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    Categories: Astronomy ListsDeep-Sky Objects

Nebulae Named After Insects

The Cocoon Nebula trailed by the dark nebula Barnard 168

Nebulae are large clouds of interstellar dust and ionized gases which provide the basic building blocks from which the stars and solar systems are created. These stellar nurseries are mostly composed of hydrogen (90%) and helium (10%), but with a further 0.1% of heavy elements, such as carbon, nitrogen, magnesium, potassium, calcium, and iron.

Nebulae are also amongst the biggest structures in the universe, and can be more than hundreds of light-years across, with their diffuse clouds of gas forming into imaginative and colorful shapes, allowing astronomers to let their imaginations run wild when naming some of them.

However, if there is a reason why nebulae that are named after insects resemble insects more closely than their land animal or aquatic counterparts, for instance, it is probably because some insects have such weird and unusual shapes themselves. Nonetheless, many nebulae are shaped by processes that are not always understood, and if some nebulae do turn out to look like insects, we have all the more reason to marvel at their fascinating shapes, forms, and structures.

Cocoon Nebula

Image Credit: Neil Fleming, David Plesko

-Nebula type: Combined reflection / emission nebula
-Constellation: Cygnus
-Coordinates: RA 21h 53m 28.7s|Dec. + 47° 16′ 01″
-Distance: 3,300 light years
-Diameter: 15 light years
-Magnitude: 7.2
-Other designations: IC 5146, Caldwell19, Sh 2-125

The Cocoon Nebula strongly resembles the cocoon of a silkworm,
which in this case has a red, glowing hue as a result of hydrogen gas being excited by the young, hot blue star at its center. Also visible can be seen blue, dust-reflected starlight at the edge of the molecular cloud.

Another point of interest of the Cocoon Nebula is the nearby dark nebula designated Barnard 168, which is evident by the fact that most of the stars immediately around the nebula are obscured by this dark nebula. Together,  the  Cocoon Nebula and Barnard 168, seen at the top of this page, are an inseparable part of the viewing experience, with the latter forming a dark trail behind the cocoon.

Bug Nebula

Image Credit: Don Goldman

-Nebula type: Planetary nebula
-Constellation: Scorpius
-Coordinates: RA 17h 13m 44.211s|Dec. -37° 06′ 15.94″
-Distance: ~ 3,400 light years
– Diameter: 2 light years
-Magnitude: 7.1
-Other designations: NGC 6302, PK 349+01 1, Bipolar Nebula, Butterfly Nebula, Sharpless 6, RCW124, Gum 60, Caldwell 69

The Bug Nebula is notable for the fact that it is the most complex nebula ever found, which is likely due to the fact that the central star in the nebula is estimated to have a temperature of more than 250,000 degrees Celsius, which makes it one of the hottest stars known to exist in the Milky Way galaxy. Although the star is now a white dwarf with only about 64% of the Sun’s mass, its high temperature suggests that it must have been exceedingly large and massive in its youth.

As with other bipolar planetary nebulae, the “waist” of the Bug Nebula is constrained by a torus of dust (that can be seen here as a dark dust lane running across its center), that has prevented the nebula from expanding into a spherical shape. However, the really strange aspect of the dust in this torus is that it contains various carbonates, which represents the first discovery of carbonates outside of the solar system. Nonetheless, since carbonates require a water-rich environment to form, the presence of carbonates in the dust is hotly disputed, even though the torus is also known to contain crystalline water ice, among other substances.

Tarantula Nebula

Image Credit: TRAPPIST / E. Jehin / ESO

-Nebula type: Combined emission nebula and HII region
-Constellation: Dorado
-Coordinates: RA 05h 38m 38s |Dec. -69° 05.7′
-Distance: 160,000 light years
-Diameter: 600 light years
-Magnitude: 8
-Other designations: NGC 2070, Doradus Nebula, Dor Nebula, 30 Doradus

It is not difficult to see the shape of a cosmic spider clinging to the leading edge of the Large Magellanic Cloud, and especially in this image, that shows enormous and extended areas of star formation as the “legs” of the spider.

In reality, the Tarantula Nebula is the most active star-forming region in the Local Group of Galaxies, and the largest such region with an estimated diameter in excess of 650 light years. It is also very bright; if it were placed at the same distance from Earth as the Orion Nebula (M42) situated 1,500 light years away, it would be bright enough to cast shadows on the Earth’s surface. The Tarantula contains the star cluster NGC 2017, which in turn, includes the extremely luminous clump of stars designated R136, which supplies most of the radiation that lights up the nebula. The estimated combined mass of the whole star cluster is about 450,000 solar masses, which suggests that it might evolve into a true globular cluster in the far distant future.

Minkowsky’s Butterfly

Image credit: ESA / Hubble

-Nebula type: Bipolar planetary nebula
-Constellation: Ophiuchus
-Coordinates: RA 17h 05m 37.952s|Dec. -10° 08′ 34.58”
-Distance: 2,100 light years
-Diameter: 1.4 light years
-Magnitude: 14.7
-Age: ± 1, 200 years
-Other designations: M2-9, Twin Jet Nebula, Butterfly Nebula, PNG 010.8+18.0

While it is not visible in this image, the brightly glowing central star is being orbited by a companion star that is preventing the outflow of gas from expanding into a spherical shape, since the interaction between the two stars has created a disc of gas and dust around the “waist” of the nebula. As a result, all out flowing material is being channelled, or collimated, into two jets, which some observers have also likened to the wings of a butterfly.

This structure has all been called the Siamese Squid Nebula, no doubt due to the fact that it does indeed resemble two squid that are conjoined at their heads, although a more appropriate name would be the Twin Jet Nebula, which is how this striking nebula is more commonly known.

Ant Nebula

Image Credit: NASA / ESA / Hubble Space Telescope

-Nebula type: Planetary nebula
-Constellation: Norma
-Coordinates: RA 16h 17m 13.392s|Dec. -51° 59′ 10.31?
-Distance: 8,000 light years
– Diameter: 2 light years
-Magnitude: 13.8
-Other designations: ESO 225-9, Chamber of Horrors

While it is not difficult to see the shape of a common garden ant in this nebula, it is not so easy to determine the mechanisms that have shaped the structure. The Ant nebula has variously been described as consisting of “…two spherical bipolar lobes, two outer large filamentary hour-glass shaped columns, two cone-shaped rays, and a planar, radially expanding, elliptically shaped chakram”, which collectively, form a complex of three “nested” pairs of bipolar lobes and an equatorial ellipse.

One possible explanation for the complex structure of the nebula is that it contains a symbiotic binary system, and that powerful gravitational effects twist and shape the out flowing gas as it leave the inner regions of the nebula. Another theory states that the dense gas at the centre of the nebula may have different origin than the gas in the lobes. While this hypothesis might work, it requires a giant companion to create the dense inner region, and a white dwarf to supply the ionized photons that form and light up the lobes. However, the problem with the second hypothesis is that the two required stars have not yet been found, meaning that the mystery of the nebula’s formation remains unresolved.

Papillon Nebula

Image Credit: M. Heydari-Malayeri (Paris Observatory) et al., ESA and NASA

-Nebula type: High Excitation Blob (HEB)
-Constellation: Large Magellanic Cloud (Located in the constellation Dorado)
-Distance: 170,000 light years
-Diameter: 2 light years
-Other designations: N159, IRAS 05240-6948

This composite image shows yet another nebula named after a butterfly, but in this case, it represents a rare class of nebula that are dense, compact, high extinction structures compared to “normal” H II (star forming) regions in the Magellanic Clouds. Put in another way, High Excitation Blobs are the dust clouds that surround newly formed, massive stars, and can be thought of as the birth cocoons that enshroud newly formed massive stars.

In this case, the inset image shows detail of the bright yellow spot in the larger structure, an enormous complex of churning gas and dust clouds designated N159. By way of comparison, the small fraction of the complex (shown as the inset) only spans about 2 light years, while the larger complex spans across more than 150 light years.

Although there is some speculation as to what formed the butterfly shape shown here, most investigators believe that there are several massive stars buried within the “body” of the butterfly, whose solar winds combine to blow in-falling material away from the centre, and hence into two bipolar lobes.

Red Spider Nebula

Image Credit: ESO

-Nebula type: Planetary nebula
-Constellation: Sagittarius
-Coordinates: RA 18h 05m 13.1s|Dec. -19° 50′ 34.9″
-Distance: 3,000 – 8, 000 light years
-Diameter: Unknown
-Magnitude: 13.0
-Other designations: NGC 6537

Although the star in the centre of this striking nebula is surrounded by dust that makes determining its exact nature difficult, it is generally believed to a white dwarf, which is not uncommon in itself. However, this particular white dwarf emits a 10,000K, 300 km/sec solar wind that piles up the gas in the nebula against the surrounding interstellar medium in “waves” that are at least 100 billion km high.

The waves are created when the out flowing gas encounters surrounding material that prevents the outflow, much like how waves are created when water piles up along the seashore when the beach floor rises. In the case of the Red Spider Nebula, the solar wind from the central white dwarf drives the out flowing gas and dust into areas of least resistance in the surrounding material, which has created the “legs” of the spider.

This particular white dwarf is also one of the hottest such stars known- estimates of its temperature range from about 150,000K to more than 500,000K, and while the upper limit is disputed by some investigators, the lower limit is widely accepted to be possible.

Butterfly Nebula

Image Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona

-Nebula type: Planetary nebula
-Constellation: Monoceros
-Coordinates: RA 07h 09m 22.52s|Dec. -0° 48′ 23.6″
-Distance: 2,000 light years
-Diameter: 0.33 light years
-Magnitude: 11.6
-Other designations: NGC 2346

Not to be confused with several other nebulae named after butterflies, this bright and conspicuous planetary nebula is located close to the celestial equator, and is one of the most intensely studied planetary nebulae on account of its unusually cool central star.

In this case, the central star is spectroscopic binary system with a period of about 16 days. Moreover, the star is also variable, and while the exact reasons for its variability remain uncertain, it is generally believed to be the result of a cloud of dust that is orbiting the system. This is borne out by the fact that the observed dust is unusually luminous in infrared light, which is characteristic of dust that is heated to a high temperature.

In terms of its structure, this nebula is thought to have formed when one of the stars in the binary system had engulfed its companion when it reached the red giant phase. In practice, this meant that the companion was located within the larger star, which in turn, resulted in the solar wind of the engulfed star blowing the outer layers of the red giant into a lobe on either side of the giant star’s now exposed core, thereby creating the butterfly shape shown here.

 

 

Peter Christoforou :