Editing Sirius (section)

== Observation ==
[[File:Hubble heic0206j.jpg|thumb|right|upright=1.2|Sirius (''bottom'') and the constellation [[Orion (constellation)|Orion]] (''right''). The three brightest stars in this image—Sirius, [[Betelgeuse]] (''top right'') and [[Procyon]] (''top left'')—form the [[Winter Triangle]]. The bright star at top center is [[Gamma Geminorum|Alhena]], which forms a cross-shaped asterism with the Winter Triangle.]]

With an [[apparent magnitude]] of −1.46, Sirius is the brightest star in the [[night sky]], almost twice as bright as the second-brightest star, [[Canopus]].<ref name="Holberg2007-xi"/> From [[Earth]], Sirius always appears dimmer than [[Jupiter]] and [[Venus]], and at certain times also dimmer than [[Mercury (planet)|Mercury]] and [[Mars]].<ref name="Espenak-Mars"/> Sirius is visible from almost everywhere on Earth, except latitudes [[List of northernmost settlements|north of 73°&nbsp;N]], and it does not rise very high when viewed from some northern cities (reaching only 13°&nbsp;above the horizon from [[Saint Petersburg]]).<ref name="Holberg2007-82"/> Because of its [[declination]] of roughly −17°, Sirius is a [[circumpolar star]] from latitudes south of [[73rd parallel south|73°&nbsp;S]]. From the [[Southern Hemisphere]] in early July, Sirius can be seen in both the evening where it sets after the [[Sun]] and in the morning where it rises before the Sun.<ref name="Stargazers2000"/> Along with [[Procyon]] and [[Betelgeuse]], Sirius forms one of the three [[vertex (geometry)|vertices]] of the [[Winter Triangle]] to observers in the [[Northern Hemisphere]].<ref name="Darling"/>

Sirius can be observed in [[daylight]] with the naked eye under the right conditions.<ref>{{Cite journal |last=Können |first=Gunther P. |last2=Tinbergen |first2=Jaap |last3=Stammes |first3=Piet |date=2015-02-01 |title=Naked eye visibility of Sirius in broad daylight |url=https://opg.optica.org/ao/abstract.cfm?uri=ao-54-4-B1 |journal=Applied Optics |language=EN |volume=54 |issue=4 |pages=B1–B7 |doi=10.1364/AO.54.0000B1 |issn=2155-3165}}</ref> Ideally, the sky should be very clear, with the observer at a high altitude, the star passing overhead, and the Sun low on the horizon. These conditions are most easily met around sunset in March and April, and around sunrise in September and October.<ref name="Henshaw1984"/> Observing conditions are more favorable in the Southern Hemisphere, owing to the southerly declination of Sirius.<ref name="Henshaw1984"/>

The orbital motion of the Sirius binary system brings the two stars to a minimum angular separation of 3&nbsp;[[arcsecond]]s and a maximum of 11&nbsp;arcseconds. At the closest approach, it is an observational challenge to distinguish the white dwarf from its more luminous companion, requiring a telescope with at least {{Cvt|300|mm}} aperture and excellent seeing conditions. After a [[periastron]] occurred in 1994,{{efn|
Two full 50.09&nbsp;year orbits following the periastron epoch of 1894.13 gives a date of 1994.31.
}}
the pair moved apart, making them easier to separate with a telescope.<ref name="Mullaney2008"/> [[Apoastron]] occurred in 2019,{{efn|
Two and one-half 50.09&nbsp;year orbits following the periastron epoch of 1894.13 gives a date of 2019.34&nbsp;.
}}
but from the Earth's vantage point, the greatest observational separation occurred in 2023, with an angular separation of 11.333″.<ref name="DoubleStarDatabase">{{Cite web |last=Sordiglioni |first=Gianluca |date=2016 |title=06451-1643 AGC 1AB (Sirio) |url=https://www.stelledoppie.it/index2.php?iddoppia=27936 |access-date=17 April 2020 |website=Double Star Database}}</ref>