The Sun's Possible Long Lost Twin

Live Science

There's a strange sphere of mass at the outer reaches of solar space. Did another star help put it there?

Transcript

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.

00:08 [music]

00:12 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

00:21 than the region that includes all the planets.

00:23 It extends halfway to the nearest star.

00:25 It has 100 billion objects in it, researchers think.

00:30 But the orb cloud is sort of difficult to explain.

00:34 All of the planets and most of the asteroids in our solar system

00:38 basically exist on a single disk, a flat plane.

00:41 And the reason for that is that they formed out of a disk-shaped cloud.

00:45 So they're all kind of on a line with each other.

00:48 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

00:57 and into our solar system, and they come in from just all sorts of directions.

01:02 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.

01:12 Avi Loeb, a researcher at Harvard University

01:15 known for wild and exciting ideas about how space works,

01:19 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

01:37 and end up orbiting around each other, orbiting a common point between them.

01:43 And if our sun had a binary twin when it was born

01:47 in this birth cluster full of stars that gave birth to our sun

01:50 and many other objects and would have been full of stuff,

01:54 working together, their gravity would have done a much better job

01:59 of collecting debris into an orb cloud around each star.

02:03 At least that's what Loeb says.

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 evolved

02:17 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

02:27 is a lot of scientists believe that there's actually a ninth undetected planet

02:31 in our solar system 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

02:44 are sort of clustered as if there's some sort of tugboat out there

02:48 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,

02:56 I just think it has like five to ten times the mass of the sun,

03:00 then that's even harder to explain.

03:02 How did a planet get out there so far beyond the disk

03:05 that formed all the other planets?

03:08 And Loeb said that if the binary hypothesis is true,

03:13 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.

03:28 It would likely have captured many, many other dwarf planets,

03:32 you know, small planets that don't quite reach the full planet classification

03:36 but are on the size of Pluto or Ceres

03:38 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.

03:49 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,

04:04 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,

04:17 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.

04:30 So right now, have we proved that there's a twin? No.

04:35 Do we know where it went? No.

04:37 But probably another star came by and knocked it out of orbit with our sun.

04:41 And we'll probably never find it.

04:43 So much time would have passed, billions of years,

04:46 since our sun lost its twin.

04:48 They're probably in totally different parts of the Milky Way at this point,

04:51 Loeb said.

04:52 But we might be able to show that it was once there.

04:56 That's pretty cool.

04:57 (Music)

05:02 (upbeat music)

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