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the sun and all the objects (planets, moons, asteroids, comets, dust, and gas) that orbit around it.
solar system
galaxy
— a huge group of stars, gas, and dust held together by gravity; our galaxy is the Milky Way.
star
a very hot, glowing ball of gas (like the sun) that gives off light and heat.
a large, spinning cloud of interstellar gas and dust that collapsed and formed the sun and planets.
solar nebula
orbit
the curved path an object takes as it moves around another object because of gravity (for example, a planet around the sun).
terrestrial
relating to the inner planets that are made mostly of rock and metal and have solid surfaces (Mercury, Venus, Earth, Mars).
Jovian
relating to the outer giant planets that are mostly made of gases or ices (Jupiter, Saturn, Uranus, Neptune).
a very large planet made mostly of gases such as hydrogen and helium (example: Jupiter, Saturn).
gas giant
a large outer planet that contains more ices and heavier elements like water, methane, and ammonia mixed with gas (example: Uranus, Neptune).
ice giant
asteroid belt
— a region between Mars and Jupiter made of many rocky objects (asteroids) left over from the solar system’s formation.
a round object in space that orbits the sun but is not large enough to clear its orbit of other debris (example: Ceres, Pluto).
dwarf planet
a disc-shaped area beyond Neptune filled with icy bodies and dwarf planets; a birthplace for many comets.
Kuiper Belt
Oort Cloud
a distant, spherical region of icy objects far beyond the Kuiper Belt that marks the outer edge of the sun’s influence.
comet
a small icy body that, when it nears the sun, heats up and develops a glowing head and often a tail made of gas and dust.
the layer of gases that surrounds a planet; it affects temperature and can support life on a planet like Earth.
atmosphere
About how long ago did our solar system form?
4.5 billion years ago
The solar system formed from a collapsing cloud of gas and dust called a:
Solar nebula
According to the passage, about what percentage of stars in the galaxy host planetary systems?
15%
How many planets revolve around our sun?
Eight
Which two categories are the planets divided into based on composition?
Terrestrial and Jovian
Which list shows the Terrestrial planets?
Mercury, Venus, Earth, Mars
Which characteristic is typical of Terrestrial planets?
Solid surfaces made of rock
What makes Earth unique in the passage?
It has water systems that support life.
The outer planets (Jovian) include
Jupiter, Saturn, Uranus, Neptune
Which statement is true about all four Jovian planets?
They have multiple moons and ring systems.