Despite its size and designation as the eighth largest constellation, Draco, the “dragon” constellation, is not particularly prominent. The name Draco literally means “dragon” (translated from Latin). For the ancient Greeks, Draco was associated with Ladon, the mythical dragon that guarded the golden apples of the Hesperides. As part of his 12 labors, Heracles killed Ladon and stole the golden apples, which is why the constellation Hercules is depicted near Draco.
History of the Dragon Constellation
In ancient Egypt, the main star of Draco (alpha Draconis) was known as “Thuban,” meaning “head of the serpent.” When designing the pyramids, the Egyptians made sure that all pyramids had one side facing north, with an entrance passage geometrically aligned so that Thuban was visible at night.
Draco was well known to Greek astronomers, and became one of the 48 constellations included by Ptolemy in his 2nd-century AD treatise, the Almagest. In traditional Arabic astronomy, Draco is not depicted as a dragon. Instead, it was seen as part of a larger constellation, which they called “Camels of the Mother” (al’awa’id).
This consisted of two hyenas (or wolves) represented by Eta Draconis and Zeta Draconis attacking a baby camel (a foal), represented by a faint star near Beta Draconis. This foal was protected by four female camels represented by Beta Draconis, Gamma Draconis, Nu Draconis, and Xi Draconis. The nearby tripod of stars, composed of Upsilon, Tau, and Sigma Draconis, represented the nomads who owned the camels and were camped nearby.
How to find the Dragon constellation
Draco is located in the third quadrant of the northern hemisphere and can be seen at latitudes between +90° and -15°. It is the eighth largest constellation in the night sky and covers an area of 1083 square degrees. The easiest way to spot it is to look for the “Big Dipper” and the “Little Dipper” in the night sky and see what lies between them.
There, between the two spoons, is the tail of the dragon/serpent. In the center is Thuban (alpha Draconis). Together with Edasich (iota Draconis), which is to the right and below the alpha star of the constellation, Thuban marks the boundary between the tail of the dragon/serpent and its coiled body.
Another way to find Draco is to start by locating Vega, the fifth brightest star in the night sky and the brightest star in the constellation Lyra. Vega is located at the easternmost tip of Lyra, and a stone’s throw away from Draco’s brightest star – Eltanin (also known as Gamma Draconis). This star, together with Beta (Rastaban), Epsilon, and Nu Draconis, forms the head of the dragon.
Location of Draco
Draco is circumpolar, which means that it never sets below the horizon and is always visible in the Northern Hemisphere, but cannot be seen in the Southern Hemisphere.
- Right ascension: 17 hours
- Declination: 65 degrees
- Visible between 90 and 15 degrees below zero
- Best seen in July at 9 p.m. local time.
Name and meaning
The name derives from the Latin term draconem, meaning “huge snake,” and the constellation literally winds its way across the northern sky.
According to the Greco-Roman source, Draco was one of the Giants who fought against the Olympian gods for ten years. In the course of this battle, Draco was killed by the goddess Minerva, who threw him into the sky. In the process, Draco’s body twisted and froze at the North Celestial Pole before it could straighten up.
Stars, galaxies, and planets
The stars in the constellation Draco are not very bright. The dragon’s head consists of four stars (Beta, Gamma, Nu, and Xi Draconis) in a trapezium just north of Hercules. From there, the dragon’s body winds its way across the sky, ending between the Big and Little Dippers. From early to mid-October, a meteor shower known as the Draconids appears to radiate from Draco’s head.
Other stars in the constellation include Thuban (Alpha Draconis), which forms the tail. Because the Earth wobbles on its axis (called precession), Thuban was the North Star around 2600 BC when the ancient Egyptians were building the pyramids.
- Draco consists of several double stars, including Eta Draconis and 20 Draconis.
- The Cat’s Eye Nebula is also contained within the constellation.
- The constellation encompasses several faint galaxies, including the Draco Dwarf Galaxy, one of the least luminous galaxies with a diameter of about 3,500 light-years.
- A handful of exoplanets have been found in Draco so far, such as:
- Kepler-10b (around the star Kepler-10), which was the smallest rocky Earth-sized planet detected outside the solar system when it was announced in 2011.
- Kepler-10c, which has the same parent star, was nicknamed “the Godzilla of Earths” after it was announced in 2014. This is because the rocky world has a mass 17 times greater than Earth’s, making it more likely to be a “mini-Neptune” than a “super-Earth,” with a thick gaseous envelope.
- A Jupiter-sized planet named TrES-2b was announced in 2011, and was found orbiting the sun-like star GSC 03549-02811. The star only reflects about 1 percent of the light that falls on it, and it was classified as the darkest planet found so far at the time of its discovery.
Characteristics of the brightest stars
Many prominent stars and Deep Sky Objects are associated with the constellation Draco.
Eltanin
The brightest star in this constellation is Eltanin (aka Etamin, Gamma Draconis), an orange giant star located about 148 light-years from Earth. Its traditional name derives from the Arabic ra’s at-tinnin, meaning “dragon’s head” (or “snake’s head”).
Aldibain
The second brightest star is Aldibain (Eta Draconis), a binary system composed of a yellow giant star and a yellow subdwarf located approximately 92.1 light-years from Earth. These two components are called Athebyne (Eta Draconis A and B), are separated by at least 140 AU, and have an orbital period of at least 1,000 years.
Rastaban (Beta Draconis)
A yellow giant star located 362 light-years from Earth. Its traditional name is derived from the Arabic ra’s ath-thu’ban (“head of the serpent/dragon”), a meaning it shares with both Thuban and Eltanin.
Altais (Delta Draconis)
Then there is Altais (Delta Draconis), a yellow giant star located 97.4 light-years away. The traditional name of the star derives from the Arabic Al Tais, meaning “the goat.” Aldhibah (Zeta Braconis) is next, a blue giant star that is 330 light-years away. The star’s name means “the hyenas” in Arabic and is sometimes also called Nodus III (the Third Node), referring to a loop in Draco’s tail.
Thuban (Alpha Draconis)
Thuban (alpha Draconis), a double star system consisting of a blue-white giant star and a companion (a red or white dwarf) located about 309 light-years from Earth. Thuban was the North Star from 3942 to 1793 BC (when it moved further north). Due to the effects of precession, it will once again become the North Star around 21,000 CE. The traditional name of the star comes from the Arabic word thu’ ban, meaning “the serpent.”
Arrakis (Mu Draconis)
Then there is Arrakis (Mu Draconis), which science fiction fans will recognize as the central location in Frank Herbert’s Dune series. Arrakis is a double star system composed of two white dwarf main sequence stars that are about 85 light-years from Earth. The name derives from the Arabic word al-Raqis, meaning “the dancer.”
The constellation is also home to a number of recently discovered exoplanets. In 2007, a planet comparable in size to Jupiter was discovered around Alsafi (Sigma Draconis). In 2009, a super-Jupiter was discovered orbiting 42 Draconis. Meanwhile, the Kepler-10 system has two planets that were discovered in 2011. The first (Kepler-10b) is a rocky planet orbiting the star with a period of 0.8 days, while the second (Kepler-10c) has an orbital period of 42.3 days.
The constellation Draco is also associated with the Eta Draconids meteor shower in February, which was discovered on February 4, 2011. On this occasion, observers observed six meteors in a short period of time that had a common point of origin. The source of these meteors was a long-period comet unknown until then.
Deep Sky Objects
In terms of Deep Sky Objects, Draco is home to the Cat’s Eye Nebula (M94, NGC 6543), a planetary nebula located approximately 3,000 light-years from Earth. Its name comes from the way it appears when viewed by the Hubble Space Telescope (although it appears as a blurry blue-green disk when viewed with an amateur telescope). The complex shape of this nebula is due to gravitational interactions between the multiple star system at its center.
There is also the Spindle Galaxy (aka Messier 102), a spiral or lenticular galaxy about 50 million light-years away. The galaxy is notable for its extended dust disk, seen exactly edge-on, which is unusual for a lenticular galaxy (hence the question of classification). The constellation is also home to the Draco Dwarf Galaxy, a spheroidal galaxy that is 260,000 light-years away and is one of the faintest satellite galaxies of the Milky Way.
Next is Abell 2218, a galaxy cluster located about 2.345 billion light-years away that contains thousands of galaxies and a mass equal to 10,000 of them. In 2004, this cluster was used as a gravitational lens to locate the most distant object ever observed in the universe—a galaxy that formed just 750 million years after the Big Bang.
Draco is also home to the quasar Q1634+706, which is the most distant object (12.9 billion light-years) visible with amateur telescopes. There is also the Great Wall of Hercules-Corona Borealis, a massive galactic superstructure that has an unusually high number of gamma-ray bursts (GRBs). It is possibly the largest known structure in the universe and covers part of the southern region of Draco.
