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In our solar system, nine planets circle around our Sun. The Sun is in the middle while the planets travel in circular paths (called orbits) around it. These nine planets travel in the same direction (counter- clockwise looking down from the Sun's north pole).
Mercury
Mercury is the smallest planet in the solar system, Mercury is bright when viewed from Earth. It can only be seen in morning and evening twilight. The first of two spacecraft to approach Mercury was Mariner 10 from 1974 to 1975, The second was the MESSENGER spacecraft.
Physically, Mercury is similar in some aspects to the Moon. It is heavily cratered,has no atmosphere and it has a large iron core.
Before the 4th century BC, Greek astronomers believed the planet to be two separate objects: one visible only at sunrise, which they called Apollo; the other visible only at sunset, which they called Hermes.
Venus
Venus is the second-closest planet to the Sun. Venus has been known since prehistoric times, it is the brightest natural object in the night sky, except for the Moon. Like Mercury, it was popularly thought to be two separate bodies: Eosphorus as the morning star and Hesperus as the evening star, but the Greek astronomers knew better.
Earth
Earth is the third planet from the Sun and is the largest of the planets in the Solar System in diameter, mass and density.
Home to millions of species, including humans, Earth is the only place in the universe where life is known to exist. Scientific evidence indicates that the planet formed 4.54 billion years ago, and life appeared on its surface within a billion years.
About 71% of the surface is covered with salt-water oceans, the remainder consisting of continents and islands; liquid water is necessary for all known life and is not known to exist on any other planet's surface.
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after Mars, the Roman god of war.
Until the first flyby of Mars by Mariner 4 in 1965, it was thought that there might be water on the planet's surface. Still, of all the planets in our Solar System other than Earth, Mars is the most likely to harbor liquid water, and perhaps life.
Mars is currently home to three functional orbiting spacecraft: Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter. The surface is also home to the two Mars Exploration Rovers (Spirit and Opportunity). These Mars Exploration Rovers suggests that Mars previously had water on its surface, while observations also indicate that small geyser-like water flows have occurred in recent years.
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is two and a half times as massive as all of the other planets in our Solar System combined. Jupiter, along with Saturn, Uranus and Neptune, is classified as a gas giant.
The planet was known by astronomers of ancient times and was associated with the mythology and religious beliefs of many cultures. The Romans named the planet after the Roman god Jupiter. Its the third brightest object in the night sky after the Moon and Venus.
The planet Jupiter is primarily composed of hydrogen with a small amount of helium; it may also have a rocky core of heavier elements under high pressure. The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. Surrounding the planet is a faint planetary ring system and a powerful magnetosphere. There are also at least 63 moons, the largest of these moons, has a diameter greater than that of the planet Mercury.
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Along with the planets Jupiter, Uranus and Neptune it is classified as a gas giant (also known as a Jovian planet, after the planet Jupiter). It was named after the Roman god Saturnus, equated to the Greek Kronos (the Titan father of Zeus) and the Babylonian Ninurta. Saturn's symbol represents the god's sickle.
Wind speeds on Saturn can reach 1,800 km/h, significantly faster than those on Jupiter. Saturn has a planetary magnetic field intermediate in strength between that of Earth and the more powerful field around Jupiter.
Saturn has a prominent system of rings, consisting mostly of ice particles with a smaller amount of rocky debris and dust. Sixty known moons orbit the planet. Titan, Saturn's largest and the Solar System's second largest moon.
Uranus
Uranus is the seventh planet from the Sun and the third-largest and fourth-most massive planet in the solar system. It is named after the ancient Greek god Uranus. Uranus was the first planet discovered in modern times. This was also the first discovery of a planet made using a telescope.
It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (-224 °C). It has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane thought to make up the uppermost layer of clouds.
Like the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons. Seen from Earth, Uranus' rings can appear to circle the planet like an archery target and its moons revolve around it like the hands of a clock. In 1986, images from Voyager 2 showed Uranus as a virtually featureless planet in visible light. However, terrestrial observers have seen signs of seasonal change and increased weather activity in recent years.
Neptune
Neptune eighth and farthest planet from the Sun in the Solar System. It is the fourth largest planet by diameter, and the third largest by mass. The planet is named after the Roman god of the sea.
Discovered on September 23, 1846, Neptune was the first planet found by mathematical calculations rather than regular observation. Neptune has been visited by only one spacecraft, Voyager 2, which flew by the planet on August 25, 1989.
Neptune's atmosphere is primarily composed of hydrogen and helium along with traces of methane. Neptune also has the strongest winds of any planet in the solar system, measured as high as 2,100 kilometres per hour. Neptune's temperature at its cloud tops is usually close to -218 °C (55.1 K), one of the coldest in the solar system. The temperature in Neptune's centre is about 7,000 °C (7,270 K), which is comparable to the Sun's surface.
If you think we did forgot Pluto. we didn't because Pluto is so small that it is now called a Dwarf Planet.
So there are only eight planets in the solar system now.
