The order of the planets from closest to the Sun outwards is; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and finally Neptune. The largest planet in the solar system is Jupiter, followed by Saturn, Uranus, Neptune, Earth, Venus, Mars with the smallest being Mercury.
A year in Mercury is just 88 days long. One day on Mercury lasts the equivalent of 176 Earth days.
Mercury has wrinkles. As the iron core of the planet cooled and contracted, the surface of the planet became wrinkled. Scientist have named these wrinkles, Lobate Scarps.
Mercury is only the second hottest planet. Despite being further from the Sun, Venus experiences higher temperatures. The surface of Mercury which faces the Sun sees temperatures of up to 427°C, whilst on the alternate side this can be as low as -173°C. This is due to the planet having no atmosphere to help regulate the temperature.
Only two spacecraft have ever visited Mercury. Owing to its proximity to the Sun, Mercury is a difficult planet to visit. During 1974 and 1975 Mariner 10 flew by Mercury three times, during this time they mapped just under half of the planet’s surface. On August 3rd 2004, the Messenger probe was launched from Cape Canaveral Air Force Station, this was the first spacecraft to visit since the mid 1970’s.
A day on Venus lasts longer than a year. It takes 243 Earth days to rotate once on its axis. The planet’s orbit around the Sun takes 225 Earth days, compared to the Earth’s 365.
Mars is home to the tallest mountain in the solar system, Olympus Mons, a shield volcano. It is 21km high and 600km in diameter. Despite having formed over billions of years, evidence from volcanic lava flows is so recent many scientists believe it could still be active.
Mars has the largest dust storms in the solar system. They can last for months and cover the entire planet. The seasons are extreme because its elliptical (oval-shaped) orbital path around the Sun is more elongated than most other planets in the solar system.
Pieces of Mars have fallen to Earth. Scientists have found tiny traces of Martian atmosphere within meteorites violently ejected from Mars, then orbiting the solar system amongst galactic debris for millions of years, before crash landing on Earth. This allowed scientists to begin studying Mars prior to launching space missions.
Jupiter is the fourth brightest object in the solar system. Only the Sun, Monnn, Venus are brighter. It is one of five planets visible to the naked eye from Earth.
Jupiter has the shortest day of all the planets. It turns on its axis once every 9 hours and 55 minutes. The rapid rotation flattens the planet slightly, giving it an oblate shape.
Jupiter orbits the Sun once every 11.8 Earth years. From our point of view on Earth, it appears to move slowly in the sky, taking months to move from one constellation to another.
Eight spacecraft have visited Jupiter. Pioneer 10 and 11, Voyager 1 and 2, Galileo, Cassini, Ulysses, and New Horizons missions. The Juno mission is its way to Jupiter and will arrive in July 2016. Other future missions may focus on the Jovian moons Europa, Ganymede, and Callisto, and their subsurface oceans.
Saturn orbits the Sun once every 29.4 Earth years. Its slow movement against the backdrop of stars earned it the nickname of “Lubadsagush” from the ancient Assyrians. The name means “oldest of the old”.
Saturn has 150 moons and smaller moonlets. All are frozen worlds. The largest moons are Titan and Rhea. Enceladus appears to have an ocean below its frozen surface.
Four spacecraft have visited Saturn. Pioneer 11, Voyager 1 and 2, and the Cassini-Huygens mission have all studied the planet. Cassini continues to orbit Saturn, sending back a wealth of data about the planet, its moons, and rings.
Uranus turns on its axis once every 17 hours, 14 minutes. The planet rotates in a retrograde direction, opposite to the way Earth and most other planets turn.
Uranus makes one trip around the Sun every 84 Earth years. During some parts of its orbit one or the other of its poles point directly at the Sun and get about 42 years of direct sunlight. The rest of the time they are in darkness.
Uranus is the Coldest Planet. With minimum atmospheric temperature of -224°C Uranus is the coldest planet in the solar system. The upper atmosphere of Uranus is covered by a methane haze. This hides the storms that take place in the cloud decks.
Only one spacecraft has flown by Uranus. In 1986, the Voyager 2 spacecraft swept past the planet at a distance of 81,500 km. It returned the first close-up images of the planet, its moons, and rings.
First woman in space – 16th June 1963 – Valentina Tereshkova in Vostok 6
First man on the moon – 20th July 1969 – Neil Armstrong from Apollo 11
The Sun is large enough that approximately 1.3 million Earths could fit inside (if squashed in) or if the Earths retained their spherical shape then 960,000 would fit.
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust. Examples of galaxies range from dwarfs with as few as ten million stars to giants with a hundred trillion stars, each orbiting their galaxy’s own center of mass. There are probably more than 170 billion galaxies in the observable universe.
The nucleus of a comet is made of ice and can be as small as a few meters across to giant boulders a few kilometres across.
Most meteorites are one of three types: stony, stony-iron, or iron.
