Stars, They're Just Like Us: A Chat With a Chill Astronomer

By Jia Tolentino | May 22, 2015 | 3:50pm

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Being the big, bright, volatile and self-destructive balls of gas they are, stars aren’t really just like us. Or—wait a minute.

As I found out during my brief foray into writing Midweek Madness on this website, which forced me to overcome both my powerful face-blindness and overwhelming apathy towards celebrity, I feel nothing—dead, even, and not in the emoji way—at the sight of a tabloid snap of an actress shoving Whole Foods bags into the trunk of her car. However, as I have known all my life, I feel quite alive (in a dead way) when I consider the larger physical forces that manage even the vaguest contours of similarity between humans and real stars.

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Life without life, death without tragedy: stars aren’t exactly like us, but might be better. I consulted Michael Williams, a former astronomer who got his PhD at Oxford and taught at Columbia before swerving—”for all the usual reasons,” he said, in a warm British accent—to a lane outside of academia. He took a break from his data science work at a startup
to answer my incredibly dumb questions about astronomy.

Okay. The first way I thought that stars are just like us is that they’re known for their groupings, and the coolest-looking groups get the most attention. A constellation is a clique, maybe. A galaxy is a country.

Yes. There are definitely scales of communities of stars, just like with people: star clusters, galaxies, groups of galaxies. But constellations are strange ones.

Because they’re arbitrary groupings?

The names we give them are arbitrary, yes, and the shapes are very abstracted. But the really weird thing about them comes from the fact that stars exist in three-dimensional space, but we see them in two-dimensional space. So, some of the stars in constellations are much further away than the others. For an alien on another planet, the Big Dipper won’t look like the Big Dipper to her.

You know, my favorite page on Wikipedia is “The Timeline of Far Future Events”—a list of things that physicists know are going to happen in the very distant future. One of the first things on the list is that the constellations will no longer exist. The stars won’t be where they used to be.

You could say that this is sort of the way that, when everyone leaves college or whatever, friendship cliques dissolve.

That sounds like a really cool list.

It’s quite depressing. It’s a list of inevitable destruction.

I find inevitable destruction incredibly comforting and freeing!

Nothing matters when you think about that scale.

How wonderful. Okay, another idea that’s probably wrong: stars are made of plasma, and humans are also made of plasma. But not the same kind of plasma?

Totally different type of plasma. Plasma, the fourth state, only really exists in extremely high-temperature environments. The plasma in your blood just happens to share its name.

I also read that stars contain “degenerate matter,” which—I can’t speak for everyone here, but my body also contains that.

“Degenerate” is an exciting word whose technical meaning in physics is super dull. Let’s say you’ve got two tennis balls and you push them together—they can only get so close, because they have a boundary and an edge. That’s what’s happening in degenerate matter: the particles are touching, so you can’t squash it down any more.

I take back that it’s dull, though. This idea of degeneracy is a really important result from quantum mechanics, whose rules dictate that two things can’t exist in the same place. It’s this that prevents the densest stars, neutron stars, from collapsing completely under their tremendous pressure.

My degeneracy also keeps me from collapsing under pressure, I’d say. Okay, next one: some stars are stars among stars, big and bright and famous. Some stars are stars, just like us! What’s the most famous star?

Well, the sun is the most famous star.

Oh yeah. Uh…

Luckily, from the point of view of astronomy, the sun—which we narcissistically consider the most important—is not an outlier. It’s a common type of star. After the sun, the next closest star is Proxima Centauri, and it’s got a companion star, Alpha Centauri. Many stars have companion stars, exist in binary systems. About half, maybe. Close to the percentage of people who are married.

Stars are married!

They’re in arranged marriages, I’d say. The stars don’t get a lot of say in the matter. And they are contentious marriages. In binary systems, one star is usually slightly bigger than the other, and if it’s very big it’ll destroy the other. That’s how Type 1A supernovae happen: a star is big, burning very violently, steals a little bit of fuel from its companion, and then the system explodes, and the space around it is sterilized: the radiation renders life impossible around the exploded star.

Stars: size matters, just like with us.

There’s a range, a spectrum of stars, taxonomized by seven letters, OBFGAKM. (The mnemonic device is “Oh, be a fine girl and kiss me.”) It starts with the hottest stars, the biggest stars—the littler stars are cooler.

And the difference in size is enormous, not like humans, where we exist from about five to seven feet tall. The biggest stars are thousands, millions of times bigger than the average star.

Star size is more analogous to income level, maybe: some stars are one-percenters. Most stars are normal size, middle class—like we all think we are.

Also, if you’re above a certain size, your death is going to be explosive. If you weigh more than eight times the mass of our sun, you won’t be able to fade away. You’re going to explode.

Bigger stars die faster, right?

Yes. If you’re a really big star, your lifetime is really short.

RIP Whitney. Do all stars have planets?

A star forms out of gas and garbage that condenses. Most of that gas and garbage will end up in the star; the rest of it will float around the neighborhood. That’s how our solar system formed.

So, in the past 10 years, we’ve discovered quite a lot of exoplanets—planets around other stars. We know they exist. But does every star have one? It’s difficult to say, because it’s difficult to prove the negative. Planets are easier to find the bigger they are. But if we can’t see them, it still doesn’t mean they aren’t there.

Are planets like house plants? Things that sort of depend on the star but are just there?

You could say there’s the same risk of over-watering and under-watering, if you want to keep your house plant alive. And the Earth, of course, is in exactly the right spot. A tiny, tiny bit closer and we’d be over-watered; a tiny bit farther and we’d be Mars.

I think one of the earliest things kids learn about stars is that the light you’re seeing may actually have been extinguished a long time ago. That some stars have an afterlife like Shakespeare.

Yes. And we don’t remember Shakespeare’s friend from the pub, we remember Shakespeare. We don’t remember a bright star that existed a million years ago—we remember the brightest star from a million years ago.

The brightest objects we see in the universe are not stars, actually; they’re quasars. A supermassive black hole seems to put out a huge amount of energy when it’s forming, and we see it billions of years after it happens—in some cases, essentially seeing back to the beginning of time.

And, as for our own sun, the light takes eight minutes to reach us. If the sun was obliterated, eight minutes would pass before we knew.

I would like to see a movie about that. The last eight minutes of light. Okay, just one last thing: stars are like us because they self-destruct?

Yes. Their fate is sealed the moment they’re born. Stars are weirdly very simple systems: if you give me the mass and the temperature of a star, I can tell you how old it is, and how long it’ll be till it dies. It’s a very determined life for stars. They’re on the train tracks and they can’t get off. They have no freedom.

Sort of like us!

Yes. Nothing matters.

Are there any other ways stars are just like us?

One thing that you haven’t mentioned that a lot of people are always bringing up is the literal fact that we’re made of stardust. I find it a bit of a facile, glib metaphor, but it’s also true.

The universe, when it formed 13.8 billion years ago, was just hydrogen and helium. That was it. You can’t have a good time with hydrogen and helium. And stars are factories for turning these elements into heavier elements, carbon and so on. When a star dies, it throws its seed over the universe—and after a few rounds of this, you end up with a star like the sun. A star forming out of material that had been through a few stars, had been enriched, had heavier elements. One of the things that formed out of all that garbage is: people.

Image via nasa.gov

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