Styx (moon)

Styx, also called (134340) Pluto V, is a tiny moon that goes around the dwarf planet Pluto. It was found in 2012 using the Hubble Space Telescope. It is the smallest of Pluto's five known moons. Scientists saw Styx when the New Horizons spacecraft flew by Pluto in 2015 and took pictures of Pluto and its moons.

Styx is very small, about 16 kilometers (9.9 miles) across at its widest point. It is the second moon closest to Pluto and takes about 20.1 days to go around Pluto once. Styx was discovered one year after another moon called Kerberos.

Discovery and observations

Styx was found by a team led by astronomer Mark R. Showalter. They used images from the Wide Field Camera 3 on the Hubble in June and July 2012. The discovery was announced on 11 July 2012. Styx is much smaller and dimmer than Pluto and even Pluto’s smallest moons.

The discovery happened while getting ready for the New Horizons spacecraft to fly by Pluto on 14 July 2015. Finding another small moon around Pluto made people worry that more tiny objects might be there, which could be dangerous for the spacecraft. But New Horizons safely flew through the area without finding any extra moons or rings.

Origin

Pluto has moons that might have formed after Pluto crashed into a big object in space long ago. These moons could have come from the pieces left after the crash, just like how Earth’s Moon may have formed from an old crash. The way the moons move around Pluto might have helped collect the pieces.

Physical characteristics

Styx was first thought to be between 10 and 25 kilometers wide. Later, scientists measured it to be about 16 kilometers long, 9 kilometers wide, and 8 kilometers tall. Scientists believe Styx formed from pieces left after a collision. This likely left mostly water ice behind.

Orbit

Animation of moons of Pluto around the barycenter of Pluto – Ecliptic plane

Front view

Side view

   Pluto ·    Charon ·    Styx ·    Nix ·    Kerberos ·    Hydra

Styx orbits the Pluto–Charon barycenter at a distance of 42,656 km. It sits between the orbits of Charon and Nix. All of Pluto's moons travel in orbits that are almost circular and lie in the same plane.

Its orbital period is 20.16155 days. Together with the moons Nix, Kerberos, and Hydra, Styx helps create an unusual pattern of orbits. Styx's rotation changes quickly.

Naming

Before Pluto's moons were found, a writer named Edmond Hamilton mentioned three moons of Pluto in his 1940 science fiction book. He named them Charon, Styx, and Cerberus.

When Styx was found, it got the minor planet designation S/2012 (134340) 1 because it was the first moon found around Pluto in 2012. It's often called "P5," meaning it was the fifth moon of Pluto to be found.

Names for Pluto's moons come from stories about the god Pluto in old classical mythology. In 2013, people were asked to vote online for names for two of the newly found moons. Actor William Shatner, famous for playing Captain James T. Kirk in Star Trek, suggested the names Vulcan and Romulus. Vulcan won the vote, but it couldn't be used. On 2 July 2013, the group that decides on space names officially chose Styx as the name for P5.