Editing Leo (constellation) (section)

===Stars===
{{See also|List of stars in Leo}}
Leo contains many bright stars, many of which were individually identified by the ancients. There are nine bright stars that can be easily seen with the naked eye, four of the nine stars are either first or second magnitude which render this constellation especially prominent. Six of the nine stars also form an [[asterism (astronomy)|asterism]] known as "The Sickle," which to modern observers may resemble a backwards "[[question mark]]", The sickle is marked by six stars: [[Epsilon Leonis]], [[Mu Leonis]], [[Zeta Leonis]], [[Gamma Leonis]], [[Eta Leonis]], and [[Regulus|Alpha Leonis]]. The rest of the three stars form an isosceles triangle, [[Beta Leonis]] (Denebola) marks the lion's tail and the rest of his body is delineated by [[Delta Leonis]] and [[Theta Leonis]].{{sfn|Ridpath|Tirion|2001|pp=166-167}}
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* [[Regulus]], designated [[Alpha Leonis (star)|Alpha Leonis]], is a blue-white [[main-sequence]] star of magnitude 1.34, 77.5 light-years from Earth. It is a [[double star]] divisible in binoculars, with a secondary of magnitude 7.7. Its traditional name (Regulus) means "the little king".
* [[Beta Leonis]], called Denebola, is at the opposite end of the constellation to Regulus. It is a blue-white star of magnitude 2.23, 36 light-years from Earth. The name Denebola means "the lion's tail".
* Algieba, [[Gamma Leonis]], is a [[binary star]] with a third optical component; the primary and secondary are divisible in small telescopes and the tertiary is visible in binoculars. The primary is a gold-yellow [[giant star]] of magnitude 2.61 and the secondary is similar but at magnitude 3.6; they have a period of 600 years and are 126 light-years from Earth. The unrelated tertiary, [[40 Leonis]], is a yellow-tinged star of magnitude 4.8. Its traditional name, Algieba, means "the forehead".
* [[Delta Leonis]], called Zosma, is a blue-white star of magnitude 2.58, 58 light-years from Earth.
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Other named stars in Leo include [[Mu Leonis]], Rasalas (an abbreviation of "Al Ras al Asad al Shamaliyy", meaning "The Lion's Head Toward the South"); and [[Theta Leonis]], Chertan.<ref>{{cite web|title=Star Names|first=R. H. |last=Allen|url=https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Leo*.html}}</ref><ref name="IAU-CSN">{{cite web |url=https://www.iau.org/public/themes/naming_stars/#n4 | title=List of IAU-approved Star Names |access-date=24 January 2022}}</ref>

{| class="wikitable sortable"
|+Brightest Stars of Leo
|-
!Proper Name
!Bayer Designation
!Light Years
!Apparent Magnitude
|-
|Regulus
|[[α Leonis]]
|style="text-align: right;"|79
|style="text-align: right;"|1.35
|-
|Denebola
|[[β Leonis]]
|style="text-align: right;"|36
|style="text-align: right;"|2.14
|-
|Algieba
|[[γ Leonis]]
|style="text-align: right;"|130
|style="text-align: right;"|2.08
|-
|Zosma
|[[δ Leonis]]
|style="text-align: right;"|58
|style="text-align: right;"|2.56
|-
|Algenubi
|[[ε Leonis]]
|style="text-align: right;"|247
|style="text-align: right;"|2.98
|-
|Adhafera
|[[ζ Leonis]]
|style="text-align: right;"|274
|style="text-align: right;"|3.33
|-
|Al Jabhah
|[[η Leonis]]
|style="text-align: right;"|1,270
|style="text-align: right;"|3.49
|-
|Chertan
|[[θ Leonis]]
|style="text-align: right;"|165
|style="text-align: right;"|3.32
|-
|Rasalas
|[[μ Leonis]]
|style="text-align: right;"|124
|style="text-align: right;"|3.88
|}
[[File:Sidney Hall - Urania's Mirror - Leo Major and Leo Minor.jpg|thumb|left|Leo, with Leo Minor above, as depicted in ''[[Urania's Mirror]]'', a set of constellation cards published in London c.1825]]Leo is also home to a bright [[variable star]], the [[red giant]] [[R Leonis]]. It is a [[Mira variable]] with a minimum magnitude of 10 and normal maximum magnitude of 6; it periodically brightens to magnitude 4.4. R Leonis, 330 light-years from Earth, has a period of 310 days and a diameter of 450 [[solar diameter]]s.{{sfn|Ridpath|Tirion|2001|pp=166-168}}

The star [[Wolf 359]] (CN Leonis), one of the [[List of nearest stars|nearest stars]] to Earth at 7.8 [[light-year]]s away, is in Leo.  Wolf 359 is a [[red dwarf]] of magnitude 13.5; it periodically brightens by one magnitude or less because it is a [[flare star]].{{sfn|Ridpath|Tirion|2001|pp=166-168}} [[Gliese 436]], a faint star in Leo about 33 light-years away from the Sun, is orbited by a transiting Neptune-mass [[extrasolar planet]].<ref>{{cite news|url=https://www.theglobeandmail.com/servlet/story/RTGAM.20040831.wplanet20831a/BNStory/specialScienceandHealth |title=Astronomers discover smallest "exoplanets" yet |location=Toronto |url-status=dead |archive-url=https://web.archive.org/web/20090116080659/http://www.theglobeandmail.com/servlet/story/RTGAM.20040831.wplanet20831a/BNStory/specialScienceandHealth/ |archive-date=January 16, 2009 }}</ref>

The [[carbon star]] CW Leo ([[IRC +10216]]) is the brightest star in the night sky at the infrared N-band (10 μm wavelength).

The star [[SDSS J102915+172927]] (Caffau's star) is a population II star in the [[galactic halo]] seen in Leo. It is about 13 billion years old, making it one of the oldest stars in the Galaxy. It has the lowest [[metallicity]] of any known star.

Modern astronomers, including [[Tycho Brahe]] in 1602, excised a group of stars that once made up the "tuft" of the lion's tail and used them to form the new constellation [[Coma Berenices]] (Berenice's hair), although there was precedent for that designation among the ancient Greeks and Romans.<ref>L. Phil Simpson (Springer 2012) Guidebook to the Constellations: Telescopic Sights, Tales, and Myths, p. 235 ({{ISBN|9781441969415}}).</ref>