Astronomers in the US have discovered some of the most distant stars ever found in our galaxy, especially in the galactic halo, an extended spheroidal region surrounding the galaxy’s main body. Thanks to these new observations, scientists now have a clearer picture of the halo’s outer limits.

In particular, 208 variable stars of the RR Lyrae type were found, and the most distant of them is located at a distance of more than a million light years from Earth and is located almost halfway to the Andromeda galaxy neighboring us, which is about 2.5 million light years.

These ancient stars have a predictable, changing brightness (it fluctuates in a repeating cycle) and are therefore ideal as a reference point for measuring galactic distances.

The exploration is redefining what constitutes the outermost reaches of the galaxy.

“A new study is redefining what makes up the outermost reaches of our galaxy. In fact, our galaxy and Andromeda are so large that there is almost no gap between the two galaxies,” said UC Santa Cruz professor of astronomy and astrophysics Raja Guha Thakurta, who made the announcement at the American Astronomical Association meeting. Society in Seattle.

Astronomers have pointed out that the surrounding halo, made up of various scattered stars, is much larger than our galaxy’s main disk, which is no more than 100,000 light years in diameter. Our solar system with the Earth is located in one of the spiral arms of the disk. At the center of the disk is a central “bulge” and around it is a halo containing the oldest stars in our galaxy, extending hundreds of thousands of kilometers in all directions.

The halo is difficult to study because it is so far from Earth and its stars are very rare compared to those in the central galactic disk. On the other hand, the halo is dominated by dark matter and therefore contains most of the total galactic mass.

Based on previous estimates, the halo extends up to 300 kiloparsecs, or about one million light-years from the galactic center (one kiloparsec equals 3,260 light-years), but the new study extends the halo’s outer limit to at least 320 kiloparsecs.

Source: RES-IPE