Ten things you don’t know about the Milky Way Galaxy
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So you’ve lived here all your life — in fact, everyone has — but what do you really know about the Milky Way galaxy? Sure, you know it’s a spiral, and it’s 100,000 light years across. And of course, BABloggees are smarter, more well-read, and better looking than the average population, but be honest: do you know all ten of these things? Really?Liar.
So let’s see if these really are Ten Things You Don’t Know About the Milky Way Galaxy.
2) There’s a supermassive black hole at its heart.At the very center of the Galaxy, right at its very core, lies a monster: a supermassive black hole.
We know it’s there due to the effect of its gravity. Stars very near the center — some only a few dozen billion kilometers out — orbit the center at fantastic speeds. They scream around their orbits at thousands of kilometers per second, and their phenomenal speed betrays the mass of the object to which they’re enthralled. Applying some fairly basic math, it’s possible to determine that the mass needed to accelerate the stars to those speeds must tip the cosmic scales at four million times the mass of the Sun! Yet in the images, nothing can be seen. So what can be as massive as 4,000,000 Suns and yet not emit any light?
Right. A black hole.
Even though it’s huge, bear in mind that the Galaxy itself is something like 200 billion solar masses strong, so in reality the black hole at the center is only a tiny fraction of the total mass of the Galaxy. And we’re in no danger of plunging into it: after all, it’s 250,000,000,000,000,000 kilometers away.
It’s thought now that a supermassive black hole in the center of a galaxy forms along with the galaxy itself, and in facts winds blown outward as material falls in affects the formation of stars in the galaxy. So black holes may be dangerous, but it’s entirely possible the Sun’s eventual birth — and the Earth’s along with it — may have been lent a hand by the four million solar mass killer so far away.
7) 90% of it is invisible.
When you look at the motions of the stars in our galaxy, you can apply some math and physics and determine how much mass the galaxy has (more mass means more gravity, which means stars will move faster under its influence). You can also count up the number of stars in the galaxy and figure out how much mass they have. Problem is, the two numbers don’t match: stars (and other visible things like gas and dust) make up only 10% of the mass of the galaxy. Where’s the other 90%?
Whatever it is, it has mass, but doesn’t glow. So we call it Dark Matter, for lack of a better term (and it’s actually pretty accurate). We know it’s not black holes, dead stars, ejected planets, cold gas — those have all been searched for, and marked off the list — and the candidates that remain get pretty weird (like WIMPs). But we know it’s real, and we know it’s out there. We just don’t know what it is. Smart people are trying to figure that out, and given the findings in recent years, I bet we’re less than a decade from their success.
