The goal of this lab is to understand the main properties of the asteroid belt, and how astronomers can detect asteroids using visual methods.

Part 1:  The Asteroid Belt

The asteroids in our solar system primarily exist in the asteroid belt between the orbits of Mars and Jupiter.

Jupiter's gravity sorts these asteroids into distinct groups:  The Trojans, the Greeks, and the Hildas.

In the following animation, the Trojans and the Greeks are the green blobs, and the pink dots are referred to the Hildas.


The asteroids are where they are because of the "Lagrange Points" - areas where the combined force of gravity between Jupiter and the Sun equal the 'centrifugal' force of the asteroids.

In other words, the asteroids are traveling just fast enough to escape and get flung out of the system, but the gravity of the sun and Jupiter are just barely holding onto them - the net effect being that they stay in place.

The following image is a map of the Lagrange Points around Jupiter.  Can you see these points on the animation above?

Part 2: Viewing Asteroids

It may surprise you to earn that NASA does not consider the locations of asteroids when sending spacecraft through the belt.  This is because the asteroids are so small compared to how far apart they are that the odds of striking one in one billion.  This means that if NASA launched 1 billion probes through the asteroid belt, only 1 would be lost due to a collision.

Odds of an asteroid hitting Earth.

An asteroid does not give off its own light - it is a cold, dead, rock.

The amount of incident light reflected by an asteroid is referred to as its albedo.

Asteroids with a higher albedo are easier to see at opposition because they reflect more sunlight.

The only way we can spot an asteroid is if we look at it when it is opposite the Sun from us - the same as a full moon.

Think about where an asteroid must be in order for that to happen.  What is the location for the best odds of viewing one?  Try to use Stellarium to pick a range of RA and Dec for this.

Use the Minor Planet Checker to see how many minor planets are in your range!

Study the image below and try to see if you can spot any asteroids.

This GIF is of 3 images on repeat.


For the next part, consider the minor planets 2007 TA3 and 2007 TB3.

Enter those into the search field at the JPL Small-body Database Browser.