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Across the Universe, it's the normal galaxies doing all the star-making work

18 Dec 2019, 14:00 UTC
Across the Universe, it's the normal galaxies doing all the star-making work
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Sometimes, there are simple statements that can lead to profound conclusions.

For example: Stars exist.

It doesn't get more simple than that, a noun and a verb. And it's obviously true; we can see stars in the night sky, and one very bright one in the day sky. Stars exist. We also know that stars die. We've seen that happen many times, or we’ve seen what comes after.

We've also seen stars being born. You can look to practically any large cloud of gas and dust in the sky to see that, too. We also know the Sun is about 4.6 billion years old. So a little longer ago than that, a nebula brought forth our nearest star. Some stars are even older, which implies that stars were born long ago, too.

If you're an astronomer, that brings up an obvious question: Is the rate stars are being born now the same as the rate when the Universe was young? Or were more stars made back then? Fewer?

Here's another profound statement: Light takes time to move. If you see an object a light year away, you’re seeing it as it was when it emitted that light a year ago. ...

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