Any astronomers here i got a question??

IF a comet, large meteor, planetx whatever were gonna hit the earth would we be able to see it a week or so in advance as it approached? or would it hit out of the blue?


Forgive my ignorance.




[edit on 21-6-2007 by ncuncfan2006]

I am not an astronomer, but from what I have read in the past, many are not noticed. Those which are have to have their orbits plotted and then projected forwards chronologically.

If you see their movement from the side you can observe it, but if they are inbound at a steep angle then they might not be seen at all.

Couple of years ago a largish rock passed between the moon and earth and was not noticed until quite late.

Yes i remember that but if it were on a direct collision course with earth and was big 1km + it looks like some parts of the world or somewhere you would have to be able to see it at least a few days before impact.

It would take a lot of luck, and if it was big enough getting away from the coast wouldn't make any difference. With all the amateur astronomers out there they MIGHT notice it a few months, or weeks ahead of time, but as of now it wouldn't make any difference if they did, because there's no feasible way to stop it.

When you say "would we be able to see it", do you mean "with the naked eye" ? If that is the case, then we wouldn't be able to see an asteroid, we almost certainly would be able to see a large comet, and any planet sized body would be detected years before impact.



[edit on 22-6-2007 by Mogget]

Originally posted by Mogget
When you say "would we be able to see it", do you mean "with the naked eye" ? If that is the case, then we wouldn't be able to see an asteroid, we almost certainly would be able to see a large comet, and any planet sized body would be detected years before impact.



[edit on 22-6-2007 by Mogget]

So you're saying that we'd be able to see a planet sized body coming towards us with the naked eye years before its impact?

[edit on 22-6-2007 by ZikhaN]

Back in the late 90's there was an article written in AIAA's technical journal Aerospace America about "blind" NEO's. It remains the most apocalyptic technical writing I've read in my life. In this article the writer describes the near misses of "sun-side-approaching" NEOs (near earth objects) that have occurred in recent decades and the extremely short amount of time between them finally being detected and passing at their closest approach.

Summary is: If an object approaches us on a collision path with Earth and it comes from the direction of the Sun, there is the potential to not spot it until it is within days to hours of impact.

So you're saying that we'd be able to see a planet sized body coming towards us with the naked eye years before its impact?

Of course, that depends on how large the planet is. A planet as large (and reflective) as Earth would be visible to the naked eye as far away as the orbit of Saturn, and anything approaching from that distance would take several years to reach the inner Solar System. Smaller planets would obviously be fainter, but even an object the size of Mercury would be visible to the naked eye at least a year or more before any potential collision.

Originally posted by Valhall
Summary is: If an object approaches us on a collision path with Earth and it comes from the direction of the Sun, there is the potential to not spot it until it is within days to hours of impact.

This is true. It would most likely be a comet, and perhaps the only way to avoid getting completely blindsided would be to have some kind of satellites orbiting the sun that could detect something approaching. Considering the trouble we have detecting NEOs with ground-based telescopes, a solution is unlikely to be devised anytime soon.

Originally posted by ZikhaN
So you're saying that we'd be able to see a planet sized body coming towards us with the naked eye years before its impact?

Yes.

Remember that the solar system is very large and that things passing through it aren't equipped with warp engines and don't move at warp (faster than light) speeds. We typically see comets when they are months away, and a comet's center iceball is about the size of two city blocks (or smaller.)

Think how far away Saturn is... and we've always been able to see that. Mars is smaller than the Earth and yet you can wander outside and find it if you know where to look.

Asteroids are fairly small (only one in a million is the size of New York City. Most are fist-sized or car-sized chunks of rubble). The belt itself wasn't discovered until the 1800's:
www.bbc.co.uk...

So it's hard to spot a wandering bit of rubble like that compared to the comet (which has a glowing head that may be larger than the diameter of Earth) or a planet (which is large and kind of obvious.)

[edit on 25-6-2007 by Byrd]