The ‘Twins of Gemini’ is a well known zodiac constellation that represents the zodiac sign from May 21 – June 20. However, in modern times the sun passes through the Gemini constellation approximately 1 month later. Gemini is prominent in the night sky because of the two stars (Castor and Pollux) in close proximity that mark the heads of the twins, and are among the 30 brightest stars in the night sky.
The Gemini constellation is one of the original 48 constellations listed by the Egyptian mathematician Ptolemy, who lived under Roman rule in Alexandria in the 2nd century. These constellations formed the basis for the modern list agreed by the IAU. Constellations from the southern hemisphere, unable to be seen from the Mediterranean, represent the majority of additions to the list.
As the earth moves in its orbit around the sun, each night you are looking at a different portion of the sky. When looking at stars it is important to be aware of what is within your view. Northern hemisphere stargazers can group constellations into 3 groups; circumpolar, summer and winter constellations. The circumpolar constellations are in the north sky, appear to move around the north star and are visible throughout the year. The constellations in the south sky are only visible for part of the year and are grouped as either summer or winter constellations. Each is visible from between 4 to 10 months.
It is important to be aware of the specific time of year and hour of the night when deciding what to look for. These pages below show the constellations in each group so you can find the constellations that interest you. Gemini is visible in the evening sky from December to March.
CIRCUMPOLAR (year around) – Ursa Major – Cassiopeia – Ursa Minor – Draco – Cepheus
WINTER – Pegasus – Pisces – Aries – Auriga – Taurus – Orion – Canis Major – Canis Minor – Gemini – Lynx – Cancer – Leo – Winter Hexagon
SUMMER – Virgo – Libra – Scorpius – Bootes – Hercules – Lyra – Ophiuchus – Sagittarius – Aquila – Cygnus – Capricornus – Aquarius
Or use this guide to easily see which constellations are easiest to find right now:
Gemini Quick Facts:
Brightest star: Pollux, 1.15 magnitude (17th brightest star in the night sky)
Stars brighter than 3 magnitude: 4
Primary stars: 15 (2 for each head, 2 for each chest, 3 for the hands (as they are depicted holding one hand between them), 2 for each pelvis, 2 for knees of the left twin, 4 for the feet of both twins
Latitude: 10 – 35 degrees north
Northern Hemisphere Season: Winter (December – March)
Which months can you see Gemini constellation?
Gemini can be seen from September to May but is most convenient to observe from January to March. For evening viewing it is possible from December to May. For those who want to see it from September to November it is only possible in the morning before sunrise.
As time passes the constellation will gradually appear earlier in the day with ranges below showing the window of opportunity in each month. Gemini sits between 10-35 degrees north latitude. Therefore, the further south your position the higher it will appear in the night sky.
Gemini can not be seen from earth with the naked eye during summer it passes our vision in the day time. As with all zodiac constellations where the sun passes directly through their section of the sky, they are only visible for half of the year, opposite to their zodiac month. As the zodiacs appear along the perceived equator they are visible in the southern sky from the northern hemisphere and the northern sky from the southern hemisphere. At its maximum range it is possible to see Gemini at latitudes between +90 and -60. However, the lower latitudes will have visibility for longer periods of the year.
Best time to see Gemini:
Best visible at 21:00 in February
September: rises 02:30 and visible in east sky at sunrise
October: rises 24:30 and visible overhead at sunrise
November: rises 21:30 and visible high in west sky at sunrise reaching its peak at 03:30
December: rises at20:00 and visible low in west sky at sunrise reaching its peak at 01:30
January: rises at 18:00 and sets at 06:00 reaching its peak at 23:30
February: visible in east sky at sunset and sets 04:00 reaching its peak at 21:30
March: visible in southeast sky at sunset and sets at 02:00 reaching its peak at 20:00
April: visible overhead at sunset and sets at 01:00 reaching its peak at 19:00
May: visible in southeast sky at sunset and sets at 23:00
Trajectory: The constellation is between 10-35 degrees north which means that for those in low latitudes of the northern hemisphere is will pass overhead, for those in higher latitudes of the northern hemisphere it will appear in the southern sky.
Not the right time for Gemini? Have a look what constellations you can see tonight.
How to find Gemini constellation?
The starting point for identifying Gemini is Pollux the 17th brightest night star from earth. Castor and Pollux, the two stars marking the heads of the twins are themselves bright enough be found to identify Gemini. For those who do not have a bearing of the skies fortunately there are a variety of ways to identify Gemini.
If you are already familiar with one of the constellations below then it may prove the most convenient for you, if not use Orion as it is the most prominent and will also help you locate many other constellations
Option 1: Orion as pointer
The most common method if you can locate Orion is to follow a line perpendicular from Orion’s belt north east. The stars of Castor and Pollux are approximately 4 times the distance of Orion’s right shoulder.
Option 2: Ursa Major (Big Dipper) as pointer
This brings you half way to the Big Dipper of Ursa Major. accordingly if you have similarly identified this constellation then you can use it to indicate Gemini’s position. If you follow the handle of the saucepan south west around 5 times the length of the handle. Alternatively if you have also identified the complete Ursa Major constellation the path continues through the front paws of the bear and is around 2 lengths of the tail beyond them.
Option 3: Winter Hexagon
If you already identified the Winter Hexagon then you have found the brightest star in Gemini. Pollux connects stars in Canis Minor and Auriga.
Option 4: Canis Minor or the Winter Triangle
Gemini is directly north of Canis Minor. With the twins upright towards the north east and Canis Major facing north west, the small dog is directed towards Gemini’s feet. Canis Major is very close to the lower section of the twins and the distance and angle between the stars causes them to sometimes be mistaken for each other. Canis Major is closer to both Orion and Canis Major and has 2 stars very close to the head the signify the ears where Gemini does not. Additionally difference in brightness between the 2 stars in Canis Major is significantly more than Pollux and Castor.
Learn how to form the shape of Gemini constellation
The starting point for identifying the shape of Gemini always begins with Castor and Pollux. The stars marking the heads of the twins and carrying their names. To assist in recognising the shapes
Pollux the brighter of the 2 stars is on the left, and to assist in recognising the form of the twins it is helpful to know that Pollux has a shorter body but longer legs, while Castor has an elongated body with shorter legs but they are ultimately similar heights.
- The chest of Pollux can be found to the south west half the distance of Castor and at a 90 degree angle
- Castors chest is at a similar angle but around twice the distance from the head
- between these to chest stars there is a star that marks them holding hands, slighly closer to the chest of Pollux
- Pollux’s outstreched hand is a similar distance on the opposite side of his chest.
- Castors outstretched hand is also on the opposite side of his chest but is double the distance away compared to Pollux
- The pelvis of Pollux is 3 times the distance from the chest as the head.
- Castors pelvis is similarly 3 times the distance, however as the distance between his head and chest is greater so is his torso.
- Pollux’s legs then branch off at 30 degree angles towards 2 knees at a similar height to Castors pelvis. The upper sections of Pollux’s legs are similar length to his arms.
- The lower section of Pollux’s legs then are parallel following the same angle as the twins bodies.
- Castors short legs are are nearer together with only a slight change of angle from the body and are in line with Pollux’s (the four feet are in a straight line parallel to heads)
Gemini is otherwise depicted as a large U with a tail. This interpretations links the same stars but only the most prominent and forms a less obvious form. It primarily depicting the bodies of the two twins connected at the head. It is suggested that this form is easier to identify for viewers for areas with significant light pollution as it focuses only on the brightest stars in the constellation. Regardless both forms are similar and even the simplified shape is useful to learn as it follows the same primary form of the two standing forms without limbs.
Gemini in the Ancient World
Gemini is one of the zodiac constellations through which the sun passes annually. Although it is associated with the zodiac month of June it is passed by the sun in July in modern times.
The records of the the primary stars of this constellation being known as twins linked to the pantheon date back to ancient Babylon. Gemini is however linked to the story of Castor and Pollux which the major stars have adopted the names of. Leda was married to the king of Sparta and fell pregnant. She had however been seduced by Zeus and the twins were born but each with seperate fathers. Pollux the son of Zeus was an immortal demi-god. When Castor his mortal brother died Pollux requested his father to grant Castor immortality and as a result Zeus placed them among the stars.
Main stars of Gemini constelattion
Pollux (+1.14m, 34ly, 750 suns, #17)
Pollux is the name of the famous immortal twin of Leda from Greek mythology. It is the 17th brightest star with an apparent magnitude of +1.14. The distance from earth is 34 light years. It is a orange giant star that is 750 times the size of the sun. Pollux as an orbital planet with some similar attributes to our solar system. Pollux marks the head of the left twin.
Castor (+1.62m, 51ly, 6 star system, #23)
Castor is the name of the famous mortal twin of Leda from Greek mythology. It is the 23rd brightest star with an apparent magnitude of +1.62. The distance from earth is 51 light years. What appears as a single form of light to the naked eye is in fact 6 stars which are separated into 3 pairs which orbit each other. Castor marks the head of the right twin.
Alhena (+1.92m, 109ly, 35 suns, #43)
Alhena is from the Arabic word for a camel branding similar to the identifying markers you will see on the camels in Wadi Rum. It is the 43rd brightest stat with an apparent magnitude of +1.92. The distance from earth is 109ly. It is 35 times the size of the sun. Alhena marks the left foot of Pollux.
Mebsuta (+3.06m, 840ly, 2.8m suns, #185)
Mebsuta is abbreviated from the Arabic for ‘outstreched lions paw’. It is the 185th brightest star in the night sky with an apparent magnitude of +3.06. The distance from earth is 840 light years. It is supergiant 2.8 million times the size of the sun. Mebsuta marks the pelvis of Castor.
Wasat (+3.5m, 59ly, 13 suns, #287)
Wasat from the Arabic for ‘middle’. It is the 287th brightest star with an apparent magnitude of +3.5. The distance from earth is 59 light years. It is 13 times the size of the sun. Wasat marks the pelvis of Pollux.
Mekbuda (+4.2m, 1200ly, 220k suns)
Mekbuda is abbreviated from the Arabic for ‘folded lions paw’. It has an apparent magnitude of +4.2 and is 1200 light years from earth. It is 220, 00 times the size of the sun. The knee of Pollux and pelvis of castor clearly formed a lion constellation in ancient Arabic astronomy evident from the names of the nearby stars. Mekbuda marks the left knee of Pollux.
Deep sky objects
NGC 2392 – famous for its central star that is surrounded by a green disk
Geminid Meteor shower – meteor shower occuring annually around December 13, with over 100 meteors per hour
Wadi Rum is one of the best locations in the world to see the full beauty of the stars. With the combination of high altitudes, clear skies and no light pollution, you may be surprised how many stars that are visible to the naked eye. Come stay with us and spend a night under the stars.