We don't know whether it was or was not(unlikely) "the last planet vistited by Enterprise", as even though it was, in the series, this is an in-universe article. – The preceding unsigned comment was added by 126.96.36.199 (talk).
When interrogating Klaang, Silik spoke Klingonese and seemed to pronounce the name "Rigel" as raySul (in Marc Okrand's Klingon transliteration system.) If this was also how Klingons pronounce the name, and if the name was in fact a Klingon one, then the Enterprise crew's pronunciation of "Rigel" was an anglicization of raySul (similar to "Canton" being an anglicization of the name of the city of Guangzhou, China as well as the actual name of a city in Ohio.) This provides more support to the contention that the Rigel in ENT (and perhaps in the whole franchise) is most likely not the actual star Rigel. -- Astrophysicophile 16:21, 28 November 2011 (UTC)
In 2293, the location of Rigel, the primary of the Rigel system, in the Milky Way Galaxy was labeled in a star chart that was in Captain James T. Kirk's quarters aboard the USS Enterprise-A. (Star Trek VI: The Undiscovered Country, production art')
In 2366, in an alternate timeline, during the Federation-Klingon War, the location of Rigel was labeled on a tactical situation monitor in the ready room aboard the USS Enterprise-D (TNG: "Yesterday's Enterprise", display graphic)