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Types of Objects
Asteroids are small pieces of rock that orbit the Sun, mostly between Mars and Jupiter. Asteroids move quickly across the sky, so they can be seen in SDSS images (see the Asteroids project to learn more). If an asteroid moves slowly, it will show up in images as a blue dot next to a yellow dot. Fast moving asteroids show up as a red, green and blue dot in succession. Very fast moving asteroids may appear as colored streaks. Examples of each type are shown below. Asteroids that appear as blue-yellow dots trick the computer program that classifies objects, so their types are listed as stars.
Sometimes, tiny particles of rock or dust fall toward the Earth. As they enter the Earth's atmosphere, they heat up and start to glow. From the ground, we see a long, glowing trail of light that passes quickly through the sky. These trails of light are called meteors. They are also known as shooting stars.
In the Navigation tool, you can recognize meteors as long, glowing trails of light in just one color. The image to the right shows a meteor seen by the SDSS.
Galaxies form in clusters of dozens or hundreds. The SDSS has seen many clusters, including the cluster Abell 0957 shown at the right. Galaxy clusters can be so far away that individual galaxies almost look like stars!
When you see a cluster in the Navigation tool, click on one of the objects to see the object type. You might be surprised to find what you thought was a star cluster is actually a galaxy cluster!
Sometimes, when the SDSS telescope looks at a very bright object, the object's light is reflected inside the telescope. These objects can cause "ghosts". Ghosts are bands of light that appear on the images. They are usually a single color, either red, green or blue, depending on which filter was used when the ghost occurred. A typical ghost is seen at the right.
Now you're ready for the scavenger hunt! Click Next to see what objects you'll be searching for.