The entire mass of the Milky Way, measured

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The entire mass of the Milky Way, measured

Take all the empty space out of the Milky Way, and how much stuff — stars, planets, asteroids, debris and even mysterious dark matter — would you have? In other words, what is the total mass of our galaxy? Gwendolyn Eadie, a Ph.D. candidate in physics and astronomy at McMaster University in Canada, believes she may have an answer.

We don’t really have specific numbers or language to express the number, but the best we can do so far is to say that the mass of the galaxy is 7 times 1,011 solar masses, or the mass of the sun multiplied by 700 billion. In case you’re wondering, the sun has a mass of 2 nonillion (2,000,000,000,000,000,000,000,000,000,000) kilograms, which is 330,000 times the mass of Earth.

Eadie arrived at her figure using a new technique to estimate the mass of the galaxy by measuring the velocities and positions of globular star clusters that orbit the Milky Way. Deeper in space is where the numbers get even more mind-boggling, as she notes in a statement that “our galaxy isn’t even the biggest galaxy.”

Eadie and her supervisor William Harris, a professor of physics and astronomy at McMaster, are presenting their results Tuesday at the Canadian Astronomical Society’s conference in Winnipeg.