A new paper has just been published by the National Astronomical Observatories of Beijing (NAOC) and the Instituto de Astrofísica de Canarias (IAC) which lays out the claim that the diameter of the disc of the Milky Way is so massive that it would take us 200,000 light years to properly cross it from one side to the other. But as large as our galaxy is, it is worthwhile remembering that the disc of our neighbor galaxy, Andromeda, measures in at a whopping 220,000 light-years across.
The Milky Way is a type of galaxy that is known as a spiral galaxy, and these galaxies are known for having extremely thin discs. It is around these discs that you will find the vast majority of the galaxy’s stars, as Phys.org report. And because the discs themselves are so very thin, normally if you move beyond a certain point from it you are unlikely to find very many stars.
However, in the case of the Milky Way, scientists have discovered that there are actually quite a few stars that stretch out at unusually large distances from the center of the disc. Some of these stars have even been found to be three times as far away from the center of the Milky Way disc than the sun.
If you need to create a mental image of the Milky Way for yourself to imagine how our galaxy looks, just envision a huge rotating disc with a spherical halo formed around it and long spiral arms.
— Phys.org Space News (@physorg_space) May 15, 2018
As IAC researcher Carlos Allende explained, scientists were able to determine that the metals found in stars that were closer to the disc of the Milky Way would have had much larger amounts of metals in them.
“Using the metallicities of the stars in the catalogs from the high quality spectral atlases of APOGEE and LAMOST, and with the distances at which the objects are situated, we have shown that there is an appreciable fraction of stars with higher metallicity, characteristic of disc stars, further out than the previously assumed limit on the radius of the galaxy disc.”
The IAC’s Francisco Garzón further elaborated that in their new study, scientists used statistics rather than standard models, which they hoped would give them fresh new answers.
“We have not used models, which sometimes give us only the answers for which they were designed, but we have employed only the statistics of a large number of objects. The results are therefore free from a priori assumptions, apart from a few basic and well established ones.”
The new study on the 200,000 light year distance of the diameter of the disc of the Milky Way can be read in Astronomy & Astrophysics.