Pollux: The Brightest Star in Gemini – with Its Own Planet

By Alexander Merz · Updated on 2 August 2026 · Details checked on 14 September 2026

Pollux is the brightest star in the constellation Gemini: a red giant 34 light-years away – and the first giant star around which an exoplanet was confirmed.

The Brighter Twin

Pollux and Castor form the head stars of Gemini – and although Castor carries the Bayer designation Alpha, Pollux is the brighter of the two. The colour difference is appealing even to the naked eye: Pollux glows orange (a red giant, about 4,600 degrees), Castor bluish-white. In mythology, the two are the inseparable half-brothers of the Greek legend.

A Star with a Planet

Pollux is the brightest star in the sky known to be orbited by a confirmed exoplanet: Pollux b (officially Thestias), a gas giant with at least twice Jupiter’s mass, circles the giant star in about 590 days. It was discovered in 2006 using the radial-velocity method.

Observing Pollux

Best time: December to April. In winter, Gemini stands high in the southern sky, up and to the left of Orion. Nearby, the open cluster M35 at the feet of the Twins is well worth a look – a sparkling nebulous patch in binoculars, resolved into dozens of stars in a telescope. In mid-December, the Geminid meteors also appear to radiate from the region around Castor and Pollux.

Frequently Asked Questions

What is the difference between Castor and Pollux?

Pollux is the brighter, orange giant (a single star with a planet), Castor a bluish-white sextuple star system.

Does Pollux really have a planet?

Yes – Pollux b (Thestias), a gas giant with at least two Jupiter masses, confirmed since 2006.

When can you see Pollux?

In the winter and spring sky, from December to April, high in the south to the left of Orion.

Why does Pollux glow orange?

It has evolved into a red giant: larger, cooler (about 4,600 degrees) and therefore warmer in hue than the Sun.