Previous estimates of the mass of the Milky Way ranged from 500 billion to 3 trillion times the mass of the Sun. This uncertainty is primarily a function of the different means astronomers and physicists used to measure the distribution of dark matter through the galaxy. Dark matter makes up 90 percent of the galaxy's mass, but European Southern Observatory's Laura Watkins reveals that it is not possible to see and observe dark matter directly, which made it hard to get an accurate figure for the scientists. This latest mass measurement of the Milky Way weighs in at 1.5 trillion times heavier than our sun.
"Because of their great distances, globular star clusters are some of the best tracers astronomers have to measure the mass of the vast envelope of dark matter surrounding our galaxy far beyond the spiral disk of stars", said a statement from the Space Telescope Science Institute's Tony Sohn, who led the Hubble measurements. Globular clusters are very tightly bound by gravity, and the more massive a galaxy is, the faster its globular clusters move under the pull of this attracting force. While previous measurements have been along the line to sight to globular clusters, astronomers know the speed at which a globular cluster is approaching or receding from Earth.More news: Carlos Hyde signs 1-year, $3 million deal with Kansas City Chiefs
By combining the measurements from 12 clusters out to 130,000 light-years taken by Hubble over a 10-year period, coupled with measurements for 34 globular clusters out to 65,000 light-years obtained via Gaia, the team where also able to measure the sideways motion of the clusters.
In a striking example of multi-mission astronomy, measurements from the NASA/ESA Hubble Space Telescope and the ESA Gaia mission have been combined to improve the estimate of the mass of our home galaxy the Milky Way: 1.5 trillion solar masses. What scientists do know about its contents is that there is a 4-million-solar-mass supermassive black hole anchored at the centre of the galaxy.
ESA's Gaia satellite is a space telescope created to measure the positions of billions of stars with unprecedented precision. The objects (in this case globular clusters) orbit inside a larger object (in this case the Milky Way). Together, the spacecraft made a comprehensive map that let astronomers estimate the Milky Way's mass out to 1 million light-years. The space telescope uses that to its advantage by measuring fainter stars and distant clusters. Since Hubble has been observing some of these objects for ten years, it was also possible to accurately track the velocities of these clusters as well.More news: Bourigeaud thunderbastard helps Rennes to victory over Arsenal
Until now, not knowing the precise mass of the Milky Way has presented a problem for attempts to answer a lot of cosmological questions. Accurately determining the mass for the Milky Way gives us a clearer understanding of where our galaxy sits in a cosmological context.
The Milky Way isn't exactly the easiest thing to study, even if it's our galaxy. "So astronomers make simulations of how the Milky Way might have formed and evolved over billions of years and then look to see which simulations end with a galaxy looks most like the Milky Way". But that's less than half the total mass-the majority comes from dark matter. "We're inside the Milky Way, stuck about halfway out from the center, and everything we learn about it we learn from right here".
"We were lucky to have such a great combination of data", said Roeland van der Marel, of the Space Telescope Science Institute in the United States.More news: Forgetful $273M Mega Millions Winner Says Good Samaritan Helped Him Win Big