Cosmic Close Call

A red dwarf might have a planets with moons orbiting it - as in this artist concept

A red dwarf might have a planets with moons orbiting it – as in this artist concept

Seventy thousand years ago doesn’t seem so very long – not too long to imagine. Anatomically modern humans – us – date back two hundred thousand years. Hunter-gatherer cultures are at least fifty thousand years old and probably older. We were about to leave Africa and meet our Neanderthal cousins when something astounding happened in the skies above us. A red-dwarf star with its smaller companion swept by the outer reaches of our solar system.

“Passing less than a light-year from Earth, the flyby was the closest stellar near-miss identified so far, scientists reported Tuesday in Astrophysical Journal Letters.” [NatGeo] Seventy thousand years ago it clipped the Sun’s Oort Cloud. No other star will come as close for hundreds of thousands of years.

Scholz’s star moves so fast it’s no longer the closest star to our Sun. The multiple star system Alpha Centauri is our closest neighbor today, only four light-years away. Scholz’s star is already twenty light-years away.

Space is so big I never expected such a close cosmic call within the lifespan of our species. Scholz’s star is too dim to see with the unaided eye today, but it may have flared bright enough for our ancestors to puzzle over its appearance in the sky. I wonder if human beings will be here to see another star flyby. If so, they may be worried. A similarly passing star could send a bevy of comets towards Earth, possibly leading to mass extinctions. Assuming they still have the technology to watch the skies, they’ll have plenty of warning.

The paper explaining this finding is here.

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