Astronomers have discovered more than 200 variable stars of the RR Lyrae type (its brightness changes periodically according to patterns) in the stellar halo of the Milky Way. The farthest of these stars is just over 1 million light-years away from Earth, about half the distance to our neighboring galaxy, Andromeda, which is about 2.5 million light-years away. distance.
The find was made by a team that includes Raja GuhaThakurta and Yuting Feng, both from the University of California at Santa Cruz, United States. The discovery has been presented publicly at a recent meeting of the American Astronomical Society.
The brightness oscillations and other characteristic features of RR Lyrae stars make them excellent “light beacons” for measuring galactic distances. These new observations have allowed researchers to better understand the outer limits of the Milky Way’s halo.
This study is redefining what constitutes the outer limits of our galaxy, as GuhaThakurta points out. It is becoming increasingly obvious that our galaxy and Andromeda are so large that the space between them is very small.
The stellar halo of our galaxy is much larger than the disk, which is about 100,000 light-years across. Our solar system resides in one of the spiral arms of the disk. In the middle of the disk is the galactic bulge, and around it the sphere that is the halo, which contains the oldest stars in the galaxy and extends for hundreds of thousands of light-years in all directions.
Artist’s impression of the halo that surrounds the main structure of our galaxy, the Milky Way. The location of this and the two satellite galaxies are indicated in the central area. (Image: NASA/CXC/M.Weiss/NASA/CXC/Ohio State/A.Gupta et al.)
There are very few stars in the halo, compared to those in the disk and bulge. However, the halo is very rich in dark matter and contains most of the galaxy’s mass.
Dark matter is a strange class of matter that has never been directly observed (it does not emit any type of radiation) and whose nature is unknown. The presence of dark matter can be inferred from its gravitational influence on normal matter. Thanks to this, it is known that, as a general rule, there is abundant dark matter in all galaxies. (Fountain: NCYT de Amazings)