A study published recently revealed that the mass of the Milky Way Galaxy is four to five times less than previously thought. These conclusions turn upside down the data that was known until today about the galaxy that includes the planet Earth.
This result is “the fruit of the Gaia revolution,” as astronomer François Hammer, co-author of the study published by the journal Astronomy and Astrophysics, explained to AFP. Gaia, the satellite dedicated to mapping the Milky Way Galaxy, revealed the positions and movements of 1.8 billion stars, in its latest data in 2022, reports Al-Rai daily.
This represents a small portion of the total contents of our spiral galaxy, which is a disk with a diameter of about 100,000 light-years, and consists of four large arms, one of which includes our solar system, all extending around a very luminous center.
Studying Gaia data made it possible to calculate the Milky Way’s rotation curve with unprecedented accuracy, according to the study’s authors. The task is to determine the speed at which celestial bodies revolve around the center of the galaxy.
Observations of spiral galaxies had previously concluded that this curve was “flat,” meaning that once a certain distance from the center was reached, the speed of rotation was constant.
But “this is the first time that we discover that the curve descends outside its disk,” according to François Hammer, “as if there is not a lot of matter” at a distance of between 50 and 80 thousand years from the center of the galaxy.
As a result, “the mass of our Milky Way Galaxy has been recalibrated to values considered very low,” about 200 billion times the mass of the Sun, five times less than previous estimates.