Editing Sirius (section)

=== Distance ===
In his 1698 book, ''Cosmotheoros'', [[Christiaan Huygens]] estimated the distance to Sirius at 27,664&nbsp;times the [[Astronomical unit|distance from the Earth to the Sun]] (about 0.437&nbsp;light-year, translating to a parallax of roughly 7.5&nbsp;arcseconds).<ref>{{cite book |last=Huygens |first=C. |author-link=Christiaan Huygens |year=1698 |title={{math|ΚΟΣΜΟΘΕΩΡΟΣ}}, sive De terris cœlestibus earumque ornatu conjecturae |publisher=Apud A. Moetjens, bibliopolam |location=The Hague |pages=137 |language=la |url=https://catalog.lindahall.org/permalink/01LINDAHALL_INST/19lda7s/alma991342203405961}}</ref> There were several unsuccessful attempts to measure the [[Stellar parallax|parallax]] of Sirius: by [[Jacques Cassini]] (6&nbsp;seconds); by some astronomers (including [[Nevil Maskelyne]])<ref name="Maskelyne1761">{{cite journal |last=Maskelyne |first=N. |author-link=Nevil Maskelyne |year=1759 |title=LXXVIII. A proposal for discovering the annual parallax of Sirius |journal=[[Philosophical Transactions of the Royal Society]] |volume=51 |pages=889–895 |bibcode=1759RSPT...51..889M |doi=10.1098/rstl.1759.0080|doi-access=free}}</ref> using [[Nicolas-Louis de Lacaille|Lacaille]]'s observations made at the [[Cape of Good Hope]] (4&nbsp;seconds); by [[Giuseppe Piazzi|Piazzi]] (the same amount); using Lacaille's observations made at [[Paris]], more numerous and certain than those made at the Cape (no sensible parallax); by [[Friedrich Bessel|Bessel]] (no sensible parallax).<ref name="Henderson1840">{{cite journal |last=Henderson |first=T. |year=1840 |title=On the parallax of Sirius |journal=[[Memoirs of the Royal Astronomical Society]] |volume=11 | pages=239–248 |bibcode=1840MmRAS..11..239H}}</ref>

Scottish astronomer [[Thomas Henderson (astronomer)|Thomas Henderson]] used his observations made in 1832–1833 and South African astronomer [[Thomas Maclear]]'s observations made in 1836–1837, to determine that the value of the parallax was 0.23&nbsp;[[arcsecond]], and error of the parallax was estimated not to exceed a quarter of a second, or as Henderson wrote in 1839, "On the whole we may conclude that the parallax of Sirius is not greater than half a second in space; and that it is probably much less."<ref name=henderson>{{cite journal |last=Henderson |first=T. |author-link=Thomas Henderson (astronomer) |year=1839 |title=On the parallax of Sirius |journal=Monthly Notices of the Royal Astronomical Society |volume=5 |issue=2 |pages=5–7 |bibcode=1839MNRAS...5....5H |doi=10.1093/mnras/5.2.5 |doi-access=free}}</ref> Astronomers adopted a value of 0.25&nbsp;arcsecond for much of the 19th&nbsp;century.<ref name="Holberg2007-45"/> It is now known to have a parallax of nearly {{val|0.4|u=arcseconds}}.

The Hipparcos parallax for Sirius indicates a distance of {{val|8.60|u=light years}}, statistically accurate to plus or minus 0.04&nbsp;[[light year]]s.<ref name=aaa474_2_653/> Sirius&nbsp;B is generally assumed to be at the same distance. Sirius&nbsp;B has a [[Gaia Data Release 3]] parallax with a much smaller statistical margin of error, giving a distance of {{val|8.709|0.005|u=light years}}, but it is flagged as having a very large value for astrometric excess noise, which indicates that the parallax value may be unreliable.<ref name=Gaia3/>