The Astronomy Thread

Jan 2009
1,209
one would presume that some gravitational perturbations must have occurred during this passage, but this isn't discussed in the article. (I do note that the toba eruption occurred at about this same time, but it could be coincidence. Lake Toba - Wikipedia, the free encyclopedia )
Oh Lowell... Could? It most certainly IS a coincidence. :)

Lets do a quick back of the envelop calculation, shall we?

Scholz' star, actually a binary star, has a mass of 0.15 solar masses. It passes by from a distance of 0.8 light years which is about 160000 AU.

Jupiter's mass is about 0.001 solar masses, so 1/150th of the Scholz's star's mass. However, it is 'only' 5.2 AU from the Sun, so at the close approach, Earth is about 4.2 AU away.

We can now calculate quickly the ratio of gravitational effects that Jupiter and Scholz's star have on Earth during that close pass. Remember, gravity scales proportional to the mass, but inversely to the square of the distance. So:
Jupiter's effect / Scholz's star's effect
= (1/150) * (160000/4.2)^2 = about 10 million.

The difference of Jupiter's pull between the farthest point (~6.2 AU) and the closest (~4.2 AU) = (4.2/6.2)^2 = 0.46 => Jupiter's gravitational effect at the closest point doubles in comparison to its farthest away point. If you take into account that at the closest point, Jupiter pulls 'against' Sun, and at the most distant one, 'with' Sun, you could say that the net contribution changes three-folds. So about 30 million times the effect of the Scholz's star.

In other words, if Scholz's star's gravitational pull 70000 years ago from 0.8ly away would trigger a supervolcano on Earth, Jupiter would make that look like a fart in a bath every ~1.1 years when Earth does the closest pass (taking a bit longer than a year since Jupiter moves during the year, too).

And, as everyone knows, the Moon has even more of a gravitational effect on Earth than Jupiter (about 100 times stronger, due to being so close): the tides. I haven't been noticing supervolcanos popping out every 24h of the Earth's rotation, or even on a monthly cycle.

QED.
 
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Lowell2

Ad Honorem
Jun 2014
6,541
California
Oh Lowell... Could? It most certainly IS a coincidence. :)

Lets do a quick back of the envelop calculation, shall we?

Scholz' star, actually a binary star, has a mass of 0.15 solar masses. It passes by from a distance of 0.8 light years which is about 160000 AU.

Jupiter's mass is about 0.001 solar masses, so 1/150th of the Scholz's star's mass. However, it is 'only' 5.2 AU from the Sun, so at the close approach, Earth is about 4.2 AU away.

We can now calculate quickly the ratio of gravitational effects that Jupiter and Scholz's star have on Earth during that close pass. Remember, gravity scales proportional to the mass, but inversely to the square of the distance. So:
Jupiter's effect / Scholz's star's effect
= (1/150) * (160000/4.2)^2 = about 10 million.

The difference of Jupiter's pull between the farthest point (~6.2 AU) and the closest (~4.2 AU) = (4.2/6.2)^2 = 0.46 => Jupiter's gravitational effect at the closest point doubles in comparison to its farthest away point. If you take into account that at the closest point, Jupiter pulls 'against' Sun, and at the most distant one, 'with' Sun, you could say that the net contribution changes three-folds. So about 30 million times the effect of the Scholz's star.

In other words, if Scholz's star's gravitational pull 70000 years ago from 0.8ly away would trigger a supervolcano on Earth, Jupiter would make that look like a fart in a bath every ~1.1 years when Earth does the closest pass (taking a bit longer than a year since Jupiter moves during the year, too).

And, as everyone knows, the Moon has even more of a gravitational effect on Earth than Jupiter (about 100 times stronger, due to being so close): the tides. I haven't been noticing supervolcanos popping out every 24h of the Earth's rotation, or even on a monthly cycle.

QED.
Thanks for the mathematics calculation. Destroyed a fun wild speculation but I'd rather have facts, even if they are less spectacular. I suppose if it was big enough to affect Earth it would have totaled the solar system.

But still, since this star apparently zipped thru the oort cloud and since even pluto was found via orbital affects, it's hard to believe that something this size wouldn't have had SOME gravitational influence that would result from it's passing, even if there were none to Earth. It certainly seems that it could have disturbed some of those nifty asteroids and slightly altered the orbit of some -- it passes thru at the wrong time to provide any explanation for Uranus being on it's side or for the 65 million year old dinosaur wipe out but I still think there should be SOME evidence of it's passing thru.

The asteroid that killed off the dinosaurs MAY have come from the oort cloud (NASA - Origin of Dinosaur-Killing Asteroid Remains a Mystery [ame=http://en.wikipedia.org/wiki/Chicxulub_impactor]Chicxulub impactor - Wikipedia, the free encyclopedia[/ame]

The latest theory on Uranus is a series of small impacts after formation Series of bumps sent Uranus into its sideways spin, new research suggests -- ScienceDaily but given the theory of Earth & Moon's formation as a result of a "mars size" impact, How Was the Moon Formed?I don't know if a bunch of "small impacts" would simply tilt a planet.
 
Jan 2009
1,209
But still, since this star apparently zipped thru the oort cloud and since even pluto was found via orbital affects, it's hard to believe that something this size wouldn't have had SOME gravitational influence that would result from it's passing, even if there were none to Earth. It certainly seems that it could have disturbed some of those nifty asteroids and slightly altered the orbit of some -- it passes thru at the wrong time to provide any explanation for Uranus being on it's side or for the 65 million year old dinosaur wipe out but I still think there should be SOME evidence of it's passing thru.
Well, you'll have to recall that this happened 0.8 light years away. That is on the edges of the Oort cloud. There is a whole lot of nothing out there. Certainly it would have disturbed some Oort cloud objects that happened to be close to it. But I am willing to trust the statement in the article you linked by the guys who actually study these encounters with simulations, that you'd need a close encounter in the inner Oort cloud to trigger a 'comet storm'. Inner Oort cloud is about 2000–20000 AU, so the star in question would have needed to come almost ten times closer than it did. Even if it did perturb some very very far away comets into orbits that would take them into the inner solar system, the chances of one actually hitting EARTH is very small. Jupiter, with is stronger gravitational field, is our shield and savior, tending to suck in comets and thus clear them from the circulation.

Of course, no way of proving that such a killer comet hasn't been sent on its way 70000 years ago, negatives being impossible to prove, but I am not going to lose any sleep over it. And neither should you. :)

Also, managed to find this gem while looking up asteroid impact frequencies:
http://en.wikipedia.org/wiki/Global_catastrophic_risk#Asteroid_impact said:
In 1.4 million years, the star Gliese 710 is expected to start causing an increase in the number of meteoroids in the vicinity of Earth when it passes within 1.1 light years of the Sun and perturbing the Oort cloud. Dynamic models by García-Sánchez predict a 5% increase in the rate of impact.[107] Objects perturbed from the Oort cloud take millions of years to reach the inner Solar System.
So millions of years for the perturbed comets to even reach the inner solar system, and a minor increase of 5%. That is solidly in the 'minor to the point of almost insignificant' in my book, when crunching the probabilities. Gliese 710 is also 4 times as massive as Scholz's Star is, so that 1.1 ly encounter is equivalent to 0.55 ly encounter for SS, which means roughly that you'd expect half the effect for SS. However, it also depends on the encounter speed, and SS apparently zipped by very quickly, having less time to mess with the outer Oort Cloud. All signs point to: 'Nothing to get exited about.'

Instead, you can worry about the fact that the estimates of the big asteroid impacts, of the 1km size 'this is going to suck' -class hits, is about one every half a million years. So it is likely to happen some day. Granted, give humanity another 100 years or so to tinker with space industry and we will be able to tweak those orbits... unless, of course, it is a cosmic bulls-eye that I deemed very improbable at the start: zooming in from the outer Oort cloud with pinpoint accuracy and high velocity, leaving not enough time to do much at all about it. Sweet dreams; you are welcome. :p
 
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Jan 2009
1,209
If you take into account that at the closest point, Jupiter pulls 'against' Sun, and at the most distant one, 'with' Sun, you could say that the net contribution changes three-folds. So about 30 million times the effect of the Scholz's star.
I made a small mistake there. The 10 million was the closest point, and the farthest point would be half that, so 5 million. So I should have said 15 million times the effect of the Scholz' star. Doesn't change my point, though. :)
 

Lowell2

Ad Honorem
Jun 2014
6,541
California
Well, you'll have to recall that this happened 0.8 light years away. That is on the edges of the Oort cloud. There is a whole lot of nothing out there. Certainly it would have disturbed some Oort cloud objects that happened to be close to it. But I am willing to trust the statement in the article you linked by the guys who actually study these encounters with simulations, that you'd need a close encounter in the inner Oort cloud to trigger a 'comet storm'. Inner Oort cloud is about 2000–20000 AU, so the star in question would have needed to come almost ten times closer than it did. Even if it did perturb some very very far away comets into orbits that would take them into the inner solar system, the chances of one actually hitting EARTH is very small. Jupiter, with is stronger gravitational field, is our shield and savior, tending to suck in comets and thus clear them from the circulation.

Of course, no way of proving that such a killer comet hasn't been sent on its way 70000 years ago, negatives being impossible to prove, but I am not going to lose any sleep over it. And neither should you. :)

Also, managed to find this gem while looking up asteroid impact frequencies:

So millions of years for the perturbed comets to even reach the inner solar system, and a minor increase of 5%. That is solidly in the 'minor to the point of almost insignificant' in my book, when crunching the probabilities. Gliese 710 is also 4 times as massive as Scholz's Star is, so that 1.1 ly encounter is equivalent to 0.55 ly encounter for SS, which means roughly that you'd expect half the effect for SS. However, it also depends on the encounter speed, and SS apparently zipped by very quickly, having less time to mess with the outer Oort Cloud. All signs point to: 'Nothing to get exited about.'

Instead, you can worry about the fact that the estimates of the big asteroid impacts, of the 1km size 'this is going to suck' -class hits, is about one every half a million years. So it is likely to happen some day. Granted, give humanity another 100 years or so to tinker with space industry and we will be able to tweak those orbits... unless, of course, it is a cosmic bulls-eye that I deemed very improbable at the start: zooming in from the outer Oort cloud with pinpoint accuracy and high velocity, leaving not enough time to do much at all about it. Sweet dreams; you are welcome. :p
I'm not worried. It just seemed like a good idea for a fictional story. it still is, but the odds make it far more unlikely than I was hoping for.
 
Jan 2009
1,209
I'm not worried. It just seemed like a good idea for a fictional story. it still is, but the odds make it far more unlikely than I was hoping for.
Ah, I see. Well, there was Algol 7.3 million years ago, but it passed quite far away, 9.8 ly. Still, as its (total component) mass is around 5.8 solar masses (about 40 times Scholz' star), it would still be like SS passing around 1.6 ly. Meaning 25% of the effect. But the longer time span would make it more believable that if something got nudged into an inner solar system orbit, it would actually be arriving about now. I mean, given that it is fiction, strange coincidences do happen, and it is just the background story to justify a comet on a collision course.

Of course you could easily handwave something like a black hole brushing the outer Oort cloud, and we wouldn't necessarily even know about it, if it is a single black hole without a companion we wouldn't be able to see it. Getting a 'doomsday' comet shower might be a bit more difficult, though, as you'd have to bring the black hole to about 10 000 AU... But still handwaveable, although black holes are rather more uncommon than things like Scholz' Star. But if you need it for your story, you can justify it. :)
 

Lowell2

Ad Honorem
Jun 2014
6,541
California
Ah, I see. Well, there was Algol 7.3 million years ago, but it passed quite far away, 9.8 ly. Still, as its (total component) mass is around 5.8 solar masses (about 40 times Scholz' star), it would still be like SS passing around 1.6 ly. Meaning 25% of the effect. But the longer time span would make it more believable that if something got nudged into an inner solar system orbit, it would actually be arriving about now. I mean, given that it is fiction, strange coincidences do happen, and it is just the background story to justify a comet on a collision course.

Of course you could easily handwave something like a black hole brushing the outer Oort cloud, and we wouldn't necessarily even know about it, if it is a single black hole without a companion we wouldn't be able to see it. Getting a 'doomsday' comet shower might be a bit more difficult, though, as you'd have to bring the black hole to about 10 000 AU... But still handwaveable, although black holes are rather more uncommon than things like Scholz' Star. But if you need it for your story, you can justify it. :)
thanks! :D
 

Lowell2

Ad Honorem
Jun 2014
6,541
California
Does dark matter cause mass extinctions and geologic upheavals? -- ScienceDaily Research by New York University Biology Professor Michael Rampino concludes that Earth's infrequent but predictable path around and through our Galaxy's disc may have a direct and significant effect on geological and biological phenomena occurring on Earth. In a new paper in Monthly Notices of the Royal Astronomical Society, he concludes that movement through dark matter may perturb the orbits of comets and lead to additional heating in Earth's core, both of which could be connected with mass extinction events. While traveling through the disc, the dark matter concentrated there disturbs the pathways of comets typically orbiting far from Earth in the outer Solar System, Rampino observes. This means that comets that would normally travel at great distances from Earth instead take unusual paths, causing some of them to collide with the planet.

But even more remarkably, with each dip through the disc, the dark matter can apparently accumulate within Earth's core. Eventually, the dark matter particles annihilate each other, producing considerable heat. The heat created by the annihilation of dark matter in Earth's core could trigger events such as volcanic eruptions, mountain building, magnetic field reversals, and changes in sea level, which also show peaks every 30 million years. Rampino therefore suggests that astrophysical phenomena derived from Earth's winding path through the Galactic disc, and the consequent accumulation of dark matter in the planet's interior, can result in dramatic changes in Earth's geological and biological activity

-- seems a bit of a stretch, but it's an interesting theory.
 
Jan 2009
1,209
-- seems a bit of a stretch, but it's an interesting theory.
Yeah, it is interesting, but... on a very quick read (and dark matter is not my specialty, mind you), I came away with having some reservations:

1) First of all, we still don't know if dark matter is actually composed of WIMPs. If not, that might cut off the whole heating of Earth argument.

2) The argument is slightly circular: Randall & Reece (2014) ASSUME that there is a ~35 Myr periodicity of impacts, and then try to fit a a dark matter disk that would explain that. They come away with 10 M_sol/pc^-2 surface density with a scale height of 10pc. Then Rampino (2015) quotes R&R (2014) that there may be such a disk and comes to the conclusion that this thin dark matter disk would cause the periodicity. Well of course it would, since it was fitted to that assumption. Granted, he is just pointing out that possibility: 'if this dark matter model is correct, then it would explain this and imply the heating'.

3) Rampino (2015) quotes the total surface density of the galaxy in solar neighborhood to be between 43 and 84 M_sol / pc^-2 and the surface density due to visible matter as 40 M_sol / pc^2 (Stothers 1998). However, Rampino seems to have forgotten the interstellar medium, the gas and dust in the Galactic disk, or believes that contribution to be small. Bovy & Rix (2013) do not seem to share that opinion, they quote the numbers as 38 M_sol/pc^-2 for the stars and 13 (same units) for the interstellar medium, and conclude: "These direct dynamical measurements of disk properties are in good agreement with measurements derived from star counts, leaving little room for dark matter in a disk-like configuration." There are uncertainties to that value too, of course, and doesn't necessarily rule out a dark matter disk, but to use that disk as a given is a bit too much (see point 2 about circular reasoning).

4) R&R use ~35 Myr cratering periodicity & plane-crossing while Rampino is quoting a range of different periodicities: volcanism 26-27 Myr, mass extinctions 26-30 Myr (favoring 27 Myr), geomagnetic reversals ~30 Myr, cratering between 30-37 Myr (or 31+-5 Myr) and Sun's crossing of the Galactic mid-plane 33+-3 Myr (although 42 Myr has been suggested, too). In addition, many other researchers don't find significant ~30 Myr periodicity in mass extinctions or cratering. So that, to a non-expert like me, seems to indicate that: a) we are not really sure about the cycles (if they exists even, and if they do, what is the actual periodicity) and if we were b) they do not seem to match up nicely. I mean, would you say that a 24h cycle and a 32h cycle are a perfect match? I wouldn't.


I repeat that I am not the expert of this particular subfield, and I only quickly read through the three papers mentioned in above (didn't read Stothers 1998). At least the thin dark matter disk (Rampino, Randall & Reece) all point out that this is just hypothetical at this point and GAIA satellite's measurements of star kinematics (velocity) are needed to narrow down the error bars and to find out if we have evidence for such a disk.

So yeah, an interesting possibility which -may- rest on a faulty premise (is there a periodicity that needs to be explained, and if so, does it match with Sun's movement in the Galaxy?), not much evidence to back it up yet, and we will know better in a few years once the GAIA results are in and analyzed.
 

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