Color Correcting the Cosmos: Neptune Not So Blue, Study Shows

Pick up a picture book of the planets in our solar system, and you’re likely to see photos of two richly blue planets. One is ours, of course. The other is Neptune. It's the farthest planet from the sun (sorry, Pluto!). It surely seems to be a pretty planet. Yet the nature of Neptune’s blue may not be as true as scientists have thought.

In photos sent to Earth by the Voyager 2 spacecraft in 1989, Neptune appears to be a deep blue color. Its closest neighbor planet, Uranus, is a paler shade of bluish green. That didn’t sit right with some scientists. They questioned how such a thing could be. After all, in terms of size, atmosphere, and mass, the two planets are nearly the same.

It turns out Voyager’s first photos had been tweaked. This fact was unearthed by planetary physicist Patrick Irwin of Oxford University. When the craft sent the pics to Earth, scientists altered the picture to highlight Neptune’s clouds. That made the planet appear far bluer than it really is. The revised pictures featured captions noting the change. But the notion of a gorgeous blue Neptune was so dazzling that the scientific community basically forgot the pics had been changed at all. 

"Even though the (altered) color was known at the time amongst planetary scientists — and the images were released with captions (stating) it — that (note) had become lost over time," Irwin wrote in the study. It was published this month in the Monthly Notices of the Royal Astronomical Society. Using new images from NASA's Hubble Space Telescope and European Space Agency's Very Large Telescope, Irwin revealed that Neptune’s real shade is a Uranus-esque green.

Time to break out the crayons!

Photo from NASA/JPL-Caltech.

Reflect: Why might it be important to question and verify information, even when it comes from trusted sources like scientific institutions?