As our sphere orbits Sun,
So Sun orbits Black Hole
At the center of our galaxy,
As eternity unfolds.
In a quarter billion earthly years
Our solar system circles round,
Weaves thru the mid galactic plane
Where other stars are densely found.
Fifteen times since life began
We have circum-rotated,
And ten times in each orbit grand
The planet’s devastated.
Our Sun’s own cloud of comets
On the solar system’s edge
Are jostled from their sedate paths,
Fall inward from their ledge.
With corresponding timing
Ancient craters have been found.
It seems Earth’s plagued with comet storms
As the cosmic year spins round.
Life sized model
Bombardments are not good for life.
Half a dozen times
Mass extinctions cleared our world
As doomsday peals chimed.
Things have been quiet for some time
Since dinosaurs disappeared.
The Sun careens past cosmic dust,
Dark matter, stars, and fears.
Such grand cosmic motion can only be estimated, and the number of Earth’s mass-extinctions depends on your definition, but our movement through the galaxy makes me feel very small and oblivious.
space.com on extinctions and comet strikes
Wikipedia on Galactic year
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.