PDA

View Full Version : Scholzís star's near miss 70,000 years ago



Swift
2019-Feb-26, 09:31 PM
NASA.gov (https://exoplanets.nasa.gov/blog/1549/a-passing-star-our-suns-near-miss/)


Stars jostling around the galaxy arenít quite like a cosmic game of pool. But they do have occasional near misses as they speed past each other. Back when spears and stone points were the height of human technology, astronomers say, our solar system had a close encounter of the interstellar kind.

The brief visitor was Scholzís star, and it might have grazed the outer edge of the solar systemís distant Oort Cloud about 70,000 years ago Ė carrying its companion, a likely brown dwarf, along for the ride.

Itís unclear whether the near miss was close enough to give objects in the Oort Cloud, our solar systemís halo of dormant comets, a gravitational nudge to fall toward the Sun. But the interstellar trespasser highlights a sometimes-forgotten reality: On long time scales, stars seem to fly around like sparks from a campfire, occasionally coming close enough to disturb each otherís cometary clouds.

...

ďIn less than 15 minutes, we figured out that this star had passed within a light-year of the solar system, 70 or 80 thousand years ago,Ē he said.

The closest stars to our Sun today are the three in the Alpha Centauri system, about four light-years away. But if there were a star one light-year away, that could very well approach or even intersect with the outermost edge of the Oort Cloud.

antoniseb
2019-Feb-27, 01:23 PM
Space.com's article (https://www.space.com/40043-star-grazed-our-solar-system-disrupted-orbits.html) says early human likely saw it, but I have my doubts. It is currently about 20 light years away at about 18th magnitude, and 20 time closer it would be 400 times brighter, so maybe 11th magnitude. Early humans didn't see that.

Swift
2019-Feb-27, 01:41 PM
Space.com's article (https://www.space.com/40043-star-grazed-our-solar-system-disrupted-orbits.html) says early human likely saw it, but I have my doubts. It is currently about 20 light years away at about 18th magnitude, and 20 time closer it would be 400 times brighter, so maybe 11th magnitude. Early humans didn't see that.
The NASA article agrees with you. They did mention that at closest approach, if the star had flared, it might have been visible.

George
2019-Feb-27, 09:07 PM
Space.com's article (https://www.space.com/40043-star-grazed-our-solar-system-disrupted-orbits.html) says early human likely saw it, but I have my doubts. It is currently about 20 light years away at about 18th magnitude, and 20 time closer it would be 400 times brighter, so maybe 11th magnitude. Early humans didn't see that.
Assuming no trajectory changes since the encounter, and using the Wiki values for Scholz, my quicky Excel work shows it came to about 0.85 lyr. ~53,800 years ago. It also agrees with your 11th mag. figure (11.4).

Spacedude
2019-Feb-27, 10:01 PM
If Star Scholz did graze our Oort Cloud (58-70 thousand years ago) are there any guesses/calculations on how long it would take for the earliest perturbed objects to reach the inner solar system? When it comes to Scholz I know nothing.

Grey
2019-Feb-27, 10:58 PM
Well, using this calculator (http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/starff.html) (which is intended for an entirely different purpose, but which I think works here), the freefall time for one solar mass from 0.85 light years is about 2.2 million years. This should be applicable for some small object even if the one solar mass star has already collapsed. So if Scholz's star stopped some hypothetical comet dead in its orbit at that distance, that's how long it should take to reach the inner solar system. I guess in principle it might slingshot something straight for the Sun at a much higher initial velocity, but that's not enormously likely, and doesn't seem like it would change things by more than an order of magnitude. So my guess is, they aren't here yet, and won't be here for quite some time.

Spacedude
2019-Feb-28, 12:16 AM
Thanks Grey!!

....and Hornblower below....

Hornblower
2019-Feb-28, 12:45 AM
Scholz's flyby velocity was about 60 miles per second relative to us, so it could easily have caused a slingshot effect sufficient to get some comets here in 70,000 years. My rough calculations show that their velocity at 1 AU from the Sun would be on the order of 1% greater than that for a parabolic orbit. That should be sufficiently hyperbolic to be recognized as such, should any of them come close enough to be seen. Those that were merely jostled enough to have their perihelia moved in from what otherwise would have been a wide miss would arrive in some 2.2 million years, by which time the culprit will be several hundred light-years away on its hit-and-run course. At this point I do not know which ones would be more numerous. Our orbital mechanics experts certainly can calculate a probable distribution based on an inferred distribution of Oort could comets.

Hornblower
2019-Feb-28, 03:16 AM
Addendum: I found some references that were useful for my doodling. First, some equations from which I could calculate the hyperbolic eccentricity corresponding to the aforementioned hypothetical velocity.

http://www.bogan.ca/orbits/kepler/orbteqtn.html

Wiki list of observed parabolic and hyperbolic comets in recorded history.

https://en.wikipedia.org/wiki/List_of_hyperbolic_comets

I found that an eccentricity of about 1.03 corresponded to my assumed velocity. In the comet list I found only one that was close to that, C/2008 J4 (McNaught). I do not have the means to tell whether or not its incoming trajectory was consistent with a close encounter with Scholz.

bknight
2019-Feb-28, 12:11 PM
If Planet X is real I wonder whether this encounter might have skewed its orbit?

Hornblower
2019-Mar-08, 02:07 AM
If Planet X is real I wonder whether this encounter might have skewed its orbit?

The theoretically estimated semimajor axis of this object is only about 1/100 of the closest approach of Scholz. It would have been tweaked a bit rather than seriously disturbed.

George
2019-Mar-08, 04:29 PM
I noticed that the SIMBAD data (http://simbad.u-strasbg.fr/simbad/sim-ref?bibcode=2015AJ....149..104B) was different than Wiki's, slightly. It shows 6.0 parsecs (19.6 lyrs.) distance. The simple vector math shows it was 0.93 lyr. distance at closest approach and it happened ~58,650 years ago.


Scholz's flyby velocity was about 60 miles per second relative to us, so it could easily have caused a slingshot effect sufficient to get some comets here in 70,000 years. If so, then they may still be on their way, arriving in about 11,000 years or so, perhaps sooner for the closer objects affected.

Hornblower
2019-Mar-09, 03:20 AM
The disturbed comets would have a wide range of slingshot delta V, depending on how close they were to the star during its passage. I can envision fast ones that already have come and gone, somewhat slower ones that are just now arriving, and progressively slower ones arriving between now and the 2.4 million years from now for those that were brought to a near standstill by the star. I don't have the know-how to estimate when the arrivals here would be most frequent.

George
2019-Mar-09, 09:35 PM
The disturbed comets would have a wide range of slingshot delta V, depending on how close they were to the star during its passage. I can envision fast ones that already have come and gone, somewhat slower ones that are just now arriving, and progressively slower ones arriving between now and the 2.4 million years from now for those that were brought to a near standstill by the star. I don't have the know-how to estimate when the arrivals here would be most frequent. Yep, I oversimplified it. Objects close to the path that were flung (reflung? :) ) inward at much greater speed than others. If we assume a 1 lyr. radius for the edge of the Oort Cloud, and the 0.92 lyr passage is correct, then it would only have had about 1500 years to act on those objects, using the same speed it has now 83.8 kps.

If you find that a significant number of objects flung might have an average velocity around 6% that of Schulz, then perhaps your search for recent candidates should be of even greater interest.

24073