Post by Andrei Tchentchik on Jun 24, 2019 16:11:08 GMT 2
(.#215).- 10 billion years ago, a galaxy violently hit our Milky Way.
10 billion years ago, a galaxy violently hit our Milky Way.
By Tristan Vey - Posted on 11/01/2018 at 10:57
The data from the European satellite Gaia have made it possible to build this splendid image of our galaxy seen by the slice. ESA.
The shape of our galaxy is the fruit of a distant collision with a galaxy five times smaller, confirm today the data of the European satellite Gaia. We have completely absorbed it since.
10 billion years ago, a galaxy hit ours, the Milky Way. We find the trace of this cosmic accident in the strange trajectory of millions of stars that circulate in our galaxy on more elongated trajectories and in the opposite direction. The data of the European satellite Gaia, which has since 2013 an unprecedented record of stars in our galaxy, confirm today this scenario to which it provides some details, reports a study published Wednesday in the journal Nature.
The strange position of these stars in the classification chart that compares surface temperature and luminosity only reinforces the idea that this is a population of "foreign" stars that have migrated into our world. galaxy. "We were certain of our interpretation only after associating Gaia's data with the additional information of chemical composition measured from the ground by the APOGEE program", adds Carine Babusiaux, researcher at the University of Grenoble Alpes and second author of the study.
The new observations now fit perfectly with the models according to which this "impactor" was unique and probably much larger than previously imagined. He had to make about a tenth of the current Milky Way. The equivalent of one of the Magellan clouds. But since our galaxy was smaller at the time, the mass ratio between the two objects was likely to be 1 in 5 at the time of the collision, the researchers say.
The incidental galaxy has long been absorbed by our Milky Way. Its stars would form a large part of the interior "halo", a set of old stars that do not circulate in the main disc but are isolated around everywhere. The whole halo forms a spheroidal structure that is not generally distinguished on the traditional representations of our galaxy, since most of the 10 billion stars that compose it form a large flattened spiral with a thicker "bulb" in the center.
This collision would have disturbed the initial shape of our galaxy. Millions of paintings would have been "moved" to form the "thick disc", a set of sparsely concentrated stars that envelops the main "thin disc" that concentrates most of the stars of our galaxy.
An expected collision with Andromeda
"The Gaia satellite was built to answer such questions" about the youth of our galaxy, says Amina Helmi, a researcher at the University of Groningen, the Netherlands, and the first author of this new study. "We can now say that this is how our galaxy was formed in those remote times. It's fantastic. It's so beautiful, it makes you feel so big and so small at the same time. "
Our neighbor Andromeda is also the result of a gigantic cosmic collision, but this one happened much more recently. In a few billion years, it will finally be up to our two galaxies to merge together. The show could be striking ... and deadly. Because if the stars do not collide in galactic collisions, the two objects being composed mostly of vacuum, the fusion of the two supermassive black holes that are located in their heart should emit gigantic amounts of energy that we would be likely fatal.
F I N .
10 billion years ago, a galaxy violently hit our Milky Way.
By Tristan Vey - Posted on 11/01/2018 at 10:57
The data from the European satellite Gaia have made it possible to build this splendid image of our galaxy seen by the slice. ESA.
The shape of our galaxy is the fruit of a distant collision with a galaxy five times smaller, confirm today the data of the European satellite Gaia. We have completely absorbed it since.
10 billion years ago, a galaxy hit ours, the Milky Way. We find the trace of this cosmic accident in the strange trajectory of millions of stars that circulate in our galaxy on more elongated trajectories and in the opposite direction. The data of the European satellite Gaia, which has since 2013 an unprecedented record of stars in our galaxy, confirm today this scenario to which it provides some details, reports a study published Wednesday in the journal Nature.
The strange position of these stars in the classification chart that compares surface temperature and luminosity only reinforces the idea that this is a population of "foreign" stars that have migrated into our world. galaxy. "We were certain of our interpretation only after associating Gaia's data with the additional information of chemical composition measured from the ground by the APOGEE program", adds Carine Babusiaux, researcher at the University of Grenoble Alpes and second author of the study.
The new observations now fit perfectly with the models according to which this "impactor" was unique and probably much larger than previously imagined. He had to make about a tenth of the current Milky Way. The equivalent of one of the Magellan clouds. But since our galaxy was smaller at the time, the mass ratio between the two objects was likely to be 1 in 5 at the time of the collision, the researchers say.
The incidental galaxy has long been absorbed by our Milky Way. Its stars would form a large part of the interior "halo", a set of old stars that do not circulate in the main disc but are isolated around everywhere. The whole halo forms a spheroidal structure that is not generally distinguished on the traditional representations of our galaxy, since most of the 10 billion stars that compose it form a large flattened spiral with a thicker "bulb" in the center.
This collision would have disturbed the initial shape of our galaxy. Millions of paintings would have been "moved" to form the "thick disc", a set of sparsely concentrated stars that envelops the main "thin disc" that concentrates most of the stars of our galaxy.
An expected collision with Andromeda
"The Gaia satellite was built to answer such questions" about the youth of our galaxy, says Amina Helmi, a researcher at the University of Groningen, the Netherlands, and the first author of this new study. "We can now say that this is how our galaxy was formed in those remote times. It's fantastic. It's so beautiful, it makes you feel so big and so small at the same time. "
Our neighbor Andromeda is also the result of a gigantic cosmic collision, but this one happened much more recently. In a few billion years, it will finally be up to our two galaxies to merge together. The show could be striking ... and deadly. Because if the stars do not collide in galactic collisions, the two objects being composed mostly of vacuum, the fusion of the two supermassive black holes that are located in their heart should emit gigantic amounts of energy that we would be likely fatal.
F I N .
