It’s another week and another round of Nebula March Madness! The theme of Round 2 is “What’s it made of?” In this round, we’ll take a look at what makes up the eight remaining nebulae named for animals. But before we jump into Round 2, let’s recap what happened in Round 1.
Birds: Eagle and Parrot’s Head
Mammals: Cat’s Paw and Otter
Sea creatures: Crab and Turtle
Bugs: Butterfly and Tarantula
To be honest, some of these surprise me. Eagle, Otter, and Crab were all expected, but I thought *for sure* both the Horsehead and Manatee would pull through. Heck, I thought the Manatee Nebula had a good shot for making the final round! But alas, the sea cow was defeated by an armored menace.
What is a nebula?
A nebula is a cloud of gas and dust in outer space. Nebulae vary in size and composition and can have atomic, ionized, or even molecular gas. Some nebulae consist of molecular clouds which are sometimes affectionately called stellar nurseries (if they contain star-forming regions, that is!).
Nebulae are often named for what observers think they look like, and I've selected 16 nebulae that have been named for animals. I've divided these up into those named for birds, mammals, sea creatures, and bugs, and each week we will eliminate a handful of nebulae and learn a bit more about the rest.
ROUND 2: What's it made of?
This round focuses on what types of matter—or stuff—make up the remaining nebulae. Since the compositions of these nebulae are quite similar, I'll also throw in astronomical objects (or types of objects)—like stars or clusters—that reside in these regions.
BIRDS: Eagle Nebula vs. Parrot’s Head Nebula
The Eagle Nebula, located in the constellation Serpens, is part of a diffuse emission nebula, or HII (“H-two”) region. An emission nebula is formed of partially ionized gas that emit light at various wavelengths. HII is ionized atomic hydrogen, or H⁺, and is present in regions where star formation has recently taken place. The Eagle Nebula is home an estimated 8100 stars that are mostly concentrated to the northwest of the famous “Pillars of Creation”. There are several other active star-forming regions of gas and dust located in the nebula as well.
The Parrot’s Head Nebula, often called the Seagull Nebula, is also an HII region that is actively forming stars in the constellation Monoceros. It is roughly circular and centered about the star HD 53367, but the emission region is often described to include the open clusters NGC 2335 and NGC 2343, along with neighboring dust clouds that help define its birdlike shape.
MAMMALS: Cat’s Paw Nebula vs. Otter Nebula
The Cat’s Paw Nebula, sometimes referred to as the Bear Claw Nebula, is an emission nebula and star-forming region located in the constellation Scorpius. In addition to being an HII region, it may contain tens of thousands of stars, but many of them are concealed by the nebula’s dust. The Cat’s Paw Nebula is home to a number of hot young stars, each of which is about 10 times as massive as the Sun and formed only within the last few million years, which are responsible for the nebula’s glow.
The Otter Nebula, officially NGC 604, is also an HII region located inside the Triangulum Galaxy. The gas in the Otter Nebula is ionized by a cluster of massive stars—around 200 stars of spectral type O, which are the most massive (100,000 solar masses) and hottest stars—in its center. However, this cluster is less compact than other clusters, such as that in the Tarantula Nebula.
SEA CREATURES: Crab Nebula vs. Turtle Nebula
The Crab Nebula is a supernova remnant in the constellation of Taurus with numerous filaments emitting visible light. These filaments are remnants of the atmosphere of the progenitor star (the star that exploded as the supernova) and are made up largely of ionized helium and hydrogen. The filaments also contain carbon, oxygen, nitrogen, iron, neon, and sulphur, all of which were fused from hydrogen and helium inside the star as it aged. A prominent feature of the Crab Nebula is a helium-rich torus (geometrical shape like that of a ring donut) stretching from east to west across the pulsar, a quickly-rotating object with emission coming from either end (think lighthouse in space) that is the result of the star’s core collapse.
The Turtle Nebula is a planetary nebula in Hercules, which is an expanding shell of ionized gas ejected from aging red giant stars. Such a phenomenon is thought to last only a few tens of thousands of years at the end of a star’s life. Planetary nebulae such as the Turtle Nebula spits elements fused in the star’s core into the interstellar medium. This nebula has hot gas jets streaming through an older shell of relatively cool gas. Despite the term “planetary nebula”, this type of nebula has nothing to do with the actual observations of planets.
BUGS: Butterfly Nebula vs. Tarantula Nebula
The Butterfly Nebula in Scorpius is a bipolar planetary nebula with complex structure not typically observed in these types of objects. At its center is a white dwarf surrounded by a particularly dense disk of gas and dust that may have caused the bipolar outflows. It is also thought that there is a second pair of lobes from previous mass loss. There has been evidence of carbonates, crystalline silicates, crystalline water ice, and quartz, making for some extraordinary dust chemistry. (However, some of these detections remain disputed). Unlike most environments that are either oxygen-rich or carbon-rich, the Butterfly Nebula contains characteristics of both types of chemistry.
Our final nebula of this round is the Tarantula Nebula in the constellation Dorado. This nebula is an HII region in the Large Magellenic Cloud. It is one of the largest HII regions in the Local Group (which consists of more than 50 galaxies near the Milky Way). This nebula is extremely luminous, especially for a non-stellar object. If it were as close as the Orion Nebula (about 1,300 lightyears instead of 160,000 lightyears), it would cast visible shadows at night. Its luminosity is due to the star cluster NGC 2070 at its center, which is thought to be a globular cluster in the making. The Tarantula Nebula contains other star clusters that are much older, some of which contain stars that have already gone supernova.
Which nebulae are your picks? Share in the comments, and don't forget to follow along on Twitter!
All information sourced from Wikipedia.