According to a research, low-mass stars are born in pairs, including the Sun

A pair of stars in their dense core within the Perseus cloud (Image courtesy SCUBA-2 survey image by Sarah Sadavoy, CfA)
A pair of stars in their dense core within the Perseus cloud (Image courtesy SCUBA-2 survey image by Sarah Sadavoy, CfA)

An article published in the journal “Monthly Notices of the Royal Astronomical Society” describes a study on the diffusion of binary systems composed of low-mass stars. The astronomers Sarah Sadavoy of the Smithsonian Astrophysical Observatory and Steven Stahler of the University of Berkeley studied very young stars in the molecular cloud of the constellation of Perseus concluding that that kind of stars is always born in pairs, including the Sun.

Observations show that systems formed by two or more stars are common but for a long time astronomers have been wondering whether they were born that way or those were stars born separately and only later tied by gravitational bonds. Various research have been revealing the details of star formation mechanisms thanks to the observation of very young stars. This research focused on low-mass stars, such as the Sun or smaller, to find out if it’s normal for two or more stars to be born together.

Between 2013 and 2015, the VLA Nascent Disk and Multiplicity (VANDAM) survey captured images of Perseus’ molecular cloud, a huge cloud of gas and dust around 750 light years from Earth. In some regions within it, the formation of various stars has become a perfect subject for the study of the early stages of their life. One of the teams that studied that data detected two mechanisms behind the formation of multiple star-based star systems.

In the research conducted by Sarah Sadavoy and Steven Stahler, other observations from the Gould Belt survey were combined with those of the VANDAM survey that revealed egg-shaped cocoons around the young stars called dense cores. By putting together all the data, the two astronomers created a census of single and double stars in Perseus, finding that there were 55 young stars in 24 multiple systems, including 19 binaries and 5 more than two stars, and 45 Single star systems.

Sarah Sadavoy and Steven Stahler discovered that all binary systems with distant companions, those whose distance is over 500 times that between the Earth and the Sun, were very young, with stars that were less than 500,000 years old. These systems also tended to be aligned with the longest axis of the egg-shaped dense core. Binary stars that are a little older, up to a million years old, were close companions, many of them distant between them about 200 times that between Earth and the Sun, didn’t show any tendency to align with the major axis of the egg-shaped core.

Part of the Sarah Sadavoy and Steven Stahler’s research was based on simulations to get an idea of the cases when the pair splits after the birth. For this reason they’ll need to test it further, also by observing other molecular clouds where new stars are forming. The theory that low-mass stars always come up in pairs revives the idea that the Sun has a twin as well.

Immediately after the publication of this research, new speculations appeared about Nemesis, the hypothetical Sun’s twin, which might be a brown dwarf, for someone linked to great extinctions. Those are pure speculation so it’s possible that new discoveries in the future will allow us to debunk them for good. In any case, there will be researchers interested in looking for Sun’s twin, which could now be very far away.

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