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Article says it was last seen 14 years ago, so it's obviously not some asteroid we've been monitoring too recently that just inexplicably disappeared like I, so

by JAFTEM 13y ago

Article says it was last seen 14 years ago, so it's obviously not some asteroid we've been monitoring too recently that just inexplicably disappeared like I, someone who doesn't know much about astronomy, assumed from the title. We apparently were just wrong in calculating its trajectory..

mathattack 13y ago
The "incoming" in the title suggests a trajectory aimed at grabbing eyeballs and clickthroughs. :-)
- jneal 13y ago
  As does "goes missing near Earth" I don't think going missing 14 years ago equates to going missing near Earth.
  - aaronem 13y ago
    3.4 million kilometers at closest approach doesn't even equate to "near Earth". But what better can you expect from the New Scientist?
splat 13y ago
Exactly, calculating trajectories (accurately) is very difficult. I did a summer project at JPL where we would take astrometric measurements of various minor planets (including Pluto) and then update the trajectories. Even a big, well studied object like Pluto could easily be an arcsecond or two away from where it was "supposed" to be. (For reference, at Pluto's distance, that would be ~30,000 km off.) But it's also possible that it's right where it should be and is too faint to be detected. Asteroids are very hard to detect because they're faint and they move -- so you can't expose the image for a long time to detect a fainter image. All you would get would be a faint streak across the image.
- ZoF 13y ago
  Not if you moved the lens in time with the supposed trajectory.
  - splat 13y ago
    Yes, tracking is one technique to get around this. It's generally difficult (though not impossible!) for a few reasons. The first is that most telescopes are set up to track the sky -- they can move pretty uniformly along with the rotation of the earth, but they're much jerkier when moving to other locations on the sky. In an alt-az telescope this doesn't matter, but most telescopes aren't built on alt-az mounts. The other reason this is difficult to do is because it's hard to guide the telescope. The bright guide stars you're using to correct for the small motions the telescope is making due to wind, etc. are now moving in your field of view and can't be used to guide the telescope. Finally, you have to know the trajectory pretty well to do this. You have to not only know how fast to move the telescope, but the right direction to move the telescope. This can be done for a well studied object where the uncertainty in the trajectory is pretty small. But if the object hasn't been observed for 14 years, you probably won't have very good knowledge of its trajectory.

by JAFTEM 13y ago

mathattack 13y ago

The "incoming" in the title suggests a trajectory aimed at grabbing eyeballs and clickthroughs. :-)

jneal 13y ago
As does "goes missing near Earth" I don't think going missing 14 years ago equates to going missing near Earth.
- aaronem 13y ago
  3.4 million kilometers at closest approach doesn't even equate to "near Earth". But what better can you expect from the New Scientist?

splat 13y ago

Exactly, calculating trajectories (accurately) is very difficult. I did a summer project at JPL where we would take astrometric measurements of various minor planets (including Pluto) and then update the trajectories. Even a big, well studied object like Pluto could easily be an arcsecond or two away from where it was "supposed" to be. (For reference, at Pluto's distance, that would be ~30,000 km off.) But it's also possible that it's right where it should be and is too faint to be detected. Asteroids are very hard to detect because they're faint and they move -- so you can't expose the image for a long time to detect a fainter image. All you would get would be a faint streak across the image.

ZoF 13y ago
Not if you moved the lens in time with the supposed trajectory.
- splat 13y ago
  Yes, tracking is one technique to get around this. It's generally difficult (though not impossible!) for a few reasons. The first is that most telescopes are set up to track the sky -- they can move pretty uniformly along with the rotation of the earth, but they're much jerkier when moving to other locations on the sky. In an alt-az telescope this doesn't matter, but most telescopes aren't built on alt-az mounts. The other reason this is difficult to do is because it's hard to guide the telescope. The bright guide stars you're using to correct for the small motions the telescope is making due to wind, etc. are now moving in your field of view and can't be used to guide the telescope. Finally, you have to know the trajectory pretty well to do this. You have to not only know how fast to move the telescope, but the right direction to move the telescope. This can be done for a well studied object where the uncertainty in the trajectory is pretty small. But if the object hasn't been observed for 14 years, you probably won't have very good knowledge of its trajectory.