Categories: Stars

Star Facts: Bellatrix

Bellatrix (“female warrior”) is a bluish-white giant star located 250 light years away in the constellation of Orion, where it marks the giant’s western “shoulder”. It is the 3rd brightest star in Orion, with an apparent magnitudes of 1.64, but only the 27th most luminous star in the night sky. Its location close to the sky’s 10th brightest star, an enormous red giant called Betelgeuse, makes it one of the easiest stars to recognise, with Bellatrix best seen in December and January.

Quick Facts

• Constellation: Orion
• Coordinates: RA 05h 25m 07.86325s| Dec +06° 20′ 58.9318″
• Distance to Earth: 250 light years
• Star Type: Blue Giant (B2 III)
• Mass: 8.4 solar
• Radius: 6 solar radii
• Apparent Magnitude: 1.64
• Luminosity: App. 6,400 sol
• Surface Temperature: 22,000K
• Rotational Velocity: 46 km/sec
• Age: 20 million years
• Other Designations: Bellatrix, Gamma Orionis, Amazon Star

Physical Properties

Bellatrix is a B2 III variable star with a temperature of 22,000K, and whose brightness ranges between apparent magnitudes of 1.59 and 1.64. It is rapidly depleting its hydrogen fuel and has started to evolve off the main sequence on its way to becoming a true giant. It is expected to become an orange giant within a few million years, and has already developed a gaseous shell that signals the start of its transformation. At its present 8.4 solar masses, Bellatrix is also close to being considered a supernova candidate.

Popular Fiction

Bellatrix also featured in popular fiction. The author of the Harry Potter series, J.K. Rowling named a Death Eater, a character in one of the novels, “Bellatrix Lestrange”, as an allusion to the character’s nature. The star also featured in the movies; in the original, 1968 version of Planet of the Apes, one stranded astronaut was of the opinion that they were marooned on a planet orbiting the star Bellatrix, but another correctly pointed out that the star is yellow-white, whereas if they were orbiting Bellatrix, the star would have a distinctly blue tinge to it. It turned out the survivors were on Earth, and not on a planet around Bellatrix.

Peter Christoforou :