Wednesday , April 21 2021

ESA's Gaea Spacecraft locates ghost galaxy lurking on the outskirts of the Milky Way




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Astronomers have unexpectedly discovered a dwarf "low-ghost" dwarf galaxy on the outer edges of our own Milky Way.

What would Antlia 2 look like if you could see it, for example, from Chile.Credit: G. Torrealba (Academia Sinica, Taiwan), V. Belokurov (Cambridge, UK and CCA, New York, USA) based on the image of ESO / S. Brunier

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After scanning the latest batch of data from the European Space Agency's (ESA) Gaia spacecraft, an international team of astronomers has found the most diffuse galaxy with the least surface brightness ever detected. Now dubbed Antlia 2, for the constellation in which it is found, it is officially a new satellite galaxy of the Milky Way.

"It is not entirely clear how this galaxy has become so ghostly," Gabriel Torrealba, a team leader and astrophysicist at the Sinica Academy at the Taiwan Institute of Astronomy and Astrophysics (ASIAA), told me.

About one-third of the Milky Way's diameter, Torrealba notes that Antlia 2 is about the same size as the Great Magellanic Cloud (CML), but shines about 10,000 times weaker.

Such low-brightness galaxies have very low star formation rates and produce very few supernovae, as noted earlier here.

Part of the reason why Antilia 2 was not seen so far was simply that it lies in an inherently difficult part of the galactic plane to be observed. & Nbsp; It is a region full of dust and an overabundance of bright stars near the galactic center.

But the team was able to use about a hundred pulsating stars, called RR Lyrae, to probe the interior and identify the Antlia 2 in this galactic area of ​​dodge.

"The avoidance zone is basically that part of the sky obscured by the Milky Way's disk seen from Earth," Torrealba said. "The Milky Way disc has a lot of gas and stars, making it extremely crowded and complex."

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Because of this complexity, says Torrealba, any kind of study becomes very difficult to do. Gaia is able to dig in the Zone of Prevention, he says, because it provides proper high-quality motions of stars behind the central disc of our Milky Way. That is, it is capable of tracking stars as they move through the celestial sphere.

Antlia 2 is a gigantic low mass dwarf galaxy.Credit: J. Sanders (Cambridge, UK) based on the image of the Gaia Data Processing and Analysis Consortium (DPAC); A. Moitinho / A. F. Silva / M. Barros / C. Barata, University of Lisbon, Portugal; H. Savietto, Fork Research, Portugal.

Located behind the galactic disk, the team reports in the magazine Royal Astronomical Society Monthly News that Antlia 2 was found using Gaia's latest Data Release 2 (DR-2) data, as well as ground tracking observations with the Anglo-Australian Telescope in Australia. And although it is clearly a satellite, it never reaches more than 130,000 light years from the Milky Way.

Torrealba says Antlia 2 is probably one of the oldest dwarf galaxies in the universe, but he and his colleagues are still intrigued by how it became so diffuse.

"One possibility is that Antlia 2 was much more massive in the past, and when it fell into the Milky Way, it lost its mass to become more diffuse," Torrealba said.

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A problem with this idea says that Torrealba is that instead of growing, galaxies tend to shrink at the same time as they lose the stars.

"There seems to be no (as yet) limit on how the diffuse, low-bright galaxy can get," Stacy McGaugh, an astronomer at Case Western Reserve University in Cleveland, who did not participate in the study, told me.

One of the biggest questions is how many of these dwarf galaxies may be lurking in our own galaxy. The authors note that the Milky Way can still have between one and three undetected dwarf galaxies, each with 100,000 or more star masses.

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Astronomers have unexpectedly discovered a dwarf "low-ghost" dwarf galaxy on the outer edges of our own Milky Way.

What would Antlia 2 look like if you could see it, for example, from Chile.Credit: G. Torrealba (Academia Sinica, Taiwan), V. Belokurov (Cambridge, UK and CCA, New York, USA) based on the image of ESO / S. Brunier

CONTINUED ARTICLE AFTER ADVERTISING

After scanning the latest batch of data from the European Space Agency's (ESA) Gaia spacecraft, an international team of astronomers has found the most diffuse galaxy with the least surface brightness ever detected. Now dubbed Antlia 2, for the constellation in which it is found, it is officially a new satellite galaxy of the Milky Way.

"It is not entirely clear how this galaxy has become so ghostly," Gabriel Torrealba, a team leader and astrophysicist at the Sinica Academy at the Taiwan Institute of Astronomy and Astrophysics (ASIAA), told me.

About one-third of the Milky Way's diameter, Torrealba notes that Antlia 2 is about the same size as the Great Magellanic Cloud (CML), but shines about 10,000 times weaker.

Such low-brightness galaxies have very low star formation rates and produce very few supernovae, as noted earlier here.

Part of the reason why Antilia 2 had not been seen so far was simply that it lies in an inherently difficult part of the galactic plane to be observed. It is a region full of dust and an overabundance of bright stars near the galactic center.

But the team was able to use about a hundred pulsating stars, called RR Lyrae, to probe the interior and identify the Antlia 2 in this galactic area of ​​dodge.

"The avoidance zone is basically that part of the sky obscured by the Milky Way's disk seen from Earth," Torrealba said. "The Milky Way disc has a lot of gas and stars, making it extremely crowded and complex."

CONTINUED ARTICLE AFTER ADVERTISING

Because of this complexity, says Torrealba, any kind of study becomes very difficult to do. Gaia is able to dig in the Zone of Prevention, he says, because it provides proper high-quality motions of stars behind the central disc of our Milky Way. That is, it is capable of tracking stars as they move through the celestial sphere.

Antlia 2 is a gigantic low mass dwarf galaxy.Credit: J. Sanders (Cambridge, UK) based on the image of the Gaia Data Processing and Analysis Consortium (DPAC); A. Moitinho / A. F. Silva / M. Barros / C. Barata, University of Lisbon, Portugal; H. Savietto, Fork Research, Portugal.

Located behind the galactic disk, the team reports in the magazine Royal Astronomical Society Monthly News that Antlia 2 was found using Gaia's latest Data Release 2 (DR-2) data, as well as ground tracking observations with the Anglo-Australian Telescope in Australia. And although it is clearly a satellite, it never reaches more than 130,000 light years from the Milky Way.

Torrealba says Antlia 2 is probably one of the oldest dwarf galaxies in the universe, but he and his colleagues are still intrigued by how it became so diffuse.

"One possibility is that Antlia 2 was much more massive in the past, and when it fell into the Milky Way, it lost its mass to become more diffuse," Torrealba said.

CONTINUED ARTICLE AFTER ADVERTISING

A problem with this idea says that Torrealba is that instead of growing, galaxies tend to shrink at the same time as they lose the stars.

"There seems to be no (as yet) limit on how the diffuse, low-bright galaxy can get," Stacy McGaugh, an astronomer at Case Western Reserve University in Cleveland, who did not participate in the study, told me.

One of the biggest questions is how many of these dwarf galaxies may be lurking in our own galaxy. The authors note that the Milky Way can still have between one and three undetected dwarf galaxies, each with 100,000 or more star masses.


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