Stunning snaps of Neptune and Triton

Infrared image of Neptune
Infrared image of Neptune (Credit: Mike Brown/CalTech)

Here are a couple of views of Neptune as you have probably never seen the planet before. They were captured earlier today by astronomer Mike Brown using a 10-meter (33 ft) telescope at the W. M. Keck observatory on Hawaii.

Neptune with its largest moon Triton
Neptune with its largest moon Triton. Click to enlarge. (Credit: Mike Brown/CalTech)

Neptune is so distant that most amateur astronomers have only ever seen it as a small dot in binoculars – if they have ever seen it at all. Through telescopes it usually appears as a bluish but fairly bland disk which is our view of sunlight refected from the clouds that permanently shroud it.

But the icy world dazzles in orange with some bright features in its atmosphere in the pictures from Mike. That is because he was observing in infrared light from the observatory site 4,145 metres (13,600 ft) above sea level.

One of Mike’s images is a wide-angle view and includes largest moon Triton, which is thought to be a captured Kuiper Belt object which might therefore be much like ex-planet Pluto. Such remote worlds are especially interesting to Mike, a professor at the California Insitute of Technology, whose research centres on the icy bodies out beyond Neptune. His work was largely instrumental in seeing Pluto demoted to the level of dwarf planet in 2006 and so not for nothing does he rejoice in the Twitter name of @plutokiller.

Mike told Skymania News during his observing session: “The funny thing about the images is that they are sort of an unintended by-product of what we’re doing. Our main goal for the night is to try to understand the different regions on Triton – where is the methane, where is the nitrogen, how do the surface frosts vary with season on the moon?

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“So most of the night we were collecting spectra rather than pretty pictures. But to set up on Triton we had to image it first, and I just thought it was so spectacular that I should post it.”

Mike explained the dramatic appearance of different features in the photo of Neptune. He said: “The big difference is doing the imaging in the infrared where methane absorbs most of the photons. So the bright places are high clouds where the sunlight reflects off of them before it had a chance to pass through much of the atmosphere. Dark is clear atmosphere full of methane absorption.”

With its inner neighbour Uranus, Neptune is one of the solar system’s ice giants. It was only discovered in 1846 and, since it takes 165 years to circle the Sun, it is completing its first orbit this year since that time.

If you compare the two images of Neptune you can see that the planet has clearly rotated between them. It turns once on its axis in a little over 16 hours.

Observations from Voyager 2 as it flew past in 1989 revealed a dark storm on Neptune plus bright clouds racing at incredible speeds of up to 700 miles (1,100 km) per hour.

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By Paul Sutherland

Paul Sutherland has been a professional journalist for nearly 40 years. He writes regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy, plus he has authored three books on astronomy and contributed to others.

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