PDA

View Full Version : Observing Earth from the Asteroid Belt



Taylor Harbin
05-21-2017, 05:17 AM
Brainstorming a new science fiction piece about aliens witnessing the KT extinction event from space. What I've read thus far shows that, depending on which asteroid you're sitting on, the distance between us and them is about 2-3 Astronomical Units, but that can change depending on either the planet's or the asteroid's revolution around the Sun. Since the technology level is not exactly comparable to ours, I'm just trying to figure out when the Earth would be closest, and therefore, prime for observation from a post on, say, an asteroid very close to Mars. Also trying to figure out how to make some aliens capable to surviving in the belt yet remain undetected (whole point is that we're being watched without knowing). Hope the question makes sense.

MaeZe
05-21-2017, 05:46 AM
You can get some specific distances and orbits from JPL's Near Earth Object project:

https://cneos.jpl.nasa.gov/ca/neo_ca_intro.html

Space.com also has a wealth of data:

http://www.space.com/16105-asteroid-belt.html

The most common mistake movies make re asteroids, they are not close together. If you were in the asteroid belt, you'd be lucky to see more than one at a time because the distance between objects is large. Consider how far apart they must be if there are only 16 or so very large asteroids:
Some asteroids are large, solid bodies — there are more than 16 in the belt with a diameter greater than 150 miles (240 km). The largest asteroids, Vesta, Pallas and Hygiea, are 250 miles (400 km) long and bigger. The region also contains the dwarf planet Ceres. At 590 miles (950 km) in diameter, or about a quarter of the size of our moon, Ceres is round yet is considered too small to be a full-fledged planet. However, it makes up approximately a third of the mass of the asteroid belt.

Taylor Harbin
05-22-2017, 06:45 AM
You can get some specific distances and orbits from JPL's Near Earth Object project:

https://cneos.jpl.nasa.gov/ca/neo_ca_intro.html

Space.com also has a wealth of data:

http://www.space.com/16105-asteroid-belt.html

The most common mistake movies make re asteroids, they are not close together. If you were in the asteroid belt, you'd be lucky to see more than one at a time because the distance between objects is large. Consider how far apart they must be if there are only 16 or so very large asteroids:

Thanks. Looks like this is going to take some time to digest.

Casey Karp
05-22-2017, 06:54 AM
You might also give some thought to just how good (i.e. poor) a view the aliens are going to have at that distance. Turn the situation around: given how poor our observations of Mars are, how much could we see of what the aliens are doing on an asteroid beyond Mars' orbit? Granted, your aliens won't have to deal with the miles of atmosphere we're looking through, but even so, I'd think they'll have to have one hell of a big telescope out there in order to see Earth with any kind of interesting detail.

(Take the above with a grain of salt. I'm not up on the physics of telescope resolution.)

Taylor Harbin
05-22-2017, 07:02 AM
You might also give some thought to just how good (i.e. poor) a view the aliens are going to have at that distance. Turn the situation around: given how poor our observations of Mars are, how much could we see of what the aliens are doing on an asteroid beyond Mars' orbit? Granted, your aliens won't have to deal with the miles of atmosphere we're looking through, but even so, I'd think they'll have to have one hell of a big telescope out there in order to see Earth with any kind of interesting detail.

(Take the above with a grain of salt. I'm not up on the physics of telescope resolution.)

Good thoughts, and perhaps I will move them a bit closer. They are not able to see in much detail, just enough to see that the atmosphere has been disturbed ("Hm, that blue planet doesn't look too blue today. What's going on?"). One of the plot points involves Earth being closest to this alien hideout once a year.

This might be more of what Asimov's guidelines call "character-oriented" without extremely hard science behind it. We'll see.