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What if hypervelocity star came near Sun?
According to this article, the mysterious super-high speed stars are
more numerous and fastest than previously though. What if one of these "hypervelocity" stars came through Sun's neighborhood? How dangerous it could be for life on Earth? What would be safe distance a star moving at about 700 - 1000 km/s could get near Sun without disrupting the planetary system? http://space.newscientist.com/channe...ays-stars.html Puny black holes can eject Milky Way's stars NewScientist.com news service David Shiga Tiny black holes near the galaxy's centre can fling stars out of the Milky Way at break-neck speeds, a new study suggests. Previously, only the supermassive black hole there was thought to be able to produce these "hypervelocity" stars. The researchers say the small black holes could actually be ejecting more stars than the central black hole does on its own, and that observing the stars could shed light on the elusive population of mini-black holes themselves. Physicist Jack Hills at Los Alamos National Laboratory in New Mexico, US, predicted in 1988 that the monster black hole at our galaxy's centre should disrupt pairs of stars, capturing one and launching the other out of the galaxy altogether. Since 2004, astronomers have found nine stars travelling at high speed out of our galaxy - all presumably flung there by the giant black hole, which weighs about 3.6 million times the mass of the Sun. But a new study suggests that many of the ejected stars are getting kicked out by a swarm of much smaller black holes at the galaxy's centre. The study was carried out by Ryan O'Leary and Avi Loeb, both at the Harvard Smithsonian Center for Astrophysics in Cambridge, Massachusetts, US. Close encounters The smaller black holes are about 10 times more massive than the Sun. Some studies suggest as many as 25,000 small black holes may orbit the supermassive black hole at the galaxy's centre, having migrated there from other parts of the galaxy after being nudged out of their original orbits by passing stars. When one of these little black holes near the galactic centre passes very close to a star, it can sometimes fling the star out of the galaxy, while itself moving closer to the supermassive black hole, the study says. This process could eject stars at an even greater rate than the disruption of binary stars by the supermassive black hole itself, Loeb says. "The rate could account for a substantial fraction or maybe most of the events we have seen so far," he told New Scientist. If so, studying the sheer number of hypervelocity stars, as well as their trajectories and speeds, could help astronomers determine how many black holes are there and how they are distributed in space, Loeb says. These have proven to be elusive subjects of study because existing telescopes do not have the resolution to see within a fraction of a light year of the central supermassive black hole, where these little black holes are thought to be concentrated most heavily. Speed limit Margaret Geller, an astronomer at the Smithsonian Astrophysical Observatory who was on the team that found the first hypervelocity star in 2004, says encounters with small black holes could account for some of the ejected stars. She says it is not likely to account for all such stars, however. "It's tough for them to get the highest velocity objects," she told New Scientist. The fastest known hypervelocity star is moving at 709 kilometres per second with respect to the galaxy. The star would have been slowed by the galaxy's gravity on its way out, so it must have been moving at about 1200 kilometres per second initially. But Loeb argues that small black holes can eject stars at up to 2000 kilometres per second, fast enough to explain all known hypervelocity stars. He and Geller agree that searching for even faster stars would be a good way to test the small black hole mechanism. The supermassive black hole could fling stars out with starting velocities of 4000 kilometres per second, faster than anything the small black holes could account for, Loeb says. "If the velocity distribution does extend to high speeds, then it argues for the other mechanism," he says. |
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What if hypervelocity star came near Sun?
"tracy" wrote in message oups.com... | According to this article, the mysterious super-high speed stars are | more numerous and fastest than previously though. What if one of these | "hypervelocity" stars came through Sun's neighborhood? In hypothetical sentences introduced by 'if' and referring to past time, where conditions are to be deemed 'unfulfilled', the verb will regularly be found in the pluperfect subjunctive, in both protasis and apodosis. -- Donet, "Principles of Elementary Latin Syntax" | How dangerous | it could be for life on Earth? About the same as a bacterium in a crematorium. It might even be fatal. | | What would be safe distance a star moving at about 700 - 1000 km/s | could get near Sun without disrupting the planetary system? The speed is irrelevant, presence is. You don't seem to grasp the scale of the Universe or even the scale of the Solar System. Suppose you have a cluster of 4 pixels (dots) in the middle of your monitor screen to represent the sun, like this: ---- o ---- (Sun, drawn too big) Then | | | | -- . ---- (Mercury) | | | | | -- . -- (Venus) | | | | | -- ' -- (Earth and Moon) Jupiter (still a dot -- . --- ) is about where your ceiling is. Saturn is then in your kitchen, the NEAREST star is at the end of the street, and the imaginary black hole at the galactic centre is in the next city. You have a far better chance of winning the lottery than meeting another star up close and personal. Androcles |
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What if hypervelocity star came near Sun?
"tracy" ha scritto nel messaggio
oups.com... According to this article, the mysterious super-high speed stars are more numerous and fastest than previously though. What if one of these "hypervelocity" stars came through Sun's neighborhood? How dangerous it could be for life on Earth? What would be safe distance a star moving at about 700 - 1000 km/s could get near Sun without disrupting the planetary system? http://space.newscientist.com/channe...ays-stars.html Puny black holes can eject Milky Way's stars NewScientist.com news service David Shiga CUT Sorry for bad English. Alfa Centaur sistem (three stars) it's at 4.4 l.y. (around 200,000 A.U.), it's not a problem for Solar Sistem, Barnard Star shall be in the future a 3 l.y. and too it shall be not a problem for Solar Sistem, then when a star is certainly dangerous for our sistem? When its (minimal) distance from the Sun is 60 A.U., it can to send Neptune in a parabolic orbit and disturb heavy the orbit of other planets, so much that the life on the Earth can to be seriously in danger, and this if the star has the same mass of the Sun, if its mass is biggest it can to do the same from a biggest distance: for to have a save life on the Earth a star with the same mass of Sun must to be distant at minimum some hundred of A.U., the Astronomer think that similar passages occured in the last 4.5 billion of years around 10-20 time in the past. The speed it's too important: it's better a quick star that a slow star because more shall be the time at a little distance from the Sun more are possibilities that the planets should be perturbed, and an other factor it's the inclination of its path respect Solar Sistem, the inclination influence the duration of the meeting with the Solar Sistem and then the following effects. In all cases a star passing at some thousands od A.U. fron the Sun it do a fall of comet toward the Sun from Oort cloud with possibility that some fall on the Earth, there are evidence that 2 stars in the recent past accross the Oort cloud. Sao 67174 |
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What if hypervelocity star came near Sun?
"tracy" wrote in message oups.com... According to this article, the mysterious super-high speed stars are more numerous and fastest than previously though. According to the group charter, this is off-topic for soc.history.what-if. What if one of these "hypervelocity" stars came through Sun's neighborhood? It would be a bad thing. However, this is all off-topic. -- Posted via a free Usenet account from http://www.teranews.com |
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What if hypervelocity star came near Sun?
tracy wrote:
According to this article, the mysterious super-high speed stars are more numerous and fastest than previously though. What if one of these "hypervelocity" stars came through Sun's neighborhood? How dangerous it could be for life on Earth? What would be safe distance a star moving at about 700 - 1000 km/s could get near Sun without disrupting the planetary system? http://space.newscientist.com/channe...ays-stars.html ... Lets cut it as this point and look at the requirements for an effect. First passing through a solar system is very low probability. Second it has to pass close enough to a planet to impart enough momentum to do something significant. Those odds are also very low. Very significant is very very low. But as to what would happen you need a serious program to deal with orbital mechanics of the planets and then fly a few thousand through the solar system and get a feel for the results. Some simple consideration, on average "half" the planets are going to be on the wrong side of the sun to be seriously affected. The closer to the sun the less affected. Being tossed out of the solar system is much more likely than falling into the sun but equally likely with a highly elliptic orbit. There is really not good answer other than learn the orbital mechanics and think it through for yourself. There is no way to give a decent answer without the listener knowing the subject. -- Consider Jews have said they will continue to try to murder Nasrallah, the leader of Hezbollah, but he has not said he will try to murder the leader of Israel. Who is the most civilized? -- The Iron Webmaster, 3704 nizkor http://www.giwersworld.org/nizkook/nizkook.phtml Mission Accomplished http://www.giwersworld.org/opinion/mission.phtml a12 |
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What if hypervelocity star came near Sun?
tracy wrote:
According to this article, the mysterious super-high speed stars are more numerous and fastest than previously though. What if one of these "hypervelocity" stars came through Sun's neighborhood? How dangerous it could be for life on Earth? What would be safe distance a star moving at about 700 - 1000 km/s could get near Sun without disrupting the planetary system? Depends on the mass of the star, just how fast, perhaps its angle with respect to the plane of the eclptic and how much perturbation (you can have detectable, but harmless changes) you consider disruptive. All in all though, I'd say having another star (or stellar mass object) pass within tens of billions of miles is not a good thing. Even just stirring up the Oort Cloud or KBOs could result in signifigant matter falling into the inner sloar system, and some of those rocks could have our name on it.... -- Frank You know what to remove to reply... Check out my web page: http://www.geocities.com/stardolphin1/link2.htm "To confine our attention to terrestrial matters would be to limit the human spirit." - Stephen Hawking |
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What if hypervelocity star came near Sun?
Sorcerer kirjutas: "tracy" wrote in message oups.com... | According to this article, the mysterious super-high speed stars are | more numerous and fastest than previously though. What if one of these | "hypervelocity" stars came through Sun's neighborhood? In hypothetical sentences introduced by 'if' and referring to past time, where conditions are to be deemed 'unfulfilled', the verb will regularly be found in the pluperfect subjunctive, in both protasis and apodosis. -- Donet, "Principles of Elementary Latin Syntax" | How dangerous | it could be for life on Earth? About the same as a bacterium in a crematorium. It might even be fatal. | | What would be safe distance a star moving at about 700 - 1000 km/s | could get near Sun without disrupting the planetary system? The speed is irrelevant, presence is. Actually, the speed is relevant. The Solar System might - at a very low probability as explained by previous poster below - experience a close encounter with a star. It might be a disc star like Toliman or Sirius at a rather low relative speed, or a halo star like Barnard Runner or Arcturus at higher velocity, or a rare hypervelocity star ejected from Galactic core at yet faster speed. The faster the star is, the smaller the danger. After all, what disrupts the Solar System is the gravity of the star. The gravitational acceleration at a given distance is independent of the speed of the disturbing star. But the faster the star, the less time it spends near Solar System, and the less momentum the planets will accumulate. You don't seem to grasp the scale of the Universe or even the scale of the Solar System. Suppose you have a cluster of 4 pixels (dots) in the middle of your monitor screen to represent the sun, like this: ---- o ---- (Sun, drawn too big) Then | | | | -- . ---- (Mercury) | | | | | -- . -- (Venus) | | | | | -- ' -- (Earth and Moon) Jupiter (still a dot -- . --- ) is about where your ceiling is. Saturn is then in your kitchen, the NEAREST star is at the end of the street, and the imaginary black hole at the galactic centre is in the next city. You have a far better chance of winning the lottery than meeting another star up close and personal. Androcles |
#8
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What if hypervelocity star came near Sun?
wrote in message ups.com... | | Sorcerer kirjutas: | "tracy" wrote in message oups.com... | | According to this article, the mysterious super-high speed stars are | | more numerous and fastest than previously though. What if one of these | | "hypervelocity" stars came through Sun's neighborhood? | | In hypothetical sentences introduced by 'if' and referring to | past time, where conditions are to be deemed 'unfulfilled', | the verb will regularly be found in the pluperfect subjunctive, | in both protasis and apodosis. | -- Donet, "Principles of Elementary Latin Syntax" | | | | | How dangerous | | it could be for life on Earth? | | About the same as a bacterium in a crematorium. It might even be fatal. | | | | | | What would be safe distance a star moving at about 700 - 1000 km/s | | could get near Sun without disrupting the planetary system? | | The speed is irrelevant, presence is. | | Actually, the speed is relevant. | The Solar System might - at a very low probability as explained by | previous poster below - experience a close encounter with a star. | | It might be a disc star like Toliman or Sirius at a rather low relative | speed, or a halo star like Barnard Runner or Arcturus at higher | velocity, or a rare hypervelocity star ejected from Galactic core at | yet faster speed. | | The faster the star is, the smaller the danger. After all, what | disrupts the Solar System is the gravity of the star. | The gravitational | acceleration at a given distance is independent of the speed of the | disturbing star. But the faster the star, the less time it spends near | Solar System, and the less momentum the planets will accumulate. "Danger" is not a word that is relevant except to human beings. ANY close encounter would be fatal, independent of velocity. We are talking about another sun, not a puny comet colliding with Jupiter. http://www2.jpl.nasa.gov/sl9/gif/sl9_home.gif Perhaps this might give you some idea of the delicate balance we have: http://faculty.ifmo.ru/butikov/Proje...llection1.html Pay particular attention to example 8. At first it looks stable, but it isn't. That should give you a pretty good idea of what happened to Shoemaker-Levy. Androcles | | You don't seem to grasp the scale of the Universe or even the scale | of the Solar System. | Suppose you have a cluster of 4 pixels (dots) in the middle of your | monitor screen to represent the sun, like this: | | ---- o ---- (Sun, drawn too big) | | Then | | | | | | | | -- . ---- (Mercury) | | | | | | | | | | -- . -- (Venus) | | | | | | | | | | -- ' -- (Earth and Moon) | | | Jupiter (still a dot -- . --- ) is about where your ceiling is. | Saturn is then in your kitchen, the NEAREST star is at the end of the street, | and the imaginary black hole at the galactic centre is in the next city. | You have a far better chance of winning the lottery than meeting another | star up close and personal. | Androcles | |
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What if hypervelocity star came near Sun?
Sorcerer wrote: | How dangerous | it could be for life on Earth? Depends on the star and how close it passes. It's a very unlikely event, but if it is close enough to disrupt orbits, that would be bad. Similar to "If someone fires a bullet at random somewhere on your planet, how dangerous is that to you?" Or: About the same as a bacterium in a crematorium. It might even be fatal. | | What would be safe distance a star moving at about 700 - 1000 km/s | could get near Sun without disrupting the planetary system? Depends on size of the star. Tens of AU or more. Now here is why I posted. I agree with the essence of the following bit, but have a slight correction: The speed is irrelevant, presence is. You don't seem to grasp the scale of the Universe or even the scale of the Solar System. Suppose you have a cluster of 4 pixels (dots) in the middle of your monitor screen to represent the sun, like this: ---- o ---- (Sun, drawn too big) Then | | | | -- . ---- (Mercury) | | | | | -- . -- (Venus) | | | | | -- ' -- (Earth and Moon) Jupiter (still a dot -- . --- ) is about where your ceiling is. Earth is about 10 cm from the Sun on my screen. So Jupiter would be about 52 cm away, not near the ceiling really. Saturn is then in your kitchen, Saturn is 1m away, approximately. the NEAREST star is at the end of the street, The nearest star other than the Sun is Proxima Centauri, about 4 * 10^16 m away, and on this 1:1,500,000,000,000 scale that comes out to a bit under 3 * 10^4 m away. 25 km or so... a bit further than the end of the block. This only reinforces the point the author was making. and the imaginary black hole at the galactic centre is in the next city. More like 200,000 km away. Imagine someone halfway to the Moon firing a BB at random; what is the chance he'll hit a particular dinner plate on Earth? You have a far better chance of winning the lottery than meeting another star up close and personal. Agreed, only by several orders of magnitude more so. At least, around here. (In the central parsec of the Galaxy, stars may well collide once in a while...) Androcles |
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What if hypervelocity star came near Sun?
"paulaireilly" wrote in message oups.com... | How dangerous | it could be for life on Earth? Paul, what is "it" and why are you asking? Ignorant snipping will lead people to misunderstanding who said what, don't you think? Androcles |
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