Another star almost hit us some 70,000 years ago.

[Streetwind]

http://www.space.com/28611-star-flew-through-solar-system.html

I found this a fun and interesting scenario to imagine. Apparently a red dwarf plowed through our solar system's Oort cloud some 70,000 years ago, coming as close as 0.8 lightyears to the Sun. Compare this to the more than 4 light years distance to our current nearest neighbour... that's pretty darn close, and in cosmic terms, pretty darn recent! It would have been during the most recent glacial of the current ice age (while today we are in the interglacial directly following it). Humanity was already huddling around warm fires back then, blissfully unaware of this rare cosmic event.

I wonder if some of the more puzzling orbits we see in some outer solar system objects today could be partly the result of this encounter.

[Cirocco]

weeeellll, it kinda depends on how you define the edge of the solar system. Like you said, researches estimate that the closest it came was 0.8 lightyears. That's not even near the inner oort cloud (where it could perturb asteroid/comet orbits and catapult them into the inner solar system). Maybe this sort of event could help explain some weird orbits, but I doubt this one in particular did much. The dwarf star wouldn't even have been visible to the naked eye in the night sky at closest approach.

of course I'm no astronomer so I could be talking total bullcrap right now

[magnemoe]

weeeellll, it kinda depends on how you define the edge of the solar system. Like you said, researches estimate that the closest it came was 0.8 lightyears. That's not even near the inner oort cloud (where it could perturb asteroid/comet orbits and catapult them into the inner solar system). Maybe this sort of event could help explain some weird orbits, but I doubt this one in particular did much. The dwarf star wouldn't even have been visible to the naked eye in the night sky at closest approach.

of course I'm no astronomer so I could be talking total bullcrap right now

However we know stars move around pretty randomly relatively to sun so it would be pretty obvious that closer than one light year will not be uncommon in geological time.

Makes me wonder if the Oort cloud goes so far out, or more accurate the number of Oort objects past 0.1-0.2 lightyear will be far lower than closer as they has run into closer encounters with other stars multiple times.

[-Velocity-]

I wonder if some of the more puzzling orbits we see in some outer solar system objects today could be partly the result of this encounter.

No probably not. You can guarantee that Sol has had much closer encounters with other stars in the past. Also, this star whipped past us really fast, so its gravity had very little time to act on the solar system.

The star could have perturbed some comets our way (though the chances of them hitting Earth are slim). Wikipedia claims that it would take about 2 million years for perturbed comets to reach the planets/Sun. I verified this by plugging a 0.4 light-year semi-major axis length into the formula for orbital period- it gives 4 million years. Divide that by two to get the amount of time it takes a comet to fall into the Sun from 0.8 light-years away - 2 million years. I suppose some comets could have gotten a boost and could arrive a bit sooner, but probably not a lot.

It's too bad that this encounter happened 70,000 years in the past instead of 70,000 years in the future. It would have been a perfect chance for interstellar travel if civilization were still on Earth.

Edited February 20, 2015 by |Velocity|

[Streetwind]

No probably not. You can guarantee that Sol has had much closer encounters with other stars in the past.

Actually the scientists in the article have stated the opposite - this is the closest encounter that anyone's managed to calculate, ever.

Mind you, ESA's Gaia observatory mission that's mapping the trajectories of an entire billion stars in our galaxy and nearby right now might bring up some new stars nobody has seen or thought about yet - it's conceivable, even Scholz's Star here was only discovered in 2013. That's why its trajectory has only been properly calculated now, and thus its former close encounter discovered.

But at least until Gaia's dataset is complete, which will take another couple of years, this remains the single closest encounter by any star we know of right now.

[Alshain]

Humanity was already huddling around warm fires back then, blissfully unaware of this rare cosmic event.

I'm sure blissfully unware of what it was, but if a red dwarf passed by at 0.8 light years, I'd bet they saw it.

[Streetwind]

Ordinarily it would be too dim - but the scientists speculate that the occasional solar flare event might have made it visible for a few minutes at a time. Though it would have required an exceptionally perceptive early human to notice one little extra dot of light in an entire sky full of them even if they were looking up at exactly the right moment.

[Armchair Rocket Scientist]

http://www.space.com/28611-star-flew-through-solar-system.html

I found this a fun and interesting scenario to imagine. Apparently a red dwarf plowed through our solar system's Oort cloud some 70,000 years ago, coming as close as 0.8 lightyears to the Sun. Compare this to the more than 4 light years distance to our current nearest neighbour... that's pretty darn close, and in cosmic terms, pretty darn recent! It would have been during the most recent glacial of the current ice age (while today we are in the interglacial directly following it). Humanity was already huddling around warm fires back then, blissfully unaware of this rare cosmic event.

I wonder if some of the more puzzling orbits we see in some outer solar system objects today could be partly the result of this encounter.

70,000 years ago? So, most likely any Oort Cloud objects that were perturbed back then haven't had time to reach the inner solar system.

Could this mean that in a few million years there will be a swarm of comets buzzing the inner solar system, possibly leading to a mass extinction on Earth?

[Bill Phil]

Almost hit us? 0.8 light years is a big miss on Solar System Scale...

But it's not on Galactic Scale...

[magnemoe]

Actually the scientists in the article have stated the opposite - this is the closest encounter that anyone's managed to calculate, ever.

Mind you, ESA's Gaia observatory mission that's mapping the trajectories of an entire billion stars in our galaxy and nearby right now might bring up some new stars nobody has seen or thought about yet - it's conceivable, even Scholz's Star here was only discovered in 2013. That's why its trajectory has only been properly calculated now, and thus its former close encounter discovered.

But at least until Gaia's dataset is complete, which will take another couple of years, this remains the single closest encounter by any star we know of right now.

The last 70.000 years yes, however how about the last 70 million or multiple billions. an comet with an AP of 0.8 lightyears will use 4 million years on an orbit.

Now if the star was as large as sun I guess it would disrupt lots of the comets so far out and makes me wonder how many are left there.

[Streetwind]

The last 70.000 years yes, however how about the last 70 million or multiple billions. an comet with an AP of 0.8 lightyears will use 4 million years on an orbit.

Now if the star was as large as sun I guess it would disrupt lots of the comets so far out and makes me wonder how many are left there.

No, you misunderstand. They're not looking at a time window and checking if something came close in that window.

They're calculating the orbit of a star around the galaxy (or more precisely, the tagential and radial velocities with respect to Earth). From that, they can predict where the star has been and where it will be in the future with pretty good accuracy. So it doesn't matter if it was 70 thousand or 70 million years in the past - if the star ever comes or came anywhere close to the solar system, then it's double- and triple-checked with the highest possible confidence. Such events are of high interest to the scientists. They're hunting every one of them down.

This case is limited by our ability to see and measure stars, not by the timespan since an enounter.

[-Velocity-]

Actually the scientists in the article have stated the opposite - this is the closest encounter that anyone's managed to calculate, ever.

Mind you, ESA's Gaia observatory mission that's mapping the trajectories of an entire billion stars in our galaxy and nearby right now might bring up some new stars nobody has seen or thought about yet - it's conceivable, even Scholz's Star here was only discovered in 2013. That's why its trajectory has only been properly calculated now, and thus its former close encounter discovered.

But at least until Gaia's dataset is complete, which will take another couple of years, this remains the single closest encounter by any star we know of right now.

Incorrect. Scientists have not stated that this is the closest that any star has ever come to the solar system its entire 4.6 billion years of existence. In fact, there are probably hundreds of stars out there that have come closer to the solar system than this star did. Even the Wikipedia article on Scholz's star says that stellar encounters this close (0.8 light-years) or closer should come every 9 million years, pretty frequently astronomically speaking.

[jfull]

Its pretty crazy that a star could have been less than a lightyear away from us at a time when early humans were around, but now be much further away than alpha centauri. Has anyone said how fast it's moving relative to us?

This whole thing makes me wonder how much our stellar neighborhood has changed over the time that life has existed on earth.

[-Velocity-]

Its pretty crazy that a star could have been less than a lightyear away from us at a time when early humans were around, but now be much further away than alpha centauri. Has anyone said how fast it's moving relative to us?

Supposedly its relative radial velocity is something like 80 km/s.

This whole thing makes me wonder how much our stellar neighborhood has changed over the time that life has existed on earth.

It's changed many, many times over, and we're probably somewhat lucky to be here at all. There's a reason they call it "spaceship Earth" sometimes. Since its birth, the Earth has made about 20 full trips around the galaxy.

Edited February 21, 2015 by |Velocity|