The Winter Hexagon is a hexagonal-shaped asterism with vertices at Rigel, Aldebaran, Capella, Pollux, Procyon, and Sirius. It is visible mostly upon the northern hemisphere’s celestial sphere.
Key Facts & Summary
- The Winter Hexagon is a prominent asterism, however, it cannot be seen from South Island of New Zealand, the south of Chile, Argentine, and further south.
- The asterism is prominent in the sky during the months of December to March.
- In the tropics and southern hemisphere, this asterism can be extended with the bright star Canopus in the south, thus creating a summer hexagon.
- A sort of smaller brother to the Winter Hexagon is the Winter Triangle asterism, of which Sirius and Procyon are also part of. The third member is the red giant Betelgeuse.
- One way to find to Winter Hexagon is by locating the Winter Triangle, and though it is smaller, it is easier to find since it contains three of the ten brightest stars in the night sky.
- All of the stars in the Winter Hexagon are part of different constellations.
- Rigel is the brightest star in Orion, Aldebaran is the brightest in Taurus, Capella is the brightest in Auriga, Pollux is the brightest in Gemini, Procyon is the brightest in Canis Minor, and Sirius is the brightest in Canis Major.
- Rigel is the 7th brightest star in the night sky, Aldebaran is the 14th, Capella is the 6th, Pollux is the 18th, Procyon is the 8th, and Sirius is the brightest star in the night sky. Betelgeuse is usually the 9th brightest star in the sky.
- A part of the Milky Way runs through this asterism, and this makes the Winter Hexagon a great guide towards finding deep-sky objects such as galaxies, nebulae, Messier objects, and more.
- This is because the Winter Hexagon contains parts of several constellations, such as Auriga, Canis Major, Canis Minor, Gemini, Monoceros, Orion, Taurus, Lepus, and Eridanus
The Winter Hexagon asterism contains six alpha stars, the brightest in their respective constellations. This asterism is best seen between December and March in the northern hemisphere.
In the southern latitudes, the asterism appears as a summer hexagon, as it can be extended to Canopus. This asterism is the highest in the sky at around 11 p.m. It can be seen in the southern sky in the evening in late February and early March.
The Stars of the Winter Hexagon
The stars of the Winter Hexagon are among the brightest in the sky. Each of them is unique in their own way, and they vastly dwarf our Sun from different perspectives.
Rigel, designated as Beta Orionis, is a massive blue-white supergiant variable star. Though it appears as a single star, Rigel is actually a star system, containing 4 stars. Rigel is the seventh-brightest star in the night sky.
The primary star, Rigel, is an Alpha Cygni variable star, having an apparent magnitude ranging from 0.05 to 0.18. Rigel is around 61,500 up to 363,000 times brighter than our Sun.
It is located at around 860 light-years away from us. Rigel has 7,000% of our Sun’s radius, and 2,100 % of our Sun’s mass. As time passes, Rigel will expand to an even greater size transcending into a red supergiant.
It may explode as a supernova one day. Rigel, along with Bellatrix, Betelgeuse, and Alnilam are the navigational stars of the Orion constellation. Though Rigel is the brightest star in Orion, it is occasionally outshone by Betelgeuse.
Aldebaran, designated as Alpha Tauri, is an orange-hued giant star located at around 65.3 light-years away from us. It is the 14th brightest star in the night sky, the brightest in Taurus, and it has an apparent magnitude that varies from 0.75 to 0.95.
Aldebaran is a red giant type of star, having 116% of our Sun’s mass, 4,413% of its radius, while being 439 times brighter than our Sun, though it is cooler, with temperatures of around 3,900 K.
Capella, designated as Alpha Aurigae, is the brightest star in Auriga, and the sixth brightest star in the night sky, and the third brightest in the northern celestial hemisphere after Arcturus and Vega. It has an apparent magnitude of +0.08.
Capella is a quadruple star system organized into two pairs of two stars. The primary pair is composed out of two bright yellow giant stars.
The primary star, has around 256% of our Sun’s mass, 1,198% of its radius, and it is 78.7 times brighter than our Sun The secondary star has around 248% of our Sun’s mass, 883% of its radius, and it is 72.7 times brighter than our Sun, yet being similarly as hot.
Pollux, designated as Beta Geminorum, is the 18th brightest star in the night sky, and the brightest in Gemini with an apparent magnitude of 1.14.
Pollux has around 191% of our Sun’s mass, 906% of its radius, and it is 32.7 times brighter than our Sun. Despite its impressive feats, Pollux is actually cooler than our Sun, having temperatures of around 4,586 K.
Since 1943, the spectrum of Pollux has served as one of the stable anchor points by which other stars are classified. In 2006, an exoplanet designated as Pollux b, has been confirmed to orbit the giant star.
Pollux b has an estimated mass of around 2.3 times that of Jupiter. It orbits the giant star once every 590 days. Many cultures around the world associated Pollux and Castor as two of something, such as Yin and Yang, two gazelles, two-kid goats, the brothers that founded Rome, Romulus, and Regulus, and so on.
Among the 58 stars selected for celestial navigation, Pollux is the only one listed from Gemini.
Procyon, designated as Alpha Canis Minor, is the brightest star in the Canis Minor constellation, and usually the eighth brightest star in the night sky, having a visual magnitude of 0.34.
Procyon is a binary star system, consisting of Procyon A – which is a white main-sequence star, and Procyon B, a faint white dwarf. This star system is located at around 11.45 light-years away from us, Procyon being the second-closest star to us of the Winter Triangle stars.
The primary star, Procyon A, has around 150% of our Sun’s mass, and it is around seven times brighter. In the medieval period, Procyon, along with Sirius, was among the fifteen Behenian fixed stars used in magic rituals. Apart from the Winter Hexagon asterism, Procyon also marks one of the vertices of the smaller Winter Triangle.
Sirius, designated as Alpha Canis Majoris, is the brightest star in the constellation of Canis Major, and overall the brightest star in the night sky.
Sirius is a binary star, with an apparent magnitude of -1.46, being twice as bright as Canopus, the second brightest star in Canis Major. Sirius is around 25 times brighter than our Sun, and it is located at around 8.6 light-years away from Earth.
The primary star of the Sirius star system, Sirius A, is a main-sequence star of spectral type A0 or A1. It is 200% more massive than our Sun, and it has around 171% of its radius, being more than twice as hot as our Sun.
Sirius is accompanied by a faint white-dwarf companion, the very first white dwarf to be discovered actually, designated as Sirius B. Sirius B is around 100,000 fainter than Sirius A. The ancients knew Sirius, with some records dating back as far as 4,000 years ago.
In 1868, Sirius became the first star to have its velocity measured. It is moving closer to our Solar System, and thus its brightness is increasing. Around the year 9,000, Sirius will no longer be visible from northern and central Europe.
Sirius is the closest star to Earth, of the Winter Triangle stars, and the Winter Hexagon stars, and the brightest, but only due to its proximity to us. Betelgeuse would outshine Sirius if it were closer to us.
The Winter Hexagon, along with its stars, can be used as a guide towards several interesting deep-sky objects. Many of them are within the asterism.
The Orion Nebula is located under Orion’s Belt, the Horsehead Nebula is in the vicinity of the Orion Molecular Cloud Complex, while the Cone Nebula and the Rosette Nebula in Monoceros are also within the Winter Hexagon.
A line extended from Betelgeuse to Procyon leads the way to the Rosette and Cone nebulas. The Crab Nebula can be found two-thirds of the way from Betelgeuse to Elnath. The Hyades open cluster is in the same line of sight as Aldebaran. The Pleiades can be found by extending a line from Sirius to Aldebaran.
Did you know?
- For the Polynesians, mostly in the Southern Hemisphere, the rising of Sirius marked the coming of winter, and it was an important reference for their navigation around the Pacific Ocean.
- The rising of Sirius also marked the flooding of the Nile in Ancient Egypt.
- In the Macedonian folklore, Sirius and Procyon were known as the “wolves” – Volci – circling a plow with oxen, represented by the constellation of Orion, the celestial hunter.
- Capella is sometimes associated with the goat Amalthea from the Greek mythologies.
- In two million years, the spacecraft Pioneer 10 will reach Aldebaran
- Procyon appears on the flag of Brazil, symbolizing the state of Amazonas.