September 2022 - Picture of the Month
Stephan’s Quintet (Arp 319) in Pegasus
I thought it was about time a galaxy had Picture of the Month, and when I noticed that Stephan's Quintet crosses the northern meridian at a sensible hour in September, and that I'd never featured it before, it was time to choose this image of six galaxies by Adam Block.
A quintet suggests five, but NGC 7320C on the right isn't a member of the group, being closer to us at about 35 million light-years. However several hundred million years ago it certainly was, as is plowed through group colliding with NGC 7319 in the process.
Of course, even if it seems central, NGC 7320 isn't a member either. It has to be admitted that it looks very different from the rest of the group with all that blue star formation and its clumpy HII regions. It's also much closer, like NGC 7230C, and is visually the brightest galaxy here at 13.2V magnitude.
The other four galaxies in this image form a physical group in the process of coalescing at around 300 million light-years from us. This is most obvious in NGC 7318, both the A and B halves of it, but NGC 7319 also shows significant disturbance and tidal tails extending towards NGC 7320C. Only NGC 7317 seems quiet, down there in the bottom right.
This galaxy group has been well imaged with professional scopes, including the Hubble and recently the Webb Space Telescopes, and it is a but popular visual target, but I was surprised how few amateur images I could find.
James Whinfrey - Website Administrator.
