Posted on 07/23/2002 7:00:00 PM PDT by Lorenb420
An asteroid discovered just weeks ago has become the most threatening object yet detected in space.
A preliminary orbit suggests that 2002 NT7 is on an impact course with Earth on 1 February 2019, although the uncertainties are large.
Astronomers have given the object a rating on the so-called Palermo technical scale of threat of 0.06, making NT7 the first object to be given a positive value.
From its brightness astronomers estimate it is about 2km wide, large enough to cause continent-wide devastation on Earth.
Although astronomers are saying the object definitely merits attention, they expect more observations to show it is not on an Earth-intersecting trajectory.
It was first seen on the night of 5 July, picked up by the Linear Observatory's automated sky survey programme in New Mexico, in the southern US.
Since then astronomers worldwide have been paying close attention to it, amassing almost 200 observations in a few weeks.
Dr Benny Peiser, of Liverpool John Moores University in the UK, told BBC News Online that "this asteroid has now become the most threatening object in the short history of asteroid detection".
NT7 circles the Sun every 837 days and travels in a tilted orbit from about the distance of Mars to just within the Earth's orbit.
Potential devastation
Detailed calculations of its orbit suggest many occasions when its projected path through space intersects the Earth's orbit.
Researchers estimate that on 1 February 2019 its impact velocity on the Earth would be 28km a second - enough to wipe out a continent and cause global climate changes.
However, Dr Peiser was keen to point out that future observations could change the situation.
He said: "This unique event should not diminish the fact that additional observations in coming weeks will almost certainly, we hope, eliminate the current threat."
Easily observable
According to astronomers NT7 will be easily observable for the next 18 months or so, meaning there is no risk of losing the object.
Observations made over that period - and the fact that NT7 is bright enough that it is bound to show up in old photographs - mean that astronomers will soon have a very precise orbit for the object.
Dr Donald Yeomans, of Nasa's Jet Propulsion Laboratory in California, told BBC News Online: "The orbit of this object is rather highly inclined to the Earth's orbit so it has been missed because until recently observers were not looking for such objects in that region of space."
Regarding the possibility of an impact, Dr Yeomans said the uncertainties were large.
"The error in our knowledge of where NT7 will be on 1 February 2019 is large, several tens of millions of kms," he said.
Dr Yeomans told BBC News Online that the world would have to get used to finding more objects like NT7 that, on discovery, look threatening, but then become harmless.
"This is because the problem of Near Earth Objects is now being properly addressed," he said.
Not at all; there's just not much we can do about it now. The two things we need are deliverable propulsion mechanisms (I recommend nuclear rockets for the near term) and a lot of lead time. The longer the lead time, the less integrated thrust we need. The best method would be to identify all of the potential doomsday rocks and affix solar sails to them. Small amounts of thrust could be applied continuously to the rocks without the need to replenish the fuel supply. The sails could be tacked by commands from Earth so that the thrust is always in a useful direction. After enough time, all of the rocks so equipped could be steered into orbits that don't ever cross Earth's orbit. (It is also possible that some of them could be steered so that they enter into orbit about the Earth someday.)
As for the rock that will potentially hit us in 2019, I doubt we could deliver enough delta-v to it to change the probability of collision. We don't have an efficient method of exerting thrust upon it, we don't have a vehicle capable of hauling such a thrust mechanism to it, the lead time is short enough that the integrated thrust requirements are already substantial, and those requirements are increasing as the inverse of the remaining lead time.
Then again, necessity is the mother of invention.
"The error in our knowledge of where NT7 will be on 1 February 2019 is large, several tens of millions of kms," he said.Given that the earth's radius is only 4000 miles (less than 6000km), the ratio of its cross section to the area within which the data suggest the nearest-approach to occur is less than 36 million divided by the square of 20 million. I reckon the odds against a collision are at least 10 million to one.
sounds about right--as Newspaper headlines go . . .
But as a practical matter nothing can be done until such time, if any, as we know the direction from the earth's center to the closest approach. And nothing should be done until the uncertainty is reduced to less than one million klicks. If there's still a possible problem it would be time to start working on a launch against it. You'd want to launch two, for some redundancy.
You wouldn't want to launch at all if that direction was so easily determined that you knew the collision hazzard was zero, but you'd want them to arrive as soon as you knew the direction of the closest approach. And if you were truly sure of that direction, and that you were pushing to increase the miss distance, you'd about as well to use the nukes once they arrived on target. You aren't gonna deflect it by very much, so you have to push ASAP and you have to push in the right direction.
It could be true that you can't possibly prevent the collision, because by the time you can know which way to push the asteroid is too close. But that depends on the mass of the asteroid and on how centered on the earth the asteroid is targeted. I guess you time your launch, if any, on your best guess as to how soon you have to know the direction to be able to do any good. And you decide which way to deflect only as you have the opportunity to attempt to do so.
It's all a question of how well you've measured the trajectory and how much computing power you can throw at the problem. If you've tracked it long enough, you can predict where it's going to go to within a gnat's eyebrow.
. . . and if you've tracked it long enough, it has already either hit or, more likely by far, missed by hundreds of miles. The bigger object you find, the less effect you can have on its trajectory with a given bopper--and the sooner you'd better bop it, so the effect accumulates over time.The conclusion is that you do well to detect early, and to refine your estimate of trajectory rapidly when you do detect. Does Hubble's different perspective help, and would a deep space probe be enough better to justify its cost?
I have a career path for my 12 year old.
Asteroid Exploder
LOL!!!
What's the frequemcy, Kenneth?
They don't use Hubble for tracking asteroids, and I'm not sure it could do a far better job than a smaller, ground-based telescope. The first order of business is to find the darn things, and for that you need more eyes rather than better eyes.
I'm just guessing here, but I expect that the biggest advantage to a space-based telescope would be to give you a long baseline for parallax measurements. If that's right, the goal would be to get the space-based telescope as far away from Earth as possible. Perhaps a Moon-based telescope would be a good solution.
. . . which would seem to argue for getting a telescope into deep space to get some serious parallax. Possibly a Pluto-type solar orbit?
No, that would not be useful. Most Earth-crossing asteroids are going to have orbits that are comparable to Earth's orbit, so the baseline you really need is much smaller than that. Further, you'd need one amazing telescope--a super-Hubble--to spot something so faint from that far out, and you sure can't service it out there. And finally, it would take many years to get such a device into such an orbit, assuming you had the capability to launch such an monster out there.
Wait a tick...they have only ONE data point and they have already decided we're in the clear???
I stand corrected...pardon.
Dr Yeomans added: "While we cannot completely rule out an impact possibility for 1 February 2060, it seems very likely that this possibility will soon be ruled out as well."I'll be 110 on 1 Feb, 2060. If it doesn't get me then, it probably won't get me.
Which of course it will, given Murphy's Law. These astronomers are a bit too glib with their prognostications (apologies to RadioAstronomer - who would NEVER make such an assertion without sufficient data).
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