How would one describe a typical god? Prodigiously strong, infuriatingly arrogant, formidably powerful, agelessly immortal and, of course, stunningly beautiful. That last trait, in particular, seems to distinguish the gods from the sullied and unwashed thongs of us envious Earth bound mortals Well, with one notable exception: Hephaestus, god of fire, craft and metal works. Unlike his comely Olympian cohorts, Hephaestus was a pitiably unsightly thing, a malformed monstrosity of ill-fitted parts. He came by that deformation honestly for his mother, Hera, conceived him by herself without any contribution by her husband Zeus, whose philandering ways so incensed Hera that she was determined to sire a child alone. Alas, Hera was so repulsed at the sight of her hideous baby that she flung him out of Olympus immediately after his birth. The unfortunate baby plummeted into the sea where he was saved by Thetis and the oceanid Eurynome. This kindly couple raised Hephaestus in their deep underwater cave unbeknownst to Hera who assumed -hoped- that the infant had drowned. During the nine years during which Hephaestus matured from infancy to young adulthood, he was taught the arts of healing, fishing and the craft of ironmongery, for which he immediately showed unsurpassed ability. Toward the end of his nine-year stay with Thetis and Eurynome, Hephaestus constructed a beautiful golden throne for his mother Hera. Thetis delivered it to Olympus and explained to Hera that it was a gift from her long missing son, whom Thetis had named Hephaestus, meaning "crippled god of fire." Correctly surmising that the gift was given by the son she tossed aside with disgust all those years ago, Hera accepted the throne joyfully and instructed Thetis to send Hephaestus her gratitude and appreciation for his forgiving nature. As soon as she sat down on the throne, however, she became ensnared by it and was unable to extract herself. All the other gods, even Zeus, were similarly powerless to pull Hera from the trap. Ironically, they only needed a key. Without it, they could do nothing even with all their powers. With nothing else for it, they summoned Hephaestus up to Olympus. He was gladdened to see his mother so imprisoned and when the other gods demanded that he unlock Hera, he refused. "Let this beautiful woman suffer in the throne for nine years or, perhaps, nine times ninety," he seethed. Despite the desperate pleas and earnest threats of the other gods, Hephaestus steadfastly refused to relent. Finally, Dionysus plied Hephaestus with some of his best wine. Having had no previous experience with wine, Hephaestus soon became intoxicated and drowsy. As soon as he passed out, Dionysus searched him, found the key and released Hera. Zeus then prevented the wrathful Hera from harming Hephaestus. "He must be drawn into our community," Zeus insisted as he stood between his wife and her dozing son. "He is of divine skill and will prove useful to us were we to face challenges from Titans, giants or other foes." So, in spite of Hera's fury, Hephaestus became one of the twelve Olympians and resided permanently with them. Much to the shock and amusement of the others, Zeus eventually arranged for Hephaestus to marry Aphrodite, the goddess of love and beauty. Zeus reasoned that since Aphrodite would have to be betrothed to one of the Olympians, it would be best to marry her to Hephaestus, the strongest and cleverest of them all. He believed that fear of Hephaestus' fury would discourage any of the others from attempting to seduce Aphrodite. Zeus also thought that Aphrodite would also be far too frightened to stray, as well. He was mistaken. Soon after the wedding, Aphrodite took Ares, the god of war, as her paramour. Each time Hephaestus was away, Aphrodite and Ares met for what they assumed would be a secret tryst. Unfortunately for them, Helios, the Sun god, saw all that transpired within Olympus and on Earth. He observed Aphrodite's many clandestine gatherings with Ares. Helios, being as honest and forthright as gods could ever be, felt that by not informing Hephaestus of his wife's infidelity, he was somehow complicit with it. Helios sent Hermes to tell Hephaestus that he was a cuckold. Though enraged, Hephaestus feigned ignorance of his wife's faithlessness for a while. One day he told Aphrodite he intended to visit a great forge under Vesuvius and instruct some of his devoted followers in stonecraft. "I shall be gone many days, I'm afraid," he told Aphrodite mournfully. Ares soon thereafter visited Aphrodite, just as Hephaestus assumed he would. As they lay together, the bed suddenly enveloped them, trapping them in their nakedness. Hephaestus, who hadn't left Olympus at all, but instead had gone into hiding, returned home to see Aphrodite and Ares in their ignominious position. He invited all the Olympians to go to his home to look upon his wife and her lover. Only the male divinites accepted the invitation. They all looked upon the couple, not with scorn, but with amusement and, admittedly, with a measure of envy. Apollo claimed that he would have gladly have suffered Ares' indignity as a punishment for having become Aphrodite's lover. Poseidon persuaded Hephaestus to release the couple after assuring him that Ares would pay the fine charged to adulterers. Hephaestus dissolved his marriage with Aphrodite. Despite his deformities and harsh disposition, Hephaestus would go on to have many affairs and in the process sired many children. He coupled with Algaea, one of the three graces; the sea nymph Cabeiro, and Aetna, a Sicilian nymph. He tried in vain to seduce Athena, who, determined to remain forever virginal, repelled him. Of course, Hephaestus was best known for his craftsmanship, not his erotic escapades. He forged, among other items, Hermes' winged helmet and sandals, Achilles' armor, and Eros' (Cupid's) bows. Zeus was wise to have spared Hephaestus Hera's wrath and to have incorporated him into the exalted order of Olympians. It was unfortunate that Zeus was a much more effective administrator than a matchmaker.
THE SOUTHWORTH PLANETARIUM
207-780-4249 www.usm.maine.edu/planet70 Falmouth Street Portland, Maine 04103
43.6667° N 70.2667° W
Altitude: 10 feet below sea level
Founded January 1970
Julian Date: 2459038.16
2019-2020: CLXXII
THE DAILY ASTRONOMER
Tuesday, July 7, 2020
Remote Planetarium 60: Intrinsic Variables II - Cataclysmic Variables
The final type of variable star to be discussed is cataclysmic. We can divide these into various categories.
- Type Ia Supernovae
- Type II Supernovae
- Novae
We know that electron degeneracy sustains a white dwarf's structure. Compressed electrons such as those within a white dwarf will resist further contraction. This resistance, or degeneracy prevents a white dwarf from collapsing. However, if the white dwarf remnant collects enough material so that its mass exceeds 1.44 solar masses, called the Chandrasekhar Limit, the white dwarf will explode as a Type Ia Supernova.
_____________________________________________
Rapid astronomer profile: Subrahmanyan Chandrasekhar (1910-1995) White dwarfs will explode if their masses exceed 1.44 solar masses, a value known as the Chandrasekhar Limit. Astrophysicist Dr. Subrahmanyan Chandrasekhar determined that gravitational contraction will overwhelm a white dwarf's electron degeneracy if the Chandrasekhar Limit is surpassed. In 1983, Chandrasekhar received the Nobel Prize in Physics for this discovery.
__________________________________________
According to current models, all Type Ia Supernovae should produce the same amounts of energy and therefore will be of consistent luminosity. Consequently, Type Ia Supernovae serve as reliable distance determination markers for astronomers. We will encounter Type Ia Supernovae again when we explore the realm of galaxies.
Type II Supernovae
Type II Supernova. We encountered this type before when discussing stellar nucleosynthesis:
Hydrogen into helium; helium into carbon; carbon into oxygen or nitrogen or another product. Various other fusion reactions will then occur in multiple stages until the star's core collects iron heated to three billion degrees! Iron is the end point of these reactions because iron fusion is endothermic. The energy invested into this reaction is greater than the energy the reactions impart back into the star. All lighter element reactions produce more energy than is required to produce them. (The hydrogen to helium reaction is the most energy efficient.) Consequently, when a star collects iron in its core, the balance between the star's gravitational contraction and outward energy pressure is violently disrupted. The outer layers collapse down onto the star's inner region so quickly that the gravitational potential energy is converted into kinetic energy resulting in an explosion called a Type II supernova.
A Type II supernova explodes from the inside out. The supernova energy produces all the elements heavier than iron. It also disperses this heavy element material throughout its local region, chemically enriching the interstellar medium within its vicinity. Because the Type II supernovae progenitor stars span quite a range, the energy output varies considerably. For this reason, Type II supernovae cannot serve as reliable distance indicators.
Novae
Novae, which ironically means "new," also requires a white dwarf within a binary system. However, unlike Type Ia supernovae, a nova doesn't occur when a white dwarf explodes. Instead, novae occur and recur. The white dwarf captures material from its companion star. This matter collects around the white dwarf's surface and heats dramatically. Once the temperature reaches 20 million K, the gases will undergo a Carbon-Nitrogen-Oxygen sequence of thermonuclear fusion reactions. Through this complex series of reactions involving carbon, nitrogen and oxygen, hydrogen is converted into helium. As is true with all thermonuclear fusion reactions, these fusion reactions generate energy. The rapid energy release scatters the gases collecting around the white dwarf, creating a sudden outburst of light that we see as novae: the rapid increase in a star's brightness. The amount of time during which the brightness persists varies depending on the closeness of the companion star and the amount of gas that accumulates around the white dwarf.
Unlike the periodic variables, cataclysmic variables will only occur once or at random times. For instance, recurrent novae, as their name suggests, occur repeatedly. Astronomers have catalogued ten recurrent novae in the Milky Way Galaxy as well as many extragalactic recurrent novae, such as those found within the Andromeda Galaxy.
To subscribe or unsubscribe from the Daily Astronomer: