Celebrating 40 years of Pluto’s largest moon, Charon

Charon is more than 40 years: An enhanced-color image of Charon from the New Horizons shows a variety of features, far more detailed than the in 1978, the inset image with the small bump that marked the existence of a moon.

(U. S. Naval Observatory/NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

Today, Pluto is known to sport five moons. The most massive companion, Charon, the largest moon in the solar system relative to its parent body. This moon is so big that Pluto and Charon to be classified as a binary planet system. Yet, 40 years ago, scientists didn’t even know that Charon exists.

In 1978, James Christy was using the telescope at the U. S. Naval Observatory in Arizona to refine Pluto. On 22 June, the astronomer saw a small bump on the side of the distant planet. When he examined also other statues, he observed that the point from one side to the other, cycling back and forth over Pluto 6.39-day rotation period. He thought that Pluto has a natural satellite, or on a huge mountain that towers thousands of kilometers above the surface of the planet.

Christy combed by the observatory image archives for the measure of the angle where the strain has appeared. At the same time, his colleague Robert Harrington, also at the Naval Observatory calculated what the rack should be if the bulge was a moon. Their calculations matched, but the two researchers wanted to be sure. On July 2, 1978, new images showed the rack where it should be if the function is for a moon instead of a mountain. Christy and Harrington announced the discovery five days later. [Pluto and Charon Shine in the Most Detailed Topographic Maps Ever]

Decades later, Charon’s size and proximity helped the press for the sending of NASA’s New Horizons mission to Pluto.

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“The importance of the discovery of Charon really should not be underestimated,” Alan Stern, New Horizons principal investigator from the Southwest Research Institute in Boulder, Colorado, said in a statement.

“We are on the New Horizon team owe a great debt of gratitude to Jim and Christy for his landmark discovery,” Stern said.

Gives his wife the moon

By tradition, the discoverer of a moon and a suggestion for a name for the International Astronomical Union (IAU). Christy wanted to name the moon after his wife. Although her full name is Charlene, family and friends call her “Char.” Because he had been thinking about protons and electrons, Christy added a “- ” and submitted the new name.

While waiting for the proposal to be approved, Christy checked in the dictionary. To his surprise, he found that Charon was the name of the mythological ferryman who the souls across the river Acheron, one of the mythical rivers around Pluto the underworld. The astronomer knew that the name was a perfect fit for Pluto’s companion.

“Many of the men promise their wives the moon,” Charlene Christy said, “but Jim is actually delivered.”

Charon revealed

When the New Horizons spacecraft flew by Pluto on 14 July 2015, the probe revealed that Charon was an incredible world of its own. New Horizons researchers expect a monotonous world battered by craters. Instead, the spacecraft has revealed gigantic mountains, vast canyons, red polar cap, landslides, and surface color variations.

“Even if Pluto wasn’t there, Charon would have been a great flyby goal in itself,” Grundy, a New Horizons science team co-investigator of the Lowell Observatory in Flagstaff, Arizona, said in the statement. “It is a much more exciting world than we thought.”

Charon is drawn through a canyon four times as long as the Grand Canyon and twice as deep as possible in different places. The gaps point to a titanic geological upheaval in the Charon’s early history. They also show us tips on what’s beneath the surface, researchers said.

“Massive tectonic belt tells us Charon probably had an ocean below the surface, and if the ocean is frozen, the ice would expand and crack the surface,” Cathy Olkin, New Horizons deputy project scientist from the Southwest Research Institute in Boulder, said in the statement. “This is an important finding, especially in light of the increasing scientific interest in the ocean worlds in the solar system.”

Charon the north pole is coloured red. Methane gas escaping from Pluto comes and pulls the south pole of the moon is the force of gravity, where it freezes. Ultraviolet light from the sun changes the methane into heavier hydrocarbons, and finally to red organic material known as tholins.

“Who would have thought that Pluto is a graffiti artist, spraying his companion with a red patch that covers an area the size of New Mexico?” Grundy said.

For Jim Christy, the 40-year evolution of the view of Charon from a small dot connected to Pluto on a world in its own right is great.

“When you go from this small blur in which you don’t actually see anything in huge detail New Horizons sent back, it is unbelievable,” he said.

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