Astro Bob: Webb wows with first Neptune photo / Aurora alert
NASA's flagship infrared telescope captures an amazing view of Neptune's rings. Watch for aurora on Thursday, Sept. 22.
I couldn't wait to share this new Webb image of the planet Neptune and its satellites. Part of my excitement stems from having looked at the planet just last night with my community education astronomy class. Several of the students remarked on the planet's blue color. Neptune is located about 10 degrees southwest of Jupiter in the constellation Aquarius and visible in binoculars from a reasonably dark sky. I'm planning a separate post on how to find it soon.
The very thing that makes the planet so colorful — methane gas — is the reason the planet's globe appears dim compared to Triton. Methane absorbs infrared light. Triton's about a quarter the size of our own moon and looks bright because it has next to no atmosphere — just a few whiffs of nitrogen and methane.
Triton is the only large moon in the solar system to orbit its planet backwards. Astronomers suspect it was originally an icy asteroid from the Kuiper Belt that was captured by Neptune's gravity. The eighth and outermost planet is 17 times more massive than Earth and nearly four times as large, making it the biggest player in the outer solar system.
But the rings ! So lacy and beautiful. You'll never see them in any but the largest telescopes because they're extremely dark and spindly compared to the chunky water-ice found in Saturn's rings. They're made of fine dust — primarily ice particles coated in organic compounds darkened by solar radiation. These new photos are the best made in decades of a planet so remote it takes its light 4 hours to get here.
In other space news, we may get a visit from the northern lights on Thursday night, Sept. 22. An opening in the sun's outer atmosphere, the corona, is flinging solar electrons and protons at us like an egged house on Halloween. The material is expected to arrive and possibly link into Earth's magnetic field and fire up the aurora between about 10 p.m. and 1 a.m. that evening.
For the moment, forecasters expect a minor G1 storm, with lights visible across the Upper Midwest in the lower half of the northern sky. I'll update on my Facebook page, facebook.com/astrobobking . I suspect solar activity will soon pick up as a couple of large sunspot groups recently rotated around to the sun's front side. These may grow large enough to be visible to the naked eye through a safe solar filter like a #14 welder's glass.