ASTRONOMY
Astronomy – The study of the moon, stars and other objects in space past the Earth’s atmosphere.
Ptolemy – (100-165) Greek astronomer and geographer. Believed that the Earth was the center of the
universe (geocentric). Created latitude and longitude.
Geocentric – A belief that Earth is the center of the solar system and that all other planets and the sun
rotate around it.
Copernicus – (1473-1543) Polish astronomer. Created the idea that the sun was the center of the
universe (heliocentric). He also discovered that the planets orbit in a circle around the sun.
Heliocentric – The belief that the sun is the center of the universe and that the planets orbit around it.
Galileo – (1564-1642) Italian astronomer “The father of modern astronomy”. The first to use a telescope
to look at the sky. Did a lot of work with gravity and worked to prove the heliocentric theory created by
Copernicus.
Newton – Worked with mathematics and physics. Studied gravity and created the 3 laws of motion. He
created the first reflecting telescope which is what telescopes today are based on.
Lowell/Lowell Observatory – Lived in Flagstaff, Arizona. Spent much of his life studying Mars. Created
Lowell Observatory where he discovered Pluto.
Hubble/Hubble Telescope – Created a 100 inch telescope that allowed him to look outside of our
galaxy, and discovered many more like ours. His theories and research lead to our current
understanding of how the universe was created, the big bang.
Stephen Hawking – Professor of mathematics at Cambridge. One of the most brilliant physicists since
Einstein.
Universe – The universe is everything in existence; all of the galaxies, solar systems and matter in
between. No one knows how big the universe is.
Galaxy – A collection of stars and dust bound together by gravity. There are billions of galaxies in the
universe. We are part of the Milky Way galaxy.
System – Planets, moons, asteroids, comets, and meteors that revolve around a star (sun). The name of
our system is the Solar System.
Stars – Huge hot burning balls of gas. The star found in our Solar System is called the Sun.
Planets – A large mass that orbits the Sun. Planets can be terrestrial (rocky surface) or gas giants (made
up mostly of gasses).
Moons – Large rocky masses that orbit a planet. The Earth has one moon. The moon’s name is Luna.
Comets – Chunks of ice and dirt that appear to be glowing masses with long tails and have their own
long elliptical orbits around the sun. These are often called “dirty snowballs”. Hailey’s comet, is visible
from the each every 75 years.
Asteroids – Rocky objects that are too small to be considered full-fledged planets which have their own
orbit around the sun. The region of the solar system that contains millions of asteroids in revolution
around the sun (between Mars and Jupiter) is called the asteroid belt.
Meteor/Meteorites/Meteoroids – These are all small rocky objects. The different in the ending of the
terms –or, -oid, -ite, are based on the location of the object. If the small rocky object is in space it is
called a meteoroid. When the object is burning up as it goes through the atmosphere of the earth, it is
called a meteor/meteor shower (these are what is known as shooting stars). A meteorite is a meteor
that has gone through space and the earth’s atmosphere and has landed on the earth.
Constellation – A collection of starts that make a shape. Used to tell stories long ago.
Horizon – The line where they sky meets the earth, the furthest point you can see.
Zenith – The point vertically above an observer, the highest point.
Seasons – The result of the yearly revolution of the Earth around the Sun and the tilt of the Earth’s axis.
Northern Hemisphere – The half of the planet that is north of the equator.
Southern Hemisphere – The half of the planet that is south of the equator.
Tilt – The reason for the Earth’s seasons. About 23.5 degrees from perfectly horizontal.
Axis – An imaginary line that passes through the Earth’s center beginning at the North Pole and ending
at the South Pole that the earth rotates on.
Revolution – The movement of an object around another object.
Rotation – The spinning motion of a planet on its axis.
Equator – The big circle of the Earth that is equally distant from the North Pole and the South Pole.
Day - 24 hours – the time it takes for the Earth to make one rotation on its axis.
Year – The time in which the planet completes a revolution around the sun.
Orbit – The movement of an object around another object.
Moon Phases – The different shapes of the moon as we see them from Earth. (crescent, full, new etc.)
Full Moon – The moon’s lit up side is facing the Earth. The moon appears to be completely lit up by
direct sunlight.
New Moon – The moon’s unlit side is facing the Earth. The moon is not visible.
Quarter Moon (First and Third) – One half of the moon appears to be lit up by direct sunlight.
Waxing – When the moon appears to get larger over several days.
Waning – When the moon appears to get smaller over several days.
Reflected Sunlight – This is how the moon is “lit up”, by sunlight reflected off its surface.
Eclipse – The partial or total blocking of one object in space by another.
Solar Eclipse – When the moon moves in between the Earth and the sun and blocks sunlight from hitting
the moon.
Lunar Eclipse – When the Earth moves in between the moon and the sun and blocks sunlight from
hitting the moon.
Tide – The rise and fall of ocean waters, caused by the moon.
Equinox – The time that earth’s poles point at their greatest angle toward or away from the sun
(Summer and Winter)
Solstice – The first day of spring or fall when the sun is directly over the equator.
Gravity – The force of attraction between all masses in the universe.
Star – A ball of gas and dust that emits its own light.