Difference between revisions of "1371: Brightness"

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==Explanation==
 
==Explanation==
Exoplanets are planets outside of our solar system, and exoplanet astronomers are astronomers who attempt to discover and study such planets. One method of discovering exoplanets is detecting fluctuations in a star's brightness over time.  Such fluctuations could be caused by a planet's orbit around the star, partially blocking the light that reaches an observer on Earth.  In the comic, the exoplanet astronomer is trying to observe the sun through the ground at night, observing that it has decreased in brightness compared to daytime (which it has by 100%). She then rightfully concludes that the star is orbited by at least one planet (the Earth), which is of course true.
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{{w|Exoplanets}} are planets outside of our solar system, and exoplanet astronomers are astronomers who attempt to discover and study such planets.
  
The title text refers to another method of discovering exoplanets by detecting light reflected off of them from nearby stars. Observing the light that reflects off of the Earth is in fact how was see everything around us, so one hardly needs to be an exoplanet astronomer to discover the Earth in this way.
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[[Megan]] is using a common exoplanet {{w|Exoplanet#Indirect_methods|discovery technique}} to discover a planet around a nearby star. When a planet passes between an observing astronomer and a star, the planet will block some tiny part of the light coming from that star, causing it to appear dimmer for some amount of time. The {{w|Kepler (spacecraft)|Kepler telescope}} used this technique to find evidence for exoplanets.
  
This comic shows Megan using a common [http://en.wikipedia.org/wiki/Exoplanet exoplanet] discovery [http://en.wikipedia.org/wiki/Exoplanet#Indirect_methods technique] to discover a planet (Earth) around a nearby star (the Sun). When a planet passes between an observing astronomer and a star the planet will block some of the light coming from that star causing it to appear dimmer for some amount of time. When the Earth does this, we call it [http://en.wikipedia.org/wiki/Night Night]
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But here Megan is standing on the surface of the Earth at night, looking at the ground, and therefore presumably looking in the direction of the sun. By observing that it is completely occluded at night, she correctly concludes that the Sun is orbited by at least one planet: the Earth. This is obviously an absurd usage of that method. Reasons include the fact that exoplanets are not big enough to block out all of their stars' light when seen from Earth{{Citation needed}}, making what Megan says a massive understatement, and that the period of the brightness oscillations would correspond to the length of a day, not a year as it would for exoplanets.
  
The title text alludes to using more complicated techniques to look observe light reflected off of small, dark planets like the Earth. For example, detecting [http://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets#Polarimetry polarized light] reflected from the planet's atmosphere. Since these require light from the star to reflect off of the planet, it's easier for us to image the Earth directly during daylight hours.
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The title text alludes to using more complicated techniques to observe light reflected by small planets like the Earth, for example by detecting {{w|Methods of detecting exoplanets#Polarimetry|polarized light}} reflected from the planet's atmosphere. In some sense, observing the light that reflects off of the Earth during the day is in fact how we see everything around us. It also implies that astronomers, who because of their career choice are more likely to work at night, might be completely unaware of Earth's existence in the daytime and thus surprised to "discover" it from their nighttime work.
 
 
More details at: http://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
 
  
 
==Transcript==
 
==Transcript==
:[Megan is standing on a black (night-time) background, staring at the ground.]
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:[A black panel with white text and a white Megan who is standing staring at the ground.]
 
:Megan: Based on this decrease in the star's brightness, I believe it is orbited by at least one planet.
 
:Megan: Based on this decrease in the star's brightness, I believe it is orbited by at least one planet.
  
:Exoplanet Astronomers At Night
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:[Caption below the panel:]
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:Exoplanet astronomers at night
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==Trivia==
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*The title text may also be a reference to [[1231: Habitable Zone]] where an astronomer is messed up by someone who puts a mirror in front of the telescope.
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*More details at: {{w|Methods of detecting exoplanets}}.
  
 
{{comic discussion}}
 
{{comic discussion}}
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[[Category:Comics with inverted brightness]]
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[[Category:Comics featuring Megan]]
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[[Category:Astronomy]]
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[[Category:Exoplanets]]

Revision as of 16:36, 15 August 2021

Brightness
Recently, some exoplanet astronomers have managed to use careful analysis of reflected light to discover Earth during the day.
Title text: Recently, some exoplanet astronomers have managed to use careful analysis of reflected light to discover Earth during the day.

Explanation

Exoplanets are planets outside of our solar system, and exoplanet astronomers are astronomers who attempt to discover and study such planets.

Megan is using a common exoplanet discovery technique to discover a planet around a nearby star. When a planet passes between an observing astronomer and a star, the planet will block some tiny part of the light coming from that star, causing it to appear dimmer for some amount of time. The Kepler telescope used this technique to find evidence for exoplanets.

But here Megan is standing on the surface of the Earth at night, looking at the ground, and therefore presumably looking in the direction of the sun. By observing that it is completely occluded at night, she correctly concludes that the Sun is orbited by at least one planet: the Earth. This is obviously an absurd usage of that method. Reasons include the fact that exoplanets are not big enough to block out all of their stars' light when seen from Earth[citation needed], making what Megan says a massive understatement, and that the period of the brightness oscillations would correspond to the length of a day, not a year as it would for exoplanets.

The title text alludes to using more complicated techniques to observe light reflected by small planets like the Earth, for example by detecting polarized light reflected from the planet's atmosphere. In some sense, observing the light that reflects off of the Earth during the day is in fact how we see everything around us. It also implies that astronomers, who because of their career choice are more likely to work at night, might be completely unaware of Earth's existence in the daytime and thus surprised to "discover" it from their nighttime work.

Transcript

[A black panel with white text and a white Megan who is standing staring at the ground.]
Megan: Based on this decrease in the star's brightness, I believe it is orbited by at least one planet.
[Caption below the panel:]
Exoplanet astronomers at night

Trivia


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Discussion

Funny. But of course, while this technique, when applied to the sun, correctly infers the earth, it would also infer a planet around pretty much any star except Polaris; presumably incorrectly in at least some cases. 108.162.212.24 13:39, 21 May 2014 (UTC)

I like that - good point... though, there should be a small sliver of Earth where Polaris will be visible during the "day" and will sink slightly below the horizon for the "night", so I would think you could even toss that star into the group, right? It's not EXACTLY above the north pole (it's off by almost 1 degree, I believe) Brettpeirce (talk) 15:08, 21 May 2014 (UTC)

Polaris is not visible at all in the southern hemisphere. Someone who lives exactly on the equator would in theory see it rise and set, but it's tough to observe something that's one degree above the horizon. Jim E (talk) 15:45, 21 May 2014 (UTC)

Assuming he's talking about exoplanet astronomers on Earth, the title-text would require a double reflection. Something on the day-side of the Earth would have to reflect sunlight to space, and something in space would have to reflect this reflected light back into a telescope on the day-side of the Earth. What could this be? The Moon? During a solar eclipse, or even otherwise? (light reflected off the "dark" PART of the moon (washed out by the light reflected by the illuminated part) 108.162.208.169 14:27, 23 May 2014 (UTC)

Nope. A "double reflection" does only happen at a mirror based telescope (most common today). But a refractor telescope just uses lenses to look straight into the space. A mirror at that path would just show yourself like at your bathroom, or at larger distances your house, or the Earth... --Dgbrt (talk) 22:23, 23 May 2014 (UTC)

The brilliance of a star orbited by an exoplanet appears dimmer every time the exoplanet rotates around the star, i.e. once a year in exoplanet time. But in Megan's situation, the sun is occluded by the Earth every 24 hours. Therefore she may conclude that the Earth rotates around the sun in 24 hours... Seudo (talk) 13:02, 24 May 2014 (UTC)

Please feel free to disagree - I'd love a critique - but the first time I read the title text and every subsequent time I read it, I interpret it as the human eye performing "careful analysis" of the "reflected light" from every surface around us... that is, seeing with the naked eye - no mirrors or refraction, no other heavenly bodies involved Brettpeirce (talk) 13:10, 28 May 2014 (UTC)

I'm pretty sure Randall refers to 1231: Habitable Zone because the Polarimetry Method was only successful at this exoplanet: HD 189733 b. But this observations were not done at daylight. Analysing a reflection of the Earth requires daylight, otherwise the reflected object would be black. So "recently" just refers to a former comic here but not that unique and maybe questionable findings by some astronomers. Randall would criticise this single work and media hype on a "blue" planet. An example how he is confused on press releases it this comic: 1189: Voyager 1--Dgbrt (talk) 21:13, 28 May 2014 (UTC)