The estimate of the mass of our domestic galaxy, the Milky Way, has been determined more accurately thanks to the combined use of the Hubble Space Telescope and the Gaia mission.
The mass of the Milky Way is one of the most fundamental measurements that astronomers can make about our galactic home. However, despite decades of intense effort, even the best available estimates of the mass of the Milky Way are at odds.
Now, by combining the new data from the Gaia mission of the European Space Agency (ESA) with the observations made with the Hubble Space Telescope from NASA / ESA, astronomers have discovered that the Milky Way weighs around 1.5 billion solar masses in a radius of 129,000 light years from the galactic center.
Previous estimates of the mass of the Milky Way oscillated between 500 billion and 3 billion times the mass of the Sun. This enormous uncertainty arose mainly from the different methods used to measure the distribution of dark matter, which constitutes approximately 90% of the mass of the galaxy.
"We simply can not detect dark matter directly," explains Laura Watkins (European Southern Observatory, Germany), who led the team that conducted the analysis. "That is what leads to the uncertainty present in the mass of the Milky Way: you can not accurately measure what you can not see!"
Given the elusive nature of dark matter, the team had to use an intelligent method to weigh the Milky Way, which was based on measuring the velocities of globular clusters, dense clusters of stars that orbit the spiral disk of the galaxy at great distances.
Gaia, designed to create a three-dimensional map
"The more massive a galaxy is, the faster its clusters move under the force of its gravity," explains N. Wyn Evans (University of Cambridge, United Kingdom). "Most of the previous measurements have found the speed at which a group approaches or moves away from the Earth, that is, the speed along our line of sight, but we were also able to measure the lateral movement of the groups, from where the total speed, and consequently the galactic mass, can be calculated. "
The group used the second publication of Gaia data as a basis for their study. Gaia was designed to create an accurate three-dimensional map of astronomical objects along the Milky Way and to track its movements. His second data release includes measurements of globular clusters up to 65,000 light years from Earth.
"Global clusters extend a great distance, so they are considered the best markers that astronomers use to measure the mass of our galaxy," Tony Sohn (Space Telescope Science Institute, USA) said in a statement. ), who directed the Hubble measurements.
The team combined this data with the unparalleled sensitivity and observation legacy of Hubble. The Hubble observations allowed weak and distant globular clusters to be added to the study, up to 130,000 light years from Earth. As Hubble has been observing some of these objects for a decade, it was also possible to accurately track the speeds of these groups.
"We were lucky to have a great combination of data," explained Roeland P. van der Marel (Space Telescope Science Institute, USA). "By combining the Gaia measurements of 34 globular clusters with measurements from 12 more distant Hubble clusters, we were able to determine the mass of the Milky Way in a way that it would be impossible without these two space telescopes"