ASTR 105 Lecture Notes - Lecture 8: Celestial Equator, Angular Distance, Angular Diameter
Lab AST 105 Lecture Notes 8:
• Earth Rotation
• The spin of an object around an internal axis
• Earth Revolution
• the trajectory along which Earth travels around the Sun.
• Horizon
• The horizontal line defining the lower edge of the sky
• Altitude
• The angular distance from a point on the sky to a point on the horizon directly below it.
• Latitude
• Measure of location specifying north-south position on Earth running from 0º at the
equator to 90º north (NP) and 90º south (SP).
• Longitude
• Measure of location specifing East-West location on Earth
• Angular Size
• Angular distance measured on a sphere (such has Earth or the celestial sphere) in
degrees, arcminutes, and arcseconds.
• Celestial sphere
• An imaginary transparent sphere surrounding Earth, on which positions of stars, planets,
and other celestial bodies are protected from extenstions of Earth's coordinate system
• Celestial equator (CEQ)
• The extension of Earth's equator onto the celestial sphere
• North celestial pole (NCP)
• The extension of Earth's north pole onto the celestial sphere
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• South celestial pole (SCP)
• The extension of Earth's south pole on the celestial sphere
• Polaris the North Star
• A star located at the end of the handle of the Little Dipper, in the constellation Ursa
Minor, approximately 408 light years from Earth, and almost at the north celestial pole.
• Zenith
• The point on the sky directly overhead from an observer
• Meridian
• Circular arc crossing the celestial sphere and passing through the local zenith and
celestial pole.
• Declination
• The position of an object on the celestal sphere, measured similiarly to latitude on Earth.
• Sideral day (sidereal period)
• the period of revolution of one body around another with respect to the distant stars.
• Synodic or Solar day (synodic period)
• the time between successive conjunctions of a planet with the sun.
• Small angle formula
• mathematical relation between the angular size of an object as measured on the sky and
the object's distance and physical size
• Vernal Equinox
• the equinox in spring, on about March 20 in the northern hemisphere and September 22
in the southern hemisphere.
• Summer Solstice
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