The meticulous S African observer Susan Young lives in the Kalahari Desert with her two dogs and two dobs. It's one of the worst places in the world to live—except for astronomers and meerkats, in which case it turns into one of the best places in the world.
Susan has posted three impressively detailed observing reports of supernova remnants on her blog Sand & Stars:
Of these, Sh 2-91 is the most interesting because the object is so seldom observed . It's the oldest SNR visible in amateur instrument; estimates range from 240,000 to 470,000 years. By compare, the Cygnus Loop is a tyke at 5,000–8,000 years old; the Vela SNR is 11,000–12,300 yro; and Simeis 147 in Taurus is ~40,000 yro.
In the professional literature Sh 2-91 is the least studied of all SNR: SIMBAD links only 6 papers, dating from 1976 discovery paper up to a spectral study of all the Sharpless H II emission nebs in 1995. The most informative study is Reich et al 1979. While it is a radio continuum study and depicts emission unseen by us, Section 7 starting on p.275 provides quite a bit of interesting facts on Sh 2-91 and SNRs in general. Frankly, I learned more from Susan's blog than all the SIMBAD papers combined.
The Finnish artist/sim producer named J-P Metsavianio has done a superb 3D full-rotation sim of the Cygnus Loop, as though we were at standoff radius watching it all happen. The eggshell-like surface configuration of SNRs really becomes apparent here. You can see a YouTube assemblage of many Metsavianio sims here.
=Dana in S Africa
Edited by WeltevredenKaroo, 07 August 2017 - 04:46 PM.