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What Are the Nine Planets?

In addition to Pluto, Ceres, Haumea, and Pluto, our solar system also contains the moon, comets, meteoroids, and asteroids. These objects are also known as the planets. We call them planets because the first letter of each word represents one of these luminaries in our solar system. Each planet’s position in relation to the sun is indicated by the position of the first letter of its name.

Planet Nine

A hypothetical outer-Solar System planet called ‘Planet Nine’ could exist and cause strange gravitational effects in the Solar System. Its gravitational effects could explain why some extreme trans-Neptunian objects cluster together in their orbits, 250 times further than Earth’s. It may even explain the peculiar clustering of orbits of extraterrestrial objects. Here are a few examples of objects that might be orbiting Planet Nine.

The authors calculated 121 possible orbits for the hypothetical Planet Nine and determined the likelihood that each orbit matched the orbit of Earth. They found that the mass of P9 should be 6.2+2.2-1.3 Earth masses and its semimajor axis should lie at 380+140-80 AU. Furthermore, they determined that the orbit should have an inclined angle of 16+-5 degrees from Earth’s orbital plane. However, they did not rule out the possibility that the objects orbiting P9 may be caused by other phenomena.


The definition of a planet has changed several times. While Pluto was once a planet, it was reclassified in 2006 to a dwarf planet along with Eris, Ceres, Makemake, and Haumea. Its new classification has been hailed as a victory of science over sentiment. Many people grew up thinking of Pluto as a planet and were happy that it was finally included in our solar system.

The diameter of Pluto’s largest moon, Charon, is 153 meters. It has four smaller circumbinary moons, Nix, Styx, Kerberos, and Hydra. Its orbit is elliptical and tilted, making it seem somewhat irregular. At its closest, it’s 49.7 AU from the Sun, but at its farthest point, it’s 39 AU.


Despite its low orbit, Ceres has an intriguing surface: the rocky core and an icy inner mantle. It may even contain 200 million cubic kilometers of water, which is more than twice the amount of fresh water on Earth. But, as it is too dim to be seen with the naked eye, it is only visible to those with exceptional eyesight. Ceres makes a complete orbit around Earth every 4.6 years, and makes one full rotation every nine and a half hours.

Scientists believe that Ceres formed 4.5 billion years ago, during the formation of the Solar System. When the planets were first being formed, swirling gas and dust were drawn together by the force of gravity. Scientists believe that Ceres was an embryonic planet that failed to fully develop into a planet due to the gravitational pull of Neptune, and therefore settled in its current location among the fragments of the planetary formation. This discovery made Ceres the eighth planet known at the time.


The rapid spin of Haumea allows scientists to determine its density and its mass. The asteroid is about one-tenth the mass of Pluto and measures 1,430 miles across on its longest axis. At its elongated end, the asteroid is only 619 miles across. Its mass is similar to Pluto’s, but its shape is so elongated that it may not qualify as a dwarf planet.

The orbit of Haumea varies between five and ten degrees, allowing astronomers to determine its mass. Since Haumea orbits the Sun with a high inclination, it is far away from the ecliptic plane. The asteroid is about 1.7 light-years from Earth. Observations at Palomar Mountain Digitized Sky Survey have given scientists a record of the asteroid’s motion from March 22, 1955.


The icy world of Eris is far from the Sun, and its surface is extremely cold. This icy world doesn’t have an atmosphere, but some scientists believe that ices on Eris may convert into gas as the planet approaches the Sun. Eris is one of the nine planets, and it has a density of 2.52 g/cm3. It is believed that the planet may have a liquid ocean under its crust.

The surface of Eris is slightly larger than that of Pluto. It orbits three times farther from the Sun than Pluto does. This distance makes Eris the farthest object ever seen revolving around the Sun. The planet’s orbital distance makes it similar to Russia. But Eris is so far away from the Sun that its gravity is 11 times weaker than Earth’s. It has a moon about ten times closer to Earth than the Moon. This moon is named Xena after the warrior princess from the television show.


The fifth and largest planet in the solar system, Jupiter is composed mostly of hydrogen and helium and is about 1,300 times larger than Earth. The gas giant has a thick atmosphere that is rich in both hydrogen and helium. Jupiter’s surface is very hot and its interior is extremely cold, making it one of the hottest planets in the solar system. Jupiter’s atmosphere is also very unstable, with violent storms affecting the surface.

The distance between the sun and the planets depends on their orbit around the sun. The planets orbit their sun in elliptical paths that are not perfect circles. Jupiter is the largest planet in the solar system, with twice the mass of the other nine planets. It has colorful swirling clouds that are due to the various trace gases it contains. It is a fascinating planet to observe, and one of the most famous in the solar system.


Saturn is one of the nine planets in the Solar System. The planet’s average distance from the Sun is 1.4 billion kilometers (9 AU), and its orbital speed is 9.68 km/s. It takes the planet 10,759 Earth days to complete one orbit around the Sun. The planet’s orbit is elliptical and its perihelion and aphelion distances are 9.195 AU and 9.957 AU, respectively. It has a mean-motion resonance with Jupiter, which is near 5:2 with Saturn.

Saturn is the sixth planet from the sun. It is a gas-giant planet that orbits the sun once every 29 Earth years. It does not have a solid surface, but its atmosphere is composed mainly of hydrogen. Its atmosphere is approximately 75% hydrogen and consists of numerous moons. Saturn also has seven rings around its body, which range in size from a dust speck to 10 meters.


Known by two names, Uranus and Neptune, the seventh planet from the Sun is the third largest in our solar system. The first planet discovered by a telescope was Uranus, which was initially thought to be a comet or star. But in 1782, it was universally recognized as a planet after observations by Johann Elert Bode. Then, the name Neptune was coined.

It was believed that Neptune and Uranus were created much closer to the sun. Then, the dust and gas from these bodies eventually merged to form proto-planets. The planets eventually accreted enough gas to form their solid surfaces. Scientists believe they formed between 4.5 and four billion years ago. Nonetheless, their exact formation and drifting dates are uncertain, but most astronomers are sure they were closer to the sun at the time.


Like its sister planet, Uranus, Neptune has a dense, dark soup of ammonia, water, and methane at its core. It is so far from the Sun that its atmosphere is composed of hydrogen, helium, and methane. It also has six bands of cloud, known as nebulosae, that cast shadows on the lower cloud deck.

The Kuiper Belt, a ring of frozen objects that extends from 30 to 55 times the distance of Earth from the Sun, is home to dozens of moons and comets. The Kuiper Belt may contain hundreds of thousands of comets and icy bodies. Despite its small size, Neptune’s orbit has a significant impact on this region of space. The Kuiper Belt contains several dwarf planets, as well as other icy bodies.

Pluto, discovered in 1930, was thought to be the eighth planet in our solar system. But when it crossed Neptune’s path on Feb. 11, 1999, the scientific community redefined Pluto as a dwarf planet. Despite its small size and tenuous atmosphere, Pluto is a cold, rocky world. Many scientists believed that it was nothing more than a hunk of rock in the outer reaches of our solar system. But NASA’s New Horizons spacecraft performed its first flyby of Pluto’s system on July 14, 2015.