Draco

Draco


Transit Date of principal star:
23 April


The ancient story of the Dragon concerns the Golden Apples of the Hesperides and Heracles' Eleventh Labour.

The eleventh task of Heracles (some references say it was the Twelfth) was to steal the golden apples from the apple tree which Gaia (Mother Earth) had given to Hera, Queen of the Heavens, at her wedding to Zeus.

Hera had chosen Ladon, a monstrous dragon with a hundred heads, to guard her precious tree. So Ladon would lay in the garden, coiling himself around the tree, and Hera feared no one would steal her apples.

Heracles went about collecting useful bits of information about the dragon, finding out how to fool it and steal the apples. One suggestion was to take along Atlas, who could be of some assistance.

For having opposed Zeus, Atlas had been punished by having to carry the world on his shoulders. Heracles devised the perfect plan; he offered to relieve Atlas of the terrible burden for an hour or so, long enough for Atlas to perform a favour in return: fetch the golden apples from the Garden of the Hesperides.

Atlas was in agreement; anything for a little rest. But there was one problem: the terrible dragon. Heracles saw no problem. He shot an arrow over the garden wall, killing Ladon instantly.

While Heracles hoisted up the globe, Atlas trotted off to retrieve the three golden apples. At his return Atlas found he could go on living quite happily without the weight of the world on his shoulders, so he told Heracles, "just a few more months and I'll return", planning to leave Heracles the task of carrying the worldly globe.

Heracles agreed but asked Atlas if he could get more comfortable. He begged Atlas to take the globe for a moment while he put some padding on his head. Atlas placed the apples on the ground and picked up the globe.

Heracles thanked him very much and walked away with the three apples.

As for Ladon, Hera felt miserable over its loss and placed it in the heavens, coiled around the north pole.


As it wraps itself around the northern hemisphere Draco is circumpolar, not far from the North Pole. In fact Thuban (alpha Draconis) was once the Pole Star, at about the time these stories were being told for the first time.

A very old and extensive constellation, Draco once held even more stars. Quite fittingly, Hercules is just to the east of Draco. In fact, some cartographers draw the figure of Hercules with one foot resting on the head of Draco.
Depending on the time of year one studies the constellation, its head (formed by beta, gamma, nu, and xi) takes on a different look. When beta and gamma are `on top', they look like two eyes, or perhaps the forehead. Other times of the year the face is rather indistinct.

There are a full range of Bayer stars in the constellation. While there are few deep sky objects of any interest (and just one Messier) the constellation does have a wide variety of interesting binaries to investigate, some of which are listed further below.


Thuban is the Arabic name for Dragon. To find Thuban sweep down the length of the Little Dipper and jump over to the end of the handle of the Big Dipper. Midway is found a much fainter star, which is Thuban. It is believed that the star was considerably brighter several thousand years ago.
This star was the pole star at about 2700 BC. The fact that Thuban was the Pole Star at just the time the Egyptians were building pyramids hasn't escaped the archaeologists.

The main object of the archaeologists' study is the Great Pyramid of Khufu. It is claimed that a particular passage in the pyramid was built to point at Thuban as that star dipped to its lower culmination.

However, if the above assumption is true, then the pyramid would have been built at around 2200 BC. The problem is that Khufu is about five hundred years older.

There are many books and articles on the subject (and no doubt several web pages on the Internet) for those who wish to delve deeper into the problem or to study the alignment of other stars with ancient artifacts.


Double stars in Draco:

Draco has dozens of binaries worth investigating. Below are some of the more easily resolved double star systems, and a couple not-so-easy ones.
Mu Draconis is one of the closer binaries, a slow orbit of 482 years. Presently the companion can be found at PA 14 and separation 1.91".

Nu Draconis is a splendid fixed binary, found in the dragon's head. Two similar 4.9 visual magnitude stars: PA 312 and separation 61.6".

Psi Draconis is also easily resolved: 4.9, 6.1; PA 15, separation 30.3"

Omicron Draconis has a fine colour contrast, orange and blue. Magnitudes 4.7, 7.5; PA 326, separation 34.2".

17 Draconis forms a magnificent fixed triple with 16 Draconis. 17AB: 5.5, 6.4, PA 108, separation 3.4"; 16 Draconis is component C: PA 194, separation 90.3".

26 Draconis is a close binary with orbit of 76 years. The component is currently at PA 334 and separation 1.6". There is a faint (10m) very wide third member, at PA 162 and separation 12.3'.

41 and 40 Draconis (Struve 2308) form a pleasant, fairly wide, binary of two cream-coloured stars: 5.7, 6.0: PA 232, 19.3". Note that 41 is the primary.

Struve 2398 is an extremely near binary at only 11.3 light years. It consists of two red dwarfs, 8.0, 8.5; PA 163, separation 15.3". It is thought the companion has an orbit of roughly 350 years.

The binary is found just between omicron Draconis (which to the east) and 39 Draconis.


Variable stars in Draco:

R Draconis is a Mira-type variable with a period of 245.6 days; it fluctuates from 6.7 to 13.2 magnitude. In 2000 the maximum should occur in the third week of April.

Deep Sky Objects in Draco:

Draco offers one Messier object: M102 (although this object is not universally recognised as a bona fide Messier). With several dozen other galaxies, and a bright planetary nebula, there are plenty of objects to study. Below are a few suggestions.

M102 (NGC 5866) is an edge-on galaxy with dust lane and brightly glowing centre.

The galaxy is four degrees southwest of iota Draconis.

NGC 5907 is in the same region one degree east of M102. This is another edge-on (nearly flat) galaxy with dust lane.

NGC 5985 is an inclined spiral, quite faint unless under ideal conditions.

NGC 5985 is midway between iota and theta Draconis; (NGC 5982 is in the same field to the west. This elliptical gallaxy is considerably smaller but about the same magnitude, around 12).

NGC 6543: a planetary nebula that appears as a miniscule blue-green disk. Because of its blue-green colouring, it is sometimes called the Cat's Eye Nebula. It's located halfway between delta and zeta Draconis. It's exact distance isn't known; estimates vary from 1500 to 3500 light years.


For a closer appreciation of Draco, visit the Binocular Section.


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