Group B Dwarf Planets

Dwarf planets are a little different from normal planets because well there a lot smaller,now the most common dwarf planet is pluto but theres 3 more so far.
•Makemake and Haumea

Pluto is the only dwarf planet to once have been considered a major planet. Once thought of as the ninth planet and the one most distant from the sun, Pluto is now seen as one of the largest known members of the Kuiper belt, a shadowy disk-like zone beyond the orbit of Neptune populated by a trillion or more comets. Pluto was reclassified as a dwarf planet in 2006, a change widely thought of as a demotion that has attracted controversy and debate.

The diameter of Pluto is only 2,390 km across. Just for comparison, that’s about 70% the diameter of the Moon. And it’s a fraction of the size of the Earth; about 18% of the Earth’s diameter.

In terms of volume, Pluto only has 6.39 x 109 km3. That sounds like a huge number, but it’s only 0.59% of the volume of the Earth. In other words, you could put almost 170 objects the size of Pluto inside the Earth.

The mass of Pluto is 1.3 x 1022 kg, which is only 0.2% the mass of the Earth, or 18% the mass of the Moon. Needless to say, Pluto doesn’t have very much mass at all.

The surface area of Pluto is 1.67 x 107 square kilometers. That’s only 3.3% the surface area of Earth, and about the same surface area as Russia.

If you could stand on the surface of Pluto, you would experience only 6.7% the gravity you enjoy on Earth.

With a diameter of about 975x909 km, Ceres is by far the largest and most massive (9.5 x1020 kg) body in the asteroid belt, and contains approximately a third of the mass (0.2 x1021 kg) of all the asteroids in the solar system. However, it is not the largest solar system object besides the Sun, planets, and their moons. Larger bodies have been found in the Kuiper belt including Pluto, 50000 Quaoar, 90482 Orcus, 90377 Sedna, and Eris. Recent observations have revealed that Ceres is nearly spherical in shape, unlike the irregular shapes of smaller bodies with less gravity. Having sufficient mass for self-gravity to overcome rigid body forces is one of the requirements for classification as a planet or dwarf planet.
German mathematician Karl Friedrich Gauss calculated from Piazzi's few observations that Ceres circled around the Sun once every 4.6 years or about 4 years, 220 days. Its true sidereal period is 1679.819 days. Ceres has a very small axial tilt of 4±5 degrees.

Ceres has a very primitive surface and like a young planet, contains water-bearing minerals, and possibly a very weak atmosphere and frost. Infrared observations show that the surface is warm with a possible maximum temperature of 235 K (-38°C). Ceres ranges in its visual brightness magnitude from +6.9 to +9.. At its brightest point it is just barely too dim to be seen with the naked eye.

NASA's Hubble Space Telescope observed that Ceres' surface has a large dark spot as well as a bright spot which are presumed to be crates. A second explanation for the dark spot it that it may be a darker substance in the asteroid's soil. Studies have shown that Ceres probably has a differentiated interior with a rocky core, an icy mantle that is betwee 60 to 120 km thick, and a thin dusty surface.

More will be know about Ceres when the Dawn spacecraft visits the dwarf planet in 2015. The Dawn mission is set for launch in September 2007. It will explore asteroid 4 Vesta in 2011 before arriving at Ceres.

eris is the biggest dwarf planet

Eris was discovered by Michael E. Brown, Chad Trujillo and David Rabinowitz[5] on January 5, 2005, when they were having a close look at some images of the outer Solar System taken in 2003. Dysnomia was orrigionally named Gabrielle.

Eris has a diameter of 2400km, which is slightly larger than Pluto's. In comparison, the Earth's diameter is 12,742km. Neither planets nor dwarf planets are perfect spheres, so this isn't the ideal way to measure their size but it is a reliable indicator.

It takes Eris almost 557 years to orbit the Sun and it lies 97 times further out from the Sun than the Earth (defined as 97 astronomical units - 97 AU) when at its furthest. It has a highly unusual, eccentric orbit, which means that at its closest Eris is only 38 AU from the Sun. So at some times it is closer to us (and the Sun) than Pluto is.

Because it is so distant from us, we cannot observe Eris with the naked eye or even binoculars in the same way as you can planets such as Mars or Jupiter. You'll need a very powerful telescope and plenty of amateur astronomy experience to view it, so don't expect it to be featured in our sky guide any time soon!

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