Draco: The Dragon Constellation

Draco, the Dragon, is a long winding constellation that coils between the two bears, Ursa Major and Ursa Minor. Despite its large size, Draco is often overlooked because its stars are relatively faint. However, it rewards patient observers with interesting targets including a former pole star, a famous planetary nebula, and a rich mythological heritage. Trace its serpentine path with StarGlobe.

How to Find Draco

Finding Draco requires knowing where the two Dippers are. The dragon's body winds between them, starting with its tail between the bowl of the Big Dipper and Polaris, then curving around Ursa Minor before ending in a distinctive quadrilateral of stars that forms the dragon's head.

The head of Draco is the easiest part to identify. Four stars arranged in a lopsided trapezoid sit roughly between Vega and the Guardians of the Pole (Kochab and Pherkad in Ursa Minor). Two of these stars, Eltanin and Rastaban, form the dragon's bright eyes and are the most conspicuous stars in the constellation.

From the head, the body curves north, passes above the bowl of the Little Dipper, continues past the Pointer Stars of the Big Dipper, and ends with the tail star Giausar between the two bears. Draco is circumpolar from most northern mid-latitudes.

The Stars of Draco

Eltanin (Gamma Draconis) is the brightest star in Draco at magnitude 2.2. It is an orange giant about 148 light-years away. Historically, Eltanin is significant because observations of its apparent motion by James Bradley in 1725 led to the discovery of the aberration of starlight, the first direct evidence of Earth's orbital motion around the Sun.

Thuban (Alpha Draconis), despite its alpha designation, shines at only magnitude 3.7. However, Thuban's true importance is historical: around 2700 BCE, during the age of the Egyptian pyramids, Thuban was the pole star. The narrow shafts in the Great Pyramid of Giza were oriented toward Thuban, not Polaris. Earth's axial precession gradually shifted the pole away from Thuban over the following millennia, and it will return to the vicinity of Thuban around the year 21000.

Rastaban and Grumium complete the head asterism. Eta Draconis is a yellow giant that can serve as a binocular target due to a faint companion nearby.

Deep Sky Objects

The Cat's Eye Nebula (NGC 6543) is the showpiece of Draco. This planetary nebula, located near the star Zeta Draconis, is one of the most complex and beautiful planetary nebulae known. Through a telescope, it appears as a bright blue-green disk. Images from the Hubble Space Telescope revealed an astonishing series of concentric gas shells and jet structures, making it one of the most studied objects of its kind.

Draco also contains several galaxies. NGC 5866, sometimes identified as M102 (though this attribution is disputed), is an edge-on lenticular galaxy with a prominent dust lane. The Draco Dwarf Galaxy is a small satellite galaxy of the Milky Way, too faint for visual observation but important for studies of dark matter and galaxy formation.

The Tadpole Galaxy (Arp 188), a distorted spiral with a long tidal tail caused by a gravitational encounter, lies within Draco's boundaries, though it requires large amateur telescopes to observe.

Mythology and Cultural Heritage

In Greek mythology, Draco is most commonly identified as Ladon, the hundred-headed dragon that guarded the golden apples in the garden of the Hesperides. Heracles (Hercules) slew Ladon as one of his twelve labors, and the dragon was placed in the sky by Hera. The constellation Hercules lies nearby, with his foot seemingly planted on the dragon's head.

Another myth identifies Draco as the dragon thrown by Athena during the battle between the gods and the Titans. The dragon wrapped around the celestial pole and froze there. In Babylonian astronomy, the dragon was associated with Tiamat, the primordial chaos goddess who was slain by Marduk to create the heavens and earth.

Chinese astronomy divided Draco's stars among several asterisms associated with the imperial palace, reflecting the constellation's position near the celestial pole, the center of the sky's apparent rotation.

The Draconid Meteor Shower

The Draconids, also known as the Giacobinids, are a meteor shower that radiates from the head of Draco each October. Usually a minor shower producing only a handful of meteors per hour, the Draconids have occasionally produced spectacular outbursts, with rates exceeding thousands per hour in 1933 and 1946. The shower is caused by debris from Comet 21P/Giacobini-Zinner.

Best Time to Observe

As a circumpolar constellation from mid-northern latitudes, Draco is technically visible year-round. However, the dragon's head is highest during summer evenings, from June through September, when the quadrilateral is nearly overhead. The long body can be traced any time of year when the circumpolar region is accessible.

Because Draco's stars are relatively faint, the constellation benefits from darker skies. The Cat's Eye Nebula can be found with a telescope under suburban skies, but tracing the full body of the dragon requires at least moderate darkness.

Neighboring Constellations

Ursa Major and Ursa Minor are Draco's closest companions, with the dragon threading between them. Cygnus and Lyra lie near the head, with Vega serving as a useful reference point. Hercules borders Draco to the south, and Cassiopeia and Cepheus touch it to the east. Map out this winding constellation with StarGlobe.

Quick Facts

Draco covers 1,083 square degrees, making it the 8th-largest constellation. Despite its size, it has no stars brighter than magnitude 2.2. It contains one disputed Messier object (M102) and the notable Cat's Eye Nebula. Its right ascension ranges from about 9h 22m to 20h 55m, and its declination spans from about +47 to +86 degrees.