Starship Asterisk*

Rauf wrote: ↑Mon Aug 21, 2023 8:04 am Who will have a better chance for seeing this comet, northern hemisphere observers or southern?

johnnydeep wrote: ↑Mon Aug 21, 2023 1:24 pm

Rauf wrote: ↑Mon Aug 21, 2023 8:04 am Who will have a better chance for seeing this comet, northern hemisphere observers or southern?

I think Northern, but maybe Southern observers could still view it at some points in its journey, based on what's stated at https://starwalk.space/en/news/new-comet-c2023-p1, but I've yet to find a definitive statement about the best locations for seeing it.

Click to view full size image

johnnydeep wrote: ↑Mon Aug 21, 2023 5:32 pm I kind of like the unpredictability of discovering new comets, but that also means the Earth could become an impact site for one some day. I only hope we get enough warning beforehand to at least try to do something about it, though it seems doubtful we would be successful.

Rauf wrote: ↑Mon Aug 21, 2023 6:41 pm

johnnydeep wrote: ↑Mon Aug 21, 2023 5:32 pm I kind of like the unpredictability of discovering new comets, but that also means the Earth could become an impact site for one some day. I only hope we get enough warning beforehand to at least try to do something about it, though it seems doubtful we would be successful.

Isn't discovering potentially hazardous comets easier than discovering PHAs? Comets tend to brighten as they get close to the sun, and that helps us find them easier. You can't say the same for asteroids though.

Rauf wrote: ↑Mon Aug 21, 2023 6:41 pm

johnnydeep wrote: ↑Mon Aug 21, 2023 5:32 pm I kind of like the unpredictability of discovering new comets, but that also means the Earth could become an impact site for one some day. I only hope we get enough warning beforehand to at least try to do something about it, though it seems doubtful we would be successful.

Isn't discovering potentially hazardous comets easier than discovering PHAs? Comets tend to brighten as they get close to the sun, and that helps us find them easier. You can't say the same for asteroids though.

Chris Peterson wrote: ↑Mon Aug 21, 2023 7:36 pm

Rauf wrote: ↑Mon Aug 21, 2023 6:41 pm

johnnydeep wrote: ↑Mon Aug 21, 2023 5:32 pm I kind of like the unpredictability of discovering new comets, but that also means the Earth could become an impact site for one some day. I only hope we get enough warning beforehand to at least try to do something about it, though it seems doubtful we would be successful.

Isn't discovering potentially hazardous comets easier than discovering PHAs? Comets tend to brighten as they get close to the sun, and that helps us find them easier. You can't say the same for asteroids though.

No. PHAs are almost universally in inner system orbits that are Earth-crossing or near Earth-crossing. They don't just show up from the outer system. Many comets, however, are first time visitors, and depending on where they come from, can't easily be seen against the Sun until they're too close to potentially do anything about them. Also, he search zone for comets is much larger (because asteroids are mostly fairly low inclination, whereas comets can come from any direction).

Reliable detection of comets really requires a space-based observation system. That's much less an issue with asteroids.

Rauf wrote: ↑Mon Aug 21, 2023 7:41 pm

Chris Peterson wrote: ↑Mon Aug 21, 2023 7:36 pm

Rauf wrote: ↑Mon Aug 21, 2023 6:41 pm

Isn't discovering potentially hazardous comets easier than discovering PHAs? Comets tend to brighten as they get close to the sun, and that helps us find them easier. You can't say the same for asteroids though.

No. PHAs are almost universally in inner system orbits that are Earth-crossing or near Earth-crossing. They don't just show up from the outer system. Many comets, however, are first time visitors, and depending on where they come from, can't easily be seen against the Sun until they're too close to potentially do anything about them. Also, he search zone for comets is much larger (because asteroids are mostly fairly low inclination, whereas comets can come from any direction).

Reliable detection of comets really requires a space-based observation system. That's much less an issue with asteroids.

True, most PHAs we've discovered are in inner solar system. But what about small sized TNOs with similar orbits as comets, but much harder to detect?
Asteroids from outer solar system might be common (with high eccentricities that'll get them close to the sun at some point in their orbit) , but since we don't see them that often, we might not discover them at all (because unlike comets, they don't get bright)
If however, I am mistaken, please tell me why. :ssmile:

Chris Peterson wrote: ↑Mon Aug 21, 2023 7:58 pm

Rauf wrote: ↑Mon Aug 21, 2023 7:41 pm

Chris Peterson wrote: ↑Mon Aug 21, 2023 7:36 pm
No. PHAs are almost universally in inner system orbits that are Earth-crossing or near Earth-crossing. They don't just show up from the outer system. Many comets, however, are first time visitors, and depending on where they come from, can't easily be seen against the Sun until they're too close to potentially do anything about them. Also, he search zone for comets is much larger (because asteroids are mostly fairly low inclination, whereas comets can come from any direction).

Reliable detection of comets really requires a space-based observation system. That's much less an issue with asteroids.

True, most PHAs we've discovered are in inner solar system. But what about small sized TNOs with similar orbits as comets, but much harder to detect?
Asteroids from outer solar system might be common (with high eccentricities that'll get them close to the sun at some point in their orbit) , but since we don't see them that often, we might not discover them at all (because unlike comets, they don't get bright)
If however, I am mistaken, please tell me why.

There is really nothing to suggest that there are very many outer system stony bodies. Or many bodies in Earth-crossing orbits that take them way out there. Basically, there are two populations of objects that we need to concern ourselves with. Asteroids, which are inner system bodies in small orbits, and comets, which are outer system bodies in very large orbits. (There is, of course, a small population of comets which have become much more asteroidal in their orbits, but we can treat them just as we do asteroids when it comes to identifying those that have the potential to impact the Earth.)

We can detect and catalog the vast majority of inner system bodies and then mostly forget about them, just checking a few from time to time because they could be perturbed into dangerous orbits. The challenge is comets, where we can never stop searching, and we can't effectively do so from Earth because of the Sun getting in the way of a big chunk of sky.

johnnydeep wrote: ↑Mon Aug 21, 2023 8:49 pm

Chris Peterson wrote: ↑Mon Aug 21, 2023 7:58 pm

Rauf wrote: ↑Mon Aug 21, 2023 7:41 pm

True, most PHAs we've discovered are in inner solar system. But what about small sized TNOs with similar orbits as comets, but much harder to detect?
Asteroids from outer solar system might be common (with high eccentricities that'll get them close to the sun at some point in their orbit) , but since we don't see them that often, we might not discover them at all (because unlike comets, they don't get bright)
If however, I am mistaken, please tell me why. :ssmile:

There is really nothing to suggest that there are very many outer system stony bodies. Or many bodies in Earth-crossing orbits that take them way out there. Basically, there are two populations of objects that we need to concern ourselves with. Asteroids, which are inner system bodies in small orbits, and comets, which are outer system bodies in very large orbits. (There is, of course, a small population of comets which have become much more asteroidal in their orbits, but we can treat them just as we do asteroids when it comes to identifying those that have the potential to impact the Earth.)

We can detect and catalog the vast majority of inner system bodies and then mostly forget about them, just checking a few from time to time because they could be perturbed into dangerous orbits. The challenge is comets, where we can never stop searching, and we can't effectively do so from Earth because of the Sun getting in the way of a big chunk of sky.

So, I suppose comets can come from both the Kuiper belt and the Oort cloud, but asteroids come from within the orbit of Jupiter? Do asteroids ever originate in the Kuiper belt?

Click to view full size image

Chris Peterson wrote: ↑Mon Aug 21, 2023 9:05 pm

johnnydeep wrote: ↑Mon Aug 21, 2023 8:49 pm

Chris Peterson wrote: ↑Mon Aug 21, 2023 7:58 pm

There is really nothing to suggest that there are very many outer system stony bodies. Or many bodies in Earth-crossing orbits that take them way out there. Basically, there are two populations of objects that we need to concern ourselves with. Asteroids, which are inner system bodies in small orbits, and comets, which are outer system bodies in very large orbits. (There is, of course, a small population of comets which have become much more asteroidal in their orbits, but we can treat them just as we do asteroids when it comes to identifying those that have the potential to impact the Earth.)

We can detect and catalog the vast majority of inner system bodies and then mostly forget about them, just checking a few from time to time because they could be perturbed into dangerous orbits. The challenge is comets, where we can never stop searching, and we can't effectively do so from Earth because of the Sun getting in the way of a big chunk of sky.

So, I suppose comets can come from both the Kuiper belt and the Oort cloud, but asteroids come from within the orbit of Jupiter? Do asteroids ever originate in the Kuiper belt?

Click to view full size image

"Asteroid" is generally understood to be an inner system body that formed there, while outer system bodies are typically much less rocky, composed mainly of ice, and formed by different processes.

Whether the body is made of rock or ice really doesn't matter that much beyond a certain size. You don't want either to hit us! So rather than worrying about "comets" or "asteroids", I think the way I framed it earlier makes the most sense: two populations, one of which is in pretty stable (but perturbable) orbits in the inner system and which can be cataloged, with potential problems observed more closely, and bodies that we do not know about until they get close enough to be seen the first time. The odds of an asteroid catching us by surprise are small, and getting smaller all the time as we catalog more of them, and smaller ones. Surprises will come from the outer system, likely from first time visitors that we know nothing about.