a ring of icy objects around the sun, extending just beyond the orbit of Neptune
open cluster
groups of stars that were formed from the same molecular cloud within a galaxy or at its edge
galaxy cluster
a structure that consists of hundreds or thousands of galaxies that are bound together by gravit
nebula
a huge cloud of dust and gases, mainly hydrogen and helium
asteroid
rocky fragment that orbits around the sun and is too small to be a planet
geocentric model
any theory of the structure of the solar system in which Earth is assumed to be the center of it all
rotation
the movement or path of the earth (or another celestial body) turning on its axis
Saturn
gas giant with 61 moons; has huge, thin rings made of ice, dust, and rock fragments; 6th planet from the sun
The Pleiades
an open cluster located about 440 light years from Earth
Neptune
gas giant with 14 moons, most distant planet from the sun, has the strongest winds of any planet
Milky Way
galaxy that includes our solar system, has a spiral shape
Big Bang Theory
idea that the universe began as just a single point, then expanded to how large it is now, and is still expanding
Mercury
rocky planet with no atmosphere, has a huge metallic core and its surface is covered with impact craters, 1st planet from the sun
Jupiter
gas giant with 63 moons that gives off more energy than it receives from the sun, largest planet from the solar system, 5th planet from the sun
Mars
rocky planet with a thin atmosphere; surface features include craters, valleys, deserts, and ice caps; 4th planet from the sun
galaxy
a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction
asteroid belt
a torus shaped region in the solar system, located between Jupiter and Mars, that contains many solid, irregularly shaped bodies that are smaller than planets
sun
the star at the center of our solar system
solstice
the day when the difference in length between day and night is the greatest
Uranus
gas giant with 27 moons, its rotational axis is almost horizontal to its orbit, has a thin ring system, 7th planet from the sun
Earth
rocky planet with an atmosphere of mostly oxygen and nitrogen, only planet with liquid water and life, 3rd planet from the sun
solar system
the gravitationally bound system of the sun and the objects that orbit the sun, either directly or indirectly
solar eclipse
occurs when the moon passes directly between Earth and the sun
dwarf planet
a small planetary-mass object that is in direct orbit of the sun
star
a massive self-luminous celestial body of gas that shines using its own energy, made up of mainly hydrogen and helium
axis of rotation
the imaginary line that passes through the geographic North Pole and the geographic South Pole
lunar eclipse
occurs when the moon passes through the shadow produced by earth
equinox
the day when day and night are equal length: 12 hours
heliocentric theory
theory that states that the sun is the center of the solar system and the planets and other bodies revolve around it
revolution
an object's, such as a planet's, orbital motion around another object
Venus
rocky planet with a very dense atmosphere of carbon dioxide and clouds of sulfuric acid, high surface temperature, 2nd planet from the sun
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