The Gaia Sausage: The major collision that changed the Milky Way galaxy


IMAGE: An impression of the encounter in between the Milky Way galaxy and the smaller sized Sausage galaxy about 8 billion to 10 billion years earlier. The record of this ancient encounter is …
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Credit: V. Belokurov (Cambridge, UK); Based on image by ESO/JuanCarlos Mu ñoz

NewYork City– An global group of astronomers has actually found an ancient and remarkable head-on collision in between the Milky Way and a smaller sized things, called the “Sausage”galaxy The cosmic crash was a specifying occasion in the early history of the Milky Way and improved the structure of our galaxy, making both its inner bulge and its external halo, the astronomers report in a series of brand-new documents.

The astronomers propose that around 8 billion to 10 billion years earlier, an unidentified dwarf galaxy smashed into our own MilkyWay The dwarf did not endure the effect: It rapidly broke down, and the wreckage is now all around us.

“The collision ripped the dwarf to shreds, leaving its stars moving in very radial orbits”that are long and narrow like needles, stated Vasily Belokurov of the University of Cambridge and the Center for Computational Astrophysics at the Flatiron Institute in New YorkCity The stars’ courses take them “very close to the centre of our galaxy. This is a telltale sign that the dwarf galaxy came in on a really eccentric orbit and its fate was sealed.”

The brand-new documents in the MonthlyNotices of the Royal Astronomical Society, TheAstrophysical Journal Letters and overview the significant functions of this amazing occasion. Several of the documents were led by Cambridge college student GyuChulMyeong He and associates utilized information from the European Space Agency’s Gaia satellite. This spacecraft has actually been mapping the excellent material of our galaxy, recording the journeys of stars as they take a trip through the MilkyWay Thanks to Gaia, astronomers now understand the positions and trajectories of our celestial neighbours with extraordinary precision.

The courses of the stars from the galactic merger made them the name “the Gaia Sausage,” described Wyn Evans ofCambridge “We plotted the velocities of the stars, and the sausage shape just jumped out at us. As the smaller galaxy broke up, its stars were thrown onto very radial orbits. These Sausage stars are what’s left of the last major merger of the Milky Way.”

TheMilky Way continues to hit other galaxies, such as the undersized Sagittarius dwarfgalaxy However, the Sausage galaxy was a lot more huge. Its overall mass in gas, stars and dark matter was more than 10 billion times the mass of our sun. When the Sausage crashed into the young Milky Way, its piercing trajectory triggered a great deal of chaos. The Milky Way’s disk was most likely expanded and even fractured following the effect and would require to grow back. And Sausage particles was spread all around the inner parts of the Milky Way, developing the ‘bulge’ at the galaxy’s centre and the surrounding ‘excellent halo.’

Numerical simulations of the stellar mashup can recreate these functions, stated Denis Erkal of the University ofSurrey In simulations run by Erkal and associates, stars from the Sausage galaxy go into stretched-out orbits. The orbits are additional lengthened by the growing Milky Way disk, which swells and ends up being thicker following the collision.

Evidence of this stellar renovation is seen in the courses of stars acquired from the dwarf galaxy, stated Alis Deason of DurhamUniversity “The Sausage stars are all turning around at about the same distance from the centre of the galaxy.” These U-turns trigger the density in the Milky Way’s excellent halo to reduce considerably where the stars flip instructions. This discovery was specifically pleasing for Deason, who anticipated this orbital pileup practically 5 years earlier. The brand-new work describes how the stars fell under such narrow orbits in the top place.

The brand-new research study likewise recognized a minimum of 8 big, round clumps of stars called globular clusters that were brought into the Milky Way by the Sausagegalaxy Small galaxies normally do not have globular clusters of their own, so the Sausage galaxy need to have huged enough to host a collection of clusters.

“While there have been many dwarf satellites falling onto the Milky Way over its life, this was the largest of them all,” stated Sergey Koposov of Carnegie Mellon University, who has actually studied the kinematics of the Sausage stars and globular clusters in information.



In, the authors explain the regional proof however likewise lay out clearly and specifically exactly what sort of occasion this was and what does it cost? particles it might add to the inner Milky Way halo. The scientists likewise evaluate cosmological simulations to select the mass and the time of the accretion and explain that it might have produced the thick disk.

In, the authors explain that the deposits of excellent particles from this occasion have comparable apocenters and are naturally accountable for the excellent halo break.

In, the authors show that this merger has actually brought a a great deal of globular clusters into the Milky Way, and that these stick out plainly from the rest of the stellar population.

In, the authors indicate the proof for this merger in the circulation of actions as well as emphasize the presence of the big retrograde spray of particles.

In, the authors talk about in information the retrograde particles and supply contrasts to an easy design of a huge merger.


TheFlatiron Institute is the research study department of the SimonsFoundation Its objective is to advance clinical research study through computational techniques, consisting of information analysis, modeling and simulation. The institute’s Center for Computational Astrophysics produces brand-new computational structures that permit researchers to evaluate huge huge datasets and to comprehend complex, multi-scale physics in a cosmological context. .

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