galaxies are captured in the orbit of the Milky Way (although it is impossible to determine which of them), but the question remains open.

“The Milky Way is a big galaxy, so the tidal force in it is enormous and it is very easy to destroy a dwarf galaxy after a passing once or two.” Hummer explains.

If a dwarf galaxy can survive much longer than that — as was thought for dwarf galaxies in the Milky Way — then something must bind them together, such as higher concentrations of black matterThe invisible glue that binds the universe together.

The possibility that dwarf galaxies contain an astonishing amount of dark matter has been strongly mentioned before Their star movesthat can’t be explained By the presence of natural matter alone.

The new findings suggest that dark matter does not necessarily need to be included in our models of these galaxies; Future research may investigate whether they are currently experiencing tidal turbulence with a broader set of parameters to play with.

It should also be noted that the results of the researchers do not differ from the paper 2006 who found Small and Large Magellanic Clouds They were much higher than expected, based on data from Hubble, indicating that these are not satellites of the Milky Way. It seems that this idea since abandoned At least by some researchers.

However, there is still a lot we don’t know about things in and around the Milky Way, and there is absolutely no doubt that Gaia is changing our understanding of our little corner of the universe.

“Thanks in large part to Gaia, it is now clear that the history of the Milky Way is much richer in history than astronomers previously realized,” Astrophysicist Timo Prosti says: European Space Agency.

“By investigating these tantalizing clues, we hope to uncover more fascinating chapters from our galaxy’s past.”

The search was published in Astrophysical Journal.


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