This is CBS I In The World, the proto-galaxy that becomes the Milky Way.

Dr. Ken Croswell, writing at Science News, introduces us to a discovery made by the Gaia spacecraft

whose mission is to chart the Milky Way, finding a proto-galaxy 18,000 light years across

that right now we're understanding it's where we came from.

We're part of the Milky Way, we're in the thin disk, following the thick disk, somewhere

in relationship to the black hole that's a center and then the proto-galaxy.

Now Ken, at the close of a piece of science news, you tease about what comes next.

A star's that astronomers can now scrutinize for further clues to the galaxy's birth and

early evolution.

What do we want to learn for looking at the red giants that are in the proto-galaxy?

Well, one thing, as I mentioned in the last segment that we've already learned is to

see the Milky Way's initial spin-up, that I think is really exciting.

It's transitioned from an object that didn't rotate into one that now does.

We can also now look at these stars, especially the most metal poorer of these stars, which

are presumably the oldest, and look at what chemical elements they have, because those

chemical elements, aside from the hydrogen helium, were made in a previous generation

of stars.

And there are three radical predictions for how stars of different masses make different

proportions of metals, okay?

So what we'd like to do is measure, say, how much oxygen those exploding stars made, or

magnesium, or calcium, or iron, and then that will give us clues to what the very first

stars in the Milky Way were like, stars that no longer exist.

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