Gemini (Pronounciation:Gem-in-eye, Abbrev:Gem, Latin:Geminorum) is a constellation, one of 88 constellations that the night sky is divided into. The sky is not divided up equally between the constellations. Gemini takes up 513.761 sq. degrees of the night sky which equates to 1.25% of the night sky. Gemini is the 30th largest in terms of size in the night sky.
The constellation name means The Twins . 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 17 stars that make up the main constellation. The hipparcos satellite scanned and detailed 1446 stars. There are 74 stars that can be seen with the naked eye in the constellation on a very clear night sky.
Gemini 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. Gemini is an equatorial constellation that can be seen by countries nearest the Equator.
There are 14 Extrasolar Planets (Exoplanets) in this constellation that are detailed on this site. There is a dedicated page for exoplanets in Gemini. The current largest star so far identified in the constellation of Gemini is TV Geminorum.
There are 1 deep space objects that were identified by Charles Messier in this constellation. There are 1 non-Messier deep space objects that are covered on this site and the list is below.
The image at the top right of this page was generated using Night Vision, a free to use and download application by Brian Simspon.
You can't just go to one location and arrive at the constellation because the constellation is made up of stars at different locations and different distances. The nearest main star in the constellation is at a distance of 33.79 light years and the furthest main star is a distance of 1,763.05 light years. The average distance to the main stars is 388.34 light years.
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 nearest star to Earth is Gliese 251 which is roughly about 18.22 Light Years from the Earth. The nearest star to the Earth with an exoplanet is HD 50554 which is about 97.57 Light Years.
The furthest star that is located in the constellation is HD 52961 and it is 163081.7 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 Gemini with the naked eye is 44 Geminorum. The dim star has an apparent magnitude of 6. 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.
Castor is the Alpha star in the constellation but it is not the brightest in the constellation. Castor is a multi-star system of at least three stars which with all the stars together was able to appear brighter than its twin brother Pollux. Castor represents one of the heads of the twins that this constellation is said to represent.
Although it is the brightest star in the constellation, it is afforded that title, it is instead known as Beta Geminorum instead. Pollux is a single star compared to Castor. It is a giant star and one with an exoplanet in orbit round it, something that its brother star doesn't have, a consolation prize.
Gemini is viewable at the beginning of the year in an easterly direction. It can be viewed as early as 6pm but its probably best wait until it gets higher in the sky about 9pm with it moving slightly east. For the first three months, it can be seen in an south-easterly direction gradually getting higher every month. It is possible to see it earlier as soon as it gets dark when its lower down. As the nights get shorter, you need to look later and later at which time, it will be lower on the horizon. From December, it will be visible from 8pm on the horizon, move higher as the night progresses.
Whilst Gemini might be visible before December, the best time to start looking is after November. In December, it will be visible as early as 9pm on the horizon and moving northwards over the course of the night until it peaks about five a.m. If you can't wait that late, beginning of February would be the best time when its higher in the sky about 9-10pm.
Gemini is only visible on the horizon at the beginning of the year when you look for it about 9pm but with the heads missing, its best to wait for another hour so that you can see them. They stay low on the horizon compared to where they go in the Northern hemisphere. March and April present the best time to see them in Sydney, Australia before they disappear.
In Darwin, they can reach higher in the sky, being close to the equator. You would need to stay up later. March would be the best time to see them in this location.
Zeus seduced Leda, the wife of Tyndareus whilst as a swan. Helen and Pollux were born from eggs. At the same time, Castor and Clytaemnestra were born, children of Tyndareus. Pollux was the son of a god and an immortal, he could not die. They grew up as brothers, competing against one another in competitions and Olympics. During competition between them and their cousins, Idas and Lynceus, Castor died. Pollux asked Zeus to allow him to die so that he could be with his brother which Zeus allowed.
The Geminids are one of the more spectacular meteor showers of the year. They occur at the end of the year, peaking about the 13/14th December. What makes them interesting is that they are multi-coloured rather than all just one colour.
The radiant point for the meteorites is near Castor, the Alpha star in the constellation but not the brightest. The star signifies the right head of the twins. Castor is a multiple star system that when you view closely, you will see it is not just one but a couple of stars.
Whilst meteor showers are associated with comets, this one is associated with an asteroid which was once believed to be a comet but lost all its dust and ice. The asteroid Phaethon orbits closest to the Sun than any other asteroid and has an orbit of roughly 524 days.
There are 11 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|
|Rho Geminids||28-Dec - 28 Jan||8/9 Jan||Rho Geminorum|
|Epsilon Geminids||Oct 14 - Oct 27||Oct 18||Mebsuta|
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 Gemini Star List page.
|Name||Bayer||Distance (Lt.Yr.)||Right Ascension||Declination||Spectral Type||Colour|
|Castor||Alpha Geminorum||50.87||07h 34m 36.00||+31d 53` 19.1||A2Vm||White|
|Pollux||Beta Geminorum||33.79||07h 45m 19.36||+28d 01` 34.7||K0IIIvar||Orange|
|Alhena||Gamma Geminorum||109.30||06h 37m 42.70||+16d 23` 57.9||A0IV||White|
|Wasat||Delta Geminorum||60.47||07h 20m 07.39||+21d 58` 56.4||F0IV...||Yellow/White|
|Mebsuta||Epsilon Geminorum||844.98||06h 43m 55.93||+25d 07` 52.2||A3mA6-A9||White|
|Mekbuda||Zeta Geminorum||1376.22||07h 04m 06.54||+20d 34` 13.1||G3Ibv SB||Yellow|
|Propus||Eta Geminorum||384.63||06h 14m 52.70||+22d 30` 24.6||M3III||Red|
|Theta Geminorum||Theta Geminorum||189.08||06h 52m 47.34||+33d 57` 40.9||A3III||White|
|Iota Geminorum||Iota Geminorum||120.36||07h 25m 43.68||+27d 47` 53.8||G9III+...||Yellow|
|Al Kirkab||Kappa Geminorum||141.38||07h 44m 26.87||+24d 23` 53.3||G8III||Yellow|
|Lambda Geminorum||Lambda Geminorum||100.89||07h 18m 05.61||+16d 32` 25.7||A3V...||White|
|Tejat||Mu Geminorum||231.65||06h 22m 57.59||+22d 30` 49.9||M3IIIvar||Red|
|Nu Geminorum||Nu Geminorum||544.51||06h 28m 57.79||+20d 12` 43.8||B6III||Blue/White|
|Alzirr||Xi Geminorum||58.70||06h 45m 17.43||+12d 53` 45.8||F5IV||Yellow/White|
|Tau Geminorum||Tau Geminorum||321.03||07h 11m 08.39||+30d 14` 43.0||K2III||Orange|
|Upsilon Geminorum||Upsilon Geminorum||270.90||07h 35m 55.37||+26d 53` 45.6||K5III||Orange|
|35 Geminorum||1763.05||06h 50m 25.50||+13d 24` 47.5||K3III||Orange|
|Is a Zodiac Sign||Yes|
|Area||513.761 sq. deg.|
|Percentage of Night Sky||1.25%|
|Site Exoplanet Count||14|
|Meteor Shower Count||11|
|Nearest Star||Gliese 251|
|Nearest Star with Exoplanet(s)||HD 50554|
|Largest Star||TV Geminorum|
|Dimmest Star||44 Geminorum|
|Furthest Star||HD 52961|
|Bright Star Count||74|
|Hipparcos Star Count||1446|
|Main Star Count||17|
|Messier Deep Space Object Count||1|
|Bordering / Neighbouring / Surrounding Constellations||Auriga|
*Note: The number of Non-Messier Deep Space Object Count relates to how many are covered on this site not how many there are.
|Eskimo Nebula||Planetary Nebula||2,870||+20d 54` 42.488||07h 29m 10m 7669|
|IC 443||Supernova Remnant||+22 39 36||06 18 02m 7|
|Jellyfish Nebula (IC443)||Supernova Remnant||5000||22:31:05||06h 17h 13|
|Medusa Nebula||+13 14 48.589321539||07 29 02m 7094421237|
|Messier 35 (NGC2168)||Open Star Cluster||2800||+24:20||06h 08m 9|
|NGC 2158||Open Star Cluster||11,000||24:5||06h 07h 25|
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