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Huge constellations vie for attention

Hercules — the Hero and Ophiuchus — the Serpent Bearer cover much of the summer night sky

GLENN ROBERTS glennkroberts@gmail.com @chronicleherald Glenn K. Roberts lives in Stratford, P.E.I., and has been an avid amateur astronomer since he was a small child. He welcomes comments from readers at glennkroberts@gmail.com.

Continuing with my multipart series on the summer constellations, we’ll have a look at Hercules — the Hero and Ophiuchus — the Serpent Bearer, both huge constellations that occupy a large portion of the summer night sky.

HERCULES

The constellation of Hercules is actually the Roman name for the Greek hero and strongman Heracles. In one of his many trystings with mortal women, the Greek god Zeus seduced a young mortal maiden named Alcmene, from which union she bore a son, which she named Alcides.

Fearful that his wife, Hera, would (rightly) be angered by yet another of his numerous infidelities, Zeus snuck the young Alcides into her bedroom whilst she slept and placed the boy at her breast, upon which he suckled, thereby becoming partially immortal.

Needless to say, upon waking and discovering the child at her breast, Hera, enraged, tore the helpless infant from her and flung it from the room. It is said that the milk that sprayed from Hera’s breast as she pulled the child away, splashed out into the universe, forming what would become known as the Milky Way.

Hera would bear an inordinate hatred of Alcides all his life and would be his nemesis upon numerous occasions, going so far as to cast a spell upon him which made him kill his children at a later point in his life.

When Alcides eventually came to his senses, he was filled with remorse and went to the oracle at Delphi seeking atonement for his crime. The oracle sent him to serve King Eurystheus of Mycenae for 12 years.

King Eurystheus set Alcides 10 labours (eventually there would be12), amongst which were the slaying of the Nemean Lion (beast with an impenetrable hide), which Alclides strangled and skinned, wearing the hide as protection in future deeds; the slaying of multi-headed Hydra; the stealing of the golden apples from Hera’s royal garden on Mount Atlas, guarded by the dragon Ladon (which he also slew, and which Hera placed in the night sky as Draco — the Dragon); and the retrieval (for King Eurystheus) of the three-headed dog, Cerberus, that guarded the entrance to the Underworld.

It was during these 12 labours that Alcides was ironically given the name Heracles, meaning the glory of Hera (there is no indication who gave him that name or why).

Heracles was to later die as a result of his wife, Deianeira, accidently giving him some of the Hydra’s blood as a love potion (she was tricked into doing so by the centaur Nessus, whom Heracles had shot with an arrow tipped with the Hydra’s blood).

The beast’s blood burned Heracles’ flesh so badly that he built a pyre and the flames consumed the mortal part of his body, while the gods took the immortal portion to Mount Olympus with them, before placing him in the night sky, where he is now known by the Roman name Hercules.

FIFTH LARGEST

The constellation Hercules is the fifth largest constellation in the night sky, and contains a number of breathtaking, deep sky objects, most notably the bright, magnitude +5.8 globular cluster M13 and the smaller, fainter, but denser, magnitude +6.3 globular cluster M92, both of which can be seen in binoculars (and magnificently in even a small telescope).

The constellation’s brightest star is magnitude +2.8 Kornephoros (Greek for the club bearer, for the club Hercules has raised over his head), a variable binary system located 139 light years from our sun.

A key-identifier for the constellation of Hercules is the keystone asterism that constitutes his torso. The M13 globular cluster can be found on the right side of the keystone, midway between the top and bottom stars.

Four stars make up the keystone: Pi (in the upper left corner), a giant, magnitude +3.15 star, 1,330 times as luminous as our sun and 377 light years away; Eta (in the upper right corner), magnitude +3.5 main sequence star, 50 times as luminous as our sun, located 112 light years away and estimated to be at least a billion years old — its proper name is Sophian (from the Arabic word for pure); Epsilon (in the lower left corner), a magnitude +3.9 spectroscopic double star system, about 155 light years distant; and Zeta (in the lower right corner), the brightest of the four keystone stars, is a magnitude +2.8, multi-star system, located 35 light years from our sun.

OPHIUCHUS — THE SERPENT BEARER

The other large constellation in the southern summer sky is Ophiuchus — the Serpent Bearer to the south of Hercules. It is the 11th largest constellation in the night sky and is said in Greek mythology to represent the mythical Greek healer, Asclepius, holding a large snake or serpent.

The ancient Romans believed that Asclepius learned the secret of immortality by watching one serpent heal another serpent by feeding it healing herbs. Zeus killed Asclepius with a lightning bolt because he didn’t want everyone to be immortal, but later honoured the healer by placing him in the night sky.

Interestingly, the modern medical symbol of the caduceus (a staff entwined by two serpents) represents the healing rod of Asclepius and the snakes.

The constellation’s brightest star, Rasalhague (Arabic for the head of the serpent collector), represents the healer’s head. Ophiuchus holds a long snake or serpent (some drawings show the serpent wrapped around his body, while others show it extending to either side behind his torso), which is divided, name-wise, into two sections. The serpent’s front section (with the head) is to the right and is labelled Serpens Caput (the serpent’s head), with the serpent’s hind section to the left, and labelled Serpens Caudal (the serpent’s tail).

This part of the Ophiuchus constellation, although covering a large area of the night sky, is very faint. Its brightest star, Unukalhai, is a magnitude +2.6 orange giant star located 74 light years away. The name comes from the Arabic phrase unuq al-hayyah, meaning the neck of the serpent.

The Serpens part of the Ophiuchus constellation contains the bright globular star cluster M15, as well as the famous Eagle Nebula, known for its massive star-forming region nicknamed the Pillars of Creation (well worth Googling).

THE PLANETS THIS WEEK

Saturn (mag. +0.6, in Capricornus — the Sea Goat) rises in the east-northeast around 11:30 p.m., reaching a height of 29 degrees above the southern horizon before fading into the dawn twilight by about 4:40 a.m.

Jupiter (mag. -2.4, in Pisces — the Fish) rises in the east shortly before 1 a.m., reaching 39 degrees above the southeast horizon before succumbing to the approaching dawn by 5 a.m.

Mars (mag. +0.5, in Pisces) rises in the east-northeast around 1:50 a.m., reaching an altitude of 31 degrees above the eastern horizon before fading from view by about 4:40 a.m.

Venus (mag. -3.9, in Taurus — the Bull), now moving closer to the sun with each passing day, will be briefly visible above the east-northeast horizon, rising about 4 a.m. and reaching only 13 degrees above the eastern horizon before disappearing into the glow of the rising sun by 5 a.m.

Mercury is now too close to the sun to be seen in the predawn sky.

Until next week, clear skies.

EVENTS:

• July 6: Moon at first quarter

SCIENCE

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2022-07-05T07:00:00.0000000Z

2022-07-05T07:00:00.0000000Z

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