They next examined how the winds moved throughout Pluto's surface. During most of the year, Pluto's winds over 4 kilometers (2.5 miles) blow to the west, the opposite direction of the dwarf planet's eastern spin, in a retro-rotation. But every 10 years or so, the wind blows east for 2 days before returning to its usual direction.
They concluded that Pluto has seasonal changes like other planets, with cold winters and hot summers. The atmosphere is made up of nitrogen and methane with some carbon dioxide and little else. There are no signs that Pluto has any ocean beds nor any evidence of ice caps or glaciers on its surface.
Pluto was originally classified as a planet by the International Astronomical Union (IAU), but this classification was later changed when new information about it was discovered. Today, Pluto is considered a dwarf planet because it does not meet the criteria for being a star or a planet family.
It spins practically on its side because its axis of rotation is tilted 57 degrees with regard to the plane of its orbit around the sun. Pluto, like Venus and Uranus, has a retrograde rotation, revolving from east to west. This is different from the rotation of Earth which goes from west to east.
Pluto's year is approximately 684 days, much longer than Earth's 365 days. The reason for this is that Pluto takes 250 years to complete one rotation on its axis.
The last time it was possible to observe Pluto without using a telescope was in 1930. Since then, it has been captured by the planet Neptune which always lies between Earth and Pluto at about 4.5 billion miles from Earth.
Neptune has a mass about 1,000 times that of Earth but only about 1/10th our diameter. It has taken pictures of Pluto from across its sky and we can see features on the surface of Pluto from these images.
Pluto will be returning to darkness again in about 500 years' time.
The majority of Pluto's thin atmosphere is nitrogen, with minor quantities of carbon dioxide and methane. As the thin, nitrogen-rich wind rushes across the surface, it transfers heat, ice grains, and haze particles, resulting in dark wind streaks and plains across the northern and northwest areas. This image was taken by NASA's New Horizons spacecraft as it approached within 7,000 miles (11,500 kilometers) of Pluto on July 14, 2015.
Wind has been observed throughout Pluto's history, from ancient times to the present day. Early observations of Pluto by astronomers using telescopes could not distinguish between winds that were fast enough to blow dust around or those that were too slow to lift water vapor into the air. More recent studies have shown that Pluto has a magnetic field that extends nearly around its body, which would prevent it from being blown away by gas pressure. The latest data also indicate that Pluto has at least two moons: Charon and Nix.
Pluto does have weather, though it is very different from Earth's. There are four major types of features on Pluto: craters, mountain ranges, valleys, and plains. All types of feature can appear anywhere on the planet, although they are most common near the equator where the average temperature is about -240 degrees F (-153 degrees C).
Crates range in size from hundreds of yards to more than 20 miles in diameter.
In 2015, the NASA New Horizons mission sailed by Pluto, delivering the closest and most comprehensive image of the dwarf planet to date. Pluto's thin atmosphere contains nitrogen, methane, and carbon dioxide, and while the sky are blue, the snow appears crimson due to its chemical makeup. The color comes from erythrosine, which is a pink or red pigment found in many plants and animals.
Pluto was discovered in 1930 by American astronomer Clyde W. Tombaugh. He was using the Lowell Observatory telescope on Flagstaff Mountain, Arizona when he made his discovery. Before then, astronomers thought that the Solar System was pretty much empty except for some minor planets such as Ceres, Mercury, Venus, Mars, and Jupiter.
Tombaugh decided to name the new planet after the king of underworld in Greek mythology, because he believed that it was important to have a name that would be useful for future discoveries. However, this wasn't the only reason why he named it Pluto. Also, he wanted to embarrass the astronomers who had said that the Solar System was too crowded for any more additions.
Today, we know that Pluto has seven moons: Charon, Nix, Styx, Kerberos, Antipa, Tholus, and Eris. All but one of these moons were discovered by Tombaugh himself.
Pluto did not explode. Prior to 2006, a planet was any huge astronomical entity that orbited the sun. Though Pluto still fits this requirement, it also transports tiny elements known as planetesimals during its orbit. The remaining eight planets in our solar system do not.
In March 2006, scientists concluded that a large body had once orbit ed the Sun much farther from the Earth-Sun distance than either Pluto or Neptune. This mysterious object was named "Xena". She had a diameter about 1.5 times that of Pluto and weighed almost as much. In August 2007, another large object was found in space near Pluto called "Hermes". He was also about 1.5 times as massive as Pluto.
The existence of these objects shows that planets are not eternal, but rather they evolve over time through cosmic impacts. Thus, the word "planet" is actually an adjective used to describe any celestial body that has never undergone nuclear fusion (the only way to make more heavy elements) and therefore will always be smaller than stars.
Pluto's surface is covered by frozen nitrogen and methane gas. It gets cold enough for these gases to freeze onto the planet's surface. When Jupiter crossed its path around 4.5 billion years ago, it smashed into Pluto, sending particles flying into space. Some of these particles bonded with molecules of nitrogen and methane on Pluto's surface, creating a thick layer of ice.