Skull Nebula

Planetary Nebula

NGC 246, Caldwell 56

Apparent magnitude: +10.4
Apparent dimensions: 4.0 x 3.5 arc minutes
Constellation: Cetus

Image exposure: 66 minutes

Image field of view: 17.1 x 17.1 arcmin

Image date: 2021-12-01

At last a clear night sky, which was a bit of a surprise after a couple of months of continuous 100% cloud cover and nothing much to write about. I decided to image the ghostly looking Skull Nebula with my Schmidt Cassegrain ‘scope. There were a still a few middle clouds around and a touch of high cloud too but the opportunity couldn’t be missed.

You might need a little bit of imagination but this object is called the Skull, because….. it resembles….. a human skull. 😑

Maybe it looks somewhat like a pac-man too. You decide.

It is a diffuse, dimly glowing planetary nebula, my favourite class of object, because of their beauty and because no two are identical.

It is about 1,600 light years away and its angular diameter of 4 arc-seconds equates to a physical diameter of about six light years. Our Sun will emit a planetary nebula in a few billion years time and if it reaches the same diameter, it will reach three quarters of the way to Alpha Centauri!

The nebula is dim and quite widely dispersed, meaning it is getting old by planetary nebula standards, probably more than 10,000 years.

The central star, which blew off its outer layers to form the nebula, is now revealed as a white dwarf, slightly off centre. It is a close binary star. Although my image does not separate the companion, it is more noticeably extended than the other stars in the image due to the close proximity of the secondary star.

The Skull is an interesting object and I will return to it in the future to seek a longer exposure in a clearer sky.

Cosmic Focus Observatory

34° South

Above us only sky….

34

Telescope:	Meade LX-90 200mm Schmidt-Cassegrain ; 2000 mm f/l @ f/10 (deforked).
Optics:	Astronomik light pollution filter.
Mount & Guiding:	SkyWatcher EQ6-R Pro mount.
Imaging camera:	ZWO ASI 071 MC cooled.

^{Images © Roger Powell}
G’day from Dow Nunder

🙃 I’m one of the founder members of Macarthur Astronomical Society