Leo (Pronounciation:Lee-o, Abbrev:Leo, Latin:Leonis) is a constellation, one of 88 constellations that the night sky is divided into. The sky is not divided up equally between the constellations. Leo takes up 946.964 sq. degrees of the night sky which equates to 2.3% of the night sky. Leo is the 12th largest in terms of size in the night sky.
The constellation name means The Lion . The constellation is one of the original constellations that was devised by the Ancient Greco-Egyptian astronomer Ptolemy who lived between 90 A.D. and 168 A.D.
There are 10 stars that make up the main constellation. The hipparcos satellite scanned and detailed 2128 stars. There are 80 stars that can be seen with the naked eye in the constellation on a very clear night sky.
Leo is a member constellation of the Zodiac grouping, a group of 12 star signs that astrologers use to predict someones future based on their date of birth and which constellation appeared when the Sun set. The Zodiac year may be divided up equally between the twelve signs but when they appear in the night sky no longer conforms to the Zodiac calendar. Leo is an equatorial constellation that can be seen by countries nearest the Equator.
The distance to Leo is not calculable because all the stars that make up the constellation are at various distances. The best answer for distance to Leo is to calculate the average distance of the stars.
There are 28 Extrasolar Planets (Exoplanets) in this constellation that are detailed on this site. There is a dedicated page for exoplanets in Leo. The current largest star so far identified in the constellation of Leo is CW Leonis.
There are 5 deep space objects that were identified by Charles Messier in this constellation. There are no non-Messier deep space objects in this constellation that are covered at present on this site.
The image at the top right of this page was generated using Night Vision, a free to use and download application by Brian Simspon.
The caveat of these stars are that they are catalogued on this site. If you know of a star that is nearer or further then do let me know in the comments and I'll add it to the site. The stars mentioned are from the Hipparcos catalogue or have been added because of their special status.
The furthest star that is located in the constellation is XZ Leonis and it is 108721.1 light years away from the Sun. The furthest figure is derived from either the 1997 or 2007 Hipparcos star catalogue parallax figure and it has been known to produce distances that are wrong.
The dimmest star that can be seen in Leo with the naked eye is 35 Leonis. The dim star has an apparent magnitude of 5.95. The dimmest star that a person is able to see with their naked eye is 6.0 magnitude based on the table in the reference. Ref: University of Michigan.
Algieba is a double star system and also has a planet in orbit. This may sound a little like Tatooine in Star Wars where the desert planet has two stars. The bad news with Algieba is that the planet is a giant gas planet so there's no chance of living on or finding intelligent alien life there. Algieba is not the only star in the constellation to have planets in orbit, there is also Rasalas with a planet, still sadly inhospitable.
Caffau's Star is named after Elisabetta Caffau who led a study into the star. Caffau's Star is an enigma, it shouldn't exist. Analysis of the chemicals in the star, the star is a metal poor star, consisting of mainly hydrogen and helium and not much other metals. It has been estimated that the star is about 13 Billion Years old which if true, it would mean it is one of the Oldest and Earliest Stars in the galaxy.
CW Leonis is one of the largest stars in the night sky. It is a carbon star having gone through its hydrogen and helium stages and now moving into the death stage. As the star is one of the largest and a carbon star, it makes for some interesting study.
The brightest star in the constellation is Regulus, also refered to as Alpha Leonis. The star is multiple star system with four stars including the large blue star that makes up this system. It is one of a group of major stars known that is oval (egg) in shape. The others being Vega and Achernar. The fact that Regulus has orbiting stars could well explain its shape but Vega is a solo star.
In astronomical speak, the constellation contains one of the closest stars to our own, Wolf 359. It is a small red dwarf star that is located to the bottom left of Regulus, near the border with the Sextants constellation. It lies a mere 7.86 light years away but unfortunately we don't have the space ships to travel that distance yet. Nearer stars include Proxima Centauri and Barnard's Star.
Zosma despite it having Delta designation, Zosma is brighter than the star with the Gamma designation, Algieba. Zosma is a fast moving star and it is believed that in about 518,000 years it will brighten up considerably. Zosma is a dying star and will not last as long as other stars.
Leo can be viewed at the beginning of the year from about 10pm on NE-E horizon. If you wait a month, it can be viewed at about 8pm, still on the easterly horizon but as the night carries on. March and April present a better chance to see the constellation when it will be higher in the sky at about 9pm in a easterly direction. May is a good time to see it before it starts getting too bright to see it without staying up even later. At about 10pm, it will be high in the sky to see. Failing that, you will need to wait until December to see it again but only in the really early hours.
The best time to see Leo at about 9pm is in March when it can be viewed on the horizon. As the night goes on, it will rise in the sky but not as much as it does in the northern hemisphere. April, May and June all allow for you to see the constellation at about 9pm.
Leo represents one of the labours of Hercules. He was ordered to do it as punishment for killing his wife. The lion was terrorising the area near Nemea. He killed the beast by strangling it or choking it to death. The skin was thickest of all known animals which meant all weapons were useless against it. Hercules managed to skin the Lion using tools provided to him by Athena.
There are 33 Meteor Showers that occur during the year within this constellation based on information gathered from Adam Mickiewicz University (Poland). The list below are major ones and which I have a date period for.
|Name||Activity||Peak Activity||Closest Star|
|Alpha Leonids||13-Jan - 13-Feb||24/31 Jan||Regulus|
|Southern delta Leonids||23rd February||Zosma|
|Delta Leonids||Feb 15 - Mar 10||Feb 25||Zosma|
|Sigma Leonids||9-Feb - 13 Mar||Feb 25 - 26||Sigma Leonis|
|Northern delta Leonids||27th February||Zosma|
|Rho Leonids||Feb 13 - Mar 13||Mar 1 - 4||Rho Leonis|
|Northern alpha Leonids||9th March||Regulus|
|Beta Leonids||Feb 14 - Apr 25||Mar 19/21||Denebola|
|May Delta Leonids||15th May||Zosma|
|Daytime Gamma Leonids||22th August||Algieba|
|Gamma Leonids||Aug 14-Sept 12||Aug. 25/26||Algieba|
|Daytime Chi Leonids||27th August||Chi Leonis|
|Leonids||November 13-20||Nov. 17/18||Adhafera|
The following list contains the stars that make up the constellation. For a larger list of stars in the entire constellation area, please visit the For a list of named stars, that is stars that don't start HD or HIP, please visit Leo Star List page.
|Name||Bayer||Distance (Lt.Yr.)||Right Ascension||Declination||Spectral Type||Colour|
|Regulus||Alpha Leonis||79.30||10h 08m 22.46||+11d 58` 01.9||B7V||Blue/White|
|Denebola||Beta Leonis||35.88||11h 49m 03.88||+14d 34` 20.4||A3Vvar||White|
|Algieba||Gamma Leonis||130.10||10h 19m 58.16||+19d 50` 30.7||K0III||Orange|
|Zosma||Delta Leonis||58.43||11h 14m 06.41||+20d 31` 26.5||A4V||White|
|Ras Elased Australis||Epsilon Leonis||246.72||09h 45m 51.10||+23d 46` 27.4||G0II||Yellow|
|Adhafera||Zeta Leonis||274.09||10h 16m 41.40||+23d 25` 02.4||F0III||Yellow/White|
|Al Jabhah||Eta Leonis||1269.12||10h 07m 19.95||+16d 45` 45.6||A0Ib||White|
|Chertan||Theta Leonis||165.06||11h 14m 14.44||+15d 25` 47.1||A2V||White|
|Iota Leonis||Iota Leonis||77.22||11h 23m 55.37||+10d 31` 46.9||F2IV SB||Yellow/White|
|Rasalas||Mu Leonis||124.11||09h 52m 45.96||+26d 00` 25.5||K0III||Orange|
|Is a Zodiac Sign||Yes|
|Area||946.964 sq. deg.|
|Percentage of Night Sky||2.3%|
|Site Exoplanet Count||28|
|Meteor Shower Count||33|
|Nearest Star||Wolf 359|
|Nearest Star with Exoplanet(s)||HIP 57087|
|Largest Star||CW Leonis|
|Dimmest Star||35 Leonis|
|Furthest Star||XZ Leonis|
|Bright Star Count||80|
|Hipparcos Star Count||2128|
|Main Star Count||10|
|Messier Deep Space Object Count||5|
|Bordering / Neighbouring / Surrounding Constellations||Leo Minor|
*Note: The number of Non-Messier Deep Space Object Count relates to how many are covered on this site not how many there are.
|Messier 105 (NGC3379)||Elliptical Galaxy||30,400-33,600 kly||+12:35||10h 47m 8|
|Messier 65 (NGC3623)||Spiral Galaxy||41,000-42,000 kly||+13:05||11h 18m 9|
|Messier 66 (NGC3627)||Spiral Galaxy||31,000-41,000 kly||+12:59||11h 20m 2|
|Messier 95 (NGC3351)||Spiral Galaxy||31,200-34,000 kly||+11:42||10h 44m 0|
|Messier 96 (NGC3368)||Elliptical Galaxy||28,000-34,000 kly||+11:49||10h 46m 8|
|NGC 3455||Spiral Galaxy||65 Million Ly||17:17:22.28||10h 54h 29m 72|
|NGC 3810||Spiral Galaxy||50 Million Ly||11:28:02.50||11h 40h 58m 33|
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