There's a strange sphere of mass at the outer reaches of solar space. Did another star help put it there?
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00:00Our sun might have a long-lost twig in the Milky Way.
00:03We'll never find it, but the evidence for it could be all around us.
00:12Our solar system is surrounded by something called an Oort Cloud,
00:16a vast region full of ice and debris that's much bigger than the region that includes all the planets.
00:23It extends halfway to the nearest star. It has 100 billion objects in it, researchers think.
00:30But the Oort Cloud is sort of difficult to explain.
00:34All of the planets and most of the asteroids in our solar system basically exist on a single disk, a flat plane.
00:41And the reason for that is that they formed out of a disk-shaped cloud.
00:45So they're all kind of on a line with each other.
00:48But the Oort Cloud isn't on that plane. The Oort Cloud is a sphere.
00:52And we know it's a sphere because the evidence for it is all the comets that come out of the Oort Cloud and into our solar system.
00:58And they come in from just all sorts of directions.
01:02But there's no good way, based on models of how our solar system formed, to really explain how all those objects got there and got into that arrangement.
01:11Avi Loeb, a researcher at Harvard University known for wild and exciting ideas about how space works, wrote in a new paper with his student Amir Siraj that that Oort Cloud, that vast sphere, that mysterious vast sphere full of stuff we can't explain, might be a footprint of a long-lost binary twin of our sun.
01:31Now, binary stars are pretty common in space.
01:34Two stars just that form together or get captured by one another and end up orbiting around each other, orbiting a common point between them.
01:42And if our sun had a binary twin when it was born in this birth cluster full of stars that gave birth to our sun and many other objects and would have been full of stuff, working together, their gravity would have done a much better job of collecting debris into an Oort Cloud around each star.
02:02At least that's what Loeb says.
02:05Now, we don't know for sure if this binary twin existed, but Loeb said it would do a much better job of explaining the Oort Cloud than any models of how our solar system evolves that just have the sun by itself.
02:20The good news is that there's actually a way to test whether this is true.
02:23One of the reasons that Loeb began wondering about this is a lot of scientists believe that there's actually a ninth undetected planet in our solar system drifting somewhere way out beyond Neptune, deep in the solar system, in the region of the Oort Cloud.
02:39And the reason scientists think this is that objects beyond Neptune are sort of clustered as if there's some sort of tugboat out there pulling them into formation with gravity.
02:50Now, if that's true, if there's a big, heavy planet out there, and it would be pretty heavy.
02:56I just think it has like five to ten times the mass of the sun, then that's even harder to explain.
03:02How did a planet get out there so far beyond the disk that formed all the other planets?
03:08And Loeb said that if the binary hypothesis is true, then planet nine didn't originate in our solar system.
03:16It probably originated somewhere in the cluster of stars where a sun was born, and our sun, working together with its binary twin, might have captured it.
03:25But it wouldn't have just captured planet nine.
03:28It would likely have captured many, many other dwarf planets, you know, small planets that don't quite reach the full planet classification,
03:36but are on the size of Pluto or Ceres or these objects we do see around our solar system.
03:41And if there are lots of dwarf planets out there in the Oort cloud, there's really no way our sun could have done that on its own.
03:49It would have needed a binary twin, at least according to Loeb, to capture such a wide array of planets.
03:55Right now, planet nine has not been directly detected, and there's no evidence for these other dwarf planets.
04:02But Loeb said that future telescopes, particularly a telescope called the LSST, that are coming online in the next few years,
04:10that are going to do a really good job of doing big scans of the sky, might be able to detect not just planet nine,
04:17but also these other dwarf planets, these dim, dim points of light drifting in this vast region of space.
04:23And while that wouldn't 100% prove that our sun had a binary twin, it would be very strong, suggestive evidence.
04:30So right now, have we proved that there's a twin? No.
04:35Do we know where it went? No, but probably another star came by and knocked it out of orbit with our sun.
04:41And we'll probably never find it.
04:43So much time would have passed, billions of years, since our sun lost its twin.
04:48They're probably in totally different parts of the Milky Way at this point, Loeb said.
04:52But we might be able to show that it was once there.
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