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Top Ten Moons

Updated on March 7, 2013



Galilean Moons

Family portrait of Galilean satellites
Family portrait of Galilean satellites

If a celestial object circles the Sun with a fixed period, it is called a Planet. If it circles a Planet, then it is called a Moon or satellite. Do you think moons are smaller objects? There are moons in the solar system which are larger than the planets Mercury and Pluto. There are moons with volcanoes and atmospheres. Neither Mercury nor Venus has any moons. Moons are also exciting objects to study. There are more than 170 known moons in our solar family. Here we introduce the top ten moons.

Italian astronomer Galileo Galilei discovered the four largest moons of Jupiter in 1610. This was the first time a moon was discovered orbiting a planet other than Earth. To honour Galileo, they are called the Galilean satellites. They were named as Io, Europa, Ganymede and Callisto. Ganymede is the largest moon in the solar system. It is interesting to note their orbital period (time to go around Jupiter once). Every time Ganymede circles Jupiter once, Europa makes two orbits and Io circles Jupiter four times. Like our Earth’s moon, the moons all show the same face towards Jupiter as they orbit. Is it possible that Moon is rising in the West and sets in the East? Some moons orbit Jupiter in the opposite direction from the planet's rotation. If you were in Jupiter, you could observe a quite number of moons rising in West and apparently moving towards East to set! There are about 64 moons in Jupiter’s sky including 14 ‘new’ moons (provisional moons) waiting to be named.

Shapes of moon need not be round. Mars has two odd shaped moons, Deimos and Phobos. They are small in size resulting weak gravity. Due to its small size and weak gravity, they cannot evolve into the round shape. Every hundred years it moves almost two meters closer to the surface of Mars. One day it will either crash into the planet or break up into pieces forming a ring around the planet. Phobos and Deimos always present the same face to Mars like our moon. In future Scientists may land on these moons to study the planet Mars.

So far 63 moons of the planet Saturn have been discovered including 9 new moons waiting to be named. In 1655, Christian Huygens discovered Titan, the first known moon of Saturn. It is the second largest moon in the solar system. Titan probably has a layer of liquid water under an icy shell. Sixteen of Saturn's moons keep the same face toward the planet as they orbit. Is it possible to have a moon which is neither rising nor setting? If you were in Saturn’s land you could see four fixed moons on Saturn’s sky. Four moons orbit in stable places around Saturn called Lagrangian points. The Cassini spacecraft examined salty water with organic compounds in jets from Saturn's icy moon Enceladus.

The moons of Uranus are paying homage to the famous playwright William Shakespeare who appreciated moon through his characters. They are named as Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Oberon, Titania, Umbriel, Ariel, Miranda. Because Uranus is far away in our solar system, it is very difficult to see the smaller moons of Uranus. When the spacecraft Voyager 2 visited the Uranus area in 1986, a good number (ten) of smaller moons were discovered. There are 27 known moons circling Neptune. Earlier Uranus was observed as a star as it appeared to blink out briefly several times. The blinking mystery was solved by identifying the rings blocking the starlight. Like Saturn, Uranus encircled with a band of (fifteen) rings. Do you know who is keeping these rings intact? Some of the smaller moons like Cordelia and Ophelia are responsible for shepherding those rings. These Shepherd moons orbit at the edges of the rings, and keep any dust or ice from escaping. In this area, there are eight small moons moving close by and it is a wonder how they manage not to collide each other.

Uranus' moon Ariel (white dot) and its shadow (black dot) crossing the face of Uranus
Uranus' moon Ariel (white dot) and its shadow (black dot) crossing the face of Uranus | Source

Just 17 days after a Berlin observatory discovered Neptune, a beverage and amateur astronomer, William Lassell discovered its largest moon Triton. This is the only large moon in the solar system that has a retrograde orbit. Due to this negative effect,Triton is slowly getting closer to Neptune's surface. After a very long time, this moon may crash into Neptune or break up into pieces joining the ring around the planet. There are 13 moons orbiting Neptune.

My top ten moons

  1. Triton
  2. Cordelia
  3. Ophelia
  4. Titan
  5. Deimos
  6. Phobos.
  7. Io
  8. Europa
  9. Ganymede
  10. Callisto

Which is the top most moon you think?

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