November 30, 2022

Gaia Spacecraft Reveals a New Member of the Milky Way Family

This image reveals the Milky Way as seen by Gaia. The squares represent the place of globular clusters, the triangles the place of satellite galaxies, and the small dots are excellent streams. The dots and squares in purple are objects brought into the Milky Way by the Pontus merging galaxy. Credit: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO
Our galaxy, the Milky Way, began forming around 12 billion years back. Ever since, it has been growing in both mass and size through a series of mergers with other galaxies.
Maybe most interesting is that this process has not rather completed, and by using information from ESAs Gaia spacecraft, astronomers can see it happening. This in turn permits them to reconstruct the history of our galaxy, revealing the household tree of smaller galaxies that have actually helped make the Milky Way what it is today.
The latest deal with this subject originates from Khyati Malhan, a Humboldt Fellow at the Max-Planck-Institut für Astronomie, Heidelberg, Germany, and associates. Together, they have actually evaluated information based upon Gaias early 3rd data release (EDR3) looking for the remains of smaller galaxies combining with our own. These can be discovered in the so-called halo of the Milky Way, which surrounds the disc of more youthful stars and central bulge of older stars that make up the more luminous parts of the Milky Way.

The dots and squares in purple are things brought into the Milky Way by the Pontus merging galaxy. These can be discovered in the so-called halo of the Milky Way, which surrounds the disc of more youthful stars and main bulge of older stars that consist of the more luminescent parts of the Milky Way.

When a foreign galaxy falls into our own, excellent gravitational forces known as tidal forces pull it apart. If this procedure goes slowly, the stars from the combining galaxy will form a vast outstanding stream that can be quickly distinguished in the halo. The combining galaxys stars will be more spread throughout the halo and no clear signature will be noticeable if the process goes quickly.
But the combining galaxy might contain more than simply stars. It could likewise be surrounded by a population of globular star cluster and little satellite galaxies. So, the group searched for these in the Gaia data.
In total they studied 170 globular clusters, 41 stellar streams, and 46 satellites of the Milky Way. Plotting them according to their energy and momentum exposed that 25 percent of these things fall under six distinct groups. Each group is a merger accompanying the Milky Way. There was likewise a possible seventh merger in the information.
5 had actually been previously determined on studies of stars. They are known as Sagittarius, Cetus, Gaia-Sausage/Enceladus, LMS-1/ Wukong, and Arjuna/Sequoia/I itoi. The sixth was a freshly determined merger event. The team called it Pontus, suggesting the sea. In Greek mythology, Pontus is the name of one of the very first kids of Gaia, the Greek goddess of the Earth.
Based upon the method Pontus has actually been pulled apart by the Milky Way, Khyati and associates estimate that it most likely fell into the Milky Way some 8 to 10 billion years earlier. Four of the other 5 merger occasions most likely likewise took place around this time as well. The sixth occasion, Sagittarius, is more current. It might have fallen under the Milky Way sometime in the last five to 6 billion years. As a result, the Milky Way has not yet had the ability to completely disrupt it.
Piece by piece, astronomers are fitting together the merger history of the Galaxy, and Gaia data is proving important.
On 13 June 2022, the Gaia mission will release its data release 3, which will provide much more in-depth info about the Milky Ways past, present, and future.
Referral: “The Global Dynamical Atlas of the Milky Way Mergers: Constraints from Gaia EDR3– based Orbits of Globular Clusters, Stellar Streams, and Satellite Galaxies” by Khyati Malhan, Rodrigo A. Ibata, Sanjib Sharma, Benoit Famaey, Michele Bellazzini, Raymond G. Carlberg, Richard DSouza, Zhen Yuan, Nicolas F. Martin and Guillaume F. Thomas, 17 February 2022, The Astrophysical Journal.DOI: 10.3847/ 1538-4357/ ac4d2a.

In overall they studied 170 globular clusters, 41 excellent streams, and 46 satellites of the Milky Way. Each group is a merger taking location with the Milky Way. Based upon the method Pontus has actually been pulled apart by the Milky Way, Khyati and associates estimate that it most likely fell into the Milky Way some 8 to ten billion years back.

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