The disk of our galaxy is huge. Bigger than previously thought. This has been determined by a study carried out by scientists from the Instituto de Astrofísica de Canarias (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 previously calculated: about 200,000 light years across. This distance means that if we could travel at the speed of light, it would take 200,000 years to traverse the disk of the Milky Way.
Spiral galaxies, like the Milky Way, are characterized by having a thin disk where most of the stars are found; They are limited in size, and from a certain distance we can hardly find any stars . 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 away, more than triple the distance from the Sun or even up to four times , since 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 up to distances that are not now theorized.
Scientists had previously estimated the diameter of the Milky Way to be approximately 100,000 to 180,000 light years.
“Our analysis reveals the presence of stars in the disk in a radius greater than 26 kpc -kiloparsec- (with a 99.7% probability) and more than 31 kpc (with a 95.4% probability) “, the authors point out in your study. A kiloparsec is about 3,262 light years.
The researchers have reached these conclusions after carrying out a statistical analysis of mapped data obtained with two projects – called APOGEE and LAMOST – that obtain spectra of stars , that is, information on their speed and chemical composition.
“Using the metal content of the stars in the catalogs, with the combination of high quality spectral atlases such as APOGEE and LAMOST, and the distance at which the objects are located, we have found that there is an appreciable fraction of stars beyond where the Milky Way disk was supposed to end “, explains Carlos Allende, IAC researcher and co-author of the work.
The aim of the study was to spectroscopically confirm the presence of disk stars at distances much greater than those stipulated for the disk of the Milky Way.
“We have not made use of models, which sometimes only give the answers for which they have been designed. Only statistics on a large number of objects. The results are thus free from a priori assumptions, beyond a few firmly established” , says Francisco Garzón, IAC researcher and co-author of the study.
Reference: López-Corredoira, M. et al. ” Disk stars in the Milky Way detected beyond 25 kpc from its center.” Astronomy & Astrophysics 612, April 2018. DOI: 10.1051 / 0004-6361 / 201832880
Image credit: Artist rendering by R. Hurt, SSC-Caltech, NASA / JPL-Caltech.
