Dark matter is slowing the rotation of the Milky Way, according to a new study by researchers from University College London (UCL) and the University of Oxford.
Earlier, astrophysicists tried for 30 years to predict how strong the slowdown was: now it has been measured for the first time. This gives researchers a new function for dark matter that acts as a counterweight.
The researchers analyzed observations by the Gaia space telescope of a large group of stars: a stream of Hercules, which is in resonance with a barred galaxy.
These stars are gravitationally attracted to the galactic bar. The same phenomenon occurs with the Trojan and Greek asteroids of Jupiter, which revolve around Jupiter’s Lagrange points. If the rotation of the bar (the bar of the galaxy) slows down, then the stars will begin to move further in the galaxy, maintaining their orbital period corresponding to the period of rotation of the bar.
The researchers found that the stars contain heavy metals: this confirms that they were previously in the center of the galaxy, where the star-forming gas is about 10 times richer in metals than the outer galaxy.
Using this data, the team concluded that the bridge of billions of stars and trillions of solar masses has slowed its rotation by at least 24% since its first formation.
Co-author Dr. Ralph Schönrich stated that astrophysicists have long suspected a slowing down of the bar at the center of our galaxy, but evidence of this has only recently emerged.