Pluto

Considered the ninth planet for nearly 75 years, the second biggest dwarf planet discovered in the solar system. Pluto was originally given the name of the Greek god of the underworld by 11-year-old Venetia Burney.

This is the most detailed view to date of the entire surface of the dwarf planet Pluto, as constructed from multiple NASA Hubble Space Telescope photographs taken from 2002 to 2003. The center disk (180 degrees) has a mysterious bright spot that is unusually rich in carbon monoxide frost. Pluto is so small and distant that the task of resolving the surface is as challenging as trying to see the markings on a soccer ball 40 miles away. Credit: NASA, ESA, and M. Buie (Southwest Research Institute). Photo No. STScI-PR10-06a

Space & Astronomy Wiki – the planets in the solar system –

The furthest of the original nine planets in the solar system from Sol at 3.7 billion miles (5.9 billion km) or 39.5 AU, Pluto is the second biggest dwarf planet behind Eris, which is about 28 percent more massive.

In 2005, this image from NASA’s Hubble Space Telescope was used to identify two new moons orbiting Pluto. Pluto is in the center. The moon Charon is just below it. The newly discovered moons, Nix, and Hydra are to the right of Pluto and Charon.
Credits: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the HST

Orbited by moons Charon, Nix, Styx, Kerberos, and Hydra, Pluto was discovered on February 18, 1930, by Clyde W. Tombaugh. Charon is almost 50 percent the size of Pluto and is believed to be the result of a collision between a planet-sized object and the dwarf planet early in the history of the solar system.

If the icy surface of Pluto’s giant moon Charon is cracked, analysis of the fractures could reveal if its interior was warm, perhaps warm enough to have maintained a subterranean ocean of liquid water, according to a new NASA-funded study.

With only 12, 173 miles (19, 591 km) between Pluto and Charon, astronomers and space scientists consider the pair to be a double planet system. The entire Pluto system is part of the distant Kuiper Belt, a distant disk-like region beyond the orbit of Neptune full of icy bodies formed during the early history of the solar system.

NASA’s New Horizons spacecraft took this image of Pluto’s dark side with the Sun on the other side of this distant, lonely wanderer. Sunlight filters through and illuminates complex layers of atmospheric haze. Credit: NASA/New Horizons/JHUAPL/SwRI

A day on Pluto is about 153 hours long, which is the time it takes the dwarf planet to spin once on its axis, and a year, the time it takes this distant object it orbit the Sun, takes about 248 Earth years.

The structure of Pluto is not very well understood at present. Nevertheless, spectroscopic observation from Earth in the 1970s has revealed that the planet surface is covered with methane ice. Surface temperature is -230 degrees C and the frozen methane exhibits a bright coloration. However, with the exception of the polar caps, the frozen methane surface is seen to change to a dark red on the basis of observation of eclipse by its moon Charon.
Image Credit: Lunar and Planetary Institute

What are planetary scientists saying?

Some planetary scientists think Pluto could have an ocean hidden beneath its icy surface, but this cold and distant body isn’t thought to be a place life could exist. Scientists estimate this dwarf planet has three times as much water in the form of ice as contained within the oceans of Earth.

How big is Pluto’s atmosphere? This is not a typical question one finds in planetary science. Earth’s atmosphere has an equivalent thickness – the thickness if you compress the atmosphere to uniform pressure and density – of about 10 kilometers or six miles. Compare this with the radius of Earth, 6,370 kilometers, and you see that the razor-thin thickness of Earth’s atmosphere is about 0.17% of its radius. Even if you consider the “outer limit” of Earth’s neutral atmosphere, what we call the exobase, that reaches about 600 kilometers altitude, the atmosphere’s equivalent thickness is only 10% of Earth’s radius—still very thin. So the volume of Earth’s atmosphere is tiny compared to Earth’s volume.
Michael E. Summers is a professor of Planetary Science and Astronomy at George Mason University and specializes in the study of the chemistry and dynamics of planetary atmospheres. He is a New Horizons co-investigator and member of the atmospheres science theme team.

The surface is also covered by frozen methane and nitrogen gas, which thaws as Pluto nears the Sun, forming a thin atmosphere composed primarily of nitrogen, carbon monoxide, with a little methane thrown in.

NASA’s New Horizons spacecraft took this enhanced-color image of the southeastern region of Pluto’s great plains of ice called Sputnik Planum. At lower right these plains border rugged, dark highlands that rise 1.5 miles above them. Credit: NASA/JHUAPL/SwRI

NASA’s New Horizons spacecraft is the only human envoy to be sent to the Pluto system.

For more information on Pluto go here.

Follow New Horizons as it writes space history here.

Follow NASA’s New Horizons spacecraft as it closes in on Pluto and Charon and prepares to write space history.

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