Astronomy Definitions

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Astronomy
Astronomy
The branch of science that deals with celestial objects, space, and the physical universe as a whole
Celestial Object
Celestial Object
Any object that exists in space, such as a planet, the star, or the moon.
Universe
Universe
All existing matter and space considered as a whole.
Star/Sun
Star/Sun
A celestial body made up of hot gases, mainly hydrogen, and some helium.
Planet
Planet
An object that orbits one or more stars (and is not a star itself), is spherical, and does not share its orbit with another object.
Satellite
Satellite
An artificial object or vehicle that orbits the earth, the moon, or other celestial bodies; also, a celestial body that orbits another body of larger size (for example, the moon is earth’s natural satellite.
Moon
Moon
The natural satellite of the earth.
Terrestrial Planet
Terrestrial Planet
A planet that is composed primarily of silicate rocks or metals. The terrestrial planets are the inner planets closest to the Sun: Mercury, Venus, Earth, and Mars.
Gas Giant Planet
Gas Giant Planet
Gas giants have a mostly gaseous composition, such as hydrogen and helium. The four gas giants are (in order of distance from the Sun): Jupiter, Saturn, Uranus, and Neptune. They’re larger than the ‘inner’ planets.
Astronomical Unit (AU)
Astronomical Unit (AU)
The average distance between earth and the sun, about 150 x 10^6 km.
Dwarf Planet
Dwarf Planet
A round, celestial object tat orbits around the sun; it may share its orbit with another celestial body, but it is not a satellite.
Asteroid
Asteroid
An object in space that ranges in size from a tiny speck, like a grain of sand, to 500km wide; most asteroids originate in the asteroid belt between Mars and Jupiter.
Meteoroid
Meteoroid
A piece of rock moving through space.
Meteor
Meteor
A meteoroid that hits Earth’s atmosphere and burns up.
Meteorite
Meteorite
A meteoroid that is large enough to pass though Earth’s atmosphere and reach the ground, without being totally burned up.
Comet
Comet
An object composed of rocky material, ice, and gas; comes from the Kuiper Belt or Oort Cloud.
Revolution
Revolution
The time it takes for an object to orbit around another object; Earth’s revolution around the sun is 365.24 days.
Orbit
Orbit
The gravitationally curved path of an object about a point in space.
Solar Eclipse
Solar Eclipse
The phenomenon in which the shadow of the Moon falls on Earth’s surface.
Lunar Eclipse
Lunar Eclipse
The phenomenon in which the full Moon passes into Earth’s shadow.
Constellation
Constellation
A group of stars that seem to form a distinctive pattern in the sky.
Nebula
Nebula
Giant cloud of gas and dust that is compressed to form a star.
Neutron Star
Neutron Star
A star so dense that only neutrons can exist in its core.
Supernova
Supernova
A massive explosion in which the entire outer portion of a star is blown off.
Black Hole
Black Hole
The remnant of a supernova explosion with a gravitational field so strong that nothing can escape its pull.
Galaxy
Galaxy
A huge collection of stars, planets, gas, and dust that is held together by gravity. Our galaxy is called the Milky Way.
Rotation
Rotation
The turning of an object around an imaginary axis running through it; Earth’s rotation around its axis is 24 hours.
Similarities between inner and outer planets.
They all follow an elliptical orbit, share the same orbital plane, and are spherical.
Explain the Moon’s relationship with the Earth.
The Moon’s gravity pulls on Earth’s oceans and distorts them, causing tides.
Phases of a lunar eclipse
Phases of a lunar eclipse
1. New Moon
2. Waxing Crescent
3. First Quarter
4. Waxing Gibbous
5. Full Moon
6. Waning Gibbous
7. Last Quarter
8. Waning Crescent
9. New Moon
What causes seasons?
What causes seasons?
The seasons are caused by the tilt of the Earth’s rotational axis away or toward the sun as it travels through its year-long path around the sun
Spiral Galaxies
– Band of stars that make up a ‘swirl’.
– Usually have a ‘bulge’ in the middle.
– There can be a bar of stars in the middle.
– Have organization and structure, look ‘flat’.
Elliptical Galaxies
– Can range in shape from a sphere to an oval, to oblong.
– Houses some of the oldest stars in the universe.
Categories: Astronomy