The expansion of the universe is accelerating due to mysterious dark energy. In addition, it is one of the factors that accelerate stars in galaxies. In the new study, scientists obtained the first direct measurement of the average acceleration in our home galaxy, the Milky Way.
Led by Sukanya Chakrabarti of the Institute for Advanced Study, the team used pulsar data to measure the radial and vertical acceleration of stars in and out of the galactic plane. Based on these new high-precision measurements and the known amount of visible matter in the galaxy, the researchers were able to calculate the density of the Milky Way’s dark matter without making the usual assumption that the galaxy is stationary.
“Our analysis not only provides us with the first measurement of the tiny accelerations experienced by stars in the galaxy, but also opens up the possibility of expanding the work to understand the nature of dark matter and, ultimately, dark energy,” said Chakrabarti, lead author of the paper.
Stars sweep through the galaxy at hundreds of kilometers per second, but new research shows that their speed changes at a much slower rate – a few centimeters per second. To detect this imperceptible movement, the research team relied on the ultra-precise ability to keep the time of pulsars that are widespread across the galactic plane and halo – a diffuse spherical region surrounding the galaxy.