Dysnomia (moon)

Dysnomia is a moon.

It orbits a dwarf planet named Eris. This moon is very dark. It is darker than coal.

The moon is mostly made of ice. It was found in 2005. It is the second largest moon of a dwarf planet. Dysnomia stays in a circle around Eris. It takes about half a month to go around once. This moon is a very cool find in space!

Dysnomia is a moon that orbits the dwarf planet Eris.

It is the second largest moon of a dwarf planet. Only Charon is larger. Scientists found it in September 2005.

They used big telescopes in Hawaii to see it.

Dysnomia looks very different from Eris. Eris has a bright, icy surface. Dysnomia has a very dark surface. It reflects only 5% of light. Some say it is darker than coal.

This moon is likely made of mostly ice. Scientists think it formed from a large impact. A big object may have hit Eris long ago. This hit would throw off bits of ice. Those bits then joined to make a moon.

Dysnomia stays in a nearly circular orbit. It takes about 15.786 days to go around Eris. This is about half a month. The moon and Eris are tidally locked. This means they always face each other. In the year 2239, they will eclipse each other. This means one will block the light of the other.

Dysnomia is a fascinating moon orbiting the dwarf planet Eris.

It holds a special place in our solar system. It is the second-largest moon of a dwarf planet known today. Only Charon, the moon of Pluto, is larger. Dysnomia is quite big compared to its home planet. Its diameter is between 24% and 29% of Eris's size. This large size makes it a very important object to study.

Scientists believe Dysnomia formed through a violent event. A very large object may have crashed into Eris long ago. This impact likely threw pieces of material into space. Over time, these pieces gathered together to form a moon. This is a similar way that our own Moon formed. This process also happened to other systems like Pluto and Charon. Such collisions are common among large objects in the Kuiper belt.

Researchers discovered this moon in September 2005. The team used the Keck Observatory in Hawaii. They used a special tool called adaptive optics to see clearly. This system helped them find the moon orbiting Eris. Before it had an official name, they called it Gabrielle. This was a nickname based on a character from a TV show.

In 2006, they gave it the official name Dysnomia.

Dysnomia looks very different from the planet Eris. Eris has a very bright and reflective icy surface. In contrast, Dysnomia has a very dark surface. It reflects only 5% of the visible light that hits it. Some scientists say it is even darker than coal.

This dark color is common for objects of this size. Most of the moon is likely made of ice. Its density is consistent with being mostly icy material.

Even though they look different, the two stay connected. Dysnomia orbits Eris about once every 15.786 days. This is roughly half of a month on Earth. The moon and the dwarf planet are tidally locked. This means they always show the same face to each other. Their orbit is nearly a perfect circle. In the year 2239, they will begin a period of mutual events. During this time, they will take turns blocking each other's light.

Dysnomia is the only known moon orbiting the dwarf planet Eris. It is a significant object in our solar system because it is the second-largest moon of a dwarf planet ever discovered. Only Charon, the moon of Pluto, is larger in comparison. Dysnomia is quite large relative to its parent body, spanning between 24% and 29% of Eris's diameter.

This large size makes the Eris-Dysnomia system an important subject for astronomers studying the outer reaches of our solar system.

Astronomers discovered Dysnomia in September 2005. A team at the W. M. Keck Observatory in Hawaii used a system called Laser Guide Star Adaptive Optics (LGSAO) to find it. This technology helps telescopes see more clearly by correcting for atmospheric blurring. During their observations of the brightest Kuiper belt objects, the team spotted a moon orbiting Eris on September 10, 2005.

Before it received an official name, the discoverers gave it the nickname "Gabrielle" after a character from a television show.

The official name, Dysnomia, was chosen in September 2006. The name comes from the daughter of the Greek goddess Eris. In Greek mythology, Dysnomia represents lawlessness or anarchy. The discoverer, Mike Brown, chose this name to follow the pattern of naming moons after figures associated with their primary body. This follows traditions seen with Jupiter and Saturn. Brown also noted the name shared the same first letter as his wife, Diane, similar to how the name Pluto was partially inspired by the initials of Percival Lowell.

Dysnomia has physical properties that are very different from Eris. Eris has an extremely bright, highly reflective icy surface with an albedo of 0.96. In contrast, Dysnomia has a very dark surface with an albedo of only 0.05. This means it reflects only 5% of the visible light that hits it. Some descriptions suggest its surface is darker than coal.

This dark appearance is a common characteristic for trans-Neptunian objects of this size. Observations from the Atacama Large Millimeter Array (ALMA) helped refine these measurements of its diameter and darkness.

Scientists believe Dysnomia formed through a massive impact. It likely resulted from a collision between Eris and another large Kuiper belt object. Such an impact would throw large amounts of material into space, which then coalesced to form a moon. This mechanism is similar to how the Earth's Moon formed. It is also how other binary dwarf planet systems, like Pluto and Charon, likely began. Such collisions were likely frequent in the history of the Kuiper belt.

The relationship between Eris and Dysnomia is defined by their orbit and gravity. Dysnomia orbits Eris at an average distance of approximately 37,000 kilometers. It completes one full orbit every 15.786 days, which is about half of a month. The orbit is nearly circular, with a low orbital eccentricity of 0.082. Eris and Dysnomia are also mutually tidally locked. This means they always show the same side to one another as they orbit. In the year 2239, they will experience a period of mutual events where they take turns eclipsing each other from the perspective of the Sun.

Research into the mass and composition of these bodies provides deeper insights into the outer solar system. By using Kepler's third law of planetary motion, scientists used Dysnomia's orbit to calculate the mass of Eris. They determined that Eris is 1.27 times more massive than Pluto. While the exact shape of Dysnomia is unknown, its low density suggests it is likely composed mostly of ice. This density is consistent with the mass limits found by ALMA observations. These details help astronomers understand how gravity and collisions shape the dwarf planets of our solar system.