THE STARS
MCNGC Name Constellation Map Remarks
1– 1952 Crab Nebula Taurus 17 Supernova remnant.
8– 6253 Lagoon Nebula Sagittarius 11 Easy in binoculars.
16 – 6611 Eagle Nebula Serpens 10 Nebula and cluster.
17 – 6618 Omega Nebula Sagittarius 11 Omega or Horseshoe.
20 – 6514 Trifid Nebula Sagittarius 11 Nebula with dark lanes.
27 – 6853 Dumbbell Nebula Vulpecula 8 Bright planetary.
42 – 1976 Sword of Orion Orion 16 Great Nebula.
57 – 6720 Ring Nebula Lyra 8 Bright planetary.
97 – 3587 Owl Nebula Ursa Major 1 Planetary. Elusive!
–5 57009 Saturn Nebula Aquarius 14 Planetary.
–6 37293 Helix Nebula Aquarius 14 Bright planetary.
–3 1 IC405 Flaming Star Nebula Auriga 18 Round AE Aurigae.
–9 23372 Keyhole Nebula Carina 19 Round Eta Carinae.
–1 17635 Bubble Nebula Cassiopeia 3 Faint.
–6 86729 R Coronae Aust. Nebula Corona Australis 11 Variable nebula.
–2 76888 Crescent Nebula Cygnus 8 Not bright.- 33/4 6960/92 Veil Nebula Cygnus 8 Supernova remnant.
–2 07000 North America Nebula Cygnus 8 Binocular object. - 103 2070 Tarantula Nebula Dorado 22 In Large Magellanic
Cloud round 30 Doradûs.
–3 92392 Eskimo Nebula Gemini 17 Planetary; faint.
–4 9 2237/9 Rosette Nebula Monoceros 16 Surrounds cluster NGC2244.
–– 2261 R Monocerotis Nebula Monoceros 16 Variable. Round R.
–– 2264 Cone Nebula Monoceros 16 Variable. Round S.
–– 1499 California Nebula Perseus 12 Large but not bright.
–6 96302 Bug Nebula Scorpius 11 Planetary; faint.
–4 6 1554/5 Hind’s Variable Nebula Taurus 17 Variable; round T Tauri.
––– Gum Nebula Vela 19 Supernova remnant.
–99– Coal Sack Crux 20 Dark nebula.
SELECTED NEBULAEstars are the members of the multiple Theta Orionis, the
Trapezium. The Orion Nebula is about 30 light-years
across, and is 1500 light-years away; if one could take a
2.5-centimetre (1-inch) diameter core sample right through
it, the total weight of material collected would just about
counter-balance a small coin (about 3.5 grams). Yet the
Orion Nebula is a stellar birthplace, where fresh stars are
being formed from the nebular material. It contains very
young T Tauri-type stars, which have not yet reached the
Main Sequence and are varying irregularly; there are also
immensely powerful stars which we can never see, but
which we can detect because their infra-red radiation is not
blocked by dust. Such is the Becklin–Neugebauer Object
(BN), which is highly luminous, but which will not last for
long enough to ‘bore a hole’ in the nebulosity so that its
light could escape. In fact, M42 is only a very small por-
tion of a huge molecular cloud which covers almost the
whole of Orion.
Other nebulae are within the range of small telescopes.
For instance, in Sagittarius we have the Lagoon Nebula,
which is easy to see with binoculars, and the Trifid
Nebula, which shows dark lanes of obscuring material
(Map 11). The North America Nebula, in Cygnus (Map 8)
really does give the impression of the shape of the North
American continent. It is dimly visible with the naked eye
in the guise of a slightly brighter portion of the Milky
Way, and powerful binoculars bring out its shape. It is
nearly 50 light-years in diameter; much of its illumination
seems to be due to Deneb, which is one of our cosmic
searchlights and is at least 250,000 times as luminous as
the Sun. Some nebulae are colossal; the Tarantula Nebula
round 30 Doradûs, in the Large Cloud of Magellan, would
cast shadows if it were as close to us as M42 rather
than being a full 169,000 light-years away. Other nebulae
are associated with variable stars, so that their aspect
changes; such are the nebulae associated with T Tauri,
R Monocerotis and R Coronae Australis.If nebulosity is not illuminated by a suitable star it will
not shine, and will be detectable only because it contains
enough dust to blot out the light of objects beyond. (It is
not ‘a hole in the heavens’, as William Herschel once sug-
gested.) The best example is the Coal Sack in the Southern
Cross (Map 20), near Alpha and Beta Crucis, which pro-
duces a starless area easily detectable with the naked eye.
Other dark nebulae are smaller, such as the Horse’s Head
near Zeta Orionis (Map 16), and there are dark rifts in the
Milky Way, notably in Cygnus.
There is no difference between a dark nebula and a
bright one, except for the lack of illumination. For all
we know, there may be a suitable star on the far side of
the Coal Sack, so that if we could see the Sack from a
different vantage point it would appear bright.▼ The Flame Nebula
(NGC 2024): emission nebula
in Orion. It is split into two
parts by a dark line of
obscuring dust. The nebula
is seen here in a photograph
by Gordon Rogers, using a
16-inch reflector.E152-191 UNIVERSE UK 2003mb 7/4/03 5:51 pm Page 189