# In what sense is this a meaningful description of an extra-solar planet? **URL:** \ **Category:** Factual Questions\ **Created:** [October 1, 2010, 7:29pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765 "2010-10-01T19:29:09Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Skald\_the\_Rhymer](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Skald\_the\_Rhymer](https://boards.straightdope.com/u/Skald_the_Rhymer)\ **Post date:** [October 1, 2010, 7:29pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765/1 "2010-10-01T19:29:09Z")
[From Wikipedia, regarding the newly-discovered "Goldilocks"planet:](http://en.wikipedia.org/wiki/Gliese_581_g) > [@](#): > > **Gliese 581 g** (pronounced /ˈɡliːzə/) or Gl 581 g,[2] is an extrasolar planet, orbiting the red dwarf star Gliese 581, approximately 20.5 light-years away from Earth in the constellation of Libra. The planet in question orbits Gliese 581, which is 20 light-years from Earth. It’s part of the constelllation of Libra, true enough, but constellations are pretty much artifacts of human perception. Alpha Libra is 77 light-years from Sol; Beta, 160 light-years; Gamma, 152; and Sigma, 292. Is there any way in which describing the newly discovered planet in the way quoted is anything but subtly misleading? ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [October 1, 2010, 7:32pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765/2 "2010-10-01T19:32:21Z")
I don’t understand the question… The quote gives the parent star (Gliese 581), how far from us it is (20.5 ly), and what direction to look in our sky to find it (within the constellation Libra). What was misleading? ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [October 1, 2010, 7:33pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765/3 "2010-10-01T19:33:43Z")
What’s your problem with it? Constellations may be human constructs, but in astronomy they’re also ways of breaking up the sky into recognizable portions. The description tells you where in the sky it is as seen from Earth. That strikes me as pretty basic information. Why do you think this is misleading, rather than descriptive? ---
**Author:** ![Skald\_the\_Rhymer](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Skald\_the\_Rhymer](https://boards.straightdope.com/u/Skald_the_Rhymer)\ **Post date:** [October 1, 2010, 7:36pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765/4 "2010-10-01T19:36:54Z")
> [@mlees](#): > > I don’t understand the question… > > The quote gives the parent star (Gliese 581), how far from us it is (20.5 ly), and what direction to look in our sky to find it (within the constellation Libra). > > What was misleading? > [@CalMeacham](#): > > What’s your problem with it? Constellations may be human constructs, but in astronomy they’re also ways of breaking up the sky into recognizable portions. The description tells you where in the sky it is as seen from Earth. That strikes me as pretty basic information. > Why do you think this is misleading, rather than descriptive? Probably I read the wiki too hastily. It just made it sound, to me, as if the \*planet \*were being described as being in Libra. I suppose an amateur astronomer might wish to take a gander at the star itself, in which case the constellation information is useful. It’s meaningless as regards the planet, though, as an amateur astronomer is not going to possess a telescope capable of picking it up. Anyway, looking more closely I see that the Libra remark is in reference to the star rather than the planet. Like I said, too hasty reading. ---
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [October 1, 2010, 7:48pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765/5 "2010-10-01T19:48:53Z")
It would be equally correct to say that the planet is in Libra. Astronomers define constellations not as groups of stars but as regions in the sky, with precisely delineated boundaries. So every celestial object is within some constellation. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 1, 2010, 7:59pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765/6 "2010-10-01T19:59:20Z")
Here’s an [map](http://en.wikipedia.org/wiki/File:Libra_constellation_map.svg) showing the boundaries of the astronomical constellation Libra. According to astronomical usage, everything within the dotted lines is in the constellation, even though the traditional constellation is only made up of a few stars. ---
**Author:** ![Lust4Life](https://avatars.discourse-cdn.com/v4/letter/l/ecc23a/32.png) [@Lust4Life](https://boards.straightdope.com/u/Lust4Life)\ **Post date:** [October 2, 2010, 12:19pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765/7 "2010-10-02T12:19:50Z")
No, no you’re missing the point. The planet being in Libra means that it is sensitive, artistically inclined and probably likes walking barefoot on the beach. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [October 2, 2010, 12:34pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765/8 "2010-10-02T12:34:07Z")
> [@Lust4Life](#): > > No, no you’re missing the point. > > The planet being in Libra means that it is sensitive, artistically inclined and probably likes walking barefoot on the beach. We Librans hate being stereotyped this way. _sob_ I may go down to the beach and write a poem about your insensitivity. ---
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [October 2, 2010, 12:55pm UTC](https://boards.straightdope.com/t/in-what-sense-is-this-a-meaningful-description-of-an-extra-solar-planet/555765/9 "2010-10-02T12:55:16Z")
Astronomers draw a distinction between [constellations](http://en.wikipedia.org/wiki/Constellation) and [asterisms](http://en.wikipedia.org/wiki/Asterism_%28astronomy%29). What the layperson calls a constellation, the astronomer refers to as an asterism.