This is a hydrogen alpha emission line image of IC1396 -
a large but relatively faint emission nebula lying about 2000 light years distant in the constellation of Cephus.
Looking in the body of the nebula, the twisted worm like object at 12 o’clock is VdB142, more commonly known
as "the elephant's trunk". This beautiful backlit dark nebula is more clearly discernable in this more recent
longer focal length colour narrowband image of the Elephant's Trunk.
Various other small dark nebulae are scattered over the face of IC1396, these show up well thanks to the contrast with
the emission nebula behind. The Milky Way is littered with dark nebulae but the small ones are hard to
image effectively unless they are backlit by emission nebulae such as this.
Normally you can only tell they are there by the general lack of stars in those areas.
Many dark nebulae have Bnnn catalog designations from
E E Barnard's Photographic Atlas of Selected Regions of the Milky Way.
Barnard was perhaps the original wide field astrophotographer. An interesting guy, no formal education,
he paid for his house with his various comet discoveries
(no really, US comet discoveries were awarded $200 a pop in those days),
was the discoverer of the 5th moon of Jupiter - Amalthea,
and Barnard's star - which has the highest recorded proper motion of any star relative to Sol.
Back to the image, between 2 and 3 o'clock you will find a large dark nebula (B160) that looks a little like
the head of a manta ray swooping around that side of the nebula. If the moon was included in this image it
would cover an area about the size of B160 - this gives you a good feel for the large slice of sky this image is covering.
At 8 o'clock is the bright red carbon supergiant Mu Cephei, AKA "Herschel's garnet star", sometimes know as MY Cephei.
This is one of the most massive stars visible to the naked eye, or indeed in the entire galaxy.
Its body could encompass over a billion Sols, and if it replaced Sol its envelope would extend past the orbit of Jupiter.
To get a better understanding of the relative size of this monster have a look at this
video.
