Scientists close in on the true mass of the Milky Way by calculating what they know, what they partially know and what is still uncertain | McMaster Daily News
http://dailynews.mcmaster.ca/...what-they-know-what-they-partially-know-and-what-is-still-uncertain/
It’s a problem of galactic complexity, but researchers are getting closer to accurately measuring the mass of the Milky Way Galaxy.
In the latest of a series of papers that could have broader implications for the field of astronomy, McMaster astrophysicist Gwendolyn Eadie,
working with her PhD supervisor William Harris and with a Queen’s University statistician, Aaron Springford, has refined Eadie and Harris’s
own method for measuring the mass of the galaxy that is home to our solar system.
The short answer, using the refined method, is between 4.0 X 10^11 and 5.8 X 10^11 solar masses. In simpler terms, that’s about the mass of our Sun,
multiplied by 400 to 580 billion. The Sun, for the record, has a mass of two nonillion (that’s 2 followed by 30 zeroes) kilograms, or 330 000 times
the mass of Earth. This Galactic mass estimate includes matter out to 125 kiloparsecs from the center of the Galaxy (125 kiloparsecs is almost
4 X 10^18 kilometers). When the mass estimate is extended out to 300kpc, the mass is approximately 9 X 10^11 solar masses.
Measuring the mass of our home galaxy, or any galaxy, is particularly difficult. A galaxy includes not just stars, planets, moons, gases, dust and
other objects and material, but also a big helping of dark matter, a mysterious and invisible form of matter that is not yet fully understood and
has not been directly detected in the lab. Astronomers and cosmologists, however, can infer the presence of dark matter through its gravitational
influence on visible objects.