For Y'all Data - Astronomers Abide By The Giant That Shaped The Early On Days Of Our Milky Way

Some x billion years ago, the Galaxy merged amongst a large galaxy. The stars from this partner, named Gaia-Enceladus, brand upward almost of the Milky Way's halo as well as also shaped its thick disk, giving it its inflated form. Influenza A virus subtype H5N1 description of this mega-merger, discovered past times an international squad led past times University of Groningen astronomer Amina Helmi, is instantly published inwards the scientific journal Nature.

Artistic rendering of Enceladus beingness devoured past times a Milky Way-like galaxy
[Credit: René van der Woude, Mixr.nl]

Large galaxies similar our Galaxy are the trial of mergers of smaller galaxies. An outstanding query is whether a galaxy similar the Galaxy is the production of many modest mergers or of a few large ones. The University of Groningen's Professor of Astronomy, Amina Helmi, has spent almost of her career looking for 'fossils' inwards our Galaxy which powerfulness offering some hints equally to its evolution. She uses the chemic composition, the set as well as the trajectory of stars inwards the halo to deduce their history as well as thereby to set the mergers which created the early on Milky Way.

Gaia's mo information release

The recent mo information liberate from the Gaia satellite mission final Apr provided Professor Helmi amongst information on approximately 1.7 billion stars. Helmi has been involved inwards the evolution of the Gaia mission for some 20 years as well as was business office of the information validation squad on the mo information release. She has instantly used the information to aspect for traces of mergers inwards the halo: "We expected stars from fused satellites inwards the halo. What nosotros didn't aspect to uncovering was that almost halo stars genuinely bring a shared rootage inwards i really large merger".

Thick disk

This is indeed what she found. The chemic signature of many halo stars was clearly dissimilar from the 'native' Galaxy stars. "And they are a fairly homogenous group, which indicates they part a mutual origin". By plotting both trajectory as well as chemic signature, the 'invaders' stood out clearly. Helmi: "The youngest stars from Gaia-Enceladus are genuinely younger than the native Galaxy stars inwards what is instantly the thick disk region. This way that the progenitor of this thick disk was already introduce when the fusion happened, as well as Gaia-Enceladus, because of its large size, shook it as well as puffed it up."

In a previous paper, Helmi had already described a huge 'blob' of stars sharing a mutual origin[1]. Now, she shows that stars from this blob inwards the halo are the debris from the merging of the Galaxy amongst a galaxy which was slightly to a greater extent than massive than the Small Magellanic Cloud, some x billion years ago. The galaxy is called Gaia-Enceladus, afterward the Giant Enceladus who inwards Greek mythology was born of Gaia (the public goddess) as well as Uranus (the Sky god).

The information on kinematics, chemistry, historic menses as well as spatial distribution from the native Galaxy stars as well as the remnants of Gaia-Enceladus reminded Helmi of simulations performed past times a sometime PhD student, some x years ago. His simulations of the merging of a large disc-shaped galaxy amongst the immature Galaxy produced a distribution of stars from both objects, which is totally inwards line of piece of job amongst the Gaia data. "It was amazing to aspect at the novel Gaia information as well as realize that I had seen it before!," says the astronomer.

Source: University of Groningen [November 01, 2018]


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