WASHINGTON: In the stellar halo of the Milky Way, astronomers have found more than 200 far-off variable stars known as RR Lyrae stars. Nearly half of the distance to our neighbouring galaxy, Andromeda, which is located approximately 2.5 million light-years away, is covered by the most distant stars, which are more than a million light-years from Earth.
The stars in the RR Lyrae constellation offer ideal "standard candles" for gauging galactic distances because of their distinctive pulsations and brightness. The researchers were able to determine the Milky Way's halo's outermost points thanks to these fresh data.
Raja GuhaThakurta, professor emeritus and chair of astronomy and astrophysics at UC Santa Cruz, stated that "this discovery is rethinking what comprises the outer edges of our galaxy." There is hardly any room between Andromeda and our galaxy because both of them are so massive.
The star halo, which makes up a larger portion of our galaxy than the disc, which is only around 100,000 light-years across, was described by GuhaThakurta. One of the spiral arms of the disc is where our solar system is located. The halo, which includes the galaxy's oldest stars and stretches out in all directions for hundreds of thousands of light years, is located around the central bulge, which is located in the centre of the disc.
The halo is the most challenging area to analyse since the outside borders are so far away, according to GuhaThakurta. The halo is dominated by dark matter and actually comprises the majority of the galaxy's mass, despite the disc and bulge's high stellar concentrations and the halo's sparse star population.
The new study's lead author, Yuting Feng, a PhD student at UC Santa Cruz who collaborates with Guha Thakurta, will discuss their findings in two lectures on January 9 and 11 at the American Astronomical Society meeting in Seattle.
Prior modelling studies, according to Feng, predicted that the star halo should reach a distance of around 300 kiloparsecs, or 1 million light years, from the galactic centre. (Astronomers use kiloparsecs to measure galactic distances; one kiloparsec is equivalent to 3,260 light-years.) The 208 RR Lyrae stars that Feng and his team found were located between 20 and 320 kiloparsecs away.