Yes, our random voyages through the upper realm has brought us now to Heracles himself. We decided, for once, to place the mythological section at the end of the article.  You'll see why.


THE DAILY ASTRONOMER
Thursday, June 18, 20
Remote Planetarium 53:   Nucleosynthesis II

Yesterday we started our discussion about nucleosynthesis: the process by which lighter elements are converted into heavier elements.   The very first phase of nucleosynthesis occurred when the Universe was only 10 minutes old.  This Big Bang Nucleosynthesis produced immense amounts of helium and some lithium.       The next stage of nucleosynthesis happened within stellar interiors.     All stars produce energy through the fusion of light elements.  While lower mass stars such as the Sun can only produce carbon and some oxygen, higher mass stars are able to produce the pressures and temperatures necessary to fuse even heavier elements up to iron.  Once these stars accumulate iron in their cores, the fusion processes stop as iron fusion is endothermic, meaning it requires more energy than the fusion reactions impart back into the star.        The balance between the star's inward gravitational compression and the outward energy pressure is violently disrupted.     The star will then perish as a Type II supernova.  (We are conveniently neglecting those stars that directly form black holes.) 

That brief synopsis covers the first two nucleosynthesis processes:   Big Bang and stellar.  Today, we proceed with the next four main types:
  • Explosive Nucleosynthesis
  • Neutron Star Collision
  • Black Hole Accretion Disk Nucleosynthesis
  • Cosmic Ray Spallation
Before we proceed, we wanted to show you another version of the Periodic Table of the Elements.  This one displays the elements, of course.   However, each element is color coded to indicate origin.

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EXPLOSIVE NUCLEOSYNTHESIS:
Nucleosynthesis requires tremendous amounts of energy because in order to fuse nuclei, they have to overcome the electrostatic barrier that would otherwise keep them apart.    Surpassing this barrier is only possible at extremely high temperatures.    These temperatures impart enough kinetic energy to the nuclei so as to allow them to draw close enough together to fuse.  (Here we acknowledge that quantum processes play an important role in permitting these particles to "tunnel" through the barrier. )   Once the star reaches the "iron catastrophe"  stage, the star can't fuse anymore and the star explodes. The immense energy of this explosion produces many elements heavier than iron.  

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One main mechanism for this formation is the r-process.   The r-process occurs when elements rapidly (hence the r) capture neutrons within their vicinity.       The neutron capture must be very quick so that no radioactive decay occurs prior to the arrival of the next neutron.        Research shows that such r process neutron capture can only occur in regions of extremely high neutron density, such as that within a supernova explosion field. 


NEUTRON STAR COLLISION: 
 The merger of two neutron stars also produce vast neutron swarms that allow for the r-process neutron captures necessary to produce the heaviest elements.    Based on the information contained within the Periodic Table above, we can see that neutron star mergers account for the majority of heavy element formation.    Neutron stars are the ultra-dense remnants left behind after certain Type II supernova explosions.        Neutron stars will only merge if they are part of a binary system:  i.e., both stars within the system were sufficiently massive to produce neutron stars.   These mergers can generate unfathomable amounts of energy and vast quantities of neutrons.    We remember that neutron stars consist of neutrons.  The protons and electrons within the progenitor star are crushed to such a high pressure that they fuse to produce neutrons.    For this reason we should expect neutron star collisions to produce so many heavy elements.  Also, the resultant explosion also serves to disseminate this heavy material throughout the galaxy.               
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BLACK HOLE ACCRETION DISK NUCLEOSYNTHESIS
Black hole accretion disks form when a black hole strips material away from a companion star.     The material then starts to revolve around the black hole to create a disk.   The matter close to the black hole moves much more rapidly than the matter farther away.  This differential rotation produces high energy radiation principally in the form of x-rays.    Powerful winds generated by the accretion could then disperse the fusion products into space.      The identity of the elements and their relative abundances produced in this fashion remains largely unknown.

COSMIC RAY SPALLATION
Spallation is the process by which a nucleus undergoes particle loss through interaction.  In this instance, the interaction with cosmic rays.      Despite the name cosmic rays generally consists of high energy protons and other atomic nuclei that travel through space at speed approaching that of light   This spallation is more of a disintegrative process which is responsible for the relatively high abundances of lithium, beryllium and boron, as we can see on the Periodic Table above.  


WHITE DWARF EXPLOSIONS
We notice in the Periodic Table that exploding white dwarf stars and dying low mass stars also serve as nucleosynthesis mechanisms.     White dwarf stars explode as Type I supernovae.  If a white dwarf has a binary companion, it can draw gases off the star onto its surface.   When the white dwarf accumulates enough material so that its mass is 1.44 solar masses, it will explode as a Type I supernova.     Through the neutron capture process, elements within the explosion region can form other elements.

While the processes involved in these element creation sequences are highly complex, we hope that this brief overview will provide some insight into how you came to be you:  how a Universe consisting once only of hydrogen and helium grew into one abounding in a variety of heavier material.  We can see also that some elements are produced by more than one type of nucleosynthesis.      [The two elements in gray 43 Technetium and 61 Promethium are extremely rare and their origins are uncertain.]

Tomorrow, the quiz.  Next week we begin our discussion about variable star and the cosmic distance ladder.



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Heracles:  Oh, the labors!
The name "Hercules" derives from the original name "Heracles," meaning "Glory of Hera," Hera being the goddess of femininity and, ironically, marriage.     Hera was married to her brother, Zeus, and, unlike her philandering husband, was invariably faithful.    Beleaguered by her husband's myriad trysts and powerless to avenge her humiliations on him, the most powerful of all the gods, Hera often exacted revenge on either the mortal women Zeus seduced or the children sired by his liaisons.   Hera harbored a particularly virulent hatred for the child Hercules, born of an adulterous affair between Zeus and Alcmene.   For this reason, one might consider Hercules' original name, "Heracles," to be rather curious, or even appallingly inappropriate.     Then again, as this two part article might illustrate, Hercules' triumphs over great odds would have been more than halved were it not for the machinations of his most dangerous nemesis.

One must also wonder why Hera developed such a murderous hatred for Heracles in particular, for the children born of Zeus' infidelities were numerous and Hera never exhibited the same intensity of animus toward any of them as she did toward Hercules.    Perhaps it was Hercules' traits that also incurred Hera's wrath, for he was far stronger and more courageous than any of his half siblings.   The Olympians tended to look with disfavor onto powerful mortals.   As hatred is often opaque, we might never know the true reason for Hera's deep enmity toward Hercules.   

Hercules was destined to be unique amongst mortals even before his birth.   For, it was not merely lust that actuated Zeus in his seduction of the radiantly beautiful Alcmene, granddaughter of Perseus.   Instead, he knew that a great war between the gods and the giants was imminent.    He also knew that the gods, though extremely powerful, were outmatched by the giants.*   This deficiency necessitated the conception of a great hero who would ally himself with the gods and enable them to prevail over their formidable foes.   Being both divinely beautiful and profoundly wise, Alcmene seemed the most suitable mother to sire such a great man.  She was also wholly devoted to her husband, Amphitryon, and would have thwarted even Zeus' advances had he attempted a seduction.     Zeus therefore disguised himself as Amphitryon when the real man was away at war.     He then commanded Nyx to extend the duration of night to three times itself, for he understood that conceiving such a hero would require much time.   

Hera, noticing the night distended, rightly concluded that her husband had strayed again.  Once the night ended, Hera saw at once that Zeus had been with Alcmene.      She was enraged, but at first did nothing.  She noticed that Zeus had been rather preoccupied during Alcmene's gestation.   Being rather clever, herself, Hera surmised that the child not yet born was someone particularly special to Zeus.  Her assumption was confirmed when, on the day Hercules was due to be delivered, Zeus announced that a child would be born that day who would one day rule over them all.   Hera forced Zeus to swear an oath promising to make a child born on that day supremely powerful.  Zeus swore the oath gladly, not knowing that Hera would then command Eileithyia, goddess of childbirth, to prevent Hercules' birth while inducing the premature birth of Eurystheus, future king of Tiryns.  Only when the day was over did Eileithyia permit Hercules' birth, much to the relief of the anguished Alcmene.

Hera's persecution of Hercules began literally at once.   When Hercules was only one day old, Hera cast two serpents into his crib as he slept.  The serpents' hissing awakened him and he promptly strangled them both.       While this attack hardly bothered Hercules, it terrified Alcmene, who realized that Hera, herself, was responsible for the assault.  In a panic, Alcmene conveyed Hercules outside and exposed him.    Zeus witnessed her actions and as soon as the infant Hercules lay abandoned, he conducted him up to Olympus and lay him next to Hera as she slept.   Hercules promptly nursed on Hera, as Zeus had intended, for he knew that by nursing on Hera, Hercules would be afforded both supernatural abilities and, of course, the protection of Hera, herself.    Unfortunately, Hercules bit down on Hera, causing her to awaken in agony.  The spilt milk splattered over Olympus, creating the Milky Way.     Zeus then promptly spirited Hercules away from the enraged Hera and back to his mother.   Zeus then explained to Alcmene that he was the child's father and that the child had now been endowed with both divine abilities and Hera's protection.  He instructed Alcmene to continue nurturing the child and to be secure in the knowledge that Hera could torment the child no longer.

By some accounts, Hera could no longer persecute Hercules during his youth because he had ingested her milk and was therefore under her protection.    Hera's hatred grew all the more, for not only did Zeus deceive her with his affair with Alcmene, he also prevented her from harming Hercules, himself.    Of course, this protection ended as soon as Hercules attained maturity.     Once freed from the protective bonds, Hera resumed her persecution.

Just as he became a man, Hercules married Megara, daughter of Creon, King of Thebes.    Creon offered Megara to Hercules as a token of his gratitude, for Hercules had single-handedly defended Thebes from an invasion of Minyans.       Hercules and Megara, both happily married, sired a son and daughter and seemed destined to enjoy a fruitful and prolonged marriage.  However, Hera afflicted Hercules with an insanity spell that induced him to slay his children and, some say, Megara, as well.     Before Hercules was able to slaughter hundreds more, Antikyreus remedied his insanity with an application of Hellebore.     His sanity restored, Hercules was distraught at the realization that he murdered his own family.  He moved to take his own life, but was prevented from doing so by Theseus, who told him to seek the Oracle at Delphi.   "There," Theseus assured him, "will you find the guidance to know how to atone for what you have done."

Hercules did as Theseus suggested and at the Oracle was told that he was to deliver himself into the service of  Eurystheus, who would require him to perform a series of exceedingly difficult labors.    By the completion of these labors, he would atone for his crime and would experience an apotheosis: he would be elevated to the status of a god.     Hercules delivered himself into the service of  Eurystheus, not realizing that Hera, herself, had influenced the Oracle and was confident that one of these labors would destroy Hercules outright, preventing both his apotheosis and his atonement.

THE WATER SNAKE
Within the swamps of Lerna lived a nine-headed water snake called "The Hydra."   This monstrous creature lurked within the swamp depths and often emerged to kill any people who happened to venture close to her.       Eurystheus deployed Heracles to Lerna to summon the snake from the swamp and slay her.     Heracles was permitted to bring his nephew Iolaus along, as he had proven a brave and trustworthy companion for his uncle.     Finding the monster's lair was simple enough, for all the locals knew of its location. Unfortunately, as Heracles discovered once he found and then started battling the creature, the water snake had regenerative powers.  Whenever one head was cut off, two grew in its place.  Moreover, one was immortal, so even if it were removed, it would remain alive and active.      After Heracles chopped off six heads and then realized he was confronted by a fifteen headed monster, he instructed his nephew to fetch a cauterizing iron and to burn the neck stumps as soon as the head was removed, thereby preventing further re-growth.  The heat treatments worked and, after hours of fierce fighting, Hydra was left with only the one immortal head.  This head was ten times more fierce than any of the others and even the powerful Heracles was worried that he would never be able to slice it off.   Realizing that his uncle was in peril, Iolaus punctured both of Hydra's eyes with the iron.   Hydra roared with anguish and rage, but as she was blinded, Heracles had little trouble cutting off the head,    He and his nephew then buried the head under a large boulder where it is said to still remain, alive but confined.

Eurystheus congratulated Heracles for this triumph when the warrior returned to his home.  However, as Heracles required his nephew's assistance to slay the Hydra, the King decided that it would not count as one of the labors.

THE NEMEAN LION
Next, Eurystheus sent Heracles to the land of Nemea, where it was said that an invincible lion was terrorizing the populace.     The King heard that the Lion was covered by an impenetrable hyde that he wanted for himself.   After searching for more than a month, Heracles came upon the Lion and he was astonished to behold him, for the Lion was as large as a young dragon and equally as fierce.   Heracles rapidly fired a barrage of arrows at the monster, only to see them all bounce harmlessly off the Lion.  He then charged the lion with his club, only to see his club rebound off the hyde without inflicting the slightest injury to the ferocious animal.     In desperation, Heracles wrestled the Lion to the ground and pushed his hands under the lion's chin.  He then strangled the beast and as it lay dead, Heracles snapped off one of its claws and used it to cut away the hyde.    He then ran back to Eurystheus  to deliver the prize.

The King then grew deeply frightened of Heracles, for his victory over the Nemean Lion was indicative of Heracles' immense power.    He then commanded Heracles to never approach him again, but would instead convey all future commands through emissaries.

THE HIND OF  CERYNEIA
Next, Eurystheus ordered Heracles to capture the Hind of Ceryneia.  This hind (or red female deer) was neither ferocious nor menacing.  Instead, she was wind-swift and capable of concealing herself completely within the vast Ceryneian forests in which she lived.     Heracles devoted a year of his life to pursuing the hind.   Only infrequently did he spy the animal, but as soon as he started the chase, she darted away with a speed he could never match.     He thought of slaying her with an arrow, but the Hind was under the special protection of Diana, goddess of the Moon and wild animals.    Heracles had enough trouble having been in Hera's bad graces.   He was loath to antagonize another goddess.    However, when Heracles spotted the hind drinking by a river, he decided that he would have to use violence after all, for the deer was far too fast to be captured in an open chase.   Heracles removed an arrow from his quiver as the hind drank.    However, the hind looked up quickly when he released the arrow and bolted away.  She was so quick that she almost outran the arrow...almost.  The arrow tip plunged into her side and she fell injured onto the ground.    As Heracles carried the hind back to the King, Diana and her brother Apollo materialized in the wood.  The vexed goddess demanded that Heracles explain himself.    He complied, and told her that the capture of the hind was part of the labors he needed to fulfill for the slaughter of his family.  Diana ultimately sympathized with Heracles, most likely at the urging of her brother Apollo, one of Zeus' closest companions.     The goddess healed the hind's wound with ointment and then induced a fortnight's sleep onto the hind, so that Heracles could easily convey her to the King, thereby completing the labor.  She instructed him, however, to restore the hind to her proper place in the forest.    Heracles did so.

THE ERYMANTHIAN BOAR
was indeed fearsome and vicious.    This boar was a large, wild pig with two large, sharp tusks protruding from its snout.    Residing on Mt. Erymathus, hence the name, this board would daily careen down the mountainside in search of prey, its favorite being humans.     Heracles was commanded to capture it and bring it alive to the King.  After some misadventures with a herd of centaurs over wine,* Heracles proceeded to the mountain and eventually found the boar engaged in its daily hunts.    Though Heracles could have easily slain the boar with his arrows, he had to capture it alive, so, instead, he chased the animal around the mountain in a fury.    The boar, frightened by the sight of so large and furious a human, fled from Heracles, who continued the pursuit until the boar rushed into a thicket in a state of pure exhaustion.    Heracles then rammed his spear into the thicket, which induced the boar to flee into a trap that Heracles had set up on the thicket's other side.   Heracles then carried the boar back to the city gate, but was prevented from entering at the king's behest. 

Eurystheus  had become so terrified of Heracles that he had a partially interred ceramic jar constructed into which he would hide whenever Heracles returned with whatever monster Heracles had defeated.

THE AUGEAN STABLES
Perhaps it was because Eurystheus was so frightened of the creatures he ordered Heracles to capture that the next labor didn't involve fighting a monster at all. Instead, he instructed Heracles to cleanse the stables of King Augeas.   This task might sound simple, but the stables covered many square miles and contained thousands of cows, thousands of horses and thousands of sheep.  The stables hadn't been cleaned in thirty years.  (We'll leave the ripe condition of these stables to your imagination.)  Moreover, Heracles was required to clean the stables in only one day.    While this labor wasn't exactly life threatening, it did seem impossible.    He then had an inspired idea on how to clean these stables so quickly.  Before he did so, however, he approached the King and told him that he would clean the stables in one day provided he received one tenth of the cattle.  The King, who didn't believe Heracles capable of such an act, agreed at once.      The King sent his own son to observe.

While all the animals were out grazing, Heracles tore a large opening on one wall and then just as large an opening in the opposite wall.   He then diverted the courses of two rivers, the Alpheus and the Peneus, so that they flowed through the stables, thereby cleaning them thoroughly.   Heracles then diverted the rivers back to their original courses and rapidly repaired the holes so that by the time the animals returned to the stables, they were pristine.    King Augeas was astonished, but refused to honor the terms of the agreement under the pretext of his ongoing animus with Eurystheus.    Heracles demanded payment, but was refused.    He then consulted Minos, who agreed to adjudicate the matter.     The King lost the trial as his own son testified that he witnessed his father agreeing to Heracles' terms.    The King relinquished ten percent of his cattle, but then banished both Heracles and his son from his kingdom forever.

As an added insult, Eurystheus refused to consider this task to have been an actual labor, as Heracles was paid for his work.

THE STYMPHALIAN BIRDS
Knowing that Heracles was understandably infuriated at him for not considering his stable work to have been a labor, Eurystheus next sent Heracles to kill every one of the Stymphalian Birds, human devouring birds who plagued the lakes outside of Stymphalios.     Heracles found this labor to be the most difficult yet, for he had to find every bird and kill it.  These birds were well hidden within the lakeside forests and no matter how he searched, Heracles couldn't find them.    Athena, Goddess of Wisdom then presented him with krotala, bronzed devices that Vulcan, himself, crafted to produce excruciating noise,  (Heracles was also given a supply of wax to push into his ears.)  Heracles used the krotala, which produced a series of bangs loud enough to disturb the entire countryside.  The birds, desperate to flee from that horrific noise, rose into the air en masse and Heracles rapidly killed them all with his arrows.      He gathered up all the bird cadavers and delivered them back to Eurystheus.   

THE BULL OF MINOS
After he deposited the pile of bird corpses at the city gate, Heracles was ordered to capture the beautiful bull owned by Minos, King of Crete.    It was this bull that Minos was required to sacrifice to Poseidon, God of the Seas.  Instead, Minos kept the bull for himself.  As a punishment for the king's disobedience, Poseidon cast a spell on the queen that made her fall desperately in love with the bull.    The Queen and bull sired the minotaur which the king imprisoned in a labyrinth.** 

Of all the labors, this one was by far the easiest.    Heracles traveled to Crete and found the bull in Minos' best stable.   Heracles entered the stable, quickly wrestled the bull to the ground and ensnared it.   He then delivered it back to King Eurystheus, who promptly released it.  The bull then terrorized the populace, only to be eventually slain by Theseus, the same warrior who slew the minotaur.

THE MARES OF DIOMEDES
As soon as the Cretan bull was delivered, Heracles was sent to capture the four man-eating mares of Diomedes, the king of the Bristones, a powerful tribe of Thrace.  It is said that Diomedes had used these fearsome mares to drive his chariot.     In other versions, they roamed free and constantly devoured hapless travelers.      In both versions, Heracles was said to have pursued the mares, captured them and tossed them in the boat he had stolen to reach Diomedes' kingdom.    As soon as the mares were abducted, an army of Bristone soldiers pursued Heracles and fought them as he departed to sail away.     Heracles slaughtered all his attackers to a man and brought the mares to Eurystheus.     The king, horrified at the sight of these enormous flesh eaters, set them free to eat the citizens.  However, the mares somehow managed to access the Milky Way's bridge to Olympus, where some of the wild sky creatures devoured them.


THE BELT OF HIPPOLYTE
For the ninth labor, Heracles was commanded to fetch the belt worn by Amazonian Queen Hippolyte.  The Amazons were a powerful race of women warriors living in isolation within the wilds at the world's edge.     For this labor -and with the king's consent- Heracles gathered a small army of Greek warriors to accompany him on his journey.    Heracles realized that for all his strength, he was no match for an entire army.      After embarking on a perilous journey, they came upon the Amazons.  Though highly suspicious of the Greek men, the Amazons did not move to attack them initially.     In fact, Hippolyte received Heracles cheerfully, for she had secretly fallen in love with him through Aphrodite's influence.  Aphrodite was often at odds with Hera and chose this occasion to assist Heracles so as to antagonize  Hera.   Heracles told Hippolyte that he needed her belt to complete a labor.   She offered Heracles the belt at once, provided that he stayed with her for an entire moon cycle.   Heracles agreed to this arrangement, and was astonished that attaining the belt had proven to be so simple.   After all, the war god, Mars, himself, had given Hippolyte the belt himself, as she had proven herself to be the most powerful of all Amazonian warriors.     

Hera observed the exchange between Heracles and Hippolyte.  Infuriated at the Hippolyte's acquiescence, Hera disguised herself as an Amazonian warrior.  During the first part of the moon cycle, she went to each Amazon and convinced each one that Heracles was going to kidnap the queen while each Greek warrior had intended to abduct one Amazon.    One night, the Amazons conspired to slay Heracles and the other warriors. A battle ensued, and, it is said that most of the Greek warriors were slain.    Heracles survived but, believing the assault to have been treachery authored by Hippolyte, ran her through with his sword and took the belt before departing.     He returned to the king and gave him the belt, which he, in turn, gave to his daughter as a present.

GERYON'S CATTLE
One could say that Heracles' tenth labor was perhaps the most time consuming, even more so than his year long pursuit of the Hind.    Eurystheus instructed Heracles to travel again to the world's end and capture all the cattle owned by the monster Geryon, whose body consisted of three heads and a series of arms and legs all conjoined so that the creature could see all things at once and could reach anything within his sight.     Moreover, Orthus, the two headed hound and brother of Cerberus, guarded the cattle when Geryon was not in attendance.     

Heracles traveled to the world's end within a chalice that the Sun God Helios gave to him.   Heracles traveled within this chalice to an island located between northern Africa and Europe.     Seeing that the waterway was blocked by a mountain, Heracles split the mountain into two halves and set one of the halves in Europe and the other in Africa.  In this manner he forged the Strait of Gibraltar.      When Heracles arrived on Geryon's island, the ferocious Orthus set upon him at once.     He clubbed the beast to death and proceeded to gather the cattle together.    As soon as they were all in the chalice, Geryon reached the shore and grabbed Heracles by the throat with one of his extraordinarily strong arms.    Heracles struggled to free himself and only managed to do so by falling backward, thereby sending Geryon into the ocean.  Heracles then held him down in the water by pressing his heel on Geryon's chest, causing him to drown.  During this fight, the cattle scattered and Heracles had to re capture them one by one.  Since Ortheus and Geryon were both dead, he had no more conflicts, but the task of gathering all the cattle again was exhausting.   

Heracles managed to place all the cattle back in the Chalice and sped back to the King.     All went well with the journey until they just about reached the Mycanae.   At this moment, Hera cast a gadfly into the herd of cattle and then scattered yet again.    Once more, Heracles had to find and re capture each cow.    Once they were all regrouped, he tied a rock to each cow to prevent another diaspora. 

Heracles delivered the cattle to Eurystheus who then sacrificed them to Hera.

THE APPLES OF THE HESPERIDES
Now, both Heracles and Eurystheus were both secretly enraged.  Heracles was justifiably angry as he had completed ten labors, as was required of him.  Of course, Eurystheus didn't count two of them, so two more labors remained.  Eurystheus was angry because Heracles was still alive and seemed capable of any superhuman feat he was assigned.  He decided that he had to give Heracles a truly impossible task: to fetch the apples of the Hesperides:  golden apples that Hera had given to Zeus as a wedding present.    These apples were stored in a beautiful garden and guarded by Ladon, the hundred headed dragon and Hesperides, the nymph daughters of Atlas.

The problem with performing this labor was that Heracles had no idea where the garden was located.   Also, as he searched for the garden, he encountered one antagonist after another.   He fought Kyknos, a son of Mars who envied Heracles' strength and wanted to best him in battle.  He didn't.     Soon after, he fought Antaeus, a son of Poseidon who wanted to defeat Heracles in a wrestling match.    Every time Heracles pinned Antaeus to the ground, Antaeus rose up stronger than before.   Heracles then realized that Antaeus derived him strength from the ground.  Heracles lifted him in the air and crushed him in his arms.   

Eventually, Heracles encountered the sea god Nereus who knew of the garden's location.   Nereus tried to escape from Heracles by changing his shape, for Nereus could assume any form he chose.  However, Heracles held Nereus down so that he couldn't escape no matter what he became.  In defeat, Nereus disclosed the garden's location.     He also told Heracles to visit Prometheus to learn the secret of fetching the apples.

Heracles went to the mountain where Prometheus had been chained.   As a punishment for bringing fire to mortals, Prometheus was bound to a rock and condemned to have his liver eaten by an eagle each day, only to have the liver grow back at night to be devoured the next day.   Heracles saw Prometheus bound and at daybreak, when the eagle returned, ran forth and slew the eagle.  He then released Prometheus from the chains.   In gratitude, Prometheus told him the secret of obtaining the apples.  However, Heracles would have to persuade Atlas to take them. Only Atlas would be permitted to take the apples, for his daughters guarded them and wouldn't move against their father.

Hurriedly, Heracles flew to see Atlas, who strained beneath the burden of holding up the world. Heracles offered to relieve his burden temporarily, provided that Atlas went to the Garden of the Hesperides and brought him the apples.  Atlas agreed to these terms at once.     Soon after, Atlas returned with the apples as the agonized Heracles continued to hold up the world.  Atlas told Heracles that he would take the apples to Eurystheus, himself and that Heracles could hold onto Earth forever.   Apart from appearing angry, Heracles cheerfully consented, stating that he hated the king and never wanted to set eyes on him again. However, he asked Atlas if he could take Earth back for a moment, so that Heracles could place a pad on his shoulders to alleviate the soreness.   Atlas set the apples down on the ground and took the Earth back onto his back, only to see that wretched Heracles gather up the apples and flee.

Heracles brought the apples back to Eurystheus, thereby completing the eleventh labor. However, as the apples belonged to gods, Heracles brought them back to Athena who returned them to the garden.


CERBERUS
The last labor.
Eurystheus had one last chance to destroy Heracles.    He assigned him a labor that he was convinced no mortal could perform.  He told Heracles to fetch Cerberus, the three headed hell hound, from the underworld, where the shades of the dead languished forever.        After much difficulty, Heracles came upon the only known entrance to the Underworld: a region in Taenarum where a trickling stream of black water eventually led through myriad meanderings down to Acheron, one of the five waterways leading to the underworld.   Heracles navigated this river and ultimately came upon Hades, the God of the Underworld.    He approached Hades and asked permission to deliver Cerberus up to the world of the living.      Hades said he would allow Heracles to convey Cerberus briefly to King Eurystheus, but only if he could defeat Cerberus without a weapon.    With nothing else for it, Heracles sought out Cerberus and wrestled with a creature who proved to be one of the most terrifying foes he ever faced.  Cerberus bit him repeatedly and scorched him with his fiery tail, but, still, Heracles eventually prevailed.   He bound the hellhound fast with ropes and carried him on his shoulder back the King, who, in a blind panic, demanded that the monster be immediately returned to Hades.

When Heracles returned Cerberus, he found himself able to rise out of the underworld without having to trudge back, for Heracles had experienced an apotheosis:  he had become a god, an Olympian in spirit, though still in mortal form. 

It is said that when Heracles eventually relinquished his mortal form years later and ascended to Olympus, he was finally reconciled with Hera and even married into her family.        One could say that Heracles finally atoned for both the murder of his family and also for his lineage.   


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