Our Sun May Have Been Born With a Trouble-Making Twin Called 'Nemesis'

 

(NASA/JPL-Caltech/UCLA)


A new model of star formation supports the theory that most, if not all, stars are born in a litter with at least one sibling.

Our own star at the centre of the Solar System is likely no exception, and some astronomers believe the Sun's doppelganger is to blame for the extinction of the dinosaurs.

Two researchers from UC Berkeley and the Harvard-Smithsonian Astrophysical Observatory found in 2017 that all Sun-like stars are likely formed with a companion after analysing data from a radio survey done on a dust cloud in the Perseus constellation.

In June 2017, UC Berkeley astronomer Steven Stahler said, "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."

For years, astronomers have debated if our galaxy's enormous number of binary and triple star systems are formed near to one another or if they collide after they've formed.

The 'born together' hypothesis has long been the most popular, and simulations created in recent decades have demonstrated that practically all stars are born as multiples that spin away on their own.

Unfortunately, empirical evidence supporting these models has been scarce, which makes this new work so fascinating.

"Our research advances our understanding of both how binaries develop and the role binaries play in early star evolution," Stahler added.

The researchers studied the radio waves leaking out of a dense cocoon of dust some 600 light-years away that contains an entire nursery of budding stars as part of the VLA nascent disc and multiplicity study (VANDAM for short).

The VANDAM survey allowed for a census of stars less than half a million years old, known as Class 0 stars (or "babies" in star parlance), and stars between 500,000 and 1 million years old, known as Class 1.

The scientists discovered 45 single stars, 19 binary star systems, and five star systems with more than two stars using data on the morphologies of the surrounding cloud of dust.

While their findings suggested that all stars are born as binaries, they revised their conclusion to accommodate for model constraints by stating that most stars generated inside the dense centres of dust clouds are born with a partner.

Stahler said at the time, "I believe we have the strongest evidence to date for such a statement."

When the researchers examined the distances between the stars, they discovered that all binaries separated by 500 AU or more were Class 0 and aligned with the axis of the egg-shaped cloud surrounding them.

At roughly 200 AU, Class 1 stars, on the other hand, tended to be closer together and not aligned with their 'egg's' axis.

"We don't know exactly what that implies yet," said Sarah Sadavoy of the Harvard-Smithsonian Astrophysical Observatory, "but it isn't random and must tell something about the way wide binaries arise."

Where is ours, if most stars are born with a partner?

A distance of 500 AU is approximately 0.008 light-years, or little less than three light-days. Neptune is around 30 AU away, the Voyager 1 probe is just under 140 AU away, and the nearest known star, Proxima Centauri, is 268,770 AU away.

So, if the Sun has a twin, it's probably certainly not visible from our area.

However, there is a theory that our Sun has a twin that visits every now and then to spice things up.

This hypothetical troublemaker has been given the name Nemesis and has been posited as the cause of a 27-million-year cycle of extinctions on Earth, including the one that wiped out most of the dinosaurs.

Richard Muller, an astronomer at the University of California, Berkeley, proposed 23 years ago that a red dwarf star 1.5 light-years away could travel through the icy outer reaches of our Solar System on a regular basis, stirring up material with its gravity and knocking a few more space boulders our way.

Other abnormalities on the outside of our Solar System, such as the strange, broad orbit of the dwarf planet Sedna, could be explained by a dim passing star like a brown dwarf.

There's no indication of Nemesis, but a long-lost binary companion for our Sun would be a good fit.

"We're suggesting that, sure, there was probably a Nemesis a long time ago," Stahler said.

In which case, it appears that our Sun would have gathered the most of the dust and gas, leaving its twin dark and stunted.

It's understandable that it's irritated.

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