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Owlscrying

Weighing the Milky WaY

2 posts in this topic

July 6

After pondering the weighty question of the mass of the Milky Way galaxy, astronomers have come up with an answer: 42.

That is, our galaxy weighs three times 10 to the power of 42 kilograms - a number written as 3 followed by 42 zeroes.

It seems esoteric but knowing the weight of the galaxy - the amount of matter it contains - is key to solving important astronomical problems.

Of particular interest to astrophysicist Ken Freeman is the nature of so-called dark matter. Unlike the "ordinary matter" of stars and planets, scientists have only hunches about the nature of the invisible material that, along with "dark energy", they estimate makes up 96 per cent of the universe.

What is it? How is it distributed across the universe? Does it really even exist? "That's worth knowing," said Professor Freeman, an astrophysicist along with colleagues decided to "weigh" a galaxy.

To do so, the group first estimated the "escape velocity" of the galaxy - the speed stars passing near the sun needed to attain in order to escape its gravitational pull. It did so using the line-of-sight, or radial, velocity of stars crossing the central rotating disc of the galaxy.

The data was collected by the 1.2m Schmidt Telescope of the Anglo-Australian Observatory at Siding Spring, NSW. The escape velocity, calculated at between 544km/sec and 608km/sec, allowed the team to calculate the Milky Way's mass and weight, as well as the amount of dark matter: 94 per cent.

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:lol: 42 really is the answer to everything

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