On December 18, 1966, astronomer Richard Walker observed a moon between the rings of Saturn. However, three days before this, i.e. on 15 December, a scientist named Oduin Dolphus had also seen a moon near Saturn and named it ‘Janus’. Three days later, Walker described the moon he saw as different from Janus.
The scientists of that time considered both of them as one, because both were in the same orbit. At that time scientists believed that there was only one moon, which was called ‘Janus’. Later, Walker’s discovery was found to be different. That means it was not ‘Janus’ but Saturn’s second satellite ‘Epimetheus’.
After 12 years, Walker got the credit for the discovery of Epimetheus.
Twelve years later, in 1978, Stephen M. Larson and John W. Fountain discovered that these separate reports from 1966 actually indicated the existence of two separate moons, Janus and Epimetheus. In 1980, the Voyager-1 spacecraft confirmed this and it was determined that the two moons remain close to each other in a particular orbital coordination. Later, Richard Walker, Lars and Fountain were credited with the discovery of Epimetheus.
Orbit and co-orbital position of Epimetheus
Both moons, Epimetheus and Janus, orbit Saturn at a distance of about 94,000 miles (151,000 kilometers). Their orbital period is 17 hours. Interestingly, these two moons, despite being very close to each other, are in “co-orbital” or 1:1 resonance, with their orbits differing by about 50 kilometers, causing them to rotate rapidly every 4 years. The moving moon approaches the slower moving moon. During this, due to the force of gravity both change their orbits. They come as close as 15,000 kilometers (about 6,200 miles) apart. This amazing phenomenon has not been seen anywhere else in the solar system.
Structure and features
Epimetheus is shaped like a “potato”, with an average diameter of 58 kilometers. There are several large craters on the moon’s surface, such as “Hilaira” and “Pollux,” which are more than 30 kilometers in diameter. There is an apparent flattening of the surface due to a large crater at the south pole of Epimetheus.
Saturn’s two moons were formed by the breakup of one of its satellites.
Scientists believe that Epimetheus and Janus may have been formed by the breakup of the same moon. This event must have happened in the early days of the Saturn system. The surface of both of them is ancient and dusty. From the cracks and grooves present on the surface of Epimetheus, it seems that it may have been slightly impacted by external bodies.
This moon is believed to be mainly made of water ice. Its density is less than 0.7, indicating that it is a “rubble pile”, or a collection of loose pieces held together by gravity. Dark and bright areas have also been observed on its surface. The bright areas are probably water ice, while the dark areas are caused by dust falling down the slopes.
Dust ring in the orbit of Epimetheus
A faint dusty ring has also been found in the region between Janus and Epimetheus, called the “Janus/Epimetheus Ring”. It is believed that this ring is made of particles released from the surface of these moons due to the collision of meteorites.
Mythology related to naming
Saturn’s moons are named after characters from Greek mythology. Epimetheus is named after the Greek god “Epimetheus”, who symbolizes “hindsight” or looking back. He was the brother of Prometheus (Foresight or Foresight). Craters on Epimetheus are also named for characters from Greek mythology, such as “Hilaira” and “Pollux.”
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This moon of Saturn is an important part of the solar system
Epimetheus, like Saturn’s other moons, is a unique and fascinating celestial body. Its co-orbital position, unique structure and pristine surface make it special for scientific research and space missions. Spacecraft like Cassini have given us new information about this small but exciting moon by taking close-up pictures of it. This moon helps us understand the past of the solar system and the mysteries of the Saturn system.
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major events
On 18 December 1271, Mongol ruler Kublai Khan named his empire Yuan. With this the Yuan dynasty started in Mongolia and China.
On December 18, 1642, marine explorer Tasman landed on New Zealand soil. The sea surrounding New Zealand is known as the Tasmania Sea.
Japan took membership of the United Nations on 18 December 1956.
December 18, 1787 – New Jersey became the third state to accept the US Constitution.
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