According to the new study, all stars including the Sun are born in pairs. Researchers at the University of California, Berkeley, found new stars in the Perseus constellation which their dynamics could only be explained if the proposed simulations employed only binary star systems.
They suggest that these binary star systems tend to break apart after a million years.
“If our model continues to provide a good fit to other star-forming regions, then the mass fraction of dense cores that becomes stars is double what is currently believed,” the study reads.
Our sun had a twin brother named ‘Nemesis.’
To date, astronomers had not been sure about the origin of binary and triple star systems, mainly because it is highly unlikely that stars can simply capture each other with their own gravity. Another issue is that there are way too many binary systems, which rules out gravitational capture as the primary method through which these systems form.
By running statistical models while studying the Perseus constellation, researchers saw that there had to be a twin for each star for the models to make any sense out of what they could see in the constellation. This led to the theory of every star being born in pairs, including our sun, whose twin would have been called “Nemesis.”
The only model that fit the observations was the one that took all stars as parts of binary systems, many of them being classified as “wide” binaries, in which the stars are separated by more than 500 astronomical units or 46.5 billion miles from each other. One astronomical unit is the distance from the Earth to the sun. The model indicates that Nemesis should be at least 17 times farther away than the sun is from Neptune.
The research team still needs to try out the model in other star clouds to prove the theory, although the model is the only one managing to explain how young stars are related to the clouds where they form.
“We now believe that most stars, which are quite similar to our own sun, form as binaries. I think we have the strongest evidence to date for such an assertion,” stated co-author Steven Stahler.
The key is in star formation
The Perseus constellation is 600 light-years away from Earth and is 50 light-years long. It was just recently that researchers decided to study Perseus to understand how new stars are formed within molecular clouds. This is the case of the VANDAM survey, where astronomers used the Very Large Array in New Mexico on Perseus to take note of all stars younger than 4 million years old with at least 15 astronomical units from each other.
The data from the survey was combined with the idea that stars are born inside dense cores, scattered on clouds of molecular hydrogen floating in outer space. This resulted in a model where all of the widely separated binary systems observed were very young. Additionally, the binary system’s axis was usually aligned to the axis of the dense core; older stars, on the other hand, appeared to have split from their binary systems, no longer aligning with the dense core.
Researchers proposed different explanations but stood by the one where all stars slightly more or less massive than our sun started as wide binary systems inside dense cores, which act as egg-shaped cocoons for birthing stars, and that 60 percent of these systems eventually fall apart.
“Within our picture, single low-mass, sunlike stars are not primordial, they are the result of the breakup of binaries,” Stahler suggested.
Stars are born from massive clouds of cold hydrogen and helium, eventually collapsing into a dense core after an alteration event occurs, such as collapsing with another cloud, or a supernova exploding nearby.
The cloud breaks up in small clusters of gas, eventually heating up and becoming denser. At some point, the nucleus’ pressure pairs up with its gravitational pull, stabilizing and resulting in what astronomers call a protostar. Many times, the protostar is not able to evolve into a star, transforming into a brown dwarf.
Now, if the protostar were just slightly less massive than our sun, it would heat up to the point of generating special hydrogen isotopes and causing an atomic chain reaction, transforming hydrogen to helium, a process known as hydrogen fusion. If the protostar is more massive than the sun, it will instead undergo a carbon-nitrogen-oxygen cycle to undergo hydrogen fusion.
In 1978, astronomers discovered MWC 349, a double star system in the Cygnus constellation. At the time of discovery, researchers believed that MWC 349 was a runaway from the Cygnus OB2 association, which includes some of the most massive and luminous stars found to date, including the red hypergiant NMLA Cygni, one of the largest stars ever observed, with a radius of 1,183 times the sun’s, or 5.5 astronomical units.
What’s exciting is that MWC 349 is roughly 1,000 years old, which could be explained by the new model suggesting that all stars are born in pairs.