Pluto is a dwarf planet and the second closest to the Sun of its kind. Before it was re-classified to a dwarf planet Pluto was thought to be the ninth planet in our solar system and the one furthest away from the Sun. It has recently been explored by New Horizons, the first spacecraft to ever reach Pluto and we are learning fascinating things about this far away planet.
- Pluto was discovered in 1930. It was seen using a telescope as it is too far away from Earth to be seen without the use of equipment.
- Pluto was discovered by Clyde Tombaugh and was initially thought to be a ninth planet. However even then people were unsure as to whether or not it could be classed as a planet like the other eight in the solar system.
- Pluto does not orbit the Sun like other planets in the solar system. Instead of taking a clear path around the sun Pluto goes in more of an oval and has a tilted orbit when compared with other planets. This means not only does Pluto get closer and further away from the Sun, it is also higher in the solar system on one side of the Sun than the other. Pluto actually spends 22 years of its orbit closer to the Sun than Neptune. This last happened between 1979 and 1999 and will happen again in 2227.
- It takes 248 Earth years for Pluto to orbit the Sun. This means that Pluto hasn’t made a full trip around the Sun since it was found in 1930. Scientists have predicted its orbit path.
- Pluto takes 153.3 hours to rotate on its axis. This means a day on Pluto is 6.4 Earth days.
- Pluto is in the Kuiper Belt. This is an area in space containing thousands of objects orbiting the sun. Most of these are very small and made of ice. It is sometimes called the “Third Zone” and is the space further away from the sun than Neptune.
- Pluto is 1,473 miles (2,370 kilometers) in diameter. This is quite small compared to the other eight planets in the Solar System apart from Mercury which is even smaller.
- Pluto gets its name from the Roman god of the underworld. The name was actually chosen by a young girl in England who was only 11 at the time. Her name was Venetia Burney.
- In 2006 it was decided that Pluto should no longer be classed as a planet. It is now called a dwarf planet. The decision was made after another dwarf planet named Eris was discovered in 2003 and astronomers began to talk about what actually makes a planet a planet. This was mostly their size, location and ability to clear their own orbit path. Clearing an orbit path is where a planet has enough gravity to push other items out of its way or bring them into their own atmosphere. There are five dwarf planets in total. The others are called Makemake, Ceres and Haumea.
- Of the dwarf planets, Pluto is second closest to the Sun. Ceres is the closest.
- Pluto is the second largest of the dwarf planets with Eris being the biggest by roughly 24 miles (40 kilometres) difference in their diameters.
- Pluto has 5 known moons. These are named Charon, Styx, Nix, Kerberos and Hydra. Charon is the largest of the five and is similar to the Earth’s moon – this makes it about half the size of Pluto itself. Both are tidally locked to their planets meaning the same side of the moon faces the planet at all times.
- The first spacecraft to visit Pluto was a NASA mission called New Horizons and flew by the dwarf planet in July 2015. The probe was the fastest spacecraft ever launched and left Earth on the 19th of January 2006. The mission is not over and is planned to continue until 2026 after spending a few years looking at objects in the Kuiper Belt. The spacecraft is carrying a small container holding the ashes of Clyde Tombaugh who first discovered the dwarf planet.
- Pluto is grey in colour with a slight red tinge to it. Scientists were expecting it to be a dark, bluish icy planet and were surprised to discover its rusty tint – not too different to the colours of Mars.
- The photos revealed that Pluto has a heart shape on it! This heart shape is thought to be made of ice and is changing over time. This region of the planet is now called the Tombaugh Reggio and does not have the craters that are found on the rest of the planet. This makes it likely that this region is much younger than Pluto itself and is probably no older than 100 million years. That is pretty young as far as planets go!
- Pluto’s atmosphere is made up mostly of nitrogen. There are also low levels of carbon monoxide and methane. This atmosphere actually grows bigger as the planet gets closer to the sun in its unusual orbit and some of the ice on the surface evaporates.
- Below all of the gas is a rocky core covered in ice. New information has been gathered by New Horizons on Pluto’s atmosphere that shows it to be much thinner than had been predicted. There is still a lot to learn about this, hopefully New Horizons collected enough data to answer many questions.
- Pluto has ice caps. People have thought for a long time that Pluto has ice caps and the pictures from New Horizons has proved them right. The other planets with ice caps are Earth and Mars.
- Pluto has mountains as tall as 3,500 metres (11,000 feet). Scientists think these are formed on top of layers of water and ice. Mountains on planets are usually surrounded by craters but not on Pluto, not many were discovered from the images sent back from the spacecraft. This could meant that there has been recent geological activity (still millions of years ago!) on the dwarf planet which would have smoothed the craters out.
- We do not know if Pluto has a magnetic field or not. Scientists think it probably does not have one because of how small it is and the fact that it rotates on its axis so slowly.
- Pluto is surrounded by a thick and very visible haze. This was only discovered once the New Horizons spacecraft had already passed Pluto and took a photo looking back towards the dwarf planet. Little is known about the haze at this point but it is very different to what scientists were expecting to see.
- New Horizons got closest to Pluto on the 14th of July. This allowed the spacecraft to take photos of the planet’s surface with detail that had never been seen before. Information will be downloaded until 2017 due to the distance of the spacecraft from Earth. There is still lots more information to receive and exciting things to learn about Pluto!
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