In many images of the two outer gas giants of the Solar System, Neptune typically looks rich blue while Uranus comes across as pale green. But now our new study, published in Monthly Notices of the Royal Astronomical Society, has revealed that these two ice giants are actually very similar shades of greenish blue.
The study follows our previous work in 2022 that analysed the spectra (light broken down by wavelength) of light reflected off Uranus and Neptune from several sources, including the space telescope imaging spectrograph on the Hubble space telescope. These were recorded in 2002 (Uranus) and 2003 (Neptune).
We found that the colours of Uranus and Neptune were actually remarkably similar, with Neptune appearing only slightly bluer – see the image below. The difference in colour was attributed to the difference in opacity of a layer of haze and methane ice.
