[image: 1_NS61D1AWDHRgmX78Tbm4yg.jpeg]
*Hephaestus: Fire and Fury*
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
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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
*Type Ia Supernovae*
[image: snr_type1a_420.jpg]
A Type Ia Supernova requires a binary star system in which one component is
a *white dwarf*. A white dwarf is a stellar remnant produced when a star
whose mass is less than or equal to nine solar masses ends its life cycle.
A white dwarf is a planet-sized sphere consisting primarily of oxygen,
nitrogen and carbon in their cores with hydrogen and helium along the outer
layers. If a white dwarf is part of a binary system, the tidal forces
it induces onto the other star will pull gases away from it and onto
itself. Tidal forces, also known as differential gravitational forces,
are exerted onto a large object by a smaller body. The region on the
larger object closer to the smaller one experiences a stronger pull than
regions farther away from it. If this differential force is sufficiently
powerful, larger star's outer gases will leave the star and accumulate on
and/or around the white dwarf.
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.
_____________________________________________
[image: d9bf66786b8a96c952eebd552c3bbb80.jpg]
*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*
[image: news300.jpg]
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*
[image: Making_a_Nova.jpg]
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.
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