astronomy

Solar system- Assemblage of celestial bodies made up of a central star and the satellites that orbit it

An average-sized star (the Sun) 8 major satellites (planets) Numerous small satellites (ex.

asteroids, comets and meteoroids)

Planet Distance from Sun (km)

Diameter (km)

Type Moons Rings

Mercury 57,910 4,878 Rocky None No

Venus 108,200 12,104 Rocky None No

Earth 149,600 12,756 Rocky 1 No

Mars 227,940 6,794 Rocky 2 No

Jupiter 778,330 142,800 Gas 62 Yes

Saturn 1,429,400 120,700 Gas 33 Yes

Uranus 2,870,990 51,700 Gas 27 Yes

Neptune 4,504,000 48,600 Gas 13 Yes

All the planets orbit the Sun in the same direction and in an elliptical orbit Elliptical orbit resembles a flattened

circle and means that the planets do NOT stay a constant distance from the sun

Moon-Naturally occurring satellite that orbits a planet The planet Earth has 1 moon Some planets have many moons (Ex.

Jupiter and Saturn)

Saturn’s moons

The moon orbits the Earth in almost 28 days which creates the phases of the moon Phases of the moon-Sequence

of illumination of the moon as viewed from Earth

The same side of the moon is always facing the Earth

Rotates on its axis every 24 hours Orbits the sun every 365.25 days

Earth’s axis is tilted at about 23° The tilting creates the 4 seasons

since different parts of the Earth are oriented towards the Sun at different times of the year.

When the Earth’s northern hemisphere reaches its maximum orientation with respect to the Sun, it’s called the Summer Solstice Summer Solstice-Longest calendar day

When the Earth’s northern hemisphere reaches its minimum orientation with respect to the Sun, it’s called Winter Solstice Winter Solstice-Shortest calendar day

An eclipse occurs when the Sun, Earth and moon align themselves in certain positions

Solar Eclipse occurs when the moon comes between the Sun and Earth

A lunar eclipse occurs when the Earth comes between the Sun and the moon

Asteroid-Much smaller astronomical body that orbits the Sun Most occur in the asteroid belt located

between the orbits of Mars and Jupiter

Comet-Small astronomical object made largely of ice. Solar radiation from the Sun can

vaporize the icy material to produce a comet tail called a coma

Meteoroid-Small object between the size of a rock and a dust particle

•When a meteoroid enters an atmosphere, the intense heating caused by friction with the air causes the meteoroid to vaporize and creates a streak of light called a meteor

Galaxy-Cluster of stars, gas clouds, and dust that are held together by their gravitational forces Our solar system is part of the Milky

Way Galaxy

To help discuss distances in space, astronomers use the light year Light year-The distance that light

travels in space in 1 Earth year (About 9.5 trillion kilometers)

The diameter of the Milky Way Galaxy is said to be 100,000 light years!