Nebulae of all types are among the most spectacular-looking structures in the entire Universe, and have been an endless source of intrigue and discovery for astronomers. How we perceive them, however, is often thanks to the skill of astrophotographers and imaging experts, rather than our own observing skills. In fact, many nebulae are invisible to our eyes, and we only become aware of their existence after exaggerated colors are assigned to the various emissions or components of the nebula.
With that in mind, we present a selection of nebulae of various types that are said to resemble aquatic animals to varying degrees. In some cases, the resemblance is clear, while in others a certain amount of imagination is required to make the connection. Nonetheless, whatever you see in these nebulae is less important than seeing them for what they are, namely proof of the everlasting process of star birth, star death, and the continuous, churning, evolutionary processes that shape the Universe. Let us start our tour of the cosmic oceanic depths.
Lobster Nebula
- Nebula type: Combined diffuse nebula and H II region
- Constellation: Scorpius
- Coordinates: RA 17h 24m|Dec. -34° 20”
- Distance: 8,000 light years
- Other designations: War and Peace Nebula, Lobster Nebula, Sharpless11, RCW 131, Gum 66
The appearance of a lobster in this nebula is quite striking, with some observers likening the spindly pillars of gas and dust to a rock lobster. Others, however, see a crab in its shape, hence another one of its pseudonyms being the Southern Crab.
Four stars of magnitude seven perfectly align to point towards the center of this faint emission nebula situated between 5,500 and 8,000 light-years distant, depending upon the data source. Interestingly, NGC6357 is also known as the War and Peace Nebula, since in infrared light, the eastern parts of the nebula resemble a human skull, while the western parts resemble a dove.
Whatever this nebula resembles, the fact is that it is a huge star-forming region that contains hundreds of newborn stars that are all blowing bubbles and cavities into the surrounding material, thus creating the ragged, wind-blown scene seen here. The nebula also contains an open star cluster, designated Pismis 24, which was once thought to contain a monster, 300 solar-mass star designated Pismis 24-1. However, this star was subsequently shown to be a triple-star system, which means that even so, the stars in this system remain some of the most massive stars known.
Prawn Nebula
- Nebula type: Emission nebula
- Constellation: Scorpius
- Coordinates: RA 16h 56m 54.66861s|Dec. -40° 30′ 44.4441”
- Distance: 6,000 light years
- Diameter: 250 light years
- Magnitude: 7.13
- Other designations: HD 152723, CSI-40 10986 21, Hbg 1258, SAO 227479, ALS 3854
If one looks closely, the bright orange ridge of gas and dust left of center might just resemble a prawn, albeit a prawn without legs or a tail.
In fact, the whole nebula shown here is an enormous star-forming region that contains at least four visible clumps of hot, young stars, hence the bright blue glow in parts of the nebula. It is perhaps worth mentioning that this image taken by the ESO’s VLT Survey Telescope at Paranal Observatory in Chile is the sharpest, most detailed image ever taken of this nebula.
Crab Nebula
- Nebula type: Supernova remnant
- Constellation: Taurus
- Coordinates: RA 05h 34m 31.94s|Dec. +22° 00′ 52.2”
- Distance: 6,500 ± 1,600 light years
- Diameter: ± 11 light years
- Magnitude: 8.4
- Age: ± 960 years
- Other designations: Messier 1, NGC 1952, Taurus A, Sh2-244
The Crab Nebula needs no introduction, but what may not be commonly known is that its name derives from a drawing made of it by the 3rd Earl of Rosse, who thought he saw a sand crab in the object when he observed it with his 36-inch reflecting telescope. Sand crabs are common in the UK, and although they look different from “normal” crabs, they are crabs nonetheless.
The image above is a composite of 20 or so images taken in various frequencies by the Hubble Space Telescope; while the image on the right was taken only in visible light at a wavelength of 550 nm, hence the green color. Observant readers will notice that the inner parts of the Crab nebula glows bright blue. Some investigators are of the opinion that this glow is a pulsar wind nebula that came about in different processes that formed the main nebula. Although the divisions in the nebula are superficial, the different sources of energy production within the greater structure are important tools with which astronomers study this and other similar nebulae.
Stingray Nebula
- Nebula type: Planetary nebula
- Constellation: Ara
- Coordinates: RA 17h 16m 21.071s |Dec. -59° 29′ 23.64?
- Distance: 18,000 light years
- True Diameter: 0.08 light-year
- Magnitude: 10.75
- Age: ± 50 years
- Other designations: PN G331.3-12.1, Hen 3-1357
When one discounts the absence of a “tail,” this young, tiny planetary nebula might just bear a passing resemblance to a stingray coasting through the interstellar void.
In scientific terms, the Stingray Nebula is barely out of its proto-nebula stage. Although it is currently about 130 times as big as the solar system, it is still only about one-tenth larger than most other known planetary nebula. When it was first discovered about 40 years ago, it was still in an embryonic stage, and the shell of gas that surrounded the central star was still cool, and not ionized. In a paper published in the journal Nature, the discoverer described how the object was too small to resolve with ground-based telescopes, and that the only way to identify it was to use the Hubble Space Telescope.
In the Hubble image shown above, the outer shells of expanding gas is shown to collimate (align) the continuing streams of outpouring gas from the central star into lobes, thus creating the “stingray” shape. Astronomers consider this to be a groundbreaking observation since the mechanisms that form lobes around planetary nebulae were poorly understood prior to the discovery of this nebula.
Manatee Nebula
- Nebula type: Supernova remnant
- Constellation: Aquila
- Coordinates: RA 19h 11m 49s|Dec. +04° 59′ 12”
- Distance: 18,000 light years
- Age: ± 20 000 years
- Other designations: SNR G039.7-02.0
Not much is known about this supernova remnant or its progenitor star, but its shape is probably closer to that of the animal it is named after than any other nebula known. In this image taken in radio frequencies, the mass of gas seems to mimic a manatee at rest, which drifts about on its back with its flippers crossed across its chest.
What is known is that the nebula contains the micro-quasar SS 433, but it is not at all certain whether or not the quasar and the nebula are physically related. The red glow in the background is the result of the image having been taken in both radio and infrared frequencies.
Turtle Nebula
- Nebula type: Planetary nebula
- Constellation: Hercules
- Coordinates: RA 16h 44m 29.5s |Dec. +23° 47′ 59.7”
- Distance: 6,500 light years
- Other designations: NGC 6210
While some observers report seeing the shape of a tortoise’s shell in this nebula, the name of this nebula probably has more to do with the process of its formation, than with its appearance.
In this case, the image shows a planetary nebula in the act of forming, with the dying central star periodically blowing off layers of material that expand for a while before the next layer is blown off, thus creating the bubble-within-a-bubble appearance of the nebula. The reason for the asymmetric arrangement of the bubbles is probably due to the unequal density of the interstellar medium that surrounds the nebula. In such a situation, the expanding gas and dust clouds will follow the path of least resistance; expanding into the interstellar medium at one point, while piling up against denser interstellar material at another.