{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

f10_aug31 - Ast 307 Aug 31 2010 Positions and Sizes in...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Ast 307 Ast 307 - Aug. 31, 2010 Positions and Sizes in Angular Units Angular measure & the small-angle formula Conditions for eclipses (angular diameter) Locating things on the Sky Ast 307 The Night Sky - September 2010 Tuesday evening, Spica lies a little above Venus, with Mars off to the right. By Saturday, Mars will be closer to Spica than Venus is. Jupiter is bright in the evening sky, with the Great Square of Pegasus lying to the upper left. 8/31/10 Ast 307 3 Light travels at 3 ! 10 5 km/s, fast but not infinite. It takes a while to reach us from distant objects. 2.5 million years Andromeda Galaxy 8 years Sirius 8 minutes Sun 1 second Moon Light travel time Destination The farther we look in distance, the further back we look in time. Light-travel Time 8/31/10 Ast 307 4 You can think of light as a “time machine;” the time it takes light to reach us is the “look-back time.” If we know the distance in light years, we also know how long ago the light was sent to us. “Look-back” Time
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Ast 307 Complete circle = 360° Moon 90° Places & sizes on the sky are specified in angles .
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}