Milky Way is lighter than previously believed, a young astrophysicist found.

While the exact mass of the galaxy has not been clearly determined, McMaster University's Gwendolyn Eadie is inching closer, thanks to a new measurement method she had developed.

In terms of numbers, the mass of the Milky Way is about 700 billion times larger than that of the Sun. For comparison, the Sun's mass is 2 nonillion kilograms or approximately 330,000 times bigger than the earth's mass.

"And our galaxy isn't even the biggest galaxy," says Eadie.

The Struggle Of Measuring Milky Way's Mass

Measuring galaxies, including the Milky Way, is a difficult project to embark on. This is because galaxies do not only entail planets, stars and moons, but they also include dust and dark matter, which is a mystifying and cryptic matter even experts have not come to fully understand.

Focus On Dark Matter

Although dark matter cannot be identified in the laboratory, astronomers can guess its presence via its gravitational effects on visible cosmic materials.

To measure the Milky Way and determine dark matter, Eadie particularly looked at the positions and velocities of globular star clusters surrounding the galaxy.

Eadie's Novel Technique

The gravity of each galaxy, which is directed by dark matter, determines the globular clusters (GCs). The total GC velocity should be calculated by looking along our line-of-sight and across the plane of the sky, but experts have not been successful in measuring the latter.

Hope sparks as Eadie was able to create a way to use these partially-known velocities together with those that are fully known. Aside from that, her technique can also foresee the mass present within any distance from the galaxy's center. This then makes Eadie's findings easy to compare with other results.

The full study was submitted to the Astrophysical Journal and presented at the Canadian Astronomical Society on May 31.

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