Nice stating a ;fact which can't be disproven - if Sol had a twin (and they've already named it after a Star Trek movie), we should see it as a big hunka light, even if it's 1,000,000 AU away. We haven't spotted it so I would guess either (a) it never existed or (b) see a !!!
You wait ages for a sun, then two come along at once: All stars have twins, say astroboffins
Nearly all stars, including our Sun, are born from hot, dense molecular clouds and come in pairs, according to a paper to be published in the Monthly Notices of the Royal Astronomical Society. Binary star systems are common in space. It was estimated that up to 80 per cent of massive, bright O‑type and B‑type stars are locked …
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Saturday 17th June 2017 09:27 GMT Anonymous Coward
Is ";fact" some way of trying to say "assertion"?
Sorry, I just can't let the supreme ignorance of attributing the name to some movie pass. At least try googling before posting such drivel.
I happen to share at least some of your scepticism, but I wouldn't be so arrogant as to rubbish the paper without reading it first. Meaningful criticism would require some insight into scientific method, and differences between evidence, proof, and the role of mathematical models in describing physical systems.
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Saturday 17th June 2017 09:32 GMT Flocke Kroes
How much can you get wrong in one post?
The idea of a companion star for sol named Nemesis dates back to 1984. Star Trek: Nemesis came out in 2002. I think the hypothetical star was named after the Greek goddess especially as ST:TNG only started in 1987 (Planet Vulcan predated ST:TOS by over a century).
Astronomers have already found about 50 stars within 1,000,000 AU (15.8ly). Stars move relative to each other. Scholz's star (currently 20ly away) came within 52,000 AU (0.8ly) of Sol only 70,000 years ago. The problem of identifying Nemesis is more likely to be that astronomers have already found many stars the right age and composition, but they have little idea where they were 4.7 billion years ago.
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Saturday 17th June 2017 10:58 GMT Anonymous Coward
Binary/Twin Star?
The problems I have with this theory/article are in the use of the words 'binary' & 'twin'.
A binary system is one in which two stars are gravitationally bound and orbit each other about their common barycenter. There isn't an astronomical definition of a 'twin' star.
If Sol formed in a binary system, where it was gravitationally bound with another star, then something very energetic indeed must have happened to the other star to expel it from the pairing: it wouldn't have just drifted off, as almost implied in the article; it would still be gravitationally bound to Sol.
That Sol formed in relatively close proximity to other stars is pretty certain; molecular clouds are big - even the little ones contain around 100 solar masses, in which several stars would have probably formed.
As for 'twin' - well, we've no way of knowing how similar to Sol other stars in our particular nursery were, but it's almost certain that Sol had several 'siblings'.
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Saturday 17th June 2017 13:04 GMT Rol
Re: Binary/Twin Star?
It's not beyond logic to assume the forces necessary to unbundle Sol from Nemesis, came about at ignition, and likely as not given the other gas giant/protostar a push toward ignition itself.
Thinking as to why stars like our Sun appear to come in pairs:-
Perhaps as a body travels through a nebula the material that falls into it's gravitational influence collides together many many miles behind it and thus coalesces into a substantive body, which in turn would have a similar wake of material falling into the recently travelled path.
I guess a reasonable way of demonstrating this would be to scatter iron filings onto a smooth surface and then race a very strong magnetic ball across the surface.
I would expect the filings would be drawn to the magnet, but due to the initial inertia and the speed of the ball, they would mostly end up in a line along the path the ball took. And once we factor in the likelihood that gravity would coral these individual particles together, and in a frictionless environment still be travelling in the balls general direction would eventually become a significant brake on the initial ball, and thus they end up in orbit.
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Saturday 17th June 2017 13:55 GMT james 68
Re: Binary/Twin Star?
As both stars would be losing mass then it stands to reason that their gravitational pull would weaken to the point where they would no longer be bound, sending them off rather quickly in opposite directions. Depending on specific mass, orbital distance and speed, this could have happened very early in the life of the stars.
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Sunday 18th June 2017 12:13 GMT Anonymous Coward
Re: Binary/Twin Star?
@james 68: there are a couple of problems with your idea of stellar gravity weakening due to mass-loss. The first problem is that as you increase the orbital distance between the two stars, due to the reduction of gravity due, in turn, to stellar mass-loss, you also decrease their orbital velocity. Thus as Sol and its partner drew further apart due to stellar mass-loss they would be moving more and more slowly; they would never reach "the point where they would no longer be bound, sending them off rather quickly in opposite directions" - they would just drift apart more and more slowly.
The second problem is that if Sol's gravity weakened to the extent that its partner was able to drift away then all of Sol's planets etc. would also have drifted away.
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Saturday 17th June 2017 14:57 GMT a_yank_lurker
"Nice stating a ;fact which can't be disproven" - Not having read the paper, but I suspect the model (or an improved version) would give a clue as to where to look for the twin. If the twin is there, then the theory is on much better footing. Valid theories make predictions that can be verified and explain known observations. This theory offers a possible explanation for the number of binary systems which is a known observation.
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Saturday 17th June 2017 16:37 GMT Pompous Git
"Not having read the paper, but I suspect the model (or an improved version) would give a clue as to where to look for the twin."
Not really. The paper is about star formation and QI IFF you're an astronomer. Sol is ~4.6 billion years old. Tracing even an approximate trajectory of a star over that period of time is fraught. See: n-body problemThe author of this paper proposes further tests that have the potential to falsify the theory presented.
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Monday 19th June 2017 09:34 GMT Michael H.F. Wilkinson
Just a little mathematics
1,000,000 AU is about 4.8 parsec. At this distance, a M-type dwarf like Sholz's star which has an absolute magnitude of 19.4 would have a visual magnitude of 17.8, well beyond my 8" SCT. Even when Scholz's star passed at 0.8 ly, it would be a puny mag 11.3 star, roughly 250x to faint to see with the naked eye. There are some very, very faint stars out there. In fact, they outnumber the stars of the sun's brightness or brighter by a huge margin.
It is well known that although many stars form in open clusters, these drift apart, mainly due to gravitational disruption by other objects passing by in the fairly dense galactic plane. NGC 188 (also known as Caldwell 1) is an exception, in that it is a very old open cluster, which probably wasn't disrupted, because it is some way away from the dense traffic in the plane. It is therefore easy to imagine that stars forming as a wide binary system could be disrupted, and the two would ultimately drift apart.
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Saturday 17th June 2017 09:11 GMT Pascal Monett
Seems difficult to accept
Our closest neighbor is the Centauri system, which happens to be a multi-star system. I don't think it likely that our Sun's hypothetical twin can be found there.
The second closest is Bernard's star, which is over 6 ly away. Other star systems are at over 8 light years away, but they are all multiple systems.
So, for our Sun to have a twin, it would have to be Bernard's star, but apart from the distance, one would also have to explain how it could be a twin of our Sun when it is over 2 billion years older.
The next closest single star is not even in the 26 closest list linked above, so it is over 12 ly away and that's getting ridiculously far for a so-called twin.
So, for our Sun to have a twin, it would also have to have formed with our Sun, failed to ignite, got ejected from our system and cooled down sufficiently fast to not show up on infrared satellite surveys.
That's starting to be a bit much to swallow.
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Saturday 17th June 2017 09:46 GMT Christoph
Re: Seems difficult to accept
Why do you assume that a star that has been drifting away from us for billions of years must be a close neighbour? It's not only been moving away that long, it's been pulled differently by other stars by being in a different place. Add that all up and it might be on the other side of the galaxy by now. If someone drove away from your house ten years ago, would you expect them to still be in the next street?
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Saturday 17th June 2017 10:47 GMT Anonymous Coward
Re: Seems difficult to accept
If it had been ejected only at the speed of Voyager1 - which is about 1/20,000 c - then after 2 billion years it would be 100,000 light years away. That also happens to be the diameter of our galaxy.
This means it could be any of the 100 billion stars in the Milky Way.
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Monday 19th June 2017 13:12 GMT DropBear
Re: Seems difficult to accept
"If it had been ejected only at the speed of Voyager1..."
This is a particularly startling instance of being "ninja'd" - I came to post the exact same reasoning starting from the exact same data point. I guess the problem with this sort of thing is that our intuition is worse than useless when it comes to the kind of numbers involved in astronomy. Fermi order-of-magnitude estimation method for the win, I suppose...?
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Saturday 17th June 2017 10:31 GMT Anonymous Coward
@Pascal
"So, for our Sun to have a twin, it would have to be Bernard's star, but apart from the distance, one would also have to explain how it could be a twin of our Sun when it is over 2 billion years older."
Apart from what Christoph said there's another scenario which, so far, seems to be getting ignored: apparently we're all also assuming that this sun is still alive. Why?
For all we know it could have collapsed in the mean time and is now one of the many black holes out there. Which would make it harder to spot.
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Saturday 17th June 2017 13:20 GMT Brewster's Angle Grinder
@ShelLuser
"For all we know it could have collapsed in the mean time and is now one of the many black holes out there."
The lifetime of a star is dependent upon its mass and, to a lesser extent, upon its chemical composition. The chemical composition of the sun and its companion will be identical, as they were formed from the same material at the same time. A massive disparity in mass seems unlikely, too; maybe it could be twice as big, but not ten times. So I would expect it still to be burning.
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Sunday 18th June 2017 17:36 GMT IT Poser
Re: @ShelLuser
F class stars, solar mass of 1.04-1.40, have a lifespan of 2-10 billion years. A class stars, solar mass of 1.40-2.10, have expected lifespans of 2.2 billion years or less. Since you are willing to accept Sol's former companion was potential twice as big, I don't see why it is a stretch to say that star hasn't gone poof 2+ billion years ago.
While I agree that, most likely, Sol's former companion is still burning, I still must downvote your downvote explanation.
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Saturday 17th June 2017 11:40 GMT AndrueC
Re: Seems difficult to accept
Who is 'Bernard' ?
The name is Barnard's Star
But it's an interesting possibility I suppose.
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Monday 19th June 2017 10:10 GMT Anonymous Coward
Re: Seems difficult to accept
The Sun has made about 20 orbits of the galactic core in its lifetime, travelling a total of about 3 million LY in the process - if one assumes that its orbit has been relatively unperturbed, which may not have been the case. That said, even minor perturbations over the 4 billion-odd years of the Sun's existence by the very large number of other bodies in the Galaxy could cause the Sun and any star that formed nearby to be in radically differnt parts of the galaxy by now. Note COULD. As stars out here are quite sparse though, it is still possible that an initially gravitaionally bound association of stars could remain reasonably close together. The Sun's current velocity relative to the galactic core as a fixed point is about 220 km/s, and relative to the average velocity of other stars in the neighbourhood is about 20 km/s.
Good luck trying to find any solar 'twin' out there! 8-}
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Saturday 17th June 2017 14:21 GMT Chris Gray 1
Sol-centric
You're all Sol-centric here, i.e. you are assuming that Sol formed as one of a pair, and then the other flew off. Isn't it equally likely that Sol is the one that "flew off"? In that case, the original system could have had more than 2 new-born stars, and so Sol's closest siblings are still in a multi-star group.
Also, depending on the exact mechanism that results in multiple stars forming in a close group, does it follow that the stars are very close in initial size and density? I would think it would follow that the composition of the stars would be quite similar, so perhaps what astronomers can do is look for nearby stars with similar composition, backdated to the time of formation (i.e. ignoring expected composition changes since then, which might vary depending on the kind of star that they started as).
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Sunday 18th June 2017 17:59 GMT IT Poser
Re: Sol-centric
Alpha Centauri A and B have noticeably different metallicities, 0.20 versus 0.23,and masses, 1.100M☉ versus 0.907M☉. I can think of several reasons that would explain the difference without requiring the two stars to form from different clouds.
Over the course of 4.6 billion years Sol's companion could easily have traveled hundreds of light years in a different direction. It could even be one of the stars that has been shot out of the galaxy.
I think your search area is too limited, based on the little we know.
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Saturday 17th June 2017 18:19 GMT Pompous Git
Re: Statistics
"With the number of stars in the universe, I have a hard time believing that every star has a twin."
You won't be surprised to learn then that the paper proposes no such thing. Indeed, the word "twin" occurs exactly zero times in the paper. What Sadavoy and Stahler propose is a solution to the problem of binary star formation. -
Sunday 18th June 2017 07:54 GMT Anonymous Coward
Re: Statistics
Multiples/doubles. Like matter/antimatter creation. There are natural mechanics and forces that cause a large percentage of duplications/doubles.
Take for example the wake from a boat travelling in water. You get one on one side, the other on the other side. Though a nebular collapsing would have a 3 dimensional makeup, they can no doubt test to see if it would collapse in a way (or be effected to collapse) that causes two and more dens spots for stellar formation.
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Sunday 18th June 2017 00:03 GMT Pompous Git
Re: Is it possible that they joined?
"In Section 4, we discuss the spatial relation of the binaries to their host cores. We find that most relatively wide binaries, with separations exceeding 500 au, tend to be aligned with the long axis of their parent cores. In contrast, the relatively tight binaries, with separations smaller than 500 au, have no preferred alignment. In Section 5, we test simple evolutionary models for the observed populations of embedded systems, both single and binary. We show that the observed populations are best recovered when all stars form initially as wide binaries. Finally, in Section 6, we summarize our results and propose future studies that bear on the question of binary origin."
Emphasis mine.Even if a galaxy the size of the Milky Way directly collided with a similar galaxy the chances of two stars colliding is very small. See: Collisions and Encounters of Stellar Systems What makes galactic collisions interesting is what happens to the interstellar gas.
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Monday 19th June 2017 02:51 GMT Pompous Git
Re: Is it possible that they joined?
"Interesting maybe. Me, I would be spending my time looking at the night sky watching the cosmic dance of 500 billion stars."
A very great proportion of those stars and supernovas were initiated by colliding gas clouds as in the Perseus group used in the study. No colliding gas clouds = no star nursery.
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Sunday 18th June 2017 13:44 GMT GrapeBunch
Re: Is it not right here in plain sight?
Jupiter's news on the same day 2017-06-17 was that it is the oldest planet in the solar system. It is said to have formed within a million years (just an eyeblink in UT) of the sun. So they're pushing back the envelope towards Jupiter being a failed companion of Sol. Rather like, in real life, the addon party in a minority government that haughtily lords it over the rest for four years, but then at the next election and for the next 4.599 billion years gets put in the deep freeze because everybody found it so annoying. There may be discrete reasons why it could not be so, but in my mind the main reason to dismiss the idea of Jupiter as a failed companion is that it is old and obvious. They would have mentioned it.
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Monday 19th June 2017 00:28 GMT Alan Brown
not a new idea
The idea of stars forming in pairs (from each end of a gas swirl) has been around for a while, as has the idea of planets tending to form in similar pairs. It's likely to be something that's fractal in nature.
Of course in a planetary system planets tend to collide and accrete. You might wonder if something similar happens to nascent protostars.
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Monday 19th June 2017 03:38 GMT Sorry that handle is already taken.
Re: not a new idea
They're not claiming to have come up with the idea of binary or multiple star systems. What they've done is build a statistical model to try to determine how common it is, and the output of the model that assumes it's very common resembles the observed conditions most closely.
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Monday 19th June 2017 10:45 GMT Anonymous Coward
Twin Earth ?
I'm no astronomer, but on a similar note, I recall a suggestion that there could be a twin to the earth in exactly our orbit, but 180 degrees out (so it would always be directly behind the Sun).
Now I would have thought it's existence could be deduced from gravitational effects, but the thrust of the article was it couldn't ?....
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Monday 19th June 2017 13:30 GMT DropBear
Re: Twin Earth ?
Setting aside that I don't have a tin foil hat thick enough for this sort of, uh, suggestion - nor any hard-hitting astronomical knowledge to refute it on merit - wouldn't it be wise to consider any such proposition in a highly skeptical manner simply on the basis that while we wouldn't be able to see a perfect twin of Earth on the other side of the Sun, we can see all the other planets just fine and none of them seem to have any "twins"...?
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