Astronomers spot the remnants of a long-lost galaxy eaten by the Milky Way
The Milky Way galaxy feasted on more galaxies in its early days than astronomers thought.
the Gaia A spacecraft has discovered the remnants of an ancient cosmic collision in our Milky Way, revealing a previously unknown galaxy, now dubbed “Pontus”, absorbed into the Milky Way long before our galaxy looked like it is now.
Pontus was a galaxy that strayed too close to the Milky Way and “fell” into our galaxy’s gravity about 8 to 10 billion years ago, the European Space Agency, which operates Gaia, has said. in a press release Thursday, February 17.
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Events like this merger are important for learning more about the Milky Way, ESA added, because they show the “family tree” of smaller galaxies that helped make the Milky Way what it is today. today.
Gaia launched into space nearly a decade ago, in 2013, on an ambitious mission to map the three-dimensional sky more accurately than ever before. The movements of stars and other objects near us will in turn reveal information about the composition, formation and evolution of the Milky Way, mission officials say on the Gaia website.
This latest work on galactic mergers grew out of a study of the Milky Way’s halo, which is an area filled with globular clusters of older stars, low metallicity stars and other interesting objects. “Alien galaxies” in the halo can appear in this region in different ways, depending on the speed of the collision, the ESA said in the study’s press release.
“When a foreign galaxy falls into ours, large gravitational forces called tidal forces pull it apart,” the ESA said. “If this process proceeds slowly, the stars of the molten galaxy will form a vast stellar flux which can be easily distinguished in the halo. If the process proceeds rapidly, the stars of the molten galaxy will be more dispersed in the halo and no clear signature will be visible.”
However, stars aren’t the only way we can detect a molten galaxy. If the intruder contains globular stars or small satellite galaxies, these may also appear in the halo. The new study focused on finding this data.
Scientists named the incident after Greek mythology, which identifies Pontus as one of the first children of Gaia, the earth goddess.
In addition to finding the Pontus event, the team identified five other distinct fusion clusters (already known to science) and a possible sixth in the data. The five events already known are called Sagittarius, Cetus, Gaia-Sausage/Enceladus, LMS-1/Wukong and Arjuna/Sequoia/I’itoi.
The ESA noted that Pontus and most of these other events happened around the same time, 8-10 billion years ago, but Sagittarius is more recent, 5-6 billion years ago. of years. “As a result, the Milky Way has not yet been able to fully disrupt it,” the agency added of the Sagittarius event.
A study based on the research was published Thursday, February 17, in The Astrophysical Journal, led by Khyati Malhan, an astrophysicist at the Max Planck Institute for Astronomy in Heidelberg, Germany. The work was based on an early release of Gaia’s third big data set, which is expected to drop on June 13.