The Milky Way is bigger than we thought

The disk of our galaxy is huge. Bigger than previously thought. This has been determined by a study carried out by scientists from the Institute of Astrophysics of the Canary Islands (Spain) in collaboration with experts from the National Astronomical Observatories of China (NAOC). Their findings are published in the journal Astronomy & Astrophysics.

Thus, the disk of our galaxy is larger than what had been calculated so far: about 200,000 light years in diameter. This distance means that if we could travel at the speed of light, it would take 200,000 years to cross the Milky Way disk.

Spiral galaxies, such as the Milky Way, are characterized by having a thin disk where most of the stars are found; they have a limited size and, from a certain distance, we can hardly find stars anymore. In ours, for example, it was believed that there were no disk stars at distances from the center greater than twice the distance from the Sun. However, the new study highlights that not only do they exist at this distance but there are even more. far, at more than triple the distance from the Sun or even up to four times, they have compared the abundance of metals in the stars of the galactic plane with those of the halo, discovering that there is a mixture of disk and halo to distances now untheorized.

Previously, scientists had estimated that the diameter of the Milky Way was approximately between 100,000 and 180,000 light years.

"Our analysis reveals the presence of disk stars in a radius higher than 26 kpc -kiloparsec- (with 99.7% probability) and more than 31 kpc (with 95.4% probability)," the authors point out. your study. One kiloparsec is about 3,262 light years.

Researchers have reached these conclusions after performing a statistical analysis of mapped data obtained with two projects - called APOGEE and LAMOST - that obtain star spectra, that is, information about their speed and chemical composition.

"Using the metal content of the stars of the catalogs, with the combination of high-quality spectral atlases such as APOGEE and LAMOST, and the distance to which they place the objects, we have verified that there is an appreciable fraction of stars beyond where it was supposed to end the disc of the Milky Way, "explains Carlos Allende, researcher at the IAC and co-author of the work.

The objective of the study was to spectroscopically confirm the presence of disk stars at distances much larger than those stipulated for the Milky Way disk.

"We have not made use of models, which sometimes only give the answers they were designed for, only statistics on a large number of objects, the results are therefore free of a priori assumptions, beyond a few firmly established" , says Francisco Garzon, researcher at the IAC and co-author of the study.