Astronomy Where we’re going today… • Tools for studying the Universe By the end of this class, you should be able to… Describe the three different types of telescopes. Explain how parallax is used to measure distances to stars.

Telescopes Refracting Telescope (refractor) – has two lenses – an objective that gathers, bends (refracts) and magnifies starlight and an eyepiece that magnifies the image.

Telescopes Reflecting Telescope (reflector) – uses one large curved mirror (the objective – reflects) that is used to gather and focus starlight, a small mirror that reflects the image and an eyepiece that magnifies the image.

Telescopes Radio Telescope – looks like a large satellite dish that collects radio waves (Radio waves can pass through the clouds of fine dust that lie between stars)

Parallax of Stars Parallax is the apparent change in position of a nearby object against a background when viewed from 2 different positions. We can calculate the distance to stars that are very close to us using parallax (within ~2% accuracy).

Parallax activity

From the activity… Your graph should show an inverse proportional relationship between distance and parallax. Objects located closer to the viewer have greater parallax. To measure the distance to an object near you, a short baseline will produce low parallax. Conversely, for a far object, a bigger baseline allows for greater parallax and therefore, higher accuracy. Because accuracy decreases greatly with further distances, we can’t calculate the distances of stars on the opposite side of the galaxy.

Astronomy Did we get there… Can you… Describe the three different types of telescopes. Explain how parallax is used to measure distances to stars.