They observed the most distant star in the Milky Way and it is halfway to the Andromeda galaxy
They observed the most distant star in the Milky Way and it is halfway to the Andromeda galaxy 1-214
How far does the Milky Way stretch? The answer has long remained difficult to give. But researchers now seem finally able to define the outer limits of our Galaxy. They observed the star of our Milky Way farthest from our Earth.

The Milky Way is ourGalaxy. A rather ordinary spiral galaxy which is usually said to measure around 100,000 light yearsof diameter. But this is to limit it to its simple galactic disk. Because if we include the halo that surrounds it, we must rather evoke a much larger diameter. According tomodelingthe most recent, even of the order of 2 million light-years or about 300 kiloparsecs.
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Astronomers like to measure galactic distances in kiloparsecs. One kiloparsec is 3260 light years.
They observed the most distant star in the Milky Way and it is halfway to the Andromeda galaxy 1-215
It is precisely at the confines of this halo thatastronomersfrom the University of California at Santa Cruz (United States) report, on the occasion of the meeting of the American Astronomical Society 2023, having observed some 200 variable stars of type RR Lyrae. A type of star whose researchers know well how to determine the distance at which they are. These are between 10 and 320 kiloparsecs. Among them, therefore, thestarof our most distant Milky Way from our Earth. It is more than a million light-years away from us. It's almost half the distance that separates us from our neighbour, theandromeda galaxy.
The discovery was made using data collected as part of the Next Generation Virgo Cluster Survey (NGVS) study of the Virgo Cluster, a cluster of galaxies located far beyond our Milky Way. And it is the excellent quality of this data that has allowed astronomers to reliably and accurately characterize the distances that separate us from these prominent stars captured by NGVS. The famous 200 RR Lyrae.
They observed the most distant star in the Milky Way and it is halfway to the Andromeda galaxy 1--49
Setting limits to the Milky Way
Remember that the interest of RR Lyrae stars is that they have very specific physical properties . They expand and contract regularly and repeatedly. Once such a star has been identified thanks to its pulsations and since thebrightnessactual average of these stars is always the same, astronomers use its observed brightness to calculate how far away it is.
As things are never really simple in ourUniverse, researchers must still be careful not to be misled byquasars-- even more distant objects -- that would pretend to be RR Lyrae. But this time, astronomers are convinced. This latest sample of over 200 RR Lyrae is robust.

The observations made by researchers at the University of California at Santa Cruz thus confirm the theoretical estimates of the size of the halo of our Milky Way. “An important result ,” comments Yuting Fend, lead author of the study, in a press release . For if the stars remain sparse in this halo, it nevertheless contains the major part of themassof our Galaxy -- notably in the form ofblack matter. "This study redefines what constitutes the outer limits of our Milky Way ," adds Raja GuhaThakurta, professor of astronomy and science.astrophysicsat UC Santa Cruz. “Our Galaxy and that of Andromeda are both ultimately so large that there is practically no space in between. »


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