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Goodness no! An asteroid in an elliptical orbit, for example, could be a civilization killer and might currently be undetectably far away right now. We are mi

by cjensen 10y ago

Goodness no! An asteroid in an elliptical orbit, for example, could be a civilization killer and might currently be undetectably far away right now. We are missing a lot right now, and we need to spend money on much better surveys.

jessriedel 10y ago
You are at best disputing my terminology. An object on such a highly eccentric orbit would be classified as a long-period comet, which I mentioned. Yes, you can argue semantics about whether we might still call such an object an "asteroid" if it had a certain composition or primordial origin (which would be extremely unlikely for such an orbit). But there is no sharp division between asteroid and comment composition (it's a bimodal but smooth continuum) and this isn't relevant for the purposes of tracking such objects.
- credit_guy 10y ago
  There are two families of asteroids in the asteroid belt, Alinda and Griqua, which have quite eccentric orbits, and their orbits become more and more eccentric as time passes. From time to time they come close to Mars (or other interior planet), which slings them in a random direction. Some may end up hitting us. That's how the Kirkwood gaps in the asteroid belt are formed. https://en.m.wikipedia.org/wiki/Kirkwood_gap https://en.m.wikipedia.org/wiki/Kirkwood_gap
  - jessriedel 10y ago
    Sure, but they aren't so eccentric as to evade detection because of having a very long period.
- cjensen 10y ago
  Your terminology is flat-out wrong, sorry. Asteroids and comets are not differentiated by their orbital shape. But that's not what I'm disputing. Asteroids routinely have their orbits mucked with by the planets and get thrown into (1) elliptical orbits, (2) non-planar orbits, and (3) ejected. In the first two cases, we aren't even looking for them because there is so much space that it's not worth trying. Additionally, it is not true that we have found all dangerous NEO asteroids that are in ordinary orbits. NASA is still running a program whose goal is to find 90% of these [1]. For example, in just the past week they discovered a near-Earth object in excess of 1 km [2]. [1] http://neo.jpl.nasa.gov/faq/ http://neo.jpl.nasa.gov/faq/ [2] http://neo.jpl.nasa.gov/stats/ http://neo.jpl.nasa.gov/stats/

by cjensen 10y ago

jessriedel 10y ago

You are at best disputing my terminology. An object on such a highly eccentric orbit would be classified as a long-period comet, which I mentioned. Yes, you can argue semantics about whether we might still call such an object an "asteroid" if it had a certain composition or primordial origin (which would be extremely unlikely for such an orbit). But there is no sharp division between asteroid and comment composition (it's a bimodal but smooth continuum) and this isn't relevant for the purposes of tracking such objects.

credit_guy 10y ago
There are two families of asteroids in the asteroid belt, Alinda and Griqua, which have quite eccentric orbits, and their orbits become more and more eccentric as time passes. From time to time they come close to Mars (or other interior planet), which slings them in a random direction. Some may end up hitting us. That's how the Kirkwood gaps in the asteroid belt are formed. https://en.m.wikipedia.org/wiki/Kirkwood_gap https://en.m.wikipedia.org/wiki/Kirkwood_gap
- jessriedel 10y ago
  Sure, but they aren't so eccentric as to evade detection because of having a very long period.
cjensen 10y ago
Your terminology is flat-out wrong, sorry. Asteroids and comets are not differentiated by their orbital shape. But that's not what I'm disputing. Asteroids routinely have their orbits mucked with by the planets and get thrown into (1) elliptical orbits, (2) non-planar orbits, and (3) ejected. In the first two cases, we aren't even looking for them because there is so much space that it's not worth trying. Additionally, it is not true that we have found all dangerous NEO asteroids that are in ordinary orbits. NASA is still running a program whose goal is to find 90% of these [1]. For example, in just the past week they discovered a near-Earth object in excess of 1 km [2]. [1] http://neo.jpl.nasa.gov/faq/ http://neo.jpl.nasa.gov/faq/ [2] http://neo.jpl.nasa.gov/stats/ http://neo.jpl.nasa.gov/stats/