Charon

The mission concept used a conventional chemical rocket to launch the spacecraft and a Jupiter gravity assist to send it toward the outer solar system, then switch to electric propulsion for the long, slow deceleration as it approached the Pluto system.

The study found that the spacecraft could enter orbit around Pluto and conduct a comprehensive survey of the entire system, including close-up studies of Charon and the four smaller moons, Nix, Hydra, Kerberos and Styx.

An orbiter could observe Pluto through all seasons and lighting conditions, map the entire surface at high resolution rather than the single hemisphere New Horizons captured, monitor weather patterns and atmospheric changes over years, and study how nitrogen ice migrates across the surface in response to the faint but measurable cycle of Pluto's seasons.

The scientific return from an orbiter would be comparable to what Cassini achieved at Saturn, or what the Mars Reconnaissance Orbiter continues to achieve at Mars.

The travel time to Pluto alone, using the slow, fuel-efficient electric propulsion trajectory, would be measured in decades rather than the nine and a half years New Horizons achieved.

The spacecraft would spend years decelerating as it approached, trading speed for the ability to stop, and even after entering orbit, the low-thrust propulsion system would need years more to maneuver through the Pluto system.

Using a combination of electric propulsion burns and gravity assists from Charon to change its orbital parameters, the Charon assist concept is one of the study's most innovative ideas.

Charon, Pluto's largest moon, orbits at a distance of roughly 12,000 miles from Pluto, with an orbital period of about six and a half days.

Its surface is a patchwork of nitrogen ice, methane frost and carbon monoxide ice, sculpted by processes that scientists are still working to understand.

It has five known moons, the largest of which, Charon, is so big relative to Pluto that the two orbit a common centre of gravity located in empty space between them.

The Pluto-Charon system is sometimes described as a binary world rather than a planet and moon, a gravitational partnership unique among known solar system bodies.

But Pluto is not the only dwarf planet in the Kuiper belt.

Eris, discovered in 2005, has a diameter of approximately 2,326 kilometres, making it almost the same size as Pluto, though slightly more massive.

The atmosphere inflates and deflates over centuries, rising and falling like a slow cosmic breath.

At its most distant orbital point, the atmosphere may collapse almost entirely, freezing out onto the surface as a thin frost.

Charon, Pluto's largest moon, presented its own set of revelations that proved almost as scientifically disorienting as the discoveries on Pluto itself.

Then, in 1978, astronomers discovered that Pluto had a companion, a large moon, roughly half Pluto's own diameter, orbiting so close that the two bodies are effectively a double system.

The moon was named Charon after the ferryman of the dead in Greek mythology, and its discovery immediately complicated the simple picture of Pluto as a lonesome drifter.

This was not just a rock with a rock orbiting it, this was a gravitationally locked pair, tidally bound so that the same faces always point toward each other, spinning together through the darkness like two dancers frozen in position.

In the decades that followed, astronomers discovered four more tiny moons, detected hints of an atmosphere through stellar occultation measurements and began to suspect that the surface contained exotic ices frozen solid at temperatures that defy human experience.

What it could not do is watch Pluto change.

It could not measure the thermal glow of the surface and atmosphere in the mid-infrared wavelengths where heat radiation reveals temperature variations across the globe.

It could not separate Pluto's faint thermal signal from Charon's at those wavelengths because the two bodies are so close together and so far from Earth that their infrared emissions blend into a single unresolved source for any instrument operating from near-Earth space.

It could not observe the haze over time to determine whether those organic particles were actively heating and cooling the atmosphere or merely floating passively in the sky.

It's got at least five.

But its biggest moon, called Charon, or Charon, or Charon, or C- there's about 15 ways to say it.

Uh-huh.

But Pluto's biggest moon doesn't technically, and we're getting into real technicality here, but this is why, this is what underpinned this vote.

So for all intents and purposes, practically speaking, the Moon goes around Earth.

But strictly speaking, it doesn't.

This shared point in space between Pluto and its largest moon, Charon, is actually physically outside Pluto, and that, the reason for that is because where two objects orbit each other is a, is a kind of a trade-off of how big they are and how far apart they are, and Charon's pretty big as moons go.

It's actually s- it's actually the largest moon to a larger primary, uh, i- in the solar system.

Pluto is small, only about one thousand four hundred seventy-three miles across, but it's fascinating.

It has five known moons, the largest being Charon, which is about half Pluto's size.

Pluto and Charon are so close in size that they're sometimes called a binary system.

They orbit a point in space between them rather than Charon simply orbiting Pluto.

NASA's New Horizons spacecraft flew past Pluto in July twenty fifteen, giving us our first close-up views.

The images revealed a complex world with mountains made of water, ice, vast plains of frozen nitrogen, and a thin atmosphere that extends much farther than expected.

As time went on, our ability to measure the cosmos advanced.

In 1978, Pluto's moon, Charon, was discovered.

By observing how Charon and Pluto orbited their common center of gravity, scientists could finally determine Pluto's exact mass.

Wait, if Pluto's mass is tiny, its gravitational pull is negligible.

Exactly.

Uh, it's about half the size of Pluto, actually.

It's called Charon, uh, or Charon, not Sharon.

Some people call it Sharon.

They do.

[laughs]

[laughs] Charon.

Uh-

Char's for short.