The Last Show with David Cooper
Sarah Rugheimer: Galactic Discovery We're 'On Cloud 9' With - January 9, 2026
10 Jan 2026
Chapter 1: What is the main topic discussed in this episode?
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How to break a record in just seven nights. All you have to do is become an asteroid. We are here with Sarah Rugheimer, an astrophysicist at the University of Edinburgh. Check out her Audible original, Searching for Extraterrestrial Life on audible.com. Sarah, I recently bought your Audible original. I just haven't listened to it yet. Welcome to the show also.
Amazing. Excited to hear what you think of it then.
I will let you know. Now I'm on the hook to listen to it. I just had too many credits and they're like, use some of these credits. Okay, this is a very compelling part of the interview. Let's talk about this new asteroid that Vera Rubin Observatory saw that is enormous, that is spinning really fast, that is a wild object out there. Tell me about it.
Yeah, so I think what's cool about this is you have to think about what are asteroids in general. So asteroids are sort of this leftover mess from the early solar system from when our planets were forming. And that means they're often just kind of clumps of little pebbles.
And I mean, kind of think of dust bunnies in your house under your couch, but with also bigger, slightly like bigger pebbly sort of objects and they kind of just hold together. And so what's weird about this is it can't be that. So it's spinning quite fast. And that means if it was just this sort of dust bunny collection of pebbles, it would rip apart. And so it has to be rock.
It's like a bunch of kids on those, what do you call those, rotating things in the playground. If you get it spinning fast enough, all the kids are going to fly off it.
Fly off, exactly.
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Chapter 2: What record-breaking asteroid did the Vera C. Rubin Observatory discover?
I don't even like Star Wars. Don't know why I said that. When there's enough stuff in a galaxy, gas, it kind of collapses into stars. The gravity of the mass collapses into stars. So it's very odd to have like a big cloud of gas at a galactic size with no stars. Yeah. But a new one has been discovered and it raises questions about like dark matter, the early universe.
It is a massive object emitting no light.
Yeah, so this one I think is really interesting because it's this detection of neutral hydrogen in this cloud that they're calling Cloud 9. And it's about 16 million light years away, which sounds far, but it's actually not that far. It's pretty close to us in the grand scheme of things. But it has 1 million solar masses. So that means it could contain, say, like 1 million stars. Or more, right?
Because a lot of stars are smaller than the Sun. However, they are seeing a maximum of maybe a thousand stars in this. And you just wouldn't expect something this large that has this much mass to not have stars in it. So it's this cloud of neutral hydrogen. just kind of never formed a galaxy.
And that's really interesting because it means that we're kind of looking at something that probably is what the very early embryonic stage of our galaxy was before anything really developed in the very early universe. It was just a bunch of neutral hydrogen around And then that eventually through gravity coalesced into stars and dah, dah, dah, dah, dah, you get galaxies.
But this is just hanging out in space. And that's kind of weird.
And the fact that it's close, well, relatively close, we're talking in the order of tens of millions of light years, the galaxy being what, 30 some odd billion light years in diameter?
No, our galaxy is 100,000 light years.
No, sorry, the galaxy. My words are getting mixed up. The universe itself is some 30 billion odd light years in diameter, if I'm not correct.
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Chapter 3: How do asteroids form and what are their characteristics?
It's big. So we're not actually looking that far into the distant past.
It's pretty close. Exactly. No, it's pretty close, yeah.
And you'd think these like early universe seeming objects would be very far away. So it's odd that it's close.
100%.
That was my point. I just had my orders of magnitude and then what class of objects were slightly off. Great thing I studied astronomy.
That is totally fine.
I did not do well in astronomy in undergrad, Sarah, as it's very clear.
I'll send you my exam that I give my first year undergrads and then you can you can give it a try. Please don't. You know, my husband did that. He actually got a 50 percent, which was the average of the class, despite not having taken my class, which I don't know, tells you something about our generation or a new generation.
D is for degree, as I always say. OK, OK, here's a stupid question. Maybe not. If it is invisible and it has no light, how do we know that it's there?
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