If we were to count all of the planets in our solar system, we would come up with about 86. Jupiter is the largest planet in the solar system, followed by Saturn, Uranus, and Neptune. But what about Pluto, Eris, and Ceres? These two planets are also considered as the smallest. We also have a very small number of undiscovered planets, such as Haumea.
Pluto
While the solar system is full of giant planets, Pluto is just one of many icy moons. Pluto has five moons, the largest of which is named Styx. It is approximately 6 miles (10 km) wide and is a double lobed sphere. Both Pluto and Xena are leftovers from the formation of the solar system. Pluto and Xena are not considered to be planets, but their discovery has caused a debate over their status.
While Earth has rings, Pluto is a bit different. Pluto’s surface is covered in methane ice, and scientists have studied the differences in how the ice reflects sunlight. The ice on Pluto looks like snake skin, and the penitentes on Earth are only a few meters tall. Both planets have dark streaks on their surface. Using NASA’s website, you can view Pluto in its entirety. You can also observe dark streaks on its surface, several miles long and oriented in one direction. This might be caused by harsh winds that blow across the surface of Pluto.
Although the name Pluto is unofficial, it does represent a historical figure. It was first named by a schoolgirl in Oxford, England, who had an interest in Roman mythology. Her grandfather subsequently passed the idea to the Lowell Observatory. Her suggestion was adopted and the name Pluto was officially given on March 24, 1930. In addition to Pluto, the two moons Nix and Styx were named after her grandfather.
In 2006, Pluto was downgraded from planet status. This was widely perceived as a demotion, which caused a debate in the scientific community and the public. In 2017, the scientists behind the New Horizon mission proposed a new definition of planethood, which would include rounded objects in space smaller than stars. By expanding the definition of planethood, scientists could recognize more than eight planets in the solar system.
Eris
Eris is a dwarf planet that orbits the Sun in an eccentric orbit. The distance it travels around the Sun is about seventy-five astronomical units (AU), which is about two-thirds the distance between Earth and the Sun. Light from Eris travels nine hours from the Sun, making it the smallest planet in our solar system. Its orbit takes 557 Earth years to complete, making it smaller than the Moon.
Eris is about 1,445 miles in diameter and has one moon, named Dysnomia. It takes sixteen Earth days to complete its orbit around the star. Eris was considered to be a tenth planet once, but the recent reclassification of its size has changed that opinion. Eris now possesses enough mass to surpass Pluto, but the ice mantle on Eris makes it much less dense than Pluto. Its surface is highly reflective, reflecting 96% of light.
It took a team led by Mike Brown to discover Eris in 2003. Its discovery caused some controversy within the scientific community, so the IAU clarified what makes a planet. Hence, Eris is now classified as a dwarf planet. Eris’ name has also been changed to Xena, which was used internally by the discovery team. Its name is also a reference to the character Xena in the television show.
Because Eris is so far away, astronomers could only study it when it passed in front of a dim star. This is known as an occultation. This happened only once every five years. It is believed that this occultation is the most frequent occurence in our solar system. So, there are currently seven planets in our solar system. So, what does this discovery mean for Earth?
Ceres
The asteroid belt is the region of space where many of the largest celestial objects were likely to hit, but Ceres’ low density means it was spared from impact damage. While it resembles a typical asteroid, Ceres’ location in the belt suggests it may have developed inside its own unique region without interfering with the main belt. There is a strong possibility that a large body like Ceres landed on Ceres during the last 50 million years and later spewed ammonia.
Ceres was designated a dwarf planet by the International Astronomical Union (IAU) in August 2006. The U.S. space probe Dawn studied Ceres from March 2015 to November 2018. Two bright spots on Ceres, Cerealia Facula and Vinalia Faculae, are reflective salts that form in the crater’s interior. The water from the underground reservoir percolated upward from cracks left by the crater 20 million years ago. Micrometeorite impacts did not darken the salty areas, and thus the bright spots have only recently formed.
Ceres was born in the Solar system around 4.5 billion years ago. Scientists believe that the asteroid was formed in a planetary embryo, but did not fully develop into a planet. It may have formed in the outer solar system, where ammonia is more plentiful and did not get vaporized by the Sun. In any case, it probably migrated toward the Sun via gravitational influences.
A second debate surrounds the definition of a planet. In 2006, the International Astronomical Union attempted to settle the debate, defining a planet as a body with mass that can overcome rigid body forces. The proposal made Ceres the fifth planet from the Sun, but created complications. A proposal of the IAU definition would have allowed Ceres to be categorized as a planet, but it was rejected by most astronomers.
Haumea
In the solar system, Haumea is a dwarf planet with a very bright surface. The surface is covered with a thin layer of crystalline water-ice. The surface of Haumea is extremely cold. In addition to the ice, the planet is also made up of rock. Its composition is unclear, but it’s possible that the planet is mainly made of rocky material covered in an icy shell.
Despite its size, Haumea is very tiny compared to other planets. It’s only about one-third the mass of Pluto, and is just over two-hundred and forty-two kilometers wide. Its size, however, makes it an intriguing subject for exploration, as three of these tiny worlds could fit side-by-side on Earth. Unlike its larger neighbors, Haumea is a highly unusual candidate for life, but it’s still a fascinating body to study.
The name ‘Haumea’ comes from the Hawaiian goddess of childbirth and fertility, Haumea. Its two moons are named Hi’iaka and Namaka, respectively, and are each around a hundred kilometers in diameter. Haumea’s orbital eccentricity is believed to have a result of a previous impact. The planet itself and its moons are roughly 43 astronomical units from the sun, which is a significant distance for a planet.
The dwarf planet Haumea was first discovered in 2004, and it was officially designated as a dwarf planet in 2008, allowing for better study of its structure. It orbits the Sun every 283 Earth years. Its orbit is elliptical, causing its elongated shape to stretch out like a water balloon when spun. It’s one of the densest dwarf planets in the solar system and was named after a Hawaiian goddess of childbirth.
Makemake
The distance to Makemake from the Sun is about 4,253,000,000 miles (6,847 million kilometers) and it is the second closest planet to Earth. Makemake is about 305 Earth years away, and sunlight travels to the planet in six hours and twenty minutes. Makemake completes one rotation around the Sun every 22 and a half hours, making it similar in length to Earth. The moon, nicknamed MK 2, is about 100 miles in diameter. It is also slightly brighter than Makemake itself, taking about six hours and 20 minutes to travel to it from the Sun.
The discovery of Makemake was made possible thanks to the discovery of two dwarf planets in the solar system. One of these planets, Haumea, is named for the creator god of the Rapa Nui, the natives of Easter Island. The other two planets of Haumea share their names with the Hawaiian goddess of fertility and childbirth. It’s unknown what influenced the names of these planets, but the Rapa Nui have associated them with Easter.
Makemake is the second brightest object in our solar system after Pluto. It is only slightly smaller than Pluto, but it is two-thirds the size of dwarf planet Eris. It is also significantly closer to the sun than Pluto, and it takes 310 Earth years to orbit the Sun. If it was a planet, it would be bigger than Makemake. Makemake is believed to have satellites, but there’s no solid evidence that they are life-sustaining.
A flyby through Makemake’s Kuiper Belt has aided scientists in studying the icy celestial objects in the trans-Neptunian disc. Although it may have a small atmosphere, the icy surface of the planet prevents life from developing. So it’s a waste of time to try to find life on Makemake. This is a futile quest. It may exist, but it’s not likely.