Our Sun may Have Once Had an Evil Twin

Fagjun | Published 2017-07-12 08:37

Do other stars have evil twins too?

Findings offer new evidence that newborn stars come into existence in pairs. Scientists think that our own sun may have long ago had an evil twin.

Our sun was born 4.5 billion years ago and is now a middle-aged star. It will probably stay largely the same for the next five billion years, or so. Scientists now think it's possible that our sun, as well many other stars, may have come into existence as twins. For example, the neighboring Alpha Centauri is a triplet system. Thus, there is a high possibility that our sun also had a twin at some point in time.

Scientists call this twin star Nemesis, which does sound a little sinister. There's a theory that Nemesis catapulted an asteroid that collided with Earth, which consequently killed off the dinosaurs. Astronomers have long looked for signs of Nemesis, but they have yet to find any. If Nemesis ever did exist, we don't know for sure where it is or what happened to it.

A Stellar Nursery of Multiple Star Births

A young binary star system in the Perseus molecular cloud.
[Image by J. Muzerolle (STScI)/NASA/ESA]

However, it's probable that Nemesis did in fact exist. It probably broke away from the sun and went into the Milky Way, lost in the shuffle of stars. Like an evil twin in a bad soap opera, Nemesis wreaked havoc and disappeared. Other stars, however, have stayed with their twins. Binary and multi-star systems are common in the Milky Way galaxy. Thus, scientists think it's possible that most, if not all, stars were born with a twin.

Researchers at the Smithsonian Astronomical Observatory studied the star-forming Perseus molecular cloud to find out more about multiple star births. They found 45 single-star systems, but they also found 55 young stars in 19 binary systems and five multi-star systems. Very young binary systems called wide binaries had stars that were wide apart, with at least 500 astronomical units (AU) between them. One AU is equivalent to the distance between the sun and the Earth. Stars tended to be closer together in older binary systems.

Statistical models led the researchers to conclude that all stars form with a companion or two. They start out as wide binaries, with a large distance between them. Eventually, they either come closer to each other or break apart.

Nemesis, the Theoretical Evil Twin

Where is our sun's twin?

The researchers also determined that about 60% of stars in multi-star systems eventually break apart. Thus, it's not out of the realm of possibility that the sun did once have a twin that eventually broke away. According to the findings, multi-star systems break apart within a million years after birth.

Also, even if our sun and its twin didn't break apart, it would be quite far away. Even stars in older multi-star systems are about 200 AU away from their companions. Thus, if Nemesis had stuck around, it wouldn't be easily visible.

So far, the existence of Nemesis is theoretical. However, scientists have been able to determine that the sun might have taken much of the resources stars need to grow. As a result, Nemesis possibly became dimmer and smaller. Now, who can blame Nemesis for being an evil twin?

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