Editing 1342: Ancient Stars
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==Explanation== | ==Explanation== | ||
− | [[Cueball]] | + | [[Cueball]] is making a common observation; many of the visible stars in the sky are so distant that it takes thousands years for light from that star to reach Earth. However, the brightest star, {{W|Sirius}}, also happens to be one of the nearest at a mere 8.6 {{W|Light-year|light-years}} distance (in other words, the light that was arriving from Sirius in 2014, when the comic was posted, was emitted some time around August 2005). The previous US president, {{W|George W. Bush}}, was in office from 2001 to 2009; as [[Megan]] notes, this isn't terribly impressive. |
− | The title text references the fact that most people have a hard time imagining the large scale of astronomical numbers | + | The title-text references the fact that most normal people have a hard time imagining the large scale of astronomical numbers (for example, the distance between astronomical bodies or the size of the Sun); they typically imagine them as many orders of magnitude smaller than they actually are (this is especially the case with {{W|Supernovas}} as Randall mentions in his What if [http://what-if.xkcd.com/73/ Lethal Neutrinos] - see the line with note 4). |
− | In this case, however, | + | In this case, however, they instead overestimate both the number of stars and their distance by quite a bit. It's frequently cited that about 5,000 - 10,000 stars are visible by the naked eye. The {{W|Bright Star Catalogue}} is a star catalogue that lists all stars of {{W|Apparent magnitude|stellar magnitude}} 6.5 or brighter, which is roughly every star visible to the naked eye from Earth. The catalog contains 9,110 objects, of which 9,096 are stars. To see most of these you need pretty good eyes and a very dark night. Also at any point on Earth you will of course only be able to see less than half of these as the rest are blocked by the Earth! |
− | + | Wikipedia have a list of the {{W|Visible stars|91 brightest stars}}. Of these only 59 are more than 100 light years away and only 6 are more than 1,000 light years away. The farthest on this list, {{W|Eta Canis Majoris|Aludra}}, is "only" 3,200 light years away. (The star {{W|List of stars in Cassiopeia|V762 Cas}} in the {{W|Cassiopeia (constellation)|Cassiopeia constellation}} is listed as being 14818 light years away and still having an {{W|apparent magnitude}} of 5.87 - thus being within the 6.5 limit). | |
− | There are visible objects much | + | There are visible objects much further away, like the {{w|Andromeda Galaxy}} which is 2.5 million light years away and made up of billions of stars. |
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==Transcript== | ==Transcript== | ||
− | + | :[Cueball pointing up into the night sky.] | |
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:Cueball: Just think - the light from that star was emitted thousands of years ago. It could be long gone. | :Cueball: Just think - the light from that star was emitted thousands of years ago. It could be long gone. | ||
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:Megan: That's Sirius. It's eight light-years away. | :Megan: That's Sirius. It's eight light-years away. | ||
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:Cueball: Oh. | :Cueball: Oh. | ||
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:Cueball: Just think - the light from that star was emitted in the previous presidential administration. | :Cueball: Just think - the light from that star was emitted in the previous presidential administration. | ||
− | :Megan: | + | :Megan: Mmm, doesn't pack quite the punch. |
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{{comic discussion}} | {{comic discussion}} | ||
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[[Category:Comics featuring Cueball]] | [[Category:Comics featuring Cueball]] | ||
[[Category:Comics featuring Megan]] | [[Category:Comics featuring Megan]] | ||
[[Category:Astronomy]] | [[Category:Astronomy]] |