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29 terms

MID-TERM SCI CH 19

STUDY
PLAY
astronomy
the scientific study of the universe.
year
the time required for the earth to orbit once around the sun.
month
roughly the time required for the moon to orbit once around Earth.
day
the time required for Earth to rotate once on its axis.
Ptolemaic theory
belief that earth is the center of the universe
Copernicus
thought that the sun was the center of the universe and that Earth and all planets orbit the sun.
Tycho Brahe
thought that the sun and the moon rovolved around the Earth and that all other planets revolved around the sun.
Johannes Kepler
thought that all planets revolved around the sun in eliptical orbits and that the sun was not in the exact center of the orbits - also stated three laws of planetary motion.
Galileo
one of the first to use telescopes to observe objects in space.
Isaac Newton
showed that all objects in the universe attract each other through gravitational force.
Edwin Hubble
proved that other galaxies existed beyond the edge of the Milky Way.
telescope
an instrument that collects electromagnetic radiation from the sky and concentrates it fo better observation.
refracting telescope
uses a set of lenses to gather and focus light from distant objects.
reflecting telescope
uses a curved mirror to gather and focus light from distant objects
focal point
the point where the rays of light that pass through the lens of that reflect from a mirror converge.
objective lens
collects light and forms an image at the back of the telescope.
electromagnetic radiation
the radiation associated with an electric and magnetic field
constellation
a region of the sky that contains a recognizable star pattern and that is used to describe the location of objects in space
zenith
the point in the sky directly above an observer on Earth
altitude
the angle between an object in the sky and the horizon
horizon
the line where the sky and the Earth appear to meet
celestial equator
an imaginary circle created by extending Earth's equator into space
ecliptic
apparent path of the sun across the sky throughout the year
declination
measured in degrees north or south of the celestial equator
right ascension
measured n hours eastward from the vernal equinox
circumpolar stars
stars that can be seen at all times of the year and all times of night.
light-year
the distance that light travels in one year, about 9.46 trillion kilometers
redshift
occurs when a light source is moving quickly away from an observer
blueshift
occurs when a light source is moving quickly toward and observer