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Astronomy Stack Exchange is a Question and Answer site about astronomy and astronomy related topics; the study of objects and matter outside the Earth's atmosphere and of their physical and chemical properties

The purpose of this site is to provide expert level answers to questions on:

  • Setting up, using and maintaining your astronomy related equipment

  • Astronomical observations, for all celestial objects across the entire spectral range.

  • Astrophysics and Cosmology

  • Planetary Science and Celestial mechanics

  • Data returned by space missions such as probes, rovers and satellites

  • What type of equipment will allow you to see a certain entity

What questions are off topic here?

  • Earth science, unless directly related to phenomena observable on other celestials, Solar system in general of which Earth is a constituent part, or as an origin of observational astronomy where its movement, local and global phenomena might affect observations and measurements in any way, is off-topic on Astronomy but can be asked on Physics now or Geoscience once this Stack Exchange site proposal reaches public beta.

  • Questions about maintenance and general use-age of equipment such as the Curiosity Rover. A question can be about data returned by these pieces of equipment, such as atmospheric composition and planetary composition, but questions about the tools on the rover or how the rover cleans its solar panel are off-topic

  • Questions that are purely hypothetical, for example a question such as 'Could a black hole destroy the universe' or 'What if our solar system had two suns'

  • Questions about artificial satellites whose purpose is not directly related to astronomy. You may ask about their orbit, but not their purpose, use-age and safety features

  • Questions asking for a specific brand or model of telescope, these are very time and opinion specific and are likely to incite debate

For more help, see What types of questions should I avoid asking?

How should I give an on-topic answer?

Make sure your answer adds helpful information and is a complete, stand-alone answer. Read other answers first and be sure not to completely restate information that has already been posted.

Good answers should explain why their objective information is accurate either by properly sourcing their answer or by giving enough details that the results could be derived by someone else. This is science after all!

We don't have strict formatting guidelines for citations, but a couple of links to sources doesn't hurt--and keep in mind that not all sources are equal (academic papers are generally better than Wikipedia). Where answers are derived from physical documents, mentioning the title of the source is good, but a formatted citation (using your preferred style) is better.

If you are answering a question with a more subjective bent, or if you want to take on your opinion to an already objective answer, it is fine to simply state that it is your opinion. At least this explains to everyone else where your information comes from.

Can I just use Wikipedia as my source for everything?

Whilst Wikipedia does have a wide range of information there is no way for us to measure its accuracy or validity as it is very easy for the displayed information to change over time, this has knock-on effects when the information changes drastically, perhaps due to a recent discovery.

Where possible try to use reputable sources, there are lots of astronomy and space related site out there, not least of which is NASA, and please don't forget that your source doesn't have to be a website! It could be a paper or even an astronomy magazine in some cases.

Overall you can use Wikipedia sparingly, but if you can back this up with other sources too then this is preferred.


Please look around to see if your question has been asked before. It’s also OK to ask and answer your own question, in fact this type of interaction is encouraged, especially for difficult experiences of yours!

If your question is not specifically on-topic for Astronomy.StackExchange, it may be on topic for another Stack Exchange site. If no site currently exists that will accept your question, you may commit to or propose a new site at Area51, the place where new Stack Exchange communities are democratically created.

  • $\begingroup$ This is a community wiki, feel free to suggest changes to this and if agreed on by the community we can carry the changes on over to the help center too $\endgroup$ – user96 Oct 14 '13 at 15:44
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    $\begingroup$ So, Theoretical Astronomy, Cosmology, etc. are forbidden? . $\endgroup$ – user208 Oct 15 '13 at 1:52
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    $\begingroup$ @DImension10AbhimanyuPS Forbidden is a very strong word, this is still just a rough guide, which is why it is here for discussion too, do you have examples of questions that might fall into this range? $\endgroup$ – user96 Oct 15 '13 at 6:53
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    $\begingroup$ @RhysW to give an example, you can not ask about specific details of inflation models for example? Do you really mean to forbid questions about theoretical astronomy, cosmology, and astrophysics in this way and only allow questions related to observations? $\endgroup$ – Dilaton Oct 15 '13 at 7:35
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    $\begingroup$ @Dilaton as mentioned before, forbid is a strong word, it's here for discussion to point out what we might have missed, I think I can say without a doubt that astrophysics is on topic, for theoretical astronomy, some parts might be some parts might not be, so this might need a bit more refining, and cosmology might require a more in depth discussion too (and rest assured these will definitely be topics of discussion today). Thankyou both for your suggestions! $\endgroup$ – user96 Oct 15 '13 at 7:44
  • $\begingroup$ Thanks @RhysW . Here is my first question as an example of what I mean: astronomy.stackexchange.com/q/648/92 ... ;-). Maybe the term "theoretical" could be exchange with "too hypothetical" if (what I hope) the purpose of this paragraph is not to forbid all questions that lay the focus on more theoretical considerations? $\endgroup$ – Dilaton Oct 15 '13 at 8:28
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    $\begingroup$ Hypothetical - much better phrasing and much appreciated, that's more representative of what we are trying to portray $\endgroup$ – user96 Oct 15 '13 at 8:37
  • $\begingroup$ @RhysW Why did you strike out the sentence Cosmology (the branch of astronomy that deals with the general structure and evolution of the universe.) from the lists of topics that can be asked about here? This was one of my favorite ones ... :-/ $\endgroup$ – Dilaton Oct 15 '13 at 8:44
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    $\begingroup$ @Dilaton not to worry it's not forbidden, I'm just being wary of making overarching decisions single handedly, i'd like to discuss it a bit more with fellow mods and community first, (i edited my above comment to say as much) and I have no intentions to force close your question, I am leaving it to the community to decide if it is something they agree/want to be on topic or not, this is very much early days and part of the scope refining process, hope you understand! $\endgroup$ – user96 Oct 15 '13 at 8:47
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    $\begingroup$ @RhysW I'm good with having Cosmology mentioned explicitly. $\endgroup$ – called2voyage Oct 15 '13 at 12:48
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    $\begingroup$ Your list of on-topic things is kind of strange to me. It would be better to just specify "observations in the whole electromagnetic spectrum" rather than specifying something for radioastronomy. Your definition of astrophysics is strange (and kind of too narrow). The "orbital..." sounds also strange to me. And I don't see really why to put aside planetary science (it's both astronomy and astrophysics, depending what you're doing, but it's not really an independent field). $\endgroup$ – MBR Oct 15 '13 at 15:15
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    $\begingroup$ (cont'd) So, I would put it like that: 1. setting up and using amateur telescope. 2. astronomical observations, for all celestrial objects, in the whole spectral range. 3. astrophysics. 4. Celestrial mechanics. 5. space missions (probes, rovers and telescopes). $\endgroup$ – MBR Oct 15 '13 at 15:17
  • $\begingroup$ @MBR Points taken into account, borrowed lots of your wording, with some edits, as the phrasing was good, your thoughts on the changes? $\endgroup$ – user96 Oct 15 '13 at 15:23
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    $\begingroup$ I agree with @called2voyage about explicitly including cosmology, theoretical or not. In order to understand what we see (galaxies, clusters, large scale structure, the CMB, ...) we must include a discussion about cosmology and cosmology related research. Otherwise, many good questions and answers would be suppressed. Plus, it's a crowd pleaser, and wouldn't we want to attract people to the site? When it comes to how theoretical it may be, my suggestion is if it has never been or is not currently something research has/is addressing. $\endgroup$ – astromax Nov 9 '13 at 14:48
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    $\begingroup$ (cont'd) then it shouldn't be on this site. It's okay to talk about various models of inflation (because people actually do research on this topic and have good reasons for these different models that make specific predictions which can be tested), but it's not okay to talk about a new theory the OP has come up with which ignores every last piece of evidence to the contrary (integrated over the entire history of humankind). $\endgroup$ – astromax Nov 9 '13 at 14:52

This site is for the observational science of Astronomy: how to gather data, where to look for it, with what equipment, who has done what, how we define / catalogue something, also discussing other astro societies, events, e.t.c.

I'm paraphrasing TildalWave. Feel free to edit this into a better format for the help center.

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    $\begingroup$ So, Theoretical Astronomy, Cosmology, etc. are forbidden? . $\endgroup$ – user208 Oct 15 '13 at 1:54
  • $\begingroup$ @DImension10AbhimanyuPS as mentioned, the word 'forbidden' is too strong, as RhysW said, what is on topic is still evolving and the community will decide by their votes. $\endgroup$ – user8 Oct 15 '13 at 10:44

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