Talk:Q44559

Autodescription — exoplanet (Q44559)

description: any planet beyond the Solar System

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Classification of the class exoplanet (Q44559)  

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Notified participants of WikiProject Astronomy Hi, I noted that many exoplanets in statements have instance of star, although exoplanet is not a star – cf. HR 8799 d (Q778639) v. HR 8799 c (Q1335138). Please, check it out. Thank you. --Kacir (talk) 11:42, 29 December 2019 (UTC)[reply]

@Kacir: an exoplanet is not a star but an exoplanet could have been considered as a star, it's important to store this data. For HR 8799 d (Q778639) there is a reference (that need to be checked, I don't see this information in the reference) so it should stay as it is. For HR 8799 c (Q1335138), the situation is the same but the value of instance of (P31) has been removed by Romuald 2 and the removal seem wrong (again with th caveat that the reference need to be checked). In both case, it seems the value was added by Ghuron who might tell us more. Cheers, VIGNERON (talk) 16:28, 29 December 2019 (UTC)[reply]

@Kacir, VIGNERON: of cause exoplanet is not a star, but [1] under "other object types" lists "* (HD,HR)". I'm just loading info from SIMBAD (with deprecated rank for "other object types"), feel free to delete them if you believe it is useless Ghuron (talk) 16:37, 29 December 2019 (UTC)[reply]

These values are present on Simbad because when the object appears in certain catalogs (HD, HR, Gaia...) it seems that Simbad add automatically the "star" attribute, even when it is obviously wrong (for example, on these exoplanets where no one has ever affirmated that they are stars. So even the "depreciated" statement is wrong in my opinion, it should not be present at all). Or even worse, on many galaxies because they are present in Gaia Data Release 2 (Q51905050) and because Simbad does not differenciate the concept of "source" in the catalog vs the fact that it is not necessarily a star (but I can understand that it is easier to add the attribute automatically because Gaia DR2 is a huge catalog with more than a billion stars!). And yes I've deleted the statement in HR 8799 c (Q1335138) because I've done some months ago a maintenance task where I removed all these obviously erroned statements that where marked as normal rank (Q73737153) for every constellation. Romuald 2 (talk) 17:35, 29 December 2019 (UTC)[reply]

(edit conflict) @Ghuron, Kacir, VIGNERON: HR 8799 d (Q778639) is an exoplanet (only) associated with the star HR 8799 (Q584300). It is doubtful that it would have been mistaken for a star. The SIMBAD reference does not state that it is or was identified as one. In general, any object cataloged as "HD 1234 a" (number followed by a letter designation) should not be an instance of star unless a reference explicitly states that there is ambiguity, ie. a brown dwarf (Q101600). Any HD with no trailing letter is a star. The "object type" in SIMBAD refers to the type of catalog scheme, not the type of physical object. --Mu301 (talk) 17:48, 29 December 2019 (UTC)[reply]

Thanks for the explanation, I understand better now. Romuald 2 (talk) 18:13, 29 December 2019 (UTC)[reply]

@Mu301, Romuald 2, Kacir, VIGNERON: That is an interesting hypothesis, but the problem is that I'm seeing SIMBAD data through TAP, and they expose only subset of information, shown in UI. All "other types" for HR 8799 d (Q778639) are shown as "* |Pl?|Pl "(can give you adql query for this) and I have no idea whenever they came from "catalog scheme" or actual reference. I guess the easiest way to fix this (and other instance of (P31) discrepancies) would be post-processing of loaded data here. For instance I can remove all instance of (P31)star (Q523) statements from those exoplanets. If there are any other issues, we can deal with them similar way. What do you think? Ghuron (talk) 06:50, 30 December 2019 (UTC)[reply]

This is not a "hypothesis" it is a fact. Those "codes" are merely showing that they are using an extension to Henry Draper Catalogue (Q111130) to detail exoplanets that orbit HD listed stars. Yes, all references to HD exoplanets (with a trailing letter designation) should be removed from the star instance classifcation. Those are all exoplanets, not stars. --Mu301 (talk) 07:19, 30 December 2019 (UTC)[reply]

Done, let me know if any other corrections needed Ghuron (talk) 15:00, 30 December 2019 (UTC)[reply]

I don't know if that would be feasible too for the galaxies that have an entry in the Gaia Data Release 2 (Q51905050) catalog. Some examples : NGC 1275 (Q497687), NGC 5679 (Q205266), NGC 6452 (Q731617), ... Romuald 2 (talk) 20:51, 1 January 2020 (UTC)[reply]