Neptune

In observations taken on September 7th, researchers found that Neptune’s dark spot, which recently was found to have reversed course from moving toward the equator, is still visible in this image, along with a darkened northern hemisphere. There is also a notable dark, elongated circle encompassing Neptune’s south pole. Neptune's and Uranus’ blue color is a result of the absorption of red light by the planets’ methane-rich atmosphere, combined with the same Rayleigh-scattering process that makes the Earth's sky blue. In 2021, there are few bright clouds on Neptune, and its distinct blue with a singular large dark spot is very reminiscent of what Voyager 2 saw in 1989.

About the colours

These images are a composite of separate exposures acquired by the WFC3 instrument on the Hubble Space Telescope. Several filters were used to sample medium wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are: Blue: F467M, Green: F547M, Red: F657N

About the data

The HST observations include those from program 16266 (A. Simon)