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An incredibly bright burst of energy and a dent covered with ice give us insights into planetary and universal structure.

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It's been almost a year and a half since the New Horizons space probe did the first ever fly-by of Pluto and gave us a closer look at its surface. We've learned a lot of things from this mission so far, but one of the most striking discoveries was an icy, 1,000km wide basin which makes up the western half of the area that's shaped kind of like a heart. It's called Sputnik Planitia, and now we finally know a little more about how it formed and about how its formation might have affected Pluto itself.

In two separate studies published on Wednesday in the journal Nature, researchers explored the possibility that the formation of Sputnik Planitia actually made Pluto rotate once. They're suggesting that Pluto went through something called true polar wander, where a celestial object like a planet or moon rotate so that its north and south poles change. Normally, objects spin along the axis where they have the most inertia, meaning there's more mass that's farther away from their centers, and the north and south poles are at either end of this axis. So if a planet has a bulge somewhere or even just an especially dense place, that area will usually be near the equator.  But sometimes an object's mass shifts, changing the axis where it has the most inertia. When the happens, the object might turn so that the extra mass is near the equator and the spin axis has the highest inertia again. That's true polar wander.

Lots of worlds in the solar system have gone through true polar wander, like Mars, Saturn's moon Enceladus, and our moon, and now it sounds like Pluto is joining those ranks. Sputnik Planitia started out as an impact basin, a place where an asteroid hit Pluto and carved a chunk out of the surface. You'd think that would make the basin less massive than the rest of Pluto, but actually, the rest of the dwarf planet would have shifted to compensate, so Pluto's mass was still distributed in a balanced way. Then, nitrogen, carbon monoxide, and methane ice would have filled the basin and made it more massive.  

When the researchers modeled the basin's formation, they found that all that ice would have shifted Pluto's inertia and its spin axis by as much as 60 degrees, so a sixth of a full circle. All that shifting and re-orienting moved Sputnik Planitia toward the equator and it would have had other effects, too. One of the studies suggested that this might be how some of the cracks and canyons on Pluto's surface formed. Plus, all these shifts and changes in Pluto's geology really only makes sense if there's a liquid water ocean beneath the surface, something the researchers already suspected might exist.

So Pluto's icy heart made the whole dwarf planet shift around and that shift is yet another piece of evidence that there's a liquid ocean hiding inside it. Well, the New Horizons data is helping us learn more about our own solar system, some researchers are also looking for clues about the structure of the whole universe, and in a paper published yesterday in the journal Science, astronomers found some of those clues hidden in the brightest fast radio burst, or FRB, ever detected.

Fast radio bursts are pretty much exactly what they sound like: bursts of radio waves only milliseconds long that originate somewhere in the universe and eventually get to us. By analyzing the patterns of these radio waves, researchers could learn more about the structure of all the places the FRBs passed through. The problem is, FRBs are pretty mysterious. We usually don't know why they happen or where they come from because we can't detect the source in any other way. So it's hard to even know if an FRB is being produced by something within our galaxy or as something outside it, and without knowing the source of an FRB, you can't learn much from it, but this FRB, called FRB 150807 was different. 

It was the brightest signal ever detected and it was observed by two of the detectors at the Parkes Observatory in Australia. The double detection gave the researchers enough information to pinpoint its location more precisely than any other FRB. They think this FRB probably came from a galaxy called VHS7, somewhere between 3 and 6.5 billion light years from Earth.  

When they analyzed the signal taking the possible source into account, they were able to measure the universe's magnetic field between Earth and that galaxy. This is just one measurement with one burst, but it shows the technique can work, and the researchers hope with more FRB detections, we'll be able to learn a lot more about the structure of our universe.  

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You still can't get over Pluto? Then we here at SciShow Space will get out the ice cream, cuddle up with you on the couch, and talk about how this could have happened. Pluto was demoted...