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
meerkats 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:
Sh 2-91
Cygnus Loop & Veil
Vela SNR
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.27 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 Metsavianiohas 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