I am curious that there are lots of celestial objects (planets, comets, stars, galaxies, etc.) in space. How do we name them?
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3 Answers
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Millennia ago, when only a few thousand stars, a handful of planets and nebulae, and some transient objects like supernovae and comets, were known, people usually named these objects after gods and heros, but also after everyday objects. Stellar constellations that vaguely resembled something known, was named after this. Mars is red, so it was named after the god of war; Mercury, being the fastest to complete one cycle around the Sun, was named the god of messaging and traveling.
With the advent of telescopes, so many objects are now known that we had to come up with a more pragmatic convention, so usually an object is named according to its place in some catalogue, its type, and/or it coordianates on the sky. For instance, a quasar detected at the "J2000" coordinates $\{\mathrm{dec.},\mathrm{RA}\} = \{22^\circ\, 22'\, 56'', -09^\mathrm{h}\, 46^\mathrm{m}\, 36^\mathrm{s}\}$ may be called J2222–0946. An x-ray source observed in the constellation Cygnus may be called Cyg X-1, while its binary counterpart is number 226,868 in the Henry Draper Extension Catalogue and is thus named "HDE 226868" (not to be confused with one of our site moderators).
Oftentimes, an object appears in multiple catalogues, and will thus have multiple names. For instance, a Lyman $\alpha$-emitting galaxy appears in a catalogue of Ly$\alpha$ emitters, but due to its infrared properties, it will also appear in some catalogue over dusty galaxies (though Ly$\alpha$ emitters tend to contain little dust).
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$\begingroup$ @LocalFluff: Okay, thanks for that info. But the phases are visible even without a telescope, as its brightness decreases and increases. I remembered it as this was the reason. But thanks, I'll edit. $\endgroup$– pelaNov 2, 2015 at 13:04
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$\begingroup$ Is there more or less a new catalogue still created for each telescope of survey project conducted? Is this a confusion caused by lack of understanding of what it is one is looking at, making astrophysical categorization hard other than in terms of what has been captured. Or is it about different capabilities of different observatories at different times, making them difficult to join? And is it competitive science groups intentionally making their names? I mean, "quasar", why is that still a term for an object observed? If you or anyone could develop this naming djungle, I'd be delighted. $\endgroup$ Nov 2, 2015 at 19:59
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1$\begingroup$ If a survey is small and targeting only known object, then people may stick to the old names, but I think it's fairly common to create at least a catalogue used internally in the group. For instance, I'm part of a group that observes 14 nearby — and hence already well-known — galaxies. The acronym for the survey is LARS, so although the objects already have names, we refer to them — both internally and in papers — as LARS01, LARS02, etc. I don't think this causes confusion. We do sometimes write the "original" name in a paper, for reference, but for the purpose of what we study, [cont'd below] $\endgroup$– pelaNov 3, 2015 at 7:37
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$\begingroup$ …, it doesn't really matter. Several astronomical databases exist that collect all information and references about objects (e.g. SIMBAD and NED), so typically one will resort to these places if in doubt.</br> I don't know of any competion leading to war on names, but that might be. But the reason those places exist where you can pay to have a star named after your daughter or whatever is that anybody is free to make his own catalogue and call any object whatever he pleases. $\endgroup$– pelaNov 3, 2015 at 7:46
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1$\begingroup$ It's funny that locations on Earth (and the planets and moons) and the naked eye stars, rarely have more than one single name which few questions, even across languages. But I suppose that isn't practical anymore when studying absurd objects beyond the reach of mailmen and taxi drivers. (And there's not much stellar, even quasi, about a AGN black hole, other than that it first looked like a dot in the sky, but I do realize that it's impractical to rename everything everytime astronomy advances. There'll be a big name reform once astronomy has finished its task to know everything.) $\endgroup$ Nov 3, 2015 at 9:05
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Names are only what we agree to call things. Astronomers have a practical need for names, and a romantic sense of discovery being confirmed by the naming. So Astronomers have cooperated to agree on names for astronomical objects.
In 1919 several astronomical associations merged to form the International Astronomers Union (IAU), and it is now the umbrella body to which professional astronomers and national scientific academies belong. As such what the IAU calls things is as close to "official" names as we can get. It is the IAU who set standards and guidelines for the naming of new asteroids, Trans Neptunian Objects, craters on Pluto, exoplanets, etc.
The procedure for naming is roughly: Following discovery the IAU checks that the object really exists, and which astronomer actually discovered it first (sometimes several people report a new object at about the same time, the IAU sorts out priority). The IAU then asks the discoverer to propose a name. The name must be unique, and some objects are named systematically: for example moons of Pluto are named after gods from underworld mythology. The IAU checks this and then confirms the name, if everything is okay.
Stars aren't named by the IAU, with the exception of those that already had names (mostly arabic) from ancient times. There are so many stars that naming them individually would be impractical, and they just get catalogue numbers. Most stars have many catalogue designations each from a different catalogue.
Some objects do get named by general adoption by the media, for example "Tabby's star" has not been designated as such by the IAU, but if people continue to call KIC 8462852 by that name, it may enter general use.
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One of the caveats to this question is that often one object, say a star, will have multiple names or "designations"" for example, one of the most famous stars I can think of (and, as it happens, one of my favourite) is Vega. Vega is also known as $\alpha$-Lyrae, being the brightest star in the constellation of Lyra. This is known as a Bayer designation: whereby the most of the brighter stars were assigned their first systematic names such as alpha ($\alpha$), beta ($\beta$), gamma ($\gamma$), etc. in order of brightness. The Vega name is the Latin name of the star’s parent constellation in genitive (possessive) form. The entirity of Vega's other designations and names are: Wega, Lucida Lyrae, Alpha Lyrae, α Lyrae, 3 Lyr, GJ 721, HR 7001, BD +38°3238, HD 172167, GCTP 4293.00, LTT 15486, SAO 67174, HIP 91262, 织女一. So you can see, there is really multiple names for one object on the sky, depending on which catalogue you use!