Observing Asteroids, NEOs and Comets

This project involves observing asteroids that are known and ones which have uncertain orbits and are in need of confirmation.

Image easy-to-find asteroids and see their motion against the starry background.

Asteroids are awkward, they don't stay in one place! Before your observing session check what asteroids are visible using the Asteroid Portal planner and download Astrometrica as described in the How to articles listed above.


Asteroids, also known as Minor Planets or Planetoids, are a class of astronomical object generally used to describe a diverse group of small bodies that drift around the Solar System in orbit around the Sun. A near-Earth object (NEO) is a Solar System object whose orbit brings it into close proximity with the Earth. All NEOs have a closest approach to the Sun (perihelion) of less than 1.3 AU.They include a few thousand near-Earth asteroids (NEAs), near-Earth comets, a number of solar-orbiting spacecraft, and meteoroids large enough to be tracked in space before striking the Earth.

It is thought that asteroids are the remnants of the protoplanetary disc that formed around the Sun when the Solar System was first created. Most of the small bodies came together and formed the inner, rocky planets that we see today. The rest however, remain in space as rocky debris or space junk. There are different types of asteroid out there, depending on where they are found in the Solar System, these groups include the Trojans, Greeks and Hildas (this last group is particularly strange as they have triangular orbits around the Sun). 

Hundreds of thousands of asteroids have so far been discovered and the present rate is currently about 5000 per month! The largest known asteroid has a diameter of around 950 km (compare that to the one scientists believe destroyed Dinosaurs which was a measly 10 km)! The mass of the Asteroid Belt (the dense belt of asteroids between Mars and Jupiter) is equal to about 4% of the mass of our Moon. So asteroids make up a significant proportion of our Solar System and are very important objects.

In recent years, the interest in identifying asteroids has grown quite considerably - many asteroids have been found with Earth-crossing orbits that, given enough time, could collide with Earth.

The procedure for finding new asteroids is fairly straightforward.  Any body in orbit around the Sun will appear to move slightly between two observing frames taken a time apart against the starry background (which does not move). This is what you will learn to do during this project.

Blinking Images To Find An Asteroid

For practice, or if you do not have observing time, you can do this activity with one of our example data sets. If you have a computer with Windows and if you plan to use a telescope to observe an asteroid or NEO, you will need to use Astrometrica so that you can report your results to the minor planet center. If you do not have access to a computer with Windows, or if you will only be doing this activity with sample data, you can use DS9, which is available for Windows, Mac and Linux.

You can use one of these example data sets:



Or you can search LCO’s database for asteroids or NEOs that have been observed in the past. Go to Advanced Search and in the section, “Search by category of object” choose “Interplanetary bodies.” You can narrow your search further if you want an asteroid that was observed at a certain time, or if you know the name of an asteroid you would like data for. You will need at least two images and preferably three or four.

Once you have downloaded some asteroid images you can open Astrometrica or DS9 and search for your asteroid.