Mapping the Stars

History Ancient cultures linked stars together to form patterns that represented characters from myths and objects in their lives. Today we still use many of the names given to stars centuries ago, but now we can describe their positions precisely.

Constellations Definition: –Regions of the sky that contain a recognizable star pattern and is used to describe the location of objects in space. –Every star in the sky is located in one of the 88 constellations in the sky. Understanding the location and movement of constellations helped people navigate and keep track of time.

Seeing Constellations Different constellations are seen:  From one time of the year to another. –Because the Earth revolves around the sun.  In the Northern and Southern Hemispheres. –Because different portions of the sky are visible from the N and S Hemispheres.

Finding Stars Astrolabe: –Instrument used to determine a star’s location

Finding Stars Cont. Using an astrolabe allows you to describe where a star or planet is relative to you. Scientists need a different method that describes location independently of the observer’s location. Astronomers describe the location of a star or planet in terms of the celestial sphere.

Reference Points

The Celestial Sphere

Size and Scale of Universe Nicholas Copernicus noticed that the planets appeared to move relative to each other, but that the stars did not. So he thought that the stars must be farther away than the planets. A new unit of length had to be developed to describe this distance. Light-year- distance light travels in 1 year. Equal to 9.46 trillion kilometers.

Doppler Effect Definition –How a siren seems higher pitched as it approaches and lower pitched after it passes. Same thing happens with light: –Redshift- as light moves away, light looks redder. –Blueshift- as light moves toward, light looks bluer.