Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2019 September 10
See Explanation.  Clicking on the picture will download
the highest resolution version available.

Pluto in True Colour
Image Credit: NASA, JHU APL, SwRI, Alex Parker

Explanation: What colour is Pluto, really? It took some effort to figure out. Even given all of the images sent back to Earth when the robotic New Horizons spacecraft sped past Pluto in 2015, processing these multi-spectral frames to approximate what the human eye would see was challenging. The result featured here, released three years after the raw data was acquired by New Horizons, is the highest resolution true colour image of Pluto ever taken. Visible in the image is the light-coloured, heart-shaped, Tombaugh Regio, with the unexpectedly smooth Sputnik Planitia, made of frozen nitrogen, filling its western lobe. New Horizons found the dwarf-planet to have a surprisingly complex surface composed of many regions having perceptibly different hues. In total, though, Pluto is mostly brown, with much of its muted colour originating from small amounts of surface methane energized by ultraviolet light from the Sun.

Tomorrow's picture: a big heart


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