Hot galaxies alert!

Most astronomers agree that young galaxy clusters should be relatively cool compared to older ones. But researchers recently found a very young cluster that’s hotter than the surface of the sun. More on why the finding is so shocking, plus elephant’s remarkable sniffing abilities and a new discovery about butterfly migration in this episode of Short Wave. Interested in more science news? Email us your question at [email protected] mailto:[email protected]. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:00Speaker 00

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• 0:18Speaker 01

  You're listening to Short Wave from NPR. Hey, Short Wavers, Burleigh McCoy here.

• 0:25Emily Kwong?

  And Emily Kwong.

• 0:26Speaker 01

  With our biweekly science news roundup, featuring the hosts of All Things Considered. And today, we have Scott Detrow.

• 0:33Speaker 03

  I'm only here because I heard we were talking about a hot galaxy cluster.

• 0:36Emily Kwong?

  That's how we get you in the door.

• 0:37Speaker 03

  Yeah.

• 0:37Emily Kwong?

  But how we're going to keep you is...

• 0:40Speaker 01

  Talking about also how elephants' trunks lead them to food.

• 0:44Emily Kwong?

  And we'll share a big discovery in butterfly migration.

• 0:46Speaker 03

  I'm here for all three.

• 0:47Emily Kwong?

  Well, we thank you. All that on this episode of Short Wave, the science podcast from NPR.

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• 2:22Emily Kwong?

  Okay, Scott, I know your favorite thing is space, so let's start there.

• 2:25Speaker 03

  Let's start there.

• 2:27Emily Kwong?

  Wow.

• 2:28Speaker 03

  Let's, let's, let's start off. What would you say a galaxy cluster is, though? Let's start there.

• 2:32Emily Kwong?

  It is exactly what it sounds like. It is a collection of galaxies, but kind of like a city, where each galaxy is a different building. Our galaxy, the Milky Way, is part of a cluster called the Local Group, for example. But the galaxy cluster we want to talk about, which is the subject of a new paper in Nature, was formed about 12 billion years ago, and the universe itself is only about 13.8 billion years old.

• 2:55Speaker 03

  So that's just, that's just a fast billion years, like a snap of the fingers in galaxy terms. Like, we were talking about, this, this was a baby in galactic years.

• 3:03Speaker 01

  Exactly. And current theories say that younger galaxy clusters should be relatively cool, but this one is very hot, like hotter than the surface of the sun. We talked to Jorge Moreno, an astrophysicist who didn't work on the paper, and he made an analogy to US history. He said, "If you go back a few centuries, you expect to see little buildings and horses and carriages, not a modern metropolis."

• 3:27Speaker 05

  Like, it's the late 1700s, and a city looks like Las Vegas.

• 3:31Emily Kwong?

  This galaxy cluster is poppin'. It's far hotter than scientists expected to find at this early point in the universe.

• 3:38Speaker 03

  Do researchers have any idea why it's so hot?

• 3:40Emily Kwong?

  We don't know why yet, but one of the study authors, Daji Zhou, says it is the first time a galaxy cluster this hot has been detected at such a young age.

• 3:50Speaker 01

  And this cluster also contains active galaxies. Three of them have supermassive black holes at the center, which is also surprising, given the cluster's age.

• 3:59Speaker 06

  So this forces us to rethink our current understanding of how these large structures form and evolve in the universe.

• 4:08Emily Kwong?

  Although, Scott, it is possible that this cluster is an extreme case, so we need more data.

• 4:14Speaker 03

  I have a lot of other questions that I will keep Googling, but for now, we are going to move forward to another topic, though, because we have a lot to talk about, and we got to talk about elephants.

• 4:22Emily Kwong?

  That was really good.

• 4:24Speaker 03

  Thank you. Listeners don't see that I flared my hand like a trunk, but the trunks are what we're talking about, right?

• 4:29Speaker 01

  Yes, big time. At the very tip of an elephant trunk are two nostrils, powered by nearly 2,000 olfactory genes, which is five times more than a human has, and over twice as many as dogs.

• 4:40Speaker 03

  Which makes me think if you need to sniff something out, hire an elephant, not a dog.

• 4:44Speaker 01

  True.

• 4:44Emily Kwong?

  Yeah, and if you do, pay them fairly in what they love: grass, leaves. Because elephants eat hundreds of pounds of plant a day. They are constantly making food decisions about whether to stay foraging in a patch or travel in search of a better one. And Adrian Schrader at the University of Pretoria wanted to know how their noses guide them in the wild.

• 5:05Speaker 07

  Animals don't just randomly walk across the landscape and hope to find food. And so our question really was an idea of, well, do they use the amount of food as a cue?

• 5:16Speaker 01

  Yeah, and to test this, Adrian's team built a giant maze for elephants, shaped like a Y, with walls over seven feet tall. So picture one entrance, two paths, with different quantities of food at either end.

• 5:27Speaker 03

  So it's like choosing almost between like two different Las Vegas buffets, not being able to see which one was bigger.

• 5:34Emily Kwong?

  Exactly. Four captive elephants took on this challenge. From the maze entrance, the food was about 30 feet away, so way beyond the reach of their trunks. They couldn't see because the walls were so tall. And every time, they chose the path with more food. Unless the quantity difference was less than 600 grams, which is about six to 10 trunkloads of grass. And then they tended to pick either route, which suggests they couldn't smell the difference or they just didn't care. These results were published in the journal Biology Letters.

• 6:03Speaker 01

  And Alvaro Lopez Quegoya, who was not part of the study, found the elephants' ability to discriminate food quantities remarkable. Though he points out there are a lot more smells in the wild than in the preserve where these captive elephants lived.

• 6:17Speaker 03

  This is really interesting. I'm curious, like, what is useful about this research?

• 6:22Emily Kwong?

  Well, elephants, while adorable, can damage their environments. They stomp on farmers' crops. They can knock down endangered trees. But if researchers understand elephants' use of smell, maybe they can cover plants with bad odors to protect them from hungry elephants.

• 6:36Speaker 03

  All right, so let's go from a very large animal. To a very small one. Let's talk butterflies, specifically butterfly migration. What's surprising about it?

• 6:44Speaker 01

  Yeah, so this is a migration in painted lady butterflies. They have similar coloring to monarchs, but they're smaller. They're super widespread and they have the longest migration of any butterfly. And scientists found something striking in that migration that depending on if they live in the northern or southern hemisphere, they follow completely opposite migration paths. Essentially, the equator is acting as a migration barrier for these two isolated populations.

• 7:10Speaker 03

  OK, I'm gonna, I'm gonna be honest here. This doesn't particularly surprise me, right? The seasons are opposite. This makes sense. Why is it a big deal?

• 7:18Emily Kwong?

  Fair, but this is the first time a migration barrier has been described for any insect. And to study this, researchers collected more than 300 butterflies from 38 countries across the northern and southern hemispheres.

• 7:30Speaker 01

  We talked to Aurora Garcia-Berro from the Botanical Institute of Barcelona, and she says their team looked at the butterflies' genes for months, searching for clues about what made these two populations distinct. And then one day, she found something really weird.

• 7:45Speaker 08

  And I actually thought it was an artifact. But then I showed it to my colleague and they were like completely surprised. Like, you don't know. This is so exciting.

• 7:55Speaker 03

  And this dramatic, what was it?

• 7:57Emily Kwong?

  Yeah, they found that a large chunk of DNA in the southern hemisphere butterflies was completely flipped. It was oriented the other way than the same DNA chunk in the northern hemisphere butterflies. And this chunk contains genes involved in migration.

• 8:11Speaker 03

  Whoa.

• 8:12Speaker 01

  So what they think they're seeing is one species that separated into two populations. And now their genetics are diverging too because of these different migration pathways. And this is sort of a lens into how a single species might split into two across a migration barrier. And it might explain why we see closely related species in different hemispheres. They published the results in the journal Nature Communications.

• 8:34Speaker 03

  That is really interesting. What is the thinking on the larger significance of this?

• 8:38Emily Kwong?

  Well, painted lady butterflies, while small, make up a huge biomass. In 2017, a 70-mile stretch of these butterflies blocked weather radar in Colorado. They can affect agriculture, pollination, and the health of other species. So Aurora says identifying how animals migrate is important to understanding the health of that species, yes, but also the health of all the places that species travels.

• 9:03Speaker 03

  That is so interesting. I started off thinking like, oh, yeah, everybody knows that to like having my mind kind of blown. That was a really interesting story.

• 9:09Speaker 01

  Great. That's why you come here. Thank you, Scott.

• 9:12Speaker 03

  Thank you.

• 9:17Speaker 01

  You can hear more of Scott on Consider This, NPR's afternoon podcast about what the news means for you.

• 9:23Emily Kwong?

  And for more science stories just like this one, follow Short Wave on whatever app you're listening to.

• 9:28Speaker 01

  This episode was produced by Rachel Carlson and Jordan Marie Smith. It was edited by Rebecca Ramirez and Christopher Intagliata.

• 9:35Emily Kwong?

  Tyler Jones checked the facts. Robert Rodriguez and Jay Siz were the audio engineers. I'm Emily Kwong.

• 9:41Speaker 01

  And I'm Burleigh McCoy. Thanks for listening to Short Wave, the science podcast from NPR.

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