Winter Is Coming
Orion can be seen by observers located between +85° and -75° of latitude, with the constellation’s appearance at night signalling that winter is coming. That is at least true from mid-northern latitudes where Orion is visible in the evening from November to early May, and in the morning from late July to November. From the Southern hemispheres, however, Orion is visible during the summer months where it appears upside down in the night sky.
Orion Family of Constellations
The constellation Orion is pictured as a giant hunter with a shield in his hand, a belt and sword around his waist, and surrounded by his hunting dogs Canis Major and Canis Minor. Beneath Orion’s feet, his dogs are pursuing a hare (or rabbit) in the form of the constellation Lepus who, like its wild namesake, is keeping a low profile in the celestial undergrowth. Together with Monoceros (unicorn), these five constellations form the Orion family, although the latter was only created in the 17th century to fill the large gap left clear by the ancient Greeks between Orion and Hydra.
Mostly Contains Young Blue Supergiants
All of the seven main stars in Orion, with the exception of the red super giant Betelgeuse are young blue supergiants. In order of visual magnitude, Orion’s brightest stars are as follows:
– Betelgeuse (Alpha Orionis) is a red supergiant located 642.5 light years away with a visual magnitude of 0.42. It is about 10 million years old, and is expected to end is life in a supernova explosion.ff
– Bellatrix (Gamma Orionis) is a blue-white giant star situated 240 light years away with a visual magnitude of 1.64. It is 8 times more massive than our sun, and emits around 6,400 times more light.
– Alnilam (Epsilon Orionis) is a blue supergiant around 1,300 light years away of magnitude 1.70. It is around 24 times bigger than our sun, and 250,000 more luminous.
– Alnitak (Zeta Orionis) is a triple star system found 700 light years from our solar system that shine with a visual magnitude of 1.72. Its primary component is about 20 times bigger than our sun, and around 10,000 times more luminous.
– Saiph (Kappa Orionis) is a blue supergiant 720 light years distant of magnitude 2.06. It has around 16 times the Sun’s mass, and shines 18,000 times brighter.
– Mintaka (Delta Orionis) is a multiple star system 900 light years distant with a visual magnitude of 2.25. Its primary components are two blue giant stars with over 20 solar masses, and 90,000 times the luminosity of our sun.
Contains 2 of Brightest Stars in Sky
Orion contains 2 of the 10 brightest stars in the night sky. The constellation of Orion’s brightest star is Rigel, which is the night sky’s 7th brightest star and represents the hunter’s left knee. Next brightest is Betelgeuse, which is the sky’s 10th brightest star and depicts the top right shoulder of Orion.
Orion is depicted as fighting a bull, represented by the nearby constellation of Taurus. The very bright, red star on the top left corner of Taurus is called Aldebaran and represents the eye of the bull. The constellation Taurus consists of two groups of stars called Hyades (“the rainy ones”) and Pleiades, which are a star cluster containing hundreds of young blue stars, only a handful of which can be seen with the naked eye.
Orion Chasing the Daughters of Atlas
In Greek mythology the Pleiades were the 7 daughters of the giant Atlas, who were chased over the face of the earth by Orion after becoming the object of his affections. They then begged Zeus to save them from Orion’s pursuit, and so he placed them in the night sky with the giant hunter chasing them from east to west, without ever being able to catch them.
The 3 bright stars in the constellation’s middle represent Orion’s sword belt, namely Alnilam, Mintaka and Alnitak. The equator of the sky passes close to the upper star of his belt, so that half of Orion is in the Northern hemisphere, and the other half is in the Southern hemisphere.
Below his belt you can see a curved line of 3 stars, which represent the giant’s sword. The middle star is, in actual fact, not a star but a nebula. The Orion Nebula (M42) is a huge cloud of dust and gas almost 25 light years across inside which new stars are being formed. It is 1,344 light years light years distant and at the center of the nebula are four stars, known as “The Trapezium” which help to light up much of the nebula.
Home to 2 Meteor Showers
Orion is home to two meteor showers, both of which are associated with the dust and debris trail left behind by Halley’s Comet. The Chi Orionids occurs in December each year and can produce around 5 meteors per hour, whilst its more prolific cousin, the Orionids, takes place between October 2 and November 7 with a peak on October 21 when around 20 meteors per hour can be seen.
Stars Moving Apart
The stars in Orion are gradually moving apart, but they are located at such great distances from us that the constellation will remain recognizable a long time after most of the other constellations, whose stars are closer to earth, have morphed into new shapes. One event which could cause a dramatic image change, however, would be Betelgeuse going supernova, which is predicted to happen sometime in the next million years. This will initially cause a light to shine as bright as the full moon in Orion, but a few weeks later that will fade, leaving a dark place where Orion’s shoulder once lay. As internationally recognized star expert James B. Kaler explains, “it will make a God-awful mess of the constellation Orion.”
Next Step: Mapping the night sky using Orion