2360: Common Star Types
|Common Star Types|
Title text: This article is about Eta Carinae, a luminous blue hypergiant with anomalous Fe[ii] emission spectra. For the 1998 Brad Bird film, see The Iron Giant (film).
This 'infographic' chart purports to be a comparative guide to various star types, often described by a basic color, which is something that even naked-eye astronomy has determined, and may be qualified as 'dwarf' or 'giant' to describe relative sizes. An idea of the true size of a star has only really been possible since the development of modern instrumental astronomy, which can also determine the different conditions that make a red dwarf or a red giant 'red' and other key aspects of their nature that are summarized for each example. See table below.
In true xkcd tradition, this is taken beyond reality. The pantheon of stars illustrated extend the use of 'dwarf' and 'giant' as if describing mythical or fictional beings, drawing upon others from the fantasy ilk with hues and shades that may not be typically described, or even encountered, by astronomers. The aspect information provided for these 'star' types is based upon the respective mythologies.
The title text is in the style of a Wikipedia page's hatnote / reference note. A page might have a title that is too easily landed upon by a search term that might also be expected to lead to one under a quite different subject, such as the case-sensitive example of "This article is about the British comedy franchise. For the type of star, see Red dwarf." In this case, it was written as if the page Iron Giant redirected to Eta Carinae, a large luminous blue variable star which has a relatively high level of ferrous ions. Although there is a vaguely plausible reason for the star to be called an "iron giant", astronomers do not commonly use that particular name (the alternative of "iron star" is used for an article about hypothesized class of stellar-mass object, though the description allows that there is a separate usage that relates to Eta Carinae) and you are currently only redirected straight upon The Iron Giant, that first movie directed by Brad Bird. This note was added to Wikipedia, but quickly removed.
|Yellow Dwarf||warm, stable, slowly growing||A real star type. This is the type of star that our sun is, with a lifespan measured in billions of years. The title "dwarf" is a misnomer, as the Sun is actually larger than most stars, but it was once thought to be smaller than average as larger stars turn out to be more visible than smaller stars over a given distance.|
|Red Giant||huge, cool, luminous||A real star type. When stars at about the Sun's size begin to run out of fusion fuel, they expand to become red giants, and the outer shells expand and cool. When our sun enters this phase in a few billion years, it will consume Mercury, Venus, and possibly the Earth.|
|White Dwarf||small, hot, dim||A real thing, though not a true star, but a remnant of one. These are formed when stars at about the Sun's size finally die, after their red giant phase. They are extremely dense and no longer undergo nuclear fusion. They are responsible for Type Ia supernova, a standard candle of astronomy.|
|Red Dwarf||small, cool, ancient, dim|| A real star type. The most common, smallest, and coolest type of true star in the universe. (Brown dwarfs are smaller and cooler, but do not undergo hydrogen-hydrogen fusion.) These can live for trillions of years; the first red dwarfs to form in the universe are still alive today and will be alive long after the Sun reaches its end.
Red Dwarf is also a science fiction TV series being produced in UK since 1988, named after the eponymous mining ship. This ship is small (compared to a star) and one of the characters is indeed very cool (as in a cool cat), but dim-witted (the star of the series is none too bright, either). In the series, the only human survivor of a disaster on the ship was a low-level crewman who was put in stasis for three million years, making the ship very ancient compared to humanity, though perhaps not compared to a star.
|Green Elf||old, diminishes into the West||An invention of Randall's, and a reference to the elves of Tolkien's legendarium. Tolkien's elves are immortal but slowly diminish over time, and leave Middle-earth (where The Lord of the Rings is set), sailing into the West as magic fades.|
|Blue Giant||large, hot, short-lived||A real star type. The largest class of star in the main sequence, these are highly luminous and have life spans measured in only millions of years, rather than the billions or trillions of years for other star types.|
|Teal Sphynx||cryptic, eternal||An invention of Randall's; likely a form of the Greek sphinx, which presents riddles to hapless travelers. One can only imagine what stellar riddles would be like.|
|Gray Wizard||wise, powerful, mercurial||An invention of Randall's, and also a reference to Lord of the Rings. Gandalf the Grey, a wizard, is a protagonist and the main mentor figure in The Hobbit and The Lord of the Rings, guiding and assisting the journeys within the books, often in mysterious ways that could be described as "mercurial". Gandalf later falls in battle and returns as Gandalf the White, much as stars (up to ~10 solar masses) will evolve into white dwarfs, but this evolution is not shown on this chart. Interestingly, the word for "wizard" in the Elvish language Quenya is istar (plural: istari).|
|Indigo Banshee||bright, portentous, extremely loud||An invention of Randall's, and a reference to banshees, a type of Irish spirit or ghost which wails loudly at a person's death. Indigo may also be considered a particularly loud color. May or may not be a reference to Indigo children, a pseudoscientific term used by some to describe children with unusual personalities or learning abilities. Could also represent a neutron star.|
|Beige Gorgon||dangerous to observe at optical wavelengths|| An invention of Randall's, and a reference to the Gorgon sisters in Greek Mythology, most famously Medusa. "Dangerous to observe at optical wavelengths" refers to the property of Medusa in which anyone who gazes upon her face will turn to stone. However, seeing Medusa's reflection is safe, so most astronomers should be fine. This is probably why its color is known, unlike Medusa's, whose observers have a high mortality rate. The choice of the color "beige" for this kind of "star" may be a reference to cosmic latte, the "average color" of the universe.
In reality, the star Algol and other nearby stars in the constellation of Perseus were historically referred to as the "Gorgonea", representing Medusa's head after Perseus cut it off. Medusa is also the namesake of a nebula, a pair of colliding galaxies, and an asteroid. No observers of any of these celestial bodies have been petrified.
- [A chart, with ten colored circles representing stars of different colors and sizes. Each circle has a label, with a line going from the label to the circle. Below each label is a small description in smaller font. The text is listed from the top left. Above all the circles is the following heading:]
- Common star types
- [A small yellow star.]
- Yellow dwarf
- Warm, stable, slowly-growing
- [An even smaller white star.]
- White dwarf
- Small, hot, dim
- [A very large red-orange star squishing the previous two stars into the corners of the chart.]
- Red giant
- Huge, cool, luminous
- [A small red star.]
- Red dwarf
- Small, cool, ancient, dim
- [An olive green, medium-sized star.]
- Green elf
- Old, diminishes into the west
- [A fairly large pale blue star.]
- Blue giant
- Large, hot, short-lived
- [A blue-green, medium-sized star.]
- Teal sphynx
- Cryptic, eternal
- [A small silver-colored star.]
- Gray wizard
- Wise, powerful, mercurial
- [A tiny blue star.]
- Indigo banshee
- Bright, portentous, extremely loud
- [A beige, medium-sized star.]
- Beige gorgon
- Dangerous to observe at optical wavelengths.
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