Cosmic collision with the galaxy "Sausage" remodeled Milky Way

Astronomers have discovered an ancient cosmic collision with an object, nicknamed the "sausage" galaxy, which has reshaped the structure of the Milky Way galaxy. (Image Source: University of Cambridge)

Astronomers have discovered an ancient cosmic collision with an object, nicknamed the "Sausage" galaxy, which has reshaped the structure of the Milky Way. The accident was a milestone in the early history of the Milky Way and helped shape its inner bulge and its outer halo, according to a series of studies published in monthly leaflets. Royal Astronomical Society and The Astrophysical Journal Letters

. Scientists suggest that about 8 billion to 10 billion years ago, an unknown dwarf galaxy shattered in our own Milky Way. The dwarf did not survive the impact: he quickly collapsed, and the wreck is now all around us. "The collision shredded the dwarf, letting his stars move in very radial orbits" that are long and narrow like needles, said Vasily Belokurov of the University of Cambridge in the UK. The paths of the stars take them "very close to the center of our galaxy." It's a telltale sign that the dwarf galaxy has entered a truly eccentric orbit and that its fate has been sealed. "

Researchers University of Cambridge in the United Kingdom used data from the Gaia satellite of the European Space Agency. mapped the stellar contents of our galaxy, recording the journeys of the stars during their journey through the Milky Way. Thanks to Gaia, astronomers now know the positions and trajectories of our celestial neighbors with unprecedented accuracy. The paths of the galactic fusion stars have earned them the nickname "Gaia Sausage," says Wyn Evans of Cambridge

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"We have traced the velocities of the stars, and the shape of the sausage has just fallen on us.As the smallest galaxy separated, its stars were thrown into very radial orbits.These sausage stars are what remains of the last major fusion of the Milky Way, "said Evans
The Milky Way continues to collide with other galaxies, such as the dwarf galaxy dwarf Sagittarius.However, the galaxy of the sausage was much more mbadive.Its total mbad of gas, stars and dark matter was more than 10 billion times the mbad of our Sun.When the sausage s & rsquo; is overwritten in the young Milky Way, its piercing trajectory has caused a lot of chaos. The Milky Way disk was probably puffy or even fractured as a result of the impact and should have grown back.

Sausage debris was scattered all around the inner parts of the Milky Way, creating the & quot; bulge & quot; in the center of the galaxy. "A stellar halo." Numerical simulations of galactic mashup can replicate these features, said Denis Erkal of the University of Surrey in the UK. In simulations conducted by researchers, stars of the Sausage galaxy enter into stretched orbits. The orbits are further elongated by the growing disc of the Milky Way, which swells and becomes thicker as a result of the collision. Evidence of this galactic remodeling is visible in the trajectories of stars inherited from the dwarf galaxy, says Alis Deason of the University of Durham in the UK.

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"The sausage stars all turn about the same distance from the center of the galaxy, "said Deason. These U-turns cause the density in the stellar halo of the Milky Way to decrease considerably where the stars turn. This discovery was particularly pleasing to Deason, who predicted this orbital stack nearly five years ago. The new work explains how the stars fell into such narrow orbits in the first place. The new research also identified at least eight large spherical clusters of stars called globular clusters that were introduced into the Milky Way by the sausage galaxy.

Small galaxies usually do not have globular clusters, so the galaxy of sausages must have been large enough to accommodate a collection of clusters. "Although there were many dwarf satellites falling on the Milky Way during its lifetime, it was the largest of all," said Sergey Koposov of Carnegie Mellon University in the United States , who studied the kinematics of the stars. detail.

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