Pollux: the brightest star in Gemini

~5 min
Topics:Stars

Pollux is the brightest star in the constellation Gemini. The astronomical app Sky Tonight makes it easy to find it in the sky, next to the other “twin star” Castor. Now, let’s discover some facts about this star.

Contents

Pollux: basic star facts

  • Official names: Pollux, β Geminorum, β Gem
  • Catalog designations: 78 Geminorum, HD 62509, HIP 37826, HR 2990
  • Constellation: Gemini
  • Star type: giant star
  • Right ascension: 07h 45m 18.949s
  • Declination: +28° 01' 34.316"
  • Apparent magnitude: 1.2
  • Mass: 1.9 solar masses
  • Luminosity: 32.7 L
  • Radius: 9.06 solar radius
  • Surface temperature: 4,586 K
  • Distance from the Earth: 34 light-years
  • Rotation period: 558 days

How to find Pollux in the sky?

Pollux is a giant star shining with a yellowish-orange hue. It is bright enough (mag 1.2) to be seen with the naked eye. Let’s see what can help to determine its location.

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Use the Big Dipper

One way to locate Pollux is by using the Big Dipper – one of the most recognizable star patterns in the sky. Draw a line across the Dipper’s bowl, from the star Megrez (that’s where the Dipper’s “bowl” and “handle” meet) through the star Merak (it’s at the Dipper’s bottom, diagonally from Megrez), and follow it until you see the two stars shining close together. That will be Pollux and its “twin star” Castor.

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Find Pollux via Big Dipper
The Big Dipper is a prominent asterism in the constellation Ursa Major that can help find stars and sky objects.

Use Orion’s stars

The other way to find Pollux is to use Orion’s stars as a guide. All you have to do is to find Rigel and Alnitak (bright stars in Orion), draw a line through them, and extend it to the north.

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To boost your star-finding skills, pass our quiz and train to locate the brightest stars in the sky with the help of other stars and constellations!

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Use the stargazing apps

Yet another way to find Pollux is to use a stargazing app, like Sky Tonight. This app allows you to check the location of the star with just a few taps. Look at the image below or follow the video guide and see for yourself how easy it is!

Find Pollux via Sky Tonight
One, two, three – and voila! Pollux is found. Just tap a few buttons on your smartphone screen and get an instant result – it feels like magic.

You can also combine the two methods: first, try to find Pollux with the Big Dipper or Orion’s stars, and then make sure you’re right with Sky Tonight.

When to see Pollux?

As a part of the zodiac constellation Gemini, Pollux can only be seen in the sky during certain months. The best time to see the star is from December through March in most parts of the world. Keep in mind that from the end of June to the end of July, Gemini hosts the Sun, so Pollux is in the sky during the daytime.

See Pollux next to the Moon and planets

Pollux lies close to the ecliptic, so occasionally, it meets the Moon and planets. Below is the list of celestial events featuring Pollux. Also, you can check the “Events” tab in the Sky Tonight’s calendar from time to time: there, you can find a lot of useful information about everything that happens in the night sky.

March 19, 2024: Pollux near the Moon

On March 19, at 06:44 GMT (2:44 a.m. EDT), the Moon and Pollux will share the same right ascension. The apparent distance between the two objects will be 1°36'. The star and the Moon will be visible after sunset.

April 15, 2024: Pollux near the Moon

On April 15, at 13:47 GMT (9:47 a.m. EDT), the Moon and Pollux will share the same right ascension. The apparent distance between the two objects will be 1°36'. The star and the Moon will be visible after sunset.

May 12, 2024: Pollux near the Moon

On May 12, at 22:17 GMT (6:17 p.m. EDT), the Moon and Pollux will share the same right ascension. The apparent distance between the two objects will be 1°42'. The star and the Moon will be visible after sunset.

June 9, 2024: Pollux near the Moon

On June 9, at 07:23 GMT (3:23 a.m. EDT), the Moon and Pollux will share the same right ascension. The apparent distance between the two objects will be 1°54'. The star and the Moon will be visible after sunset.

October 31, 2024: Pollux near Mars

On Halloween night, observe Mars (mag 0.1) shining on the border between the constellations Gemini and Cancer. Pollux (mag 1.2) will be at 7° from Mars. Along with Castor (1.6), it will form a straight line with the Red Planet. The objects will appear in the sky at around midnight and will climb the highest by sunrise.

You can often see bright dots near the Moon. Apart from Pollux, these could be other bright objects, such as Venus or Jupiter. When observed with the naked eye, planets can look like stars, but in fact, they are very different. To stay updated on when the Moon meets the planets, read our dedicated article.

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More facts about Pollux

Named after a Greek myth hero

In Greek mythology, Pollux, also known as Polydeuces, and his twin brother Castor were sons of the Spartan queen Leda. Castor was the mortal son of King Tyndarus, while Pollux was the immortal son of Zeus. The twins were inseparable, and when Castor died, Pollux asked Zeus that the two should share immortality, so Zeus placed them both in the sky as the constellation Gemini. Because of the myth, Castor and Pollux are often referred to as the “twin stars”, although the stars are not related.

Brightest star in Gemini, yet not an Alpha

While studying the stars, you probably noticed that the brightest star in a constellation is usually designated by the Greek letter Alpha. However, in Gemini, the Alpha star is Castor, while Pollux is Beta. This naming system was created by the German astronomer Johann Bayer in 1603. In this system, the stars within a constellation appear to be listed from brightest to dimmest. But back then, astronomers couldn't accurately measure the brightness of stars, so Bayer sorted them based on their magnitude class (first-magnitude, second-magnitude, etc.). Within each class, the stars were not necessarily arranged by brightness. Also, sometimes Bayer assigned letters to stars based on their position within a constellation, their order of rising, or for historical or mythological reasons.

Hosts a planet

Pollux is known to host a planet in its orbit called Pollux b, or Thestias. This gas giant exoplanet was discovered in 2006. It orbits its parent star at a distance similar to that of Jupiter from our Sun.

Bright star Pollux: bottom line

Pollux is the brightest star in the constellation Gemini. It can be easily observed in the night sky from December through March. You can locate Pollux by using the Big Dipper, the bright stars in Orion, or stargazing apps like Sky Tonight. It can also be found near the Moon and planets.

Topics:Stars
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