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Compare the Planets

Comparing the physical characteristics of the worlds in our solar system (and beyond)

The worlds of our solar system come in all shapes, sizes, and colors. Red-eyed Jupiter, ringed Saturn, and frigid Uranus and Neptune are giant gassy globes containing nearly all of the matter in the solar system. These Jovian planets, or gas giants, are huge worlds of air, clouds, and fluid that may have no solid surfaces no matter how deep you go. Everything else in the solar system is just rock, ice, and dust. The largest rockballs are known as the terrestrial planets: Mercury, Venus, Earth, and Mars, with our Moon usually considered part of the club, and now Vesta is applying for membership. Earth is the biggest of all the rocky worlds.

But the planets are not the only worlds of the solar system. All but two of the planets are orbited by moons, each of them a world unto itself. The largest moons are bigger than the smallest planets, and 16 or 17 would qualify as dwarf planets if they orbited the Sun. There are more than 100 Kuiper belt dwarf planets, but only one among the asteroids, Ceres.

Six solid worlds -- Venus, Earth, Mars, Titan, Triton, and Pluto -- have atmospheres dense enough to produce weather. Eris likely does, when it is near its perihelion. We have witnessed active geology on four worlds -- Earth, Io, Enceladus, and Triton -- and we suspect it on Venus, Europa, and Titan. Comparing the same processes across many worlds helps us to understand how each planet's unique composition and history influence its present state, and will help us predict what to expect on Earth in the future.

Pretty Pictures with Many Worlds

Pluto and Charon rotation sequence

Pluto and Charon rotation sequence

This animation contains 15 images captured between June 1 and 15. The images have been resized to account for the changing distance between New Horizons and the Pluto system during that time, which ranged from 50 to 35 million kilometers.

Filed under trans-neptunian objects, New Horizons, pretty pictures, Pluto, amateur image processing, Charon, dwarf planets beyond Neptune, many worlds, animation

Pluto and Charon spin among the stars (as of June 15, 2015)

Pluto and Charon spin among the stars (as of June 15, 2015)

Faint stars in the background of raw images from New Horizons allow the images to be aligned, giving us a sense of New Horizons' changing view on Pluto and Charon as it approaches the dancing pair. Images were taken between June 1 and 15, 2015. More information in this blog entry.

Filed under trans-neptunian objects, New Horizons, pretty pictures, Pluto, amateur image processing, Charon, dwarf planets beyond Neptune, many worlds, animation

Artist's concept of Pluto's moons

Artist's concept of Pluto's moons

This artist's illustration shows the scale and comparative brightness of Pluto's small satellites, as discovered by the Hubble Space Telescope over the past several years. Pluto's binary companion, Charon (discovered in 1978), is placed at the bottom for scale. Two of the moons are highly oblate. The reflectivity among the moons varies from dark charcoal to the brightness of white sand. Hubble cannot resolve surface features on the moons and so the cratered textures seen here are purely for illustration purposes.

Filed under trans-neptunian objects, pretty pictures, Pluto, scale comparisons, Charon, art, Pluto's small moons

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Section Highlights

Planetary Facts

Mass, diameter, density, gravity, orbital characteristics, presented both in metric units and measured relative to Earth.

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Asteroids and Comets Visited by Spacecraft

A comparison of all the asteroids and comets ever visited by spacecraft, up to date as of November 10 (when Deep Impact flew past Hartley 2). Vesta is not included.

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Every Round Object in the Solar System, to Scale

A correctly scaled, reasonably correctly colored view of the largest bodies in the solar system.

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