All About Our Solar System

Our solar system consists of the sun, nine planets (and their moons), an asteroid belt, and many comets and meteors. The sun is the center of our solar system; the planets, over 61 moons, the asteroids, comets, meteoroids and other rocks and gas all orbit the Sun.

Asteroids are rocky or metallic objects, most of which orbit the Sun in the asteroid belt between Mars and Jupiter. A few asteroids approach the Sun more closely. None of the asteroids have atmospheres.

A comet is a small, icy celestial body that orbits around the sun. It is made up of a nucleus (solid, frozen ice, gas and dust), a gaseous coma (water vapor, CO2, and other gases) and a long tail (made of dust and ionized gases). The tail develops when the comet is near the Sun. Its long ion tail of always points away from the sun, because of the force of the solar wind . The tail can be up to 250 million km long, and is most of what we see. Comets are only visible when they\'re near the sun in their highly eccentric orbits.

Meteoroids are small bodies that travel through space. Meteoroids are smaller than asteroids; most are smaller than the size of a pebble. Meteoroids have many sources. Most meteoroids come from asteroids that are broken apart by impacts with other asteroids. Other meteoroids come from the Moon from comets and from the planet Mars

The Sun .

Our sun is a star located at the center of our Solar System. It is a huge, spinning ball of hot gas and nuclear reactions that lights up the Earth and provides us with heat. It is 93,026,724 miles from the Earth.

The Earth is closest to the Sun around January 2 each year & it is farthest away from the Sun around July 2 each year .

The Sun is made up of gases. It is composed of about 75% hydrogen and 25% helium. This ratio is changing over time (very slowly), as the nuclear reactions continue, converting smaller atoms into more massive ones.

The Sun formed 4.5 billion years ago, as the solar system coalesced from a cloud of gas and dust.

We should not LOOK DIRECTLY AT THE SUN! Looking at the Sun can blind you or cause cataracts

The Planets
The nine planets that orbit the sun are (in order from the Sun): Mercury, Venus, Earth, Mars, Jupiter (the biggest planet in our Solar System), Saturn (with large, orbiting rings), Uranus, Neptune, and Pluto. A belt of asteroids (minor planets made of rock and metal) orbits between Mars and Jupiter. These objects all orbit the sun in roughly circular orbits that lie in the same plane, the ecliptic (Pluto is an exception; it has an elliptical orbit tilted over 17 from the ecliptic).

The inner planets (those planets that orbit close to the Sun) are quite different from the outer planets (those planets that orbit far from the Sun).

o The inner planets are: Mercury, Venus, Earth, and Mars. They are relatively small, composed mostly of rock, and have few or no moons.
o The outer planets include: Jupiter, Saturn, Uranus, Neptune, and Pluto. They are mostly huge, mostly gaseous, ringed, and have many moons (again, the exception is Pluto which is small, rocky, and has one moon). Mercury
Mercury is the planet closest to the Sun in our Solar System. This small, rocky planet has almost no atmosphere. Mercury has a very elliptical orbit and a huge range in temperature. During the long daytime (which lasts 58.65 Earth days or almost an entire Mercurian year, which is 88 days long), the temperature is hotter than an oven; during the long night (the same length), the temperature is colder than a freezer.

Mercury is a heavily cratered planet; its surface is similar to the surface of our Moon. Cratering on Mercury triggered volcanic eruptions that filled much of the surrounding area. Mercury does have a magnetic field .

Mercury is about 3,031 miles (4,878 km) in diameter. It is the second-smallest planet in our Solar System (after tiny Pluto). Mercury is a bit over one third of the diameter of the Earth. Mercury is only slightly larger than the Earth\'s moon.

Mercury\'s mass is about 3.3 x