Our Galaxy is considered fairly common for its size and structure - however, a new survey of the Milky Way "twins" showed that it stands out among them with the low activity of satellite galaxies.
Talking about our "star home", they often emphasize that we live near an unremarkable star on the periphery of the most ordinary spiral galaxy with a bulge - a compaction in the vicinity of the active center. “We use the Milky Way and its surroundings to explore absolutely everything,” says Yale University astrophysicist Marla Geha. - Every year, hundreds of papers are published on dark matter, cosmology, the formation of stars and galaxies, whose authors focus on our Galaxy as a typical case. However, it may be that the Milky Way is an exception."
In an article published in the Astrophysical Journal, Marla Geha and her colleagues analyzed data from the Satellites Around Galactic Analogs (SAGA) survey, devoted to the study of fairly large galaxies like the Milky Way, as well as their environment - smaller satellite galaxies, like our neighbors such as Large and Small Magellanic Clouds. The authors note that if the environment of our Galaxy is quite calm and imperceptible, then in most other large galaxies satellites are highly active and give birth to new young stars at a decent pace.
So far, the SAGA survey has covered only eight galaxies similar to the Milky Way, and 14 of their satellites. The data necessary for work on 13 more small galaxies were obtained thanks to earlier observations, and 11 more are awaiting refinement and addition. In the meantime, scientists have studied information on 27 satellite galaxies, in 26 of which they noted the ongoing star formation. By comparison, only about 40 percent of the Milky Way's approximately 30 satellites exhibit such activity.
“Our work puts the Milky Way in a broader context,” explains Risa Wechsler, one of the study's authors, astrophysicist at Stanford University. "The SAGA review will bring us new insights into both the formation of galaxies and the nature of dark matter." It is planned that in the next couple of years SAGA will collect data on 25 galaxies - "analogs" of the Milky Way, located within 130 million light years, and by the end of its work - at least 100.
Sergey Vasiliev