two stars passed within 1 lightyear of earth

[dragon]

Only 70000 years ago shame we missed it.

Astronomers say a red dwarf star and its brown dwarf companion passed within a light-year of our own sun 70,000 years ago, moving through the comets in the outer reaches of the Oort Cloud that surrounds our solar system.

The star is known as WISE J072003.20-084651.2, or Scholz's star. Today, it's 20 light-years away from us in the constellation Monoceros. But in a study published by Astrophysical Journal Letters, researchers say it passed right by us at a distance of 5 trillion miles (8 trillion kilometers, or 52,000 astronomical units, or 0.8 light-years). No other star has been known to come that close.

Scholz's star would typically be too faint to be seen with the naked eye from Earth, even during the close encounter. But the research team, led by the University of Rochester's Eric Mamajek, says there's a chance that our ancestors in Africa might have seen a magnetically induced flare-up.

Image: Scholz's star Michael Osadciw / University of Rochester
An artist's conception shows Scholz's star and its brown dwarf companion in the foreground during its flyby of the solar system 70,000 years ago. The sun would have appeared as a brilliant star, seen here in the background at left. Scholz's star and its companion are now about 20 light-years away.

Mamajek and his colleagues became interested in the star's trajectory after finding out that it appeared to be moving directly away from us — or toward us — at high velocity. They calculated its relative motion using observations from the Southern African Large Telescope and the Magellan Telescopes in Chile.

"Sure enough, the radial velocity measurements were consistent with it running away from the sun's vicinity — and we realized it must have had a close flyby in the past," Mamajek said in a news release.

It's good news that Scholz's star missed us, but there's even better news: Last year, a different group of astronomers reported that a different star called HIP 85605 might make a dangerous pass through the Oort Cloud 240,000 to 470,000 years from now. Now Mamajek and his colleagues say HIP 85605 won't come anywhere near that close.

link

[Flagg]

NEMESIS!

[Tribble]

Though I'm not remotely mathematically inclined, it seems to me that a star traveling 19+ light years in just 70,000 years is moving pretty damn fast.

[Borgholio]

A bit over 182,000 miles per hour. That's 3x faster than New Horizons.

[SpottedKitty]

Though I'm not remotely mathematically inclined, it seems to me that a star traveling 19+ light years in just 70,000 years is moving pretty damn fast.

Nowhere near the record-holders, though; the Wiki article on stellar Proper Motion includes info on a few nearby stars that are moving much faster than this one. The table about halfway down the page puts Barnard's Star at the top.

[Irbis]

A bit over 182,000 miles per hour. That's 3x faster than New Horizons.

Though it would be much less in practice, seeing both systems move directly away from each other.

[Simon_Jester]

Though I'm not remotely mathematically inclined, it seems to me that a star traveling 19+ light years in just 70,000 years is moving pretty damn fast.

Round it off. 20 light-years in 70000 years. By contrast, light would travel 70000 light-years in that time.

So this star is traveling 20 units of distance in the time light would cover 70000 units in.

Therefore the star is traveling at 1/3500 the speed of light. One percent is 1/100, and (1/100) times (1/35) is (1/3500).

So the star is traveling at 1/35 of one percent of light speed.

Light speed is 300 thousand kilometers in one second, so one percent of that is three thousand kilometers in one second.

So the star is traveling at 1/35 of three thousand kilometers in one second.

Three thousand divided by 35 is, uh... well, it'd be convenient if it were just 3000 divided by 30, because then the answer would be a hundred. But 35 is bigger than 30, so 3000/35 is less than 100.

So the star is traveling somewhat less (but not a lot less) than 100 kilometers per second.

[This is how my brain actually works]

[Zeropoint]

I'm not asserting that there's any connection, but it's interesting to note that the time of the stars passing Earth is within the window for the human population bottleneck.

[Purple]

I'm not asserting that there's any connection, but it's interesting to note that the time of the stars passing Earth is within the window for the human population bottleneck.

?

[Broomstick]

70,000 years ago (give or take) humanity may have been reduced to as few as just a couple thousand people. Estimates from 5,000 to 10,000 are pretty common. A VERY small population, and thus, a genetic bottleneck that severely reduced human diversity for a time.

[SpottedKitty]

For another example, cheetahs have gone through a similar bottleneck; there is evidence that it was a lot more recent than 70,000 years ago. Natural mutation will slowly bring back diversity, but the trick is surviving long enough for that to happen. Cheetahs haven't got there yet, every one alive today is very closely related to every other one, over their entire natural range. This suggests they might have been reduced to a single breeding population, small enough to have smoothed out genetic diversity in only a few generations.

[Simon_Jester]

I'm not asserting that there's any connection, but it's interesting to note that the time of the stars passing Earth is within the window for the human population bottleneck.

Well yes, but so is the Toba eruption, which happened roughly a billion times closer to the humans who were killed off to make the bottleneck possible.

So these stars have a much better alibi.