Color of Pluto

by Fraser Cain on April 24, 2008


Although astronomers talk about Pluto having large quantities of ice, it’s actually a dirty brown color. The picture associated with this story is the most accurate color map of Pluto ever made

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The image was made by ongoing observations of Pluto and Charon during a period when they were making regular transits. This is where Charon passed in front of Pluto from our vantage point, and vice versa. As Charon passed in front of Pluto, it darkened regions of the dwarf planet. Astronomers could then subtract the light from Pluto to make an accurate image of Pluto’s color. Instead of being a pure snowy ball, Pluto clearly has darker and lighter regions.

Even though Pluto is this dirty color, it still has a very high albedo – or reflectiveness. Astronomers originally calculated this reflectiveness, and assumed that Pluto was fairly large and massive, 1% of the mass of the Earth. But when Charon was discovered, this allowed them to make a very accurate mass measurement. Pluto’s mass dropped down to the official 0.24% of Earth.

We’re now just waiting for NASA’s New Horizons spacecraft to finally arrive at Pluto in 2015 to capture the first ever close up images of Pluto’s surface. To finally answer the question: what color is Pluto.

About 

Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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