The Sun's Possible Long Lost Twin
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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00:00 Our Sun might have a long-lost twin in the Milky Way.
00:03 We'll never find it, but the evidence for it could be all around us.
00:07 Our solar system is surrounded by something called an orb cloud,
00:16 a vast region full of ice and debris that's much bigger than the region that includes all the planets.
00:23 It extends halfway to the nearest star.
00:25 It has a hundred billion objects in it, researchers think.
00:30 But the orb cloud is sort of difficult to explain.
00:33 All of the planets and most of the asteroids in our solar system
00:37 basically exist on a single disk, a flat plane.
00:40 And the reason for that is that they formed out of a disk-shaped cloud.
00:44 So they're all kind of on a line with each other.
00:47 But the orb cloud isn't on that plane.
00:50 The orb cloud is a sphere, and we know it's a sphere
00:53 because the evidence for it is all the comets that come out of the orb cloud and into our solar system.
00:58 And they come in from just all sorts of directions.
01:01 But there's no good way, based on models of how our solar system formed,
01:06 to really explain how all those objects got there and got into that arrangement.
01:11 Avi Loeb, a researcher at Harvard University known for wild and exciting ideas about how space works,
01:18 wrote in a new paper with his student Amir Suraj that that orb cloud,
01:22 that vast sphere, that mysterious vast sphere full of stuff we can't explain,
01:27 might be a footprint of a long-lost binary twin of our sun.
01:31 Now, binary stars are pretty common in space.
01:34 Two stars that form together or get captured by one another and end up orbiting around each other,
01:39 orbiting a common point between them.
01:41 And if our sun had a binary twin when it was born,
01:46 in this birth cluster full of stars that gave birth to our sun and many other objects
01:52 and would have been full of stuff,
01:54 working together, their gravity would have done a much better job
01:58 of collecting debris into an orb cloud around each star.
02:02 At least that's what Loeb said.
02:05 Now, we don't know for sure if this binary twin existed,
02:08 but Loeb said it would do a much better job of explaining the orb cloud
02:14 than any models of how our solar system evolves that just have the sun by itself.
02:20 The good news is that there's actually a way to test whether this is true.
02:24 One of the reasons that Loeb began wondering about this is a lot of scientists believe
02:28 that there's actually a ninth undetected planet in our solar system,
02:32 drifting somewhere way out beyond Neptune,
02:35 deep in the solar system in the region of the orb cloud.
02:39 And the reason scientists think this is that objects beyond Neptune are sort of clustered,
02:45 as if there's some sort of tugboat out there pulling them into formation with gravity.
02:51 Now, if that's true, if there's a big, heavy planet out there,
02:55 and it would be pretty heavy, I just think it has like five to ten times the mass of the sun,
02:59 then that's even harder to explain.
03:02 How did a planet get out there so far beyond the disk that formed all the other planets?
03:06 And Loeb said that if the binary hypothesis is true,
03:12 then planet nine didn't originate in our solar system.
03:16 It probably originated somewhere in the cluster of stars where a sun was born.
03:21 And our sun working together with its binary twin might have captured it.
03:25 But it wouldn't have just captured planet nine.
03:27 It would likely have captured many, many other dwarf planets,
03:31 small planets that don't quite reach the full planet classification,
03:36 but are on the size of Pluto or Ceres or these objects we do see around our solar system.
03:41 And if there are lots of dwarf planets out there in the orb cloud,
03:45 there's really no way our sun could have done that on its own.
03:48 It would have needed a binary twin, at least according to Loeb,
03:52 to capture such a wide array of planets.
03:55 Right now, planet nine has not been directly detected,
03:58 and there's no evidence for these other dwarf planets.
04:02 But Loeb said that future telescopes, particularly a telescope called the LSST,
04:07 that are coming online in the next few years,
04:10 that are going to do a really good job of doing big scans of the sky,
04:14 might be able to detect not just planet nine, but also these other dwarf planets,
04:19 these dim, dim points of light drifting in this vast region of space.
04:23 And while that wouldn't 100% prove that our sun had a binary twin,
04:27 it would be very strong, suggestive evidence.
04:29 So right now, have we proved that there's a twin?
04:34 No.
04:35 Do we know where it went?
04:36 No, but probably another star came by and knocked it out of orbit with our sun.
04:41 And we'll probably never find it.
04:42 So much time would have passed, billions of years, since our sun lost its twin.
04:47 They're probably in totally different parts of the Milky Way at this point, Loeb said.
04:51 But we might be able to show that it was once there.
04:54 That's pretty cool.
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