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| Planets and Bright Stars |
 Title text: An old astronomer trick for distinguishing the Sun from other stars is to take multiple photos a few minutes apart and overlay them, making the Sun stand out due to its high proper motion. |
Explanation
This comic features a chart of a handful of cosmic objects (all planets or stars) and what they look like in the night sky. The joke is that they are all nearly identical dots, making the chart almost useless.
The comic shows an identification chart for some of the planets and bright stars visible at night from Earth. Bright shiny objects are often confused by people without astronomical experience, and the chart is supposed to make this easier by placing them adjacent to one another to easily see the differences. The joke is that the pictures look almost identical to one another, and therefore the chart isn't helpful at all.
The real way of distinguishing these objects is by their location in the sky. Stars can be found by using constellations, which are an apparent pattern of bright stars that make different regions of the sky distinguishable from one another. The planets can be distinguished by not belonging to the constellations, and further differentiated by their color, brightness, and movement relative to the stars (on the scale of weeks or months).
Selected objects do indeed look similar to one another in reality, but not identical. Some of them (in particular, the star Betelgeuse and the planet Mars) have a distinct reddish color, which can be seen in good conditions. The brightness is also different, and it can serve as a guide, but it's difficult to precisely judge brightness by eye, and the planets don't have a constant brightness over time. The differences are actually visible in the comic to a degree - e.g., the spots for Venus and Jupiter are slightly larger than the others - but they're subtle enough to not recognize at first glance.
Each 'object' also has a color, albeit extremely desaturated (very nearly white). If deliberately exaggerated, the comic's planets and suns are all notably non-white.
- Planets:
- Venus: the yellowy-orange hue of its cloud layers.
- Mars: the red of its surface (given more muted saturation, in the comic, for the joke to work?).
- Jupiter: the general orange hue of its combined cloud layers.
- Saturn: a more 'peachy' orange of its clouds (no obvious hint of its ring system).
- Mercury: a yellow surface (not typically noted, in true-hue images, perhaps artistic licence from its proximity to the Sun).
- Stars
- Sirius (binary system, primarily a main sequence A-type star): light blue.
- Procyon (subgiant F-type star): more light green, or yellowy-blue/cyan.
- Antares (M-type star, red supergiant): orange.
- Altair (A-type, main sequence): light blue.
- Betelgeuse (M-type, red supergiant): relatively dark red (usually visible as such in real eyes-only observations).
- Vega (A-type, main sequence): light blue.
- Polaris (ternary star-system, dominant member being an F-type yellow supergiant): extremely unsaturated cyan.
Using even a small telescope would make it easy to distinguish the planets by their brightness, size, and surface features. Additionally, using a spectroscope would allow for a measurement of the star's spectrum, which coupled with its brightness would allow an astronomer to distinguish the mentioned stars.
The title text suggests a "trick" for recognizing the Sun among other stars, suggesting measuring its proper motion (a measure of the change in apparent position against the more distant 'fixed' background of stars, as an angular rate to specify some angle per time) by overlaying several images, a similar principle to the blink comparator. This does indeed differentiate it from other stars, but there are much easier methods, such as its extreme brightness and large angular size.[citation needed] It is also completely unnecessary, except during a solar eclipse, because stars are not usually visible during the day, when the Sun is out. Additionally, "proper motion" is a term usually not used for the Sun.
Transcript
- [Caption: Planets and bright stars identification chart:]
- [A 4x3 grid of planets and stars are displayed on a black background. White text below dots of light caption which object it is. Planets and stars are represented by almost-identical slightly fuzzy dots of white light.]
- Venus
- Mars
- Jupiter
- Saturn
- Mercury
- Sirius
- Procyon
- Antares
- Altair
- Betelgeuse
- Vega
- Polaris
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