Re: [meteorite-list] Asteroid Gets Initial Elevated Risk Rating, But Impact Unlikely (Asteroid 2004 MN4)
Hi, The best chance of refining the orbit of 2004 MN4 lies in a search for sky photos of the times and places in the past when this object should have been visible. In the case of the last object with a chance of hitting the Earth in the future (in 2018), the successful search for what are called pre-discovery images from years previous to its official discovery refined the orbit enough to eliminate that future collision probability. If such images could be found for 2004 MN4's previous approaches, the further back the better, the orbit could be determined with much greater precision than observations over the next six months. The object is certainly large enough (and hence bright enough) to have shown up in past sky plates. The chief difficulty in finding such images is that the object's orbit lies mostly inside the Earth's orbit, to Sunward, where observation is difficult if not impossible for most of the year. The search would have to be for the periods each year after April 13, when the object is exterior to the Earth's orbit. You'll recall there was a very, very close approach just earlier this week by a very small object (16 feet) which also approached from the Sunward (blind) side. Often forgot in these discussions is the fact that while the probability of an impact is often low or negligible at any one crossing of the Earth's orbit, in the long run, the chance of eventually impacting with a low-inclination Earth-crossing object is virtually 100%. It takes the Earth approximately 432 seconds for its entire diameter to pass a specific point on its orbital path, creating 200 chances to be impacted at a specific point every day. In the case of an object with exactly the same inclination as the Earth which crossed the Earth's orbit on the same day at the same point every year, a collision would be inevitable at some point in that 73,050 year cycle (365.25 times 200). And objects with very low inclinations will always be perturbed, repeatedly, into and out of a matching inclination with the Earth's orbit. In other words, sooner or later, they're gonna get ya! While we are busily cataloging the easy-to-observe exterior objects, very little is being done to discover the hard-to-observe Sunward objects because the strategies are hard (i.e., expensive) to implement, like photographing the western horizon just before dawn to catch objects that have just crossed the Earth's orbit. Yet Aten class Earth crossers --- whose numbers are not well known nor even well-estimated --- are vastly more dangerous than the better cataloged Apollos and Amors, for just that reason. Sterling K. Webb - Herbert Raab wrote: Charles Viau wrote: Are our orbital calculating capabilities really good enough to project out 25 years on such a small object? Yes and no. The calculating capabilities are certainly not the limiting factor, but rather the limited amount of observations (35) on a limited number of nights (5), each with small (but a-priori unknown) error limits the accuarcy. A number of possible orbits for such an asteroid can be found that agrees with the available observations. On some of these orbits, the asteroid will have a close encounter with Earth in 2029, on others (on 1 in 300 or so) the object will collide with our home planet. There is no way to tell which of these orbits is the true path along which the asteroid moves, unless more data is collected. When additional observations are added (the object is observable until May 2005), the number of orbits compatible with the available observations will be narrowed, the uncertainty in the predicted position for 2029 will decrease, and in all likelyhood, the impact solutions will be removed. Happy holiday to all! Herbert Raab __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
RE: [meteorite-list] Asteroid Gets Initial Elevated Risk Rating, But Impact Unlikely (Asteroid 2004 MN4)
Thanks to Ron (original article) and comments by Herbert and Sterling. Fantastic facts, and one of the greatest reasons to be on this list. I sure hope that our technology can get a handle on these errant missiles before something happens that makes our collections irrelevant. Regards, CharlyV -Original Message- From: Sterling K. Webb [mailto:[EMAIL PROTECTED] Sent: Friday, December 24, 2004 2:19 AM To: Meteorite List Cc: Herbert Raab; Charles Viau Subject: Re: [meteorite-list] Asteroid Gets Initial Elevated Risk Rating,But Impact Unlikely (Asteroid 2004 MN4) Hi, The best chance of refining the orbit of 2004 MN4 lies in a search for sky photos of the times and places in the past when this object should have been visible. In the case of the last object with a chance of hitting the Earth in the future (in 2018), the successful search for what are called pre-discovery images from years previous to its official discovery refined the orbit enough to eliminate that future collision probability. If such images could be found for 2004 MN4's previous approaches, the further back the better, the orbit could be determined with much greater precision than observations over the next six months. The object is certainly large enough (and hence bright enough) to have shown up in past sky plates. The chief difficulty in finding such images is that the object's orbit lies mostly inside the Earth's orbit, to Sunward, where observation is difficult if not impossible for most of the year. The search would have to be for the periods each year after April 13, when the object is exterior to the Earth's orbit. You'll recall there was a very, very close approach just earlier this week by a very small object (16 feet) which also approached from the Sunward (blind) side. Often forgot in these discussions is the fact that while the probability of an impact is often low or negligible at any one crossing of the Earth's orbit, in the long run, the chance of eventually impacting with a low-inclination Earth-crossing object is virtually 100%. It takes the Earth approximately 432 seconds for its entire diameter to pass a specific point on its orbital path, creating 200 chances to be impacted at a specific point every day. In the case of an object with exactly the same inclination as the Earth which crossed the Earth's orbit on the same day at the same point every year, a collision would be inevitable at some point in that 73,050 year cycle (365.25 times 200). And objects with very low inclinations will always be perturbed, repeatedly, into and out of a matching inclination with the Earth's orbit. In other words, sooner or later, they're gonna get ya! While we are busily cataloging the easy-to-observe exterior objects, very little is being done to discover the hard-to-observe Sunward objects because the strategies are hard (i.e., expensive) to implement, like photographing the western horizon just before dawn to catch objects that have just crossed the Earth's orbit. Yet Aten class Earth crossers --- whose numbers are not well known nor even well-estimated --- are vastly more dangerous than the better cataloged Apollos and Amors, for just that reason. Sterling K. Webb - Herbert Raab wrote: Charles Viau wrote: Are our orbital calculating capabilities really good enough to project out 25 years on such a small object? Yes and no. The calculating capabilities are certainly not the limiting factor, but rather the limited amount of observations (35) on a limited number of nights (5), each with small (but a-priori unknown) error limits the accuarcy. A number of possible orbits for such an asteroid can be found that agrees with the available observations. On some of these orbits, the asteroid will have a close encounter with Earth in 2029, on others (on 1 in 300 or so) the object will collide with our home planet. There is no way to tell which of these orbits is the true path along which the asteroid moves, unless more data is collected. When additional observations are added (the object is observable until May 2005), the number of orbits compatible with the available observations will be narrowed, the uncertainty in the predicted position for 2029 will decrease, and in all likelyhood, the impact solutions will be removed. Happy holiday to all! Herbert Raab __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Asteroid Gets Initial Elevated Risk Rating, But Impact Unlikely (Asteroid 2004 MN4)
http://www.nctimes.com/articles/2004/12/23/special_reports/science_technology/12_23_0412_54_30.txt Asteroid gets initial elevated risk rating, but impact unlikely By JOHN ANTCZAK Associated Press December 23, 2004 LOS ANGELES (AP) -- A recently discovered asteroid that crosses Earth's orbit has been given a higher impact hazard rating than any other seen so far, but scientists say it is likely the risk will be eliminated as further observations refine projections of its orbit. Asteroid 2004 MN4, believed to be about 1,300 feet long, potentially could impact Earth in 2029, based on a limited number of initial sightings, said Donald Yeomans, manager of the Near Earth Object Program at NASA's Jet Propulsion Laboratory in Pasadena. The asteroid has been given an initial rating of 2 on the 10-point Torino Impact Hazard Scale used by astronomers to assess predictions for asteroid or comet impacts, Yeomans said Thursday. The relatively high rating, posted on the NEO program Web site, is unusual because no previously observed asteroid has been graded higher than 1. This is not a problem for anyone and it shouldn't be a concern to anyone, but whenever we post one of these things and ... somebody gets ahold of it, it just gets crazy, Yeomans said. Announcements that scientists have spotted an asteroid that cross Earth's orbit sometimes generate alarm when early analysis shows some possibility of an impact. Within a few days, usually, further observations allow scientists to refine the asteroid's orbit and eliminate the likelihood of an impact. The asteroid's estimated size has been inferred from its brightness, which assumes that its reflectivity is similar to other asteroids that have been observed. At about 1,320 feet in length, it would have about 1,600 megatons of energy, Yeomans said. In the unlikely event that it did hit, it would be quite serious. We're talking either a tsunami if it hit in the ocean, which would be likely, or significant ground damage, he said. The asteroid was discovered in June and rediscovered this month. By linking the two sets of observations we have a pretty decent orbit, so we can predict where this thing will be in the future and when we get a good orbit like that for a near-Earth asteroid we routinely ... track its motion on the computer forward for about 100 years and check for any close Earth approaches, he said. Asteroid 2004 MN4 takes less than a year to go all the way around the sun and on each orbit it passes by Earth's orbit twice, Yeomans said. It is also nearly on the same plane as Earth's orbit. On April 13th each year it does indeed cross the Earth's orbit. Now whether or not the Earth is there or not is the question, and in 2029, April 13th, we can't yet rule out an Earth impact, he said. But the impact probability, as we call it, is 300-to-1 against an impact. The asteroid, however, is the first to reach a Torino Scale 2, which means it's a bit out of the ordinary but still not of concern, he said. There were only two nights of observations when 2004 MN4 was first discovered. It was only when it was rediscovered that the orbit was secure enough to give it this designation, Yeomans said. The asteroid will be observable for the next several months and the NEO program has alerted its network of ground-based observers to include 2004 MN4 in their searches. Yeomans said there have now been about 40 observations, first from the observatory at Kitt Peak, near Tucson, Ariz., and this month from Australia and New Zealand. As we get new data the so-called error ellipsoid, or the uncertainty on where the object will be in 2029, will shrink as our knowledge of the orbit gets better, and by far the most likely situation is that a few weeks down the road we'll have a sufficient number of observations that this error ellipsoid will have shrunk to a point where the Earth is no longer included, he said. We can then rule out an Earth impact. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
RE: [meteorite-list] Asteroid Gets Initial Elevated Risk Rating, But Impact Unlikely (Asteroid 2004 MN4)
Hmmm... April 13, 2029 is a Friday... Glad I am not superstitious, but I am sure that will alarm some people. Are our orbital calculating capabilities really good enough to project out 25 years on such a small object? CharlyV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ron Baalke Sent: Thursday, December 23, 2004 4:38 PM To: Meteorite Mailing List Subject: [meteorite-list] Asteroid Gets Initial Elevated Risk Rating,But Impact Unlikely (Asteroid 2004 MN4) http://www.nctimes.com/articles/2004/12/23/special_reports/science_technolog y/12_23_0412_54_30.txt Asteroid gets initial elevated risk rating, but impact unlikely By JOHN ANTCZAK Associated Press December 23, 2004 LOS ANGELES (AP) -- A recently discovered asteroid that crosses Earth's orbit has been given a higher impact hazard rating than any other seen so far, but scientists say it is likely the risk will be eliminated as further observations refine projections of its orbit. Asteroid 2004 MN4, believed to be about 1,300 feet long, potentially could impact Earth in 2029, based on a limited number of initial sightings, said Donald Yeomans, manager of the Near Earth Object Program at NASA's Jet Propulsion Laboratory in Pasadena. The asteroid has been given an initial rating of 2 on the 10-point Torino Impact Hazard Scale used by astronomers to assess predictions for asteroid or comet impacts, Yeomans said Thursday. The relatively high rating, posted on the NEO program Web site, is unusual because no previously observed asteroid has been graded higher than 1. This is not a problem for anyone and it shouldn't be a concern to anyone, but whenever we post one of these things and ... somebody gets ahold of it, it just gets crazy, Yeomans said. Announcements that scientists have spotted an asteroid that cross Earth's orbit sometimes generate alarm when early analysis shows some possibility of an impact. Within a few days, usually, further observations allow scientists to refine the asteroid's orbit and eliminate the likelihood of an impact. The asteroid's estimated size has been inferred from its brightness, which assumes that its reflectivity is similar to other asteroids that have been observed. At about 1,320 feet in length, it would have about 1,600 megatons of energy, Yeomans said. In the unlikely event that it did hit, it would be quite serious. We're talking either a tsunami if it hit in the ocean, which would be likely, or significant ground damage, he said. The asteroid was discovered in June and rediscovered this month. By linking the two sets of observations we have a pretty decent orbit, so we can predict where this thing will be in the future and when we get a good orbit like that for a near-Earth asteroid we routinely ... track its motion on the computer forward for about 100 years and check for any close Earth approaches, he said. Asteroid 2004 MN4 takes less than a year to go all the way around the sun and on each orbit it passes by Earth's orbit twice, Yeomans said. It is also nearly on the same plane as Earth's orbit. On April 13th each year it does indeed cross the Earth's orbit. Now whether or not the Earth is there or not is the question, and in 2029, April 13th, we can't yet rule out an Earth impact, he said. But the impact probability, as we call it, is 300-to-1 against an impact. The asteroid, however, is the first to reach a Torino Scale 2, which means it's a bit out of the ordinary but still not of concern, he said. There were only two nights of observations when 2004 MN4 was first discovered. It was only when it was rediscovered that the orbit was secure enough to give it this designation, Yeomans said. The asteroid will be observable for the next several months and the NEO program has alerted its network of ground-based observers to include 2004 MN4 in their searches. Yeomans said there have now been about 40 observations, first from the observatory at Kitt Peak, near Tucson, Ariz., and this month from Australia and New Zealand. As we get new data the so-called error ellipsoid, or the uncertainty on where the object will be in 2029, will shrink as our knowledge of the orbit gets better, and by far the most likely situation is that a few weeks down the road we'll have a sufficient number of observations that this error ellipsoid will have shrunk to a point where the Earth is no longer included, he said. We can then rule out an Earth impact. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Asteroid Gets Initial Elevated Risk Rating, But Impact Unlikely (Asteroid 2004 MN4)
Charles Viau wrote: Are our orbital calculating capabilities really good enough to project out 25 years on such a small object? Yes and no. The calculating capabilities are certainly not the limiting factor, but rather the limited amount of observations (35) on a limited number of nights (5), each with small (but a-priori unknown) error limits the accuarcy. A number of possible orbits for such an asteroid can be found that agrees with the available observations. On some of these orbits, the asteroid will have a close encounter with Earth in 2029, on others (on 1 in 300 or so) the object will collide with our home planet. There is no way to tell which of these orbits is the true path along which the asteroid moves, unless more data is collected. When additional observations are added (the object is observable until May 2005), the number of orbits compatible with the available observations will be narrowed, the uncertainty in the predicted position for 2029 will decrease, and in all likelyhood, the impact solutions will be removed. Happy holiday to all! Herbert Raab __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
