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How to Identify the Constellation Gemini in the Sky

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Constellation Gemini

This constellation is one of the twelve constellations of the Zodiac. It lies along the ecliptic and is best seen in the night sky during the winter and spring seasons, in the northern hemisphere and during summer in the southern hemisphere. It´s recognizable by two bright stars which form the heads of the twins-castor and Pollux.

Gemini is seen from January till May coming out from the horizon in the early evening of this months and it sets two hours earlier with each proceeding month. During January and February, Gemini is seen coming up the horizon after dark and it will reach its highest point in the sky during February around 10:00 p.m.

Constellation Gemini in the Sky

Location of Gemini in the Sky

Gemini is located along the ecliptic-the imaginary line in the sky, where the sun, planets and moon transit. Gemini is one of the twelve constellations of the Zodiac and occupies the third place in the celestial sky, with the first being Aries. This constellation is easy to locate knowing which other constellations lie close to it.

Being the second constellation in the Zodiac, Taurus lies to the west of Gemini and Cancer in the east. Taurus is easy to spot, as it´s very prominent in the winter night sky. Auriga and Lynx are in the north and Monoceros and Canis Minor are located south of Gemini.

Gemini is recognized for its two brightest stars; Castor and Pollux The easiest way to locate these stars is to take as reference the constellation Taurus and look to the east of it or Locate Orion´s belt-three stars and then Rigel-Orion´s left foot and Betelgeuse-Orion´s left shoulder and extend an imaginary line through them that will point to the twin´s heads.

Locating Gemini in the Night Sky

Locating Gemini in the Night Sky

Locating Gemini in the Night Sky

Using Orion to find Gemini in the Sky

Orion is one of the most noticeable constellations in the winter night sky, with lots of recognizable stars. This constellation is often used by star gazers when they want to locate another celestial body. For those who are experienced at locating stars and other features in the sky, it may result easy to know their way to Gemini; however, for those who are starting to recognize the night sky features, using Orion as a reference is the most straightforward way.

During winter, Orion the hunter appears prominently high in the sky, along with other outstanding constellations and stars. This constellation is most commonly known for three stars in a row, known as Orion´s belt. Below these stars is Rigel and Saiph-Orion´s left and right feet and above then is Betelgeuse and Bellatrix-Orion´s right and left shoulders. Drawing an imaginary line-yellow straight line in the picture, starting at Rigel and extending it through Betelgeuse takes you to Castor and Pollux-the two brightest stars in Gemini.

Locating Gemini using the Big Dipper

The Big Dipper or the bowl as it is also known can be seen every night in the northern hemisphere. This is a circumpolar asterism, meaning it never sets below the horizon and is always visible by those living in the northern hemisphere. This asterism is composed of seven bright stars-four of them-Megrez, Dubhe, Phecda and Merak, comprising the bowl and three stars-Alkaid, Mizar and Alioth, giving shape to the handle.

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An imaginary line, starting at the star Megrez and extending through Merak leads to the heads of the twins in Gemini; Castor and Pollux. This is shown in the picture by a blue straight line. Not far from the Big Dipper lies the little Dipper whose tip of its handle is the north polar star. An imaginary line starting at Merak and going straight into Dubhe leads directly to the pole star, which is shown in the picture by straight while line.

Stars in Gemini

There are 85 visible stars in Gemini-the brightest of which are Pollux-an orange giant star of magnitude 1.2 at 34 light years from earth and Castor (a six star system) visible at magnitude 1.9 and located 52 light years from earth. Alhena is a blue-white star of magnitude 1.9 and situated 105 light years from earth. Mebsuta is a double star system consisting of a yellow supergiant visible at magnitude 3.1 and its companion a star of magnitude 9.2. Mekbuda is a double star system consisting of a Cepheid variable star of period 10.2 days and a companion star of 7.6 magnitude.

Propus is a binary variable star system with a period of 500 years. The primary star is a blue giant of magnitude 4.1 and the secondary is a star of magnitude 8.0. 38 Gem is a binary star system 91 light years away from earth whose primary star is a white star with a magnitude of 4.8 and a secondary yellow star of magnitude 7.8. Mu Gem is a star with an apparent magnitude of 2.9. It´s an irregular variable star which varies from 2.75 to 3.02 over a period of one day.

Deep Sky Objects in Gemini

Some of the most prominent objects in Gemini are M35, the Eskimo Nebula and the Medusa Nebula. M35 is an open cluster of magnitude 5; it covers 0.2 degrees in the sky and is visible during clear night skies. The Eskimo Nebula is a planetary Nebula with a magnitude of 9.2 and visible with a mall amateur telescope. The Medusa Nebula is a planetary nebula with an apparent magnitude of 15.9 and at 1.500 light years from earth. Geminga is a neutron star at 800 light years.

NGC 2129 is an open cluster with an angular distance of 2.5 arcminutes and lies at approximately 7,200 light years from earth. NGC 2158 is an open cluster with an apparent magnitude of 8.6 and NGC 2355 is another open cluster of stars at approximately 5,400 light years away from earth and is visible at an apparent magnitude of 9.7. Gemini does not contain too many deep sky objects due that it´s in a region that is away from the Milky Way.

Geminids Annual Meteor Shower

The Geminids are a luminous meteor shower that occurs in December and peaks on December 13-14. On the early hours of the second of these days, an estimated quantity of 120 meteors every hour can be observed and is considered as one of the most intense meteor showers of the year. The point at which the meteors seem to radiate is in the direction of the constellation Gemini; therefore, it´s said that the radiant is in Gemini.

Geminids Meteor Shower with Radiant in Gemini

Geminids Meteor Shower with Radiant in Gemini

Geminids Meteor Shower with Radiant in Gemini


For each question, choose the best answer. The answer key is below.

  1. What constellation is easily seen on the southwest of Gemini in the winter?
    • Orion
    • Aries
  2. What are the two brightest stars in Gemini?
    • Mebsuta and Propus
    • Castor and Pollux
  3. How many stars are visible in Gemini?
    • 85
    • 55
  4. What place does Gemini occupies among the constellations of the Zodiac?
    • Third
    • Second
  5. Why does Gemini only contains few Deep Sky objects?
    • It´s far away from the earth
    • It´s not located on the way of the Milky Way

Answer Key

  1. Orion
  2. Castor and Pollux
  3. 85
  4. Third
  5. It´s not located on the way of the Milky Way

Description of the constellation Gemini

© 2017 Jose Juan Gutierrez

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