2360: Common Star Types

Explain xkcd: It's 'cause you're dumb.
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Common Star Types
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).
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.

Star types[edit]

Star Note Description
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.[citation needed]


[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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I'm thinking a table (Name, appearance, summary, ¿is real?, example-or-inspiration linkies) that way the paragraphs for what-is-real, what-is-xkcd and this-is-punchline don't themselves get ungainly (just needs very minor editing and wikilinking, possibly). And apols again to the first explained who seemed to appreciate their submission as only a placeholder so I overwrote rather than integrated. 22:37, 16 September 2020 (UTC)

[1] remained on Wikipedia for all of six minutes :/ 23:40, 16 September 2020 (UTC)

There now, over a year later. :) EDIT: Oops, this links to the old revision, LOL! NiceGuy1 (talk) 03:54, 26 September 2021 (UTC)

Ten minutes, surely? Lightcaller (talk) 01:55, 17 September 2020 (UTC)

Wat. (Full text here.) Lightcaller (talk) 01:55, 17 September 2020 (UTC)

And of course Brad Pitt is a star of yet another type... 04:53, 17 September 2020 (UTC)

Re Beige Gorgon, this is the average colour of the universe: https://en.wikipedia.org/wiki/Cosmic_latte

Note that FeII spectral lines actually refer to signs of Fe+ ions (neutral is 'I', every ionisation level above that adds 1) but I can't see it mattering to anyone who doesn't read this far and it'd certainly have FeIII lines as well for 2+, or maybe I'm confused myself, so I supported the (chemistry) Ferrous association in the description with a link while I was editing nearby. 09:45, 17 September 2020 (UTC)

My opinion: I'm kinda getting bored of this types of comics here - listing some real scientific stuff and some made up. There's been a lot of them, and they seem repetitive - no real new humor. 11:30, 17 September 2020 (UTC)

YMMV? Looking at the last 100, if I include a very broad justification for inclusion I get just 20% one could say are 'this type', but sub-10% (with 2351 the most recent) if I am more realistic about comparison. And I generally like them, but each to their own. 14:10, 17 September 2020 (UTC)

...Teal Sphinx? :P 14:44, 17 September 2020 (UTC)

I'm not seeing a plausible connection to Teal Swan, myself. BunsenH (talk) 23:19, 18 September 2020 (UTC)
I don't think I believe Indigo Children is relevent, nor the Red Dwarf comedy series (in the table, though the Titletext mention as an example is Ok but is one thing among many that spoils it being concise). I mean, "mercury is (shiny) grey, the grey wizard is mercurial" makes more sense as a possibly inspirational factoid, but I don't want to add that because it's not really that explanatory. But never mind. 23:38, 18 September 2020 (UTC)

Question: What is the style guide for British vs. American Spelling (e.g., Color vs. Colour) in explain xkcd? I've seen quite a bit of that on this page. If it comes down to a vote, I think that we should stick with American spelling in general, because Randall is American. Argis13 (talk) 18:05, 17 September 2020 (UTC)

I believe the wiki standard is "consistency within an article" usually according to how the original contributors set it, where there isn't another factor (like direct quotation). Though before now I've seen perfectly consistent non-US spellings being (incompletely) systematically Americanized over an Anglicised (but possibly just Commonwealth/acceptible-everywhere-but-the-US) original. I don't think Johnson vs. Webster has yet arisen in a 'bracket' comic (or perhaps Merriam-Webster/OED to be actually current) so I don't know we can claim language-lover Randall automatically claims home-turf advantage. ;) 19:46, 17 September 2020 (UTC)

I wonder if the indigo banshee isn't referring to indigo children172.69.34.60 23:30, 17 September 2020 (UTC)

I imagine not. Sometimes a hue is just a hue. But now I think I know where the idea of the Blue Children came from, in another unrelated thing. 00:12, 18 September 2020 (UTC)

Perhaps this comic was inspired by this fact: https://www.zdnet.com/article/20-years-of-linux-on-big-iron/ 13:53, 18 September 2020 (UTC)

Um, I didnt have to solve a catchpa to edit. Anybody know why? -User:Donthaveusername 10:02, 18 September 2020

I believe reCAPTCHA has mechanisms to remember you as well as tracking your behavior on a page to see if you're human without having to pop up a CAPTCHA162.158.79.171 14:32, 23 September 2020 (UTC)

It's rather arbitrary, of course (these distinctions always are), but I had always assumed that "sphinx" was the fictional beast of myth, while "sphynx" refers to the real hairless cat breed. 06:04, 19 September 2020 (UTC)

The indigo banshee might be a neutron star, as they are the smallest stars known (<20 km radius, the indigo banshee is even smaller than the white dwarf, although not by much here just to make it differentiable), extremely hot (100,000 - 1,000,000 K: the hue shifts beyond blue into indigo territory), and often show weird activity patterns (pulsars, X-ray binaries, radio emissions, magnetic fields) when compared to live stars. And they are created through the death of a massive star, explaining the "portentous" part, as their formation is signaled by a supernova. 1572948 (talk) 06:21, 25 July 2021 (UTC)

I'm sad Randall didn't make a gag or even a reference to the Red Dwarf TV series, glad it's well represented in the explanation, at least. :) NiceGuy1 (talk) 03:54, 26 September 2021 (UTC)

The Indigo Banshee reminded me of the screaming sun from Rick and Morty. Psychoticpotato (talk) 22:19, 3 June 2024 (UTC)

Added colour...[edit]

Let me know what you think. The 𝗦𝗾𝗿𝘁-𝟭 talk stalk 11:57, 8 October 2020 (UTC)


Is the scale correct for the real stars? 11:02, 30 November 2020 (UTC)

No, not really. Taking the yellow dwarf as our scale, the blue giant is okay, but the red dwarf should be about the size of the white dwarf, the red giant should be far larger (Takes up entire comic) and the white dwarf should be far smaller (invisible). This is probably a case of artistic license. Argis13 (talk) 14:18, 25 February 2021 (UTC)

Some types of stars can vary in a wide range of sizes as well. Typical properties are shown below.

Yellow dwarf: 0.5-1.3 Rʘ; 0.3-1.2 Mʘ, 4000-6000 K, 0.05-2 Lʘ. White dwarf: 0.003-0.04 Rʘ (between Mercury and Neptune in size, oddly enough the more massive ones are generally smaller), 0.07-1.4 Mʘ, any temperature, always dimmer than their past peak luminosity as a red giant. Red dwarf: 0.09-0.5 Rʘ; 0.07-0.3 Mʘ, 1500-4000 K, 0.00001-0.05 Lʘ. Red giant: 3-2000 Rʘ; 0.3-50 Mʘ, 2500-4000 K, 0.3-650000 Lʘ. Blue giant: 2-400 Rʘ; 2-300 Mʘ, 8000-60000 K, 15-10000000 Lʘ.

Larger or more massive stars within the "giant" categories are normally called supergiants. 1572948 (talk) 06:31, 25 July 2021 (UTC)