How many dwarf planets have been discovered

To illustrate this disruption, Eris was named after the Greek goddess of discord. Since Eris is so far away, no surface details can be seen with current instruments, but astronomers have detected the presence of methane ice and believe Eris's surface is similar to that of Pluto.

A view of the dwarf planet Ceres located in the asteroid belt between the orbits of Mars and Jupiter taken by the Dawn spacecraft in Ceres is the largest object in the asteroid belt between the orbits of Mars and Jupiter. This dwarf planet alone contains about a third of all the matter found in the belt! Its near-spherical shape means that this rocky, icy body is not considered an asteroid.

While most dwarf planets orbit the Sun at the very outer edges of our solar system, Ceres is the only one located inside the orbit of Neptune. It takes Ceres 4. Scientists suspect that this unique dwarf planet may even have an ocean of liquid water hidden under a layer of ice. NASA 's Dawn spacecraft was launched in and entered into orbit around Ceres after first observing nearby asteroid Vesta. Dawn allowed astronomers to see detailed images of the dwarf planet for the first time and find out more about its composition and surface.

An artist's representation of the dwarf planet Makemake and its moon MK2. Parker SwRI. Whereas Vanth has a reddish hue common to Kuiper Belt objects, Orcus has a much lighter surface with signs of water ice. Is this system a slightly smaller version of the Pluto-Charon system? Or are these worlds something else entirely? Only a higher-resolution view will reveal the truth. Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

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Dave's Universe Year of Pluto. Groups Why Join? Astronomy Day. Dwarf planets are worlds that are too small to be considered full-fledged planets, but too large to fall into smaller categories. In recent years, there's been a lot of hubbub about Pluto losing its status as one of the planets of the solar system. Pluto is no longer considered the ninth planet in the series of major planetary objects, but instead is now just one of the many so-called "dwarf planets.

As of , delegates from the mission are trying to get Pluto's planethood status back. Astronomers estimate that there could be as many as dwarf planets in the solar system and the Kuiper Belt. But the differences between planets and dwarf planets may not be obvious at first. The International Astronomical Union defines a planet as being in orbit around the sun, has enough gravity to pull its mass into a rounded shape hydrostatic equilibrium , and has cleared its orbit of other, smaller objects.

This last criterion is the point at which planets and dwarf planets differ. A planet's gravity either attracts or pushes away the smaller bodies that would otherwise intersect its orbit; the gravity of a dwarf planet is not sufficient to make this happen. But those aren't the only ones. Other solar system bodies that are possibly dwarf planets include Sedna and Quaoar , small worlds far beyond Pluto's orbit, and VP , an object that is thought to have one of the most distant orbits found beyond the known edge of our solar system.

The object DeeDee could also be a dwarf planet , according to observations made in According to NASA , scientists think that there may be more than a hundred dwarf planets awaiting discovery.

However, the debate over the status of dwarf planets, particularly Pluto, remains a hot topic. Since the new definition, three objects in our solar system have been classified as dwarf planets: Pluto, Ceres and Eris. For 76 years until , Pluto was known as the ninth planet in our solar system.

Since then, Pluto has been relegated to dwarf planet status. Discovered in , Pluto is a member of the outer region of our solar system known as the Kuiper belt. It has a highly inclined and eccentric year orbit around the Sun. As the second-largest known dwarf planet, Pluto is approximately 2, km in diameter and is composed primarily of ice and rock. It is very difficult to precisely determine the diameter of Pluto since it is so far away. Pluto is, on average, 40 times farther from the Sun than Earth.

The New Horizons spacecraft, scheduled to arrive at Pluto in , will be able to provide us with more accurate measurements of Pluto. Pluto's surface is made almost entirely of nitrogen ice, with traces of methane and carbon monoxide. Pluto has a thin atmosphere made of the same components of its surface: nitrogen, methane and carbon monoxide.

Like a comet, Pluto's atmosphere freezes as it moves away from the Sun and the ices sublimate as it approaches the Sun. In , the discovery of Pluto's largest moon, Charon, gave scientists an opportunity to learn more about Pluto.

The two icy objects eclipsed each other from Earth's point of view from allowing scientists to more precisely determine their diameters and masses.