Nebulae are among the most beautiful, complex, and least understood objects in the entire Universe, with how we perceive them often depending upon our skill in manipulating photographic images, rather than our observation skills. Once the hidden structures of nebulae have been revealed, though, many people see shapes resembling various different objects and creatures, including ghostly apparitions.
In some cases, a certain amount of imagination is required to see an evil aspect in these otherwise beautiful objects, but in others, there is no doubt that a particular nebula closely resembles the monsters and ghosts that lived under our childhood beds. So let’s begin our tour of these spooky celestial structures.
Ghost Nebula
- Nebula type: Reflection nebula
- Constellation: Cepheus
- Distance: 1,470 light years
- True Diameter: 2 light years
- Other designations: VdB 141, Sh2-136
It is not difficult to see how this nebula got its name. Located near the star cluster NGC 7023, whose light it reflects, it bears more than a passing resemblance to popular depictions of ghosts floating through the ether, with its 2-light-year long arms outstretched as if to gather up the living. This nebula should not be confused with either the Little Ghost Nebula (NGC 6369) or the Ghost Head Nebula (NGC 2080).
The ghostly effect is strengthened by the nebula’s unearthly brownish glow, which is caused by the light emitted by several embedded stars. In scientific terms, though, the nebula is classified as a “globule,” or more precisely, a Bok globule, which are relatively small but dense clouds of mainly molecular hydrogen out of which one or more stars may form in the relatively near future.
Witch Head Nebula
- Nebula type: Reflection nebula
- Constellation: Eridanus
- Distance: 900-1,000 light years
- Apparent Diameter: 3 × 1 degrees
- Magnitude: 13
- Other designations: IC 2118, Cederblad 41
Looking at this image, one can almost hear the Witch screaming in rage at the star Rigel, whose light and solar wind both illuminate and deforms her “face.” The nebula’s blue color derives from the dust in the cloud that reflects blue light more effectively than any other color.
While the nebula is extremely faint, radio observations have revealed substantial emissions by carbon monoxide in several parts of the nebula, which suggests that stars are in the process of forming deep inside the structure. In fact, the wind-blown appearance of the molecular clouds within the Witch Head Nebula provides strong evidence that the star forming activity in the nebula is the result of the interaction between solar winds from the Orion OB1 association and the interstellar medium.
Medusa Nebula
- Nebula type: Planetary nebula
- Constellation: Gemini / Canis Minor border
- Distance: 1,500 light years
- Diameter: 4 light years
- Magnitude: 15.99
- Other designations: Sharpless 2-274, PK 205+14 1, Abel 21
Only discovered in 1955 by George O. Abell, the wispy, serpentine tendrils that make up the visible portion of this nebula are somewhat reminiscent of the snakes that the legendary Medusa of Greek mythology had for hair.
Between its discovery and the early 1970s, the Medusa Nebula was believed to be an ancient supernova remnant. However, when Soviet scientists recalculated the nebula’s rate of expansion based on the thermal characteristics of its radio emissions, they came to the conclusion that the nebula was more likely to be a planetary nebula than a supernova remnant.
While the Medusa Nebula is visible in amateur equipment, its surface brightness is very low because it is so big, which means that at least an 8-inch aperture instrument is required to see it at all.
Death Eater Nebula
- Nebula type: Planetary nebula
- Constellation: Serpens
- Apparent Diameter: 430 × 330 seconds of arc
- Magnitude: 13.1
- Age: 45,000 years
- Other designations: Sharpless 2-68
While some observers report seeing a Death Eater from the Harry Potter movies in this nebula, others see the Grim Reaper roaming through space, collecting the souls of the dead as he goes. Still others see nothing more menacing than a lost Teenage Mutant Ninja Turtle, but one must admit that the two fortuitously placed foreground stars that form the “eyes” of the spectre impart a particularly grim aspect to the overall impression of a ghoul on the prowl.
In reality, though, the Death Eater is nothing more than an old planetary nebula whose blue glow derives from the glow of the central star, while the orange hue derives from emissions caused by the nebula’s passage through the Milky Way galaxy’s disc.
Skull Nebula
- Nebula type: Planetary nebula
- Constellation: Cetus
- Distance: 1 600 light years
- Diameter: 4-6 light years
- Magnitude: 8/Central star- 11.8
- Other designations: Pac-Man Nebula, Caldwell 56
Some observers of Caldwell 56 report seeing a monstrous lizard bearing down on them. Imagine the two bright stars near the top of the frame as eyes, and the pink slash just right of center as a forked tongue protruding from the open mouth, and this nebula takes on a really grim, if not scary aspect. In reality, though, the nebula is only a run-of-the-mill planetary nebula that has the white dwarf star HIP 3678 at its heart.
Phantom Streak Nebula
- Nebula type: Planetary nebula
- Constellation: Aquila
- Distance: 7 000 light years
- Apparent Diameter: 0.1 minute of arc
- Magnitude: 11
- Other designations: NGC 6741, Jonckheere 475, GSC2 S3002120466, 2MASS J19023710-0026566, PN VV 217
With some imagination, this squared-off planetary nebula resembles a death mask or cosmic tombstone more than it does a phantom streak. While there are other known square or rectangular planetary nebulae, this one is particularly striking because of the absence of a rich, star-filled background. Note that while this nebula is visible in small telescopes, it is very small, and it has therefore escaped detection until 1882 when it was first spotted by Edward Charles Pickering.
Spectre of Death Nebula
- Nebula type: Emission nebula
- Constellation: Cygnus
- Location: Eastern reaches of the larger Veil Nebula
- Distance: 1,400 light years
- Diameter: 12 light years
Also known as the Veil Nebula, this large supernova remnant is known for its wispy, and at times, scary formations of sheets, tendrils, and filaments of gas and dust. This particular part of the eastern reaches of the Veil does not require much imagination to stand out as a menacing, overbearing ghostly figure that seems intent on smothering the observer with his bat-like “wings.”
Looking past the image of a ghost, though, this nebula consists of filaments of hydrogen atoms shown in red, and strong emissions from oxygen atoms shown here in blue-green tints.
IRAS Ghost Nebula
- Nebula type: Planetary nebula
- Constellation: Sagittarius
- Distance: 18,000 light years
- Magnitude: 12.87
- Other designations: GSC2 S2202023288, 2MASS J17451419-1756469, PK 009+05
Also known as Henize 3-1475, this wraith-like planetary nebula looks like a will-of-the-wisp dancing across a spooky marsh, or when viewed from the “top,” like a ghostly fish and its reflection cruising the space between the stars. In fact, the spindle-like shape of the nebula is caused by a torus of gas and dust around the central star that prevents the nebula from expanding into a spherical shape.
Ghost of Jupiter
- Nebula type: Planetary nebula
- Constellation: Hydra
- Distance: 1,400 light years
- Apparent Diameter: 25 seconds of arc
- Magnitude: 8.60
- Age: ± 1,500 years
- Other designations: NGC 3242
Although this planetary nebula is most commonly referred to as the Ghost of Jupiter, it is also known as The Eye Nebula, which describes the ghostly aspects of the object somewhat better. While the first appellation merely refers to the fact that it resembles the planet Jupiter in size when seen in telescopic views, the second name does justice to the view that the object resembles a disembodied eye floating in space- almost as if it is looking back at the observer.
The two red objects on either side of the nebula are called FLIERS, which are lobes of fast-moving gas being ejected from the nebula. FLIERS are most commonly tinted red in enhanced images to make them visible to human vision. The nebula is about two light years across and an easy target for small amateur telescopes, although a medium to large instrument is required to observe the nebula’s extended halo.
Trifid Nebula
- Nebula type: Combined emission, reflection, and dark nebula
- Constellation: Sagittarius
- Distance: 5 200 light years
- True Diameter: 42 light years
- Magnitude: +6.3
- Other designations: M20, NGC 6514, Sharpless30, RCW 147, Gum 76
While some observers see the delicate shape of a flower in this nebula, others see a huge, menacing spider reposing on a web, guarding a bright jewel-like star. In scientific terms, though, the Trifid Nebula is a huge star-forming region that consists of a reflection nebula (the upper, blue part), an emission nebula (the lower, red part), a dark nebula that “splits” the greater structure into three lobes, and an embedded open star cluster that is made up of more than 3,000 stars. The Trifid Nebula is big and very bright, which makes it an easy target for small amateur telescopes.
Ghost of the Moon Nebula
- Nebula type: Planetary nebula
- Constellation: Aquila
- Coordinates: RA 19h 18.5m|Dec. +06° 32’
- Other designations: NGC 6781
While the image above shows the structure of the Ghost of the Moon, telescopic views without filters show a delicate wisp of ghostly ectoplasm (the stuff of which ghosts are made) floating in space.
With an O III filter, however, the nebula shows its edges much more clearly, although the impression of a blob of ghostly ectoplasm remains. Using a UHC filter at magnifications of around 140, the dark hole in the center of the nebula becomes apparent, but somehow this only strengthens the feeling that the nebula is really a bubble of ectoplasm exhaled by a passing celestial spirit.
Spectre of Death Nebulae
- Nebula type: Reflection nebula
- Constellation: Orion
- Distance: 1,500 light years
- True Diameter: 10 light years
- Other designations: NGC 1999
Located at the edge of the enormous Orion Molecular Cloud Complex, this 10-light-year-wide bright blue reflection nebula just below the Orion Nebula looks like the face and gaping mouth of a space demon that is bearing down on the observer.
While the gaping, T-shaped hole was once assumed to be a dark nebula that was obscuring some of the background, new studies have shown that the “gaping mouth” is actually a hole blown through the nebula itself by several energetic young stars. Adding to the illusion of “hands” reaching for the observer are reddish outflows of gas and dust below the “face” that are being propelled out of the main cloud complex at velocities of several hundred km/sec.
Little Ghost Nebula
- Nebula type: Planetary nebula
- Constellation: Ophiuchus
- Distance: 2,000- 5,000 light years
- Apparent Diameter: 28 seconds of arc
- Magnitude: 12.9
- Other designations: NGC 6369, PK 002+05 1
While there are other nebulae that look like eyes, none has the malignant, baleful glare of this particular nebula. In fact, if an evil cosmic Cyclops did exist, this would be his eye staring straight back at you.
Evil cyclopean eye or not, this planetary nebula is about a light year in diameter, and the glowing “pupil” is the white dwarf that remains of the progenitor star. In this image, the false blue, green, and red colors shown here are emissions from ionized oxygen, hydrogen, and nitrogen atoms, respectively. Note that the Little Ghost Nebula should not be confused with either the similarly named Ghost Nebula (Sh2-136), or the Ghost Head Nebula (NGC 2080).
Diablo Nebula
- Nebula type: Planetary nebula
- Constellation: Vulpecula
- Distance: 1,360 light years
- True Diameter: 2.88 light years
- Magnitude: -0.6
- Age: 14,600 light years
- Other designations: M27, NGC 6853, Dumbbell Nebula, Diabolo Nebula
Also known as the Dumbbell Nebula and the Apple Core Nebula, with the two red ends marking the uneaten parts of the apple. The Diablo Nebula nevertheless has an evil-looking, greenish hue to its inner parts that reminds one strongly of a cosmic pool of radioactive toxic waste.
Apart from the fact that the Diablo Nebula was the first planetary nebula to be discovered, it is also the second biggest known such nebula, being marginally smaller than the Helix Nebula in Aquarius. Being about 100 times brighter than the Sun, the Diablo Nebula is an easy target for binoculars and small telescopes.