Template talk:Units of length used in Astronomy

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Astronomy

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Physics

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Jupiter radius / Jovian radius

I suggest adding this unit to the template, as it is useful for describing the size of both Brown dwarfs & Exoplanets. Roy guevara (talk) 16:31, 24 July 2022 (UTC)[reply]

Gigametres / terametres vs. million / billion kilometres

With the caveat that I'm not an astronomer, I question the inclusion of the large meter-based units in this template. Until viewing certain wiki articles, I had never encountered (in two college astronomy classes and a smattering of popular literature [e.g. Brian Greene, Michio Kaku, various magazine articles from the likes of New Scientist and such]) the words gigametre or terametre (or AmE equivalent) or the unit abbreviations Gm/tm. Quick internet searches for the various terms seem to bear this out: the abbreviations are lost in hits for the likes of General Motors or trademark, while the full names bring only definitions, our article Orders of magnitude (length), and unit converter tools. Meanwhile both "million kilometers"/"million kilometres" and "million km" get news articles on both celestial phenomena and human industrial achievement. Importantly, my quick searches on the Gale scientific databases I happen to have access to at work have the same results: nothing for the larger units, plenty for "million km." For the heck of it, I also used the DuckDuckGo search engine to try site:britannica.com gigametre, with four (4) results; meanwhile site:britannica.com "million km" got many pages of hits. Importantly, "Gm" ought to be deprecated anyway for needlessly causing noise if people are searching for gravitational equations - all of which use some variant of GM... or GMm... where G is the gravitational constant, not the prefix giga- (and M/m is the mass of an object, not the SI distance unit).

The long and short of all this is that even if some cutting edge astronomy journals might use Gm and tm to describe distances at approximately the AU scale, this isn't a widespread practice and readers are far more able to process and quickly comprehend x million km than Gm or tm. I would therefore suggest gigametre and terametre should be removed from this template and deprecated in our articles (where, thankfully, they mostly don't appear anyway). ZenSwashbuckler 16:22, 10 November 2025 (UTC)[reply]

gigameter and higher are mostly not used in astronomy. As you say, it's close to AU, which is a much more useful unit in astronomy. I'd suggest removing those from the template. - Parejkoj (talk) 19:00, 17 November 2025 (UTC)[reply]

Done. ZenSwashbuckler 15:43, 24 November 2025 (UTC)[reply]