Seven Myths About Pluto


Since Pluto’s discovery by Clyde Tombough in 1930, it has remained a great mystery.  It’s difficult to study since it’s about 3 billion miles away from the sun.  The Hubble Space Telescope has been able to capture images of the dwarf planet, but Hubble is really geared towards taking pictures of giant objects like galaxies, not dwarf planets–so the images we have of Pluto are fuzzy.  However, Pluto is about to get its first sharp images courtesy of the New Horizons spacecraft as it passes the dwarf planet by 7,800 miles by July 14th.  With this date looming only next month, let’s take some time to take a fresh look at Pluto and the seven biggest misconceptions that people have of it.

Myth 1:  Pluto was named after the Disney character

The famous Disney dog debuted in 1930, the same year that Pluto was discovered, but the cartoon character was initially named Rover, not Pluto  A cartoon featuring “Pluto the Pup” didn’t actually debut until 1931.  There are planets already named after mythological Gods, e.g., Mars (Roman god of War), Saturn (Roman god of Fertility), Jupiter (Roman king of the gods), and Pluto is no exception.  When it was discovered, the Lowell Observatory had the right to name the new object.  Constance Lowell proposed names such as Zeus, Percival and Constance, but these were all discarded.

The name Pluto, after the Greek god of the underworld, was proposed by Venetia Burney, an eleven-year old schoolgirl in Oxford, England.  She suggested the name in conversation to her grandfather, Falconer Madan, who passed the name to astronomy professor Herbert Hall Turner, who then cabled it to colleagues in the United States.

The name came down to Minerva, Cronus, and Pluto.  And after each member of the Lowell Observatory voted, it was unanimous that Pluto would be the new name.  So, as it turns out, Pluto the Pup was named after the planet, not the other way around.

Myth 2:  Pluto is tiny

A lot of people actually think that Pluto is very small, like an asteroid; however, the dwarf planet is actually 1,400 miles in diameter.  In fact, Pluto’s largest moon, Charon, is about 750 miles across.  Pluto is actually much larger than any other object in the Kuiper Belt–the ring of icy bodies beyond Neptune’s orbit.  The majority of objects in this belt are the size of comets, only a few kilometers across; however, Pluto and Eris (another dwarf planet) are more than 1,2400 miles across.

Myth 3:  It’s dark there all the time

Since Pluto orbits some 3 billion miles away from the sun, most people think that it’s dark there all the time.  According to Alan Stern, principal investigator for New Horizons, “The lighting on Pluto at noon isn’t as low as people think; it’s like a very grey cloudy day on Earth, or like dusk levels after sunset.”

Myth 4:  Pluto was once a moon of Neptune

This is actually an old theory that became popular shortly after Pluto’s discovery. It was disproved in 1965 when researchers found an orbital resonance–a gravitational sweet spot in which the orbits of two bodies are related by a ratio of two whole numbers–between Pluto and Neptune. This resonance prevents the two objects from ever closely approaching each other.

Myth 5:  Pluto is an ice world

Pluto’s surface is covered by a number of ices, including frozen nitrogen and frozen methane. But the density of Pluto as a whole is twice that of water ice, showing that the dwarf planet’s mass is made up of about two-thirds rock and just one-third ice. Therefore, it’s more accurate to say that Pluto is a rocky body with an icy shell.

Myth 6:  Pluto is airless

In the 1980s, it was discovered that Pluto had an atmosphere.  This atmosphere is said to mainly contain nitrogen, much like Earth’s atmosphere; however, Pluto’s air also contains carbon monoxide and methane, is much thinner than Earth’s, and it extends much farther out into space.

Earth’s atmosphere reaches 370 miles or so beyond the planet’s surface–about 10 percent of Earth’s radius.  Pluto, on the other hand, has an atmosphere that reaches out seven radii from the planet’s surface.  In other words, the volume of Pluto’s atmosphere is more than 350 times that of the dwarf planet itself.

Myth 7:  Pluto’s orbit is one of a kind

Pluto’s orbit is very different than the eight official planets in our solar system.  First of all, it’s quite elliptical, taking the dwarf planet as close as 2.75 billion miles to the sun, and as far away as 4.5 billion miles.  Second, its orbit is inclined by 17 degrees relative to Earth’s ecliptic–the plane of Earth’s path around the sun.  The eight planets all tend to lie roughly on the same plane and move around the sun in a more-or-less circular path.

However, Pluto isn’t one of a kind in its orbital anomaly.  Other Kuiper Belt objects, such as Eris and Haumea, have even more elliptical or inclined orbits.

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