Space

The Sun's "evil" twin is probably lurking beyond the Solar System

New computer simulations suggest that most stars probably begin life with a twin – including our Sun
New computer simulations suggest that most stars probably begin life with a twin – including our Sun
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New computer simulations suggest that most stars probably begin life with a twin – including our Sun
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New computer simulations suggest that most stars probably begin life with a twin – including our Sun
A radio image of a triplet star system forming, in the Perseus cloud
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A radio image of a triplet star system forming, in the Perseus cloud
The Perseus cloud appears in the sky as a black spot, since it's made up of dense gas and dust that blocks light from stars inside and behind it
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The Perseus cloud appears in the sky as a black spot, since it's made up of dense gas and dust that blocks light from stars inside and behind it
In this infrared image of the Perseus cloud captured by Hubble, the bright fan-shaped object in the bottom right is believed to be a binary star system
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In this infrared image of the Perseus cloud captured by Hubble, the bright fan-shaped object in the bottom right is believed to be a binary star system

Since the 1980s, astronomers have been searching for the Sun's "evil" twin, dubbed Nemesis due to its habit of slinging deadly asteroids our way every 26 million years or so. Lately, the Nemesis hypothesis has fallen out of favor after decades of sky surveys have turned up no trace of the star, but a new mathematical model from UC Berkeley suggests that almost every star is born with a buddy – including our Sun.

The team probed the Perseus cloud, a stellar nursery some 600 light years away, to take stock of the number of single and binary stars. Combining several data sets from different surveys, the researchers identified 19 binary-star systems and 45 single-star systems.

Intriguingly, in wide binary systems in which the two stars are further than 500 Astronomical Units (AU) apart, all of the stars were very young – under 500,000 years old. The slightly older stars – between 500,000 and 1 million years – were all closer together, about 200 AU.

"This has not been seen before or tested, and is super interesting," says Sarah Sadavoy, first author of the study. "We don't yet know quite what it means, but it isn't random and must say something about the way wide binaries form."

The Perseus cloud appears in the sky as a black spot, since it's made up of dense gas and dust that blocks light from stars inside and behind it
The Perseus cloud appears in the sky as a black spot, since it's made up of dense gas and dust that blocks light from stars inside and behind it

To try to find those answers, the team ran computer simulations to model several scenarios. There was only one way to make all the pieces fit with observations: all stars with masses about that of the Sun must start life as part of a wide binary system. Over time, an estimated 60 percent of them split up to form two single-star systems, while the rest drift closer together into tight binaries.

That means that even though the hypothetical Nemesis has never been detected, the Sun probably does have a long-lost twin, which has since migrated out into the Milky Way – it probably isn't evil, though.

"We are saying, yes, there probably was a Nemesis, a long time ago," says Steven Stahler, co-author of the study. "We ran a series of statistical models to see if we could account for the relative populations of young single stars and binaries of all separations in the Perseus molecular cloud, and the only model that could reproduce the data was one in which all stars form initially as wide binaries. These systems then either shrink or break apart within a million years."

To test its mettle, the model needs to be applied to other star-birthing clouds.

The research has been published online, and will appear in a future issue of the Monthly Notices of the Royal Astronomical Society.

Source: UC Berkeley

7 comments
Mzungu_Mkubwa
Don't mean to be "Debbie Downer" here, but maybe I'm in the wrong business. I can't believe resources are being spent (salaries + support + ?) on this kind of completely useless and entirely speculative research. What is it in aid of? How will this help further human society? Who will benefit and what is to gain? So the sun may have had another star with it in the distant past... so what? Who cares?
Bob
Another model based on a very small sample size creating very broad assumptions. How long before this declared a theory?
Victor Engel
I'm not sure what relevant point there is to this. A million years is incredibly insignificant compared to the age of the sun. If it was part of a binary system during its birth, surely the time elapsing since then has erased any significance.
Geoffrey
Where does the model show our Sun's twin might be found today?
Nathaneal Blemings
The point is the more we understand about the universe outside the earth, and how things form, the better we understand the nature of our reality, the complex physics that drives everything... which will only help us further down the line. The underlying principle of science if really to discover how everything works, for alot of people that curiosity is all that is needed to move forward.
DavidMcclellan
MzunguMkubwa, I get your point. However the problem isn't so much with the research but rather the system that creates an attitude of use it or loss it. This fosters an environment of "If you don't come up with something to use this grant for it goes back and you loss your usefulness". For this very reason more oversight is needed when using federal grant money......our money. I love science and support a certain amount of "no we don't need it but that's not a reason to shelve it" research programs. However some of programs are nothing more then cash grabs by researchers looks for any justification for their existence. Which is another problem altogether.
HoppyHopkins
If the sun once had a long lost twin, where did it go and which nearby star is it? On the other hand I just read an article that says that our solar system had a red dwarf/brown dwarf pair pass through at a distance of 0.6 and 0.8 light year about 70,000 years ago. So that might be the Nemesis source
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