While we have the approx weight of the milky way galaxy which was assumed to be about 500 billion to 1 trillion solar masses and include every star, planets, black holes dust and satellite but answering what’s the Accurate weight of our galaxay is bit complex as 85% of our galaxy is occupied with dark matter which was difficulty to measure i.e finding the weight of something which we can’t see.
With the combined data of European space agency Gaia satellite and NASA’s Hubble telescope the Accurate weight of the milky way galaxy found to be 1.5 trillion solar masses around the radius of 129,000 light years from the galactic center.
The Gaia and hubble proposed a 3D model of the movement of the globular star cluster (which is a huge cluster of stars orbiting the galactic center)
How scientists find the weight Milky way galaxy
As dark matter which we can’t see has effect on the visible matter so dark matter could be weighed through its influence on visible objects like globular star cluster.
The more massive a galaxy is the more is the velocity of globular cluster revolving around it because of gravity .
Most previous measurements have been along the line of sight to globular clusters, so astronomers know the speed at which a globular cluster is approaching or receding from Earth. However, Hubble and Gaia record the sideways motion of the globular clusters, from which a more reliable speed (and therefore gravitational acceleration) can be calculated.
Gaia was exclusively designed to create a precise three-dimensional map of astronomical objects throughout the Milky Way and track their motions. It made exacting all-sky measurements that include many globular clusters.
Hubble has a smaller field of view, but it can measure fainter stars and therefore reach more distant clusters. The new study augmented Gaia measurements for 34 globular clusters out to 65,000 light-years, with Hubble measurements of 12 clusters out to 130,000 light-years that were obtained from images taken over a 10-year period.
When the Gaia and Hubble measurements are combined as anchor points, like pins on a map, astronomers can estimate the distribution of the Milky Way’s mass out to nearly 1 million light-years from Earth and These precise measurements of globular cluster motion from Gaia and Hubble enabled the researchers to pin down the mass of the entire Milky Way.