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The History Of Pluto

Known to the Greeks as “Hades,” Pluto is the second largest known dwarf planet in our Solar System and is the tenth-largest body observed directly orbiting the Sun. Until August 24 2006, Pluto was considered a planet, but has since been acknowledged as the largest member of the Kuiper belt. To the Romans, the name “Pluto” referred to the “god of the underworld.” These names are derived from the fact the planet is located in complete darkness, because it is so far from the Sun.

Like Neptune, Pluto cannot be seen from the Earth with a simple telescope. It is located an average distance of 5.9 billion miles from the Sun. As a result of how far it is located from Earth, only a little information is known about it. The history of the discovery of Pluto started in 1905 with astronomer Percival Lowell at the Lowell Observatory. Lowell at that time was studying the force of gravity of an object. Lowell, an American astronomer, found that the force of gravity of an object, was affecting the way in which Uranus and Neptune moved around the Sun. He was convinced this object had to be another planet. Lowell continued his search for the planet, but was unable to find it, even at his death in 1916.

The work started by Lowell, was continued by Clyde Tombaugh, at the Lowell Observatory. Tombaugh was able to use a more updated telescope to take pictures of space. Tombaugh and other astronomers relied also on calculations of Lowell to discover Pluto. Even though Lowell was not alive to discover Pluto, his calculations were used to help American Clyde Tombaugh discover Pluto in 1930.

The Orbit Of Pluto

Pluto, like the other planets, has an elliptical orbit. The orbit of Pluto takes approximately 248 Earth years around the Sun. The planet rotates approximately every 6 Earth days. Pluto has a perihelion of 2.7 billion miles (4.4 billion km), and an aphelion, of 4.5 billion miles (7.4 billion kilometers). Pluto is tipped 120 degrees on its axis, and undergoes retrograde rotation. This would mean that Pluto is lying on its “side” and rotating opposite to the majority of the other planets in the galaxy.

As a result of Neptune being “close” to Pluto, Pluto will become trapped in Neptune’s orbit, for approximately 20 years, as Pluto orbits the Sun every 248 years.

Expeditions To Pluto

There have been no past expeditions to Pluto due to the distance of the planet.

The Hubble Space Telescope was able to successfully take images of Pluto in 1996. The images received showed light and dark patches located on the surface of the planet.

The “New Horizons” spacecraft was launched in 2006, and is expected to reach Pluto in 2015. The goal of this planned is to gain more knowledge about Pluto, especially its surface and typography. The “New Horizons” spacecraft will also

Exploring A Day On Pluto

With the coldest temperature of -375 degrees Fahrenheit (-225 degrees Celsius), this planet would be an inhospitable place for humans to visit. Not only is the planet cold, it is dark, making it very unattractive, as compared to the other planets. The brown surface of Pluto is covered with a landscape of ice and rocks. It is 1,455 miles in diameter, and is 67 percent in size of the Earth’s moon.

The atmosphere of Pluto is mostly frozen methane. The light and dark patches seen by the Hubble Space Telescope represent areas of nitrogen and methane respectively. There are also trace amounts of carbon monoxide in Pluto’s atmosphere. It is interesting that Pluto is not a gas planet like its nearest neighbors. This had led scientists to debate whether Pluto is actually a planet at all.

Recently, this has lead astronomers to believe that Pluto was actually similar to the Kuiper Belt Objects. The Kuiper Belt Objects are a group of objects in various sizes that located near to Pluto. Kuiper Belt Objects are actually leftover material from planet formation. Believing that Pluto is a Kuiper Belt Object has helped astronomers rationalize why Pluto is not a gas planet like the nearest planetary neighbors. The 2015 visit to Pluto was also study the Kuiper Belt Objects.

In 2005, the Kuiper Belt Objects was the site of the discovery of another object greater in size than Pluto. It is believed to be a planet with a small satellite orbiting it. This object has been given the designation 2003 UB313, and orbits every 560 Earth years around the Sun.

Scientists have not detected, and do not believe life exists on Pluto.

Pluto Demoted

On August 24, 2006, the International Astronomical Union (IAU) formally downgraded Pluto from an official planet to a dwarf planet. According to the new rules a planet meets three criteria: it must orbit the Sun, it must be big enough for gravity to squash it into a round ball, and it must have cleared other things out of the way in its orbital neighborhood. The latter measure knocks out Pluto and 2003UB313 (Eris), which orbit among the icy wrecks of the Kuiper Belt, and Ceres, which is in the asteroid belt.

(1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.

(3) All other objects except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

The Satellites Of Pluto

Charon

More specifically, the discovery of Charon specifically goes to James Christy of the United States Naval Observatory. He named the main moon of Pluto after the Greek “carrier of the dead,” who was responsible for transporting bodies to “Hades” underground.

Astronomers estimate that the distance of Charon to the surface of Pluto is 11,889 miles. Charon has a diameter of 737 miles (1,186 km). In the beginning, it was believed that Pluto was too small to possess its own satellite, until Charon was discovered in 1978. Further review by astronomers showed that the presence of Charon orbiting Pluto on photograph, dated back as far as 1965.

The surface features of Charon are thought to be similar to Pluto, and covered in water ice. To astronomers, the relationship between Pluto and Charon is unique. Charon is known for its ability to synchronize its orbit with Pluto. Therefore, when standing on Pluto, it would appear that the satellite is not moving in orbit around it, but instead suspended in mid-air.

Nix and Hydra

The other two moons orbiting Pluto are called, “Nix” and “Hydra.” The mythical word “Nix” refers to the “goddess of the darkness and night.” However, the name “Hydra,” is used in mythology to describe a nine-headed serpent.

Nix is the innermost satellite, with the small Hydra located further away from Pluto. Nix and Hydra were discovered in 2005 by scientists from the Southwest Research Institute. They were given the generic names S/2005 P 2 and S/2005 P 1 to refer to these paired satellites, but the scientists were later approved to name the satellites “Nix” and “Hydra.”

Statistics About Pluto

Discovered By	Clyde Tombaugh
Date of Discovery	1930
Average Distance from the Sun	Metric: 5,906,380,000 km English: 3,670,050,000 miles Scientific Notation: 5.90638 x 10⁹ km (39.482 A.U.) By Comparison: 39.482 x Earth
Perihelion (closest)	Metric: 4,436,820,000 km English: 2,756,902,000 miles Scientific Notation: 4.43682 x 10⁹ km (29.658 A.U.) By Comparison: 30.171 x Earth
Aphelion (farthest)	Metric: 7,375,930,000 km English: 4,583,190,000 miles Scientific Notation: 7.37593 x 10⁹ km (49.305 A.U.) By Comparison: 48.481 x Earth
Equatorial Radius	Metric: 1,151 km English: 715 miles Scientific Notation: 1.151 x 10³ km By Comparison: 0.180 x Earth
Equatorial Circumference	Metric: 7,232 km English: 4,494 miles Scientific Notation: 7.232 x 10³ km
Volume	Metric: 6,390,000,000 km³ English: 1,530,000,000 mi³ Scientific Notation: 6.39 x 10⁹ km³ By Comparison: 0.0059 x Earth
Mass	Metric: 13,000,000,000,000,000,000,000 kg Scientific Notation: 1.3 x 10²² kg By Comparison: 0.0022 x Earth
Density	Metric: 2 g/cm³ By Comparison: ~ 0.4 x Earth
Surface Area	Metric: 16,650,000 km² English: 6,430,000 square miles Scientific Notation: 1.665 x 10⁷ km² By Comparison: 0.033 x Earth
Equatorial Surface Gravity	Metric: 0.81 m/s² English: 2.7 ft/s² By Comparison: If you weigh 100 pounds on Earth, you would weigh 8 pounds on Pluto.
Escape Velocity	Metric: 4,570 km/h English: 2,840 mph Scientific Notation: 1,270 m/s By Comparison: Escape velocity of Earth is 25,022 mph.
Sidereal Rotation Period (Length of Day)	6.387 Earth days 153.3 hours By Comparison: One Earth day is 24 hours.
Sidereal Orbit Period (Length of Year)	247.92 Earth years 90,553 Earth days
Mean Orbit Velocity	Metric: 17,096 km/h English: 10,623 mph Scientific Notation: 4,749.0 m/s By Comparison: 0.425 x Earth
Orbital Eccentricity	0.2488 By Comparison: 14.9 x Earth
Orbital Inclination to Ecliptic	17.14 degrees
Equatorial Inclination to Orbit	119.61 degrees By Comparison: 5.10 x Earth
Orbital Circumference	Metric: 32,820,000,000 km English: 20,390,000,000 miles Scientific Notation: 3.282 x 10¹⁰ km By Comparison: 35.505 x Earth
Minimum/Maximum Surface Temperature	Metric: -233/-223 °C English: -387/-369 °F Scientific Notation: 40/50 K
Atmospheric Constituents	By Comparison: Earth's atmosphere consists mostly of N₂ and O₂.
Table 1: Concise statistics on the planet Pluto (N.A.S.A. 2006)

References

Encyclopedia Britannica. "Pluto." 2006. Encyclopedia Britannica Premium Service. 2006 (http://www.britannica.com/eb/article-54307)

National Aeronautics and Space Administration (N.A.S.A). “Pluto: Facts & Figures.” 2006.(http://solarsystem.nasa.gov/planets/profile.cfm?
Object=Pluto&Display=Facts).

Spinrad, Hyron. "Pluto." World Book Online Reference Center. 2004. World Book, Inc. (http://www.worldbookonline.com/wb/Article?id=ar435500).

National Aeronautics and Space Administration (N.A.S.A). “Pluto: Overview.” 2007 (http://solarsystem.nasa.gov/planets/
profile.cfm?Object=Pluto).