- Orion constellation is a group of stars aligned in a specific manner, which is most visible in the night sky during winters in the northern hemisphere.
- The constellation is named after Orion, a giant hunter in Greek mythology.
- It is often identified as the Hunter.
A constellation is nothing more than a group of stars that, when seen as a whole, creates an imaginary but obvious pattern. This pattern could represent anything from an animal to a mythological god.
Astronomers, so far, have identified a total of 88 constellations (recognized by the IAU in 1922) as observed from northern and southern hemispheres.
Out of all the 88 constellations, only a handful have gained a significant amount of popularity not only in the scientific community but among astronomy enthusiasts as well. The Orion constellation, without a doubt, is one of them.
An artist’s rendition of Orion constellation | Image Courtesy: N Sanu/Wikimedia Commons
Locating Orion, the Hunter
The Hunter is one of the most easily recognizable constellations in the night sky (from both the hemisphere). It lies on the celestial equator, an extension of the Earth’s equator into outer space.
Because of its unique location, the Orion constellation appears inverted (both upside down and left to right reversed) when observed from the southern hemisphere.
It can be best observed between the latitudes 85 degrees north and 75 degrees south during the winter season.
Features of the Constellation
The brightest star in the constellation is Rigel (Beta Orionis), which is located on the lower-left side of the Hunter (when observed from the northern hemisphere). When seen from an unaided eye, Rigel appears to be a single star, but in fact, it’s a system of four stars. The first star Rigel A is a blue supergiant.
Map of Orion constellation | Image Courtesy: Wikimedia Commons
On the lower-right side of the Hunter is Saiph or Kappa Orionis. Though a supergiant, Saiph is smaller and much fainter than Rigel.
Betelgeuse (Alpha Orionis) and Bellatrix (Gamma Orionis) act as the right and left shoulders of the constellation, respectively. A red supergiant, Betelgeuse have lately attracted widespread interest from the scientific community.
The star has a highly variable apparent magnitude (between +0.0 and +1.3), which means that it experiences systematic dimming and brightening. From time-to-time, Betelgeuse outshines Rigel (momentarily) to become the brightest star in the constellation. It is one of the biggest stars in the night sky, about a thousand times the size of our Sun.
The four stars (Rigel, Saiph, Betelgeuse, and Bellatrix) together form a quadrilateral. Located as the center of the quadrilateral is one of the most popular groups of stars (asterism) known as Orion’s belt.
It consists of three stars; Alnilam, Alnitak, and Mintaka – all three of which are at least 90,000 times more luminous than the Sun. Spotting the asterism is quite easy in the night sky as they appear consecutively in a line.
South of Orion’s belt is another group of stars and deep-sky objects that constitutes Orion the Hunter’s sword. Perhaps the most significant object in this region is the Orion Nebula, also known as Messier 42.
Orion Nebula | Image Courtesy: NASA/ESA
Located inside the Milky Way, the M42 is about 1,300 light-years from our solar system and could be the closest active star-forming region (stellar nursery) to the Earth.
A part of the Orion Nebula is the Trapezium or Trapezium Cluster – a relatively young star cluster responsible for the illumination of its surrounding region. Individual stars that are observed in this region are 42 Orionis and Theta Orionis (multiple star system).
However, the brightest member of the Orion’s Belt is Iota Orionis. It is a system of at least four stars located at a distance of 2,300 years from Earth.
Shield and the Club
North of the Betelgeuse is a string of five stars that make up Orion’s arm and club. The stars include Mu Orionis (located right above red supergiant), Nu and Xi Orionis, and Chi (X1 and X2) Orionis.
Similarly, to the west of Bellatrix is a group of six stars (collectively known as Pi Orionis) forming an arch. Together they represent the Orion’s Shield or Bow.
Interesting Facts About The Orion Constellation
Orion the Hunter is Known to Humans For Long
The oldest recovered star map is that of the Orion Constellation. In 1979, while excavating in a cave located in Ach Valley (Germany), archaeologists discovered a 32,500 years old ivory tablet. The carvings on that tablet bear a resemblance to that of Orion, the Hunter.
The Existence of Exoplanets in the Constellation is Highly Likely
Researchers have long speculated the existence of exoplanets or extrasolar planets near the stars associated with the constellation. CVSO 30, a star located about 1,200 light-years away from the Earth, is believed to host two massive gas giants; CVSO 30 b and CVSO 30 c.
The CVSO 30 planetary system (if it indeed exists) itself is unique. The relative distance of both planets from their parent star is something that has never been observed until now. While CVSO 30 b orbits the star in less than 11 hours, it takes CVSO 30 c more than 27,000 years to do the same.
It Can Be Used To Navigate Other (Prominent) Stars
Orion as a stellar guide | Image Courtesy: Mysid/Wikimedia commons
If you extend the Orion belt westward (northwest), the first bright star you encounter is Aldebaran. The star is part of the Taurus constellation and located about 65 light-years away from our Solar system.
In the exact opposite direction (southeastward) of the belt lies Sirius. It is the brightest star in the night sky and a part of the Canis Major constellation.
Procyon, the brightest star in the constellation of Canis Minor, can be found by following an imaginary line from Bellatrix through Betelgeuse extending eastward. Similarly, a line from Rigel through Betelgeuse leads us towards Pollux, a giant star in the constellation of Gemini.
Future Of the Constellation
A simulation of the Hunter’s proper motion from 50000 BC to 50000 AD
Stars never remain stationary as they continuously move throughout the galaxy. These movements are, however, too slow to witness in a human lifetime. Eventually, the stars in the Hunter constellation will move out of position and be rearranged over tens of thousands of years.
Based on the data from the Gaia and Hipparcos mission, the European Space Agency produced a simulation, which shows us how the constellation will look like in the next 450,000 years.
Betelgeuse, the red supergiant that represents the left shoulder of the Hunter constellation, is expected to explode (turn into a supernova) sometime in the next 100,000 years or so. Many new stars will be born from the molecular cloud surrounding the region as well.
Short Facts and Myths
5. One of the most noticeable meteor showers, the Orionids, appears to originate from the direction of Orion Constellation (near Betelgeuse). It is an annual meteor shower that takes place every year in the month of October.
4. The Hunter features some of the most remarkable molecular clouds and nebula ever known. One such is the Lambda Orionis Ring. At the center of the ring is Meissa (Lambda Orionis), which represents the head of Orion Constellation.
3. Below the Lambda Orionis ring is a semi-circular emission nebula known as Barnard’s loop. Both formations are part of the Orion Molecular Cloud Complex.
2. In Greek mythology, Orion and Scorpio (constellation of Scorpius) are depicted as arch enemies. According to a myth, Orion once threatened to kill every living animal on Earth. Enraged by this, Artemis (or perhaps Gaia) sent a scorpion to kill the Hunter.
The two constellations are never seen together in the night sky. While the Hunter appears during winters, Scorpius can only be seen in the summers.
1. According to author Robert Bauval and Graham Hancock, there is an intentional correlation between the position of three main pyramids in the Giza complex and the stars in Orion’s belt. This hypothesis (Orion correlation theory) remains highly controversial to date.