The sun may have a long-lost twin called Nemesis somewhere in the Milky Way

15 Jun 2017

Illustration of a hypothetical planet covered in water around the binary star system of Kepler-35 (AB). Image: NASA/JPL-Caltech

New evidence into the formation of stars now suggests that every single star – including our own sun – was created in pairs.

At the birth of our solar system, when the sun was just beginning to form, another twin star dubbed Nemesis was also forming – although the pair were certainly not identical.

That’s according to new research published by a team of astronomers and theoretical physicists in the US, which has found that every sun-like star we know of was born with a twin.

Future Human

In fact, a search for Nemesis has been ongoing for some time, as it has been theorised that the demise of dinosaurs was brought on by the second star kicking the asteroid that killed them into Earth’s orbit, despite it never being found.

The research began by conducting a radio survey of a giant molecular cloud filled with recently formed stars in the Perseus constellation, 600 light years away from Earth.

By crunching the numbers and datasets obtained from this survey, the team was able to identify a total of 19 binary star systems and 45 single stars.

After further analysing the binary star systems, something interesting emerged: the stars farthest apart, by at least 500 astronomical units (AU), were only around 500,000 years old.

By comparison, the older stars around 1m years old were found to be closer together, at around 200 AU in proximity.

Where is Nemesis?

It was only by running a number of computer simulations on various scenarios that Sarah Sadavoy and her team begin to see the pattern of all sun-like stars forming in pairs.

However, the simulations also showed that 60pc of the time, the stars end up splitting and drifting into the wider cosmos, while the remaining 40pc join together like the triplet system that exists in our neighbouring galaxy, Alpha Centauri.

This means that, potentially, the sun’s Nemesis twin is out there in the Milky Way and just hasn’t been discovered yet – and it would be pretty difficult to do so.

“The idea that many stars form with a companion has been suggested before, but the question is: how many?” Sadavoy asked.

“Based on our simple model, we say that nearly all stars form with a companion. The Perseus cloud is generally considered a typical low-mass star-forming region, but our model needs to be checked in other clouds.”

The research has been published online at

Colm Gorey was a senior journalist with Silicon Republic