Mapping the Stars Section 1-3 Summary

Patterns in the sky Constellations: sections of the sky that contain recognizable star patterns – Today scientists have agreed on names and locations There are 88 constellations The apparent locations of the constellations changes from season to season

Constellations

Finding stars in the night sky Astrolabe: tool used to describe a star’s location Terms: – Zenith: point directly above an observer – Altitude: angle between the object and Earth – Horizon: line where the Earth and sky appear to meet

Mapping the sky terms

The Path of the Stars Across the Sky Stars rise and set Apparent motion caused by the Earth’s rotation “Circumpolar stars” seem to go around the poles and can be seen at all times of the night and year – Polaris (North Star) is an example

Measuring distance in space Distance is measured in “light years” since miles would not be large enough Light year: distance light travels in one year We are actually looking into the past since it takes time for the light to reach us ***It is not a measurement of time!

The Doppler Effect An approaching sound has a higher pitch than a passing sound (think of sirens) Red shift: light from an object that is moving away appears redder than normal Wavelengths are being “Lengthened,” which corresponds to the red or left end of visible light

The Doppler continued Blue shift: light from an object that is moving toward appears bluer than normal Wavelengths are being “shortened,” which corresponds to the blue or right end of visible light

An Expanding Universe Hubble analyzed light from galaxies to study the direction they are moving He realized that all galaxies (except those close to ours) are affected by red shift This means they are moving away from us and each other