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How often does close-by star systems encounter run-away stars?
As in the rouge ones flung out of their own star system? I'm just wondering after reading about one on space.com when they took a satellite picture of a run-away star slamming through cosmic dust. This one right here: http://www.space.com/10685-runaway-s...shockwave.html. It just seems interesting though because I don't know of many Binary star systems that's near us.
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Almost never. Most of space is rather empty - the odds of running into occupied bit are very small indeed. And why are you only worried about red ones? Surely you should also care about the bleu ones...
Order of Kilopi
Two thirds of all stars are thought to be part of binary, or more, systems, but I don't think it is known how frequently one is ejected, becoming rogue.Originally Posted by Gamefreak89
My suspicion is there are many planets, pieces of, and failed stars out there floating around. As I understand it, supernovae could certainly eject some planets and companion stars from their systems. It has even been hypothesized our own system suffered such an encounter, early in its history, which could stand to reason if a nearby supernova prompted the formation of our solar system.
Good question!
And space is really not that empty. It's quite full of gas and dust, hence the shockwave seen in your link.
The bigger stuff we wouldn't see, unless it's emitting heat and moving fast.
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I agree with A.DIM. Likely no rogue star or rogue planets have passed closer than Neptune in the last 1000 years, but farther back in time is likely. If one comes closer than Neptune at 1000 year intervals on the average; Then there have be 4,600,000 passages since Earth was formed. If such passages are typical of solar systems in our galaxy, then a trillion rouge stars and planets in our galaxy and close by is probable. There are perhaps good reasons to think they do not total more than a trillion. Unless they are traveling very fast, we will likely get centuries warning of an approaching planet and about 100,000 years of an approaching star. At 1% of c proper motion, a star or planet travels one light year in 100 years, but much less than 1% of c is more likely. Cold brown dwarfs will be almost as difficult to detect as cold planets. The brown dwarfs formed more than 2 billion years ago (1/2 of them) are likely cold as a stone by now, perhaps colder than liquid nitrogen, unless they are near a heat source. I'm guessing, so please tell why this is unlikely. Neil
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Stars don't need to be rogue to encounter our solar system. Regular stars that have not been ejected from their systems do not orbit the galaxy in perfect non-intersecting orbits. The sun can encounter any star that ventures near, regardless of its history. 1000 years is too short of a period of time to expect a star to come as close as Neptune. Neptune would probably be ejected from our solar system by such an event, so it has probably never happened during the life of our solar system. If it happened every 1000 years, we would also expect a record of these extremely bright visitors throughout recorded history dating back several thousand years. According to a formula by Joan Garcia-Sanchez in the paper "Stellar Encounters with the Oort Cloud Based on Hipparcos Data", we can expect a star to pass as close as Neptune on average of once every 15 trillion years. This excludes the time the sun spent as part of a cluster when it was formed. Here's an online calculator I made so you can play with the formula and enter different values: http://orbitsimulator.com/formulas/cse.html
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Any references for all those numbers? If you assume that there have been passages closer than Neptune about once every 1000 years then (shock) you find that there have been a lot of passages of rogues... It is an unwarranted and (IMO) very bad assumption. Your conclusions are based on a small collections of bad or wildly inflated numbers. Believe me we'd know if any sizeable star had come closer than Neptune recently...I'm guessing, so please tell why this is unlikely. Neil
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That gets me thinking that a white dwarf would have some mass to it but wouldn't cause Neptune or any near by planets to be thrown out of orbit. Then again white dwarfs do lose all of their mass after the stellar nebula event right?
Order of Kilopi
No, a typical white dwarf has upwards of half a solar mass. Sirius B, one of the most massive ones known, has about a solar mass. If one came inside of Neptune's orbit, we should expect severe perturbations of the orbits of the planets.
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Hmm... I thought most yellow stars shed all of their mass after going red giant when a stellar nebula forms but oh well. Anyways wouldn't our sun keep lower mass stars from coming near our solar system?
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No, why (and how) would you think it would do that?
Order of Kilopi
You must have seen some bad writing on the topic, or heard someone quote it. There is plenty of it out there, and the Internet has only made it worse for the unwary. Anybody and his uncle can post garbage, without having it vetted by knowledgeable editors.
If another star comes in on a close encounter trajectory, the mutual gravitation of it and the Sun will make the encounter closer. There is nothing about the Sun that could repel it.Anyways wouldn't our sun keep lower mass stars from coming near our solar system?
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I see I thought objects with less mass gets ejected instead of gravitational pull between a tug a war
Order of Kilopi
You appear to have confused what happens to planets in the mix with the actions on the stars themselves. In a close encounter of two stars, a planet in orbit around one of them could be ejected by the interloper's gravitational perturbation, or it could be deflected into a tighter orbit, depending on the geometry of the encounter. In either case the motions of the vastly more massive stars are only slightly affected by these interactions with the planets. No matter what, the paths of the stars will curve toward each other as they approach minimum separation. Their gravity is always attractive, never repulsive.
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Now I see I always thought orbital simulators were meant for something... but on to the question of run-away stars when looking at the milky way how is it that billions of stars the orbit it not crash into each other? I know there is a lot of space in between some star systems but how much space does one star need? Like in order for it to be gravitationally affected by another star?
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Rough and simple approximation. The nearest stars like Alpha Centauri pass the Sun at timescales of about 100 000 years, and do so at about 1 pc or 200 000 AU. So, from the area of bullīs eye, the Sun might encounter a star coming within 0,1 pc or 20 000 AU (so the star would spend a few thousand years at closest approach) once in 10 million years. There would be a star within 2000 AU (for a few century) once in a milliard year, and over the 10 milliard year lifetime of Sun, chances are that the closest approach of a star might be 600 AU. There is one in a million chance that over the whole history of Sun, some star has its projected path within 0,6 AU of Sun, and at that distance the attraction of Sun would matter and cause the star to bend even closer to Sun.
What is the chance that any star could come within 0,01 AU of Sun, and thus collide?
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The closer the star the greater the gravity between the two thus the greater the influence of the planet's gravitational orbits right?
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Well, non-rogue stars can disturb each other's orbits. And it possible for them to collide, but not likely.
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I'm guessing on a scale of millions of years then if a star system was close to another one say in a distance of half a light year?
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If you're wondering about stars that will come close to the sun, there's Gliese 710 that will approach to about a light year some 1.4 million years from now. It's currently about 63 light years away.
Stars are, on average, about 5 light years away from their nearest neighbor in this part of the galaxy. However, approaching to about a light year of another star is not that unusual. For instance, Luyten's Star is currently only 1.2 light years away from Procyon.
Order of Kilopi
Suppose a one solar mass star passes that close to us. It would perturb the orbits of outlying Oort cloud comets and alter our system's orbit around the galactic center. It would have no major effect on the orbits of the planets, even the outermost ones.
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I was never good with Physicsthanks for clearing that up.
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So consider how to have an effect on the orbits of outermost planets.
Neptune orbits at about 5,5 km/s. Uranus orbits at about 6,7 km/s. Thus Neptune passes Uranus at about 1,2 km/s at 10 AU.
It creates noticeable perturbation of the orbit of Uranus, but not a major one.
Suppose that something passes Uranus at about 12 km/s (low range for stellar peculiar motions) at 100 AU, thus 120 AU from Sun.
It spends roughly as long attracting Uranus as Neptune does, and now the attraction to the Sun is also comparable. So the perturbation to the orbit of Uranus is similar if the body at 120 AU has about 200 times the mass of Neptune, or perhaps 10 times that of Jupiter.
Now let us consider even more massive star passing further, but at similar speed - so the passage lasts longer. The duration of passage is proportional to distance. The tidal force is proportional to the inverse cube of distance, so the total effect is proportional to inverse square of the distance, and to mass.
A body with the mass of Sun, or 1000 times the mass of Jupiter, would create a noticeable perturbation by passing at 12 km/s at a distance of 1000 AU from Uranus.
As derived above, it turns out to be the distance where a few approaches are likely over the 10 milliard year history of Solar System.
Order of Kilopi
There's a convenient Close Stellar Encounters calculator on orbitsimulator.com that calculates how often another star passes within a certain distance. Bear in mind that most of these stars will be red dwarfs.
So, for example, there would be about one encounter within 1000AU per 11 billion years.
Order of Kilopi
How?
Order of Kilopi
Depends. There are binary systems where the 2 stars are close enough that 1 of the stars can steal material off of the other and there are other star systems with 2 or more stars where the stars can be separated by thousands of astronomical units (1 AU = the distance from the Earth to the sun. At pluto's furthest point it is still under 50 au from the sun.)
Its a bit like asking how much space do you need to separate you from your neighbour. You could be in the country and have to drive for over an hour to get to them or you could be very close to your neighbour having a shared wall. How long is a piece of string?
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