Salmoneus: You're who, again?
During our daily excursions through the sub-empyreal realm we have occasionally encountered those who have displeased the gods. We remember Tantalus, who served up his son for supper; Midas, who messed up the matter about Apollo's music; Bellerophon, who buoyed himself far beyond his proper boundary; Oedipus, who, well, did exactly what the gods told him he would do, but shouldn't have done, but he unknowingly did it, anyway; Arachne, who weaved the gods' wicked acts and lewd behaviors through her loom; and Sisphyus, the scintillatingly smart schmo who outwitted the Olympians and will forever more roll rocks up the underworld's highest undulations. Well, some of those deeds were definitely audacious and so incurred the enmity of those lofty sorts who are generally loath to let things go. However, none of these aforementioned blasphemers ever proved quite as bold as Salmoneus, Sisyphus' lesser known brother. In other words, nobody else in or under Olympus was ever as quite as stupid....no, not even Midas. Officially, Salmoneus was the King of Elis, a minor kingdom at the upper northwest corner of the Peloponnese. He was also the founder of the small city of Salmone that, yes, he named for himself. That last statement should give one penetrating insight into Salmone's nature. Unofficially, Salmone was a magician. No, not a wizard. Wizards were serene sorts who gathered in secret midnight covens to summon forth silver magic from moonlight. They devoted their lives to the mastery of their craft and entered into their orders only after years of study and more than a few solemn rites of initiation. Magicians, on the other hand, were generally crackpots. They adorned their houses with impressive symbols signifying nothing and draped themselves in the most preposterously ostentatious attire, which they believed would instill wonderment in their "inferiors." (They often misinterpreted the tense silence of suppressed laughter as rapturous awe.) Of all the self-important pseudo-sorcerers who have ever slung a sceptre over their shoulders, Salmoneus was far and away the silliest. On more than one occasion he would perform magic shows for his subjects: shows replete with billowing smoke, dazzling explosions and small animals who were supposed to dance, but generally just sat on stage looking as befuddled and anxious as most of the audience members. Of course, being a king in command of armed soldiers, his magic acts generally earned thunderous applause. One day, a group of these soldiers were seen by the river. They were starting to build what would become a large metallic bridge. Also around the same time, other soldiers were constructing an immense chariot, one that would become so gilded and bejeweled as to be blindingly radiant. Salmoneus' weary subjects well knew that here again were preparations for another magic show and they braced themselves. Unfortunately, they didn't know when the performance would be scheduled so they would awaken every morning uneasily. They woke up more easily, though, on the morning of the annual festival honoring Zeus. As that festival was the year's most important religious event, the people of Salmoneus' kingdom knew that even their king would be sensible enough not to try any sleight of hand tricks then. So, when they gathered together around noon time for the festival's commencement, the people were generally relaxed and in good humour. They lit the fires to honor the Sun and sprinkled water on the grass to mimic the clouds: both of which were facets of the heavens, Zeus' domain. The subjects then danced with almost bacchanal abandon under the crystalline blue sky. They were so engrossed in the festivities that for a while they didn't notice that the king was absent. In past years he had presided over the festival. (Even his detractors conceded that he did so quite well. "If only he could have managed matters as competently on the other 364 days," they'd often say despairingly.) By mid afternoon, at the time when the feasting would begin, the people began to wonder about Salmoneus' whereabouts. Then, they heard a peal of thunder. People looked up at the sky with puzzlement. It was still cloudless. As the thunder grew louder, a stentorian voice was heard yelling and laughing. Everyone fell silent as they looked toward the source of the thunder and laughter. To their shock they saw a large gilded chariot approach the bridge. Paddles attached to the wheels beat against the ground producing the percussive claps they had mistaken for thunder. The claps became deafening when the chariot crossed the metallic bridge. Four large steeds, all painted gold, lead the chariot which the king, himself, was driving. Yet, it wasn't the faux thunder or golden steeds that left them speechless. It was the king, himself! He sported a luxuriant beard, a thick mop of curly hair encircled by a laurel wreath, and wore a himation dyed bright yellow. He stood at the chariot's top and whipped the horses frantically. As everyone stood transfixed, he drove over the bridge and declared, "I am Zeus! Bow down and worship me! I am Zeus and I am here!" The subjects cast both confused glances at their king and worried glances up at the sky. When the chariot reached the crowd he stopped the horses and then stood high atop the chariot. "I am Zeus! Worship me!" he yelled. Noticing that nobody had yet prostrated themselves before him, the king withdrew from the chariot a silver object shaped like a forked lightning bolt and hurled it into the crowd intending to instill terror. (Two cats ran away.) Frustrated by the pervasive silence and inactivity, Salmoneus jumped down to the ground. "Behold, though the sky be clear, I shall summon the rain." He then hopped up and down on one foot and then another and then the other one again. "I am Zeus and I am making rain!!" he shouted. He held his arms aloft while hopping and so lost his balance and crashed headlong into one of the horses. The startled horses careened headlong into the crowd and dragged Salmoneus with them. "Zeus's horses are making rain! Zeus's horses are...."
At that moment Hermes, who had been watching the festival and the king's antics, approached Zeus who was seated on his throne. "Well, Hermes," he said "What troubles you?" Hermes gulped. "Well...."
Every festival attendee was then running for their lives as the frenzied horses broke loose from the chariot and ran amok through the crowd. Salmoneus, still attached to one of the horses, was partially running, partially being dragged along at a frenetic pace. All the while he shouted, "I command this horse to halt! I am Zeus and I command this horse to halt!" The horse dragging the king did indeed stop when a thunderbolt smote it from the blue sky. Another thunderbolt struck the king, literally reducing him to a smoldering cinder. The other horses then grew calm as did the people they had terrorized. All the subjects then bowed below the sky so as to affirm their devotion to the real Zeus as opposed to his moral impersonator. Even though Zeus was known to mete out punishments widely and arbitrarily when vexed, in this instance he was content merely to slay the mad king who had presumed far above his station. Salmoneus was then consigned to Tartarus for an eternity of terror, torture and torment, the nature of which remains unknown to mythographers. Nobody since Salmoneus ever tried again to declare themselves to be Zeus, the grandest of all the gods. Salmoneus was unique in the annals of mythological history for having been the only mortal to have done so. (Roman Emperor Gaius Caligula doesn't count. He was a real person.) For this reason is Salmoneus remembered, albeit not by many people anymore.
THE SOUTHWORTH PLANETARIUM
207-780-4249 www.usm.maine.edu/planet
70 Falmouth Street Portland, Maine 04103
43.6667° N 70.2667° W
Altitude: 10 feet below sea level
Founded January 1970
Julian Date: 2459003.16
2019-2020: CLX
THE DAILY ASTRONOMER
Wednesday, June 3, 2020
Remote Planetarium 47: Stellar Evolution Part I: Low Mass Stars
By the time you were born into the Universe, the Sun had already been part of it for five billion years. Stellar astronomers assure us that it will continue to live in its current state for another five billion. All the while it will be fusing hydrogen into helium and generating energy in the process. After the Sun exhausts its core hydrogen reserves, it must still pass through many stages before it finally perishes as a white dwarf star. Today we shall follow the Sun's evolutionary history and so will understand how low mass stars such as the Sun evolve over time.
We'll provide the H-R Diagram "Sun track" so we can follow our parent star's progression from present day to its death. [We have already covered the time period of the Sun's birth to its presently active stage.]
The Sun is currently stable. The internal energy pressure pushing outward is balanced by the gravitational contraction. We refer to this precise balance as "hydrostatic equilibrium." However, the solar interior shall prove to be quite dynamic over long time periods. Every second, 647 million tons of hydrogen is converted into helium. As more hydrogen is fused," more helium collects and the core shrinks. The shrinking core allows the Sun's outer layers to migrate closer to the core. Consequently, the outer layer material draws closer to the core and the resultant gravitational contraction intensifies. The pressures and temperatures increase, causing an increase in the core fusion reactions. This accelerated fusion will increase the Sun's luminosity by one percent every 100 million years. While the Sun remains on the main sequence, it will slowly migrate upward and slightly toward the left as a result of this increased temperature and luminosity.
In 1.1 billion years, the Sun will be 10% brighter than it is today. Earth and the other planets will become significantly hotter as a consequence. This increased heat will render Earth uninhabitable around this time. Long before the Sun exhausts its hydrogen reserves, Earth will have become furiously hot and devoid of life.
In approximately five billion years, the Sun will have grown more than 58% more luminous than it is today. Also, it will have depleted its core hydrogen, leaving an ultra hot helium "ash." Without any energy pressure, the core will shrink rapidly and its temperature will increase. Meanwhile an outer hydrogen burning layer will form around the core. Within this layer hydrogen will continue to fuse into helium. The Sun's outer layers will expand and cool. The Sun will then become a red giant. Although its effective temperature will be lower than it is presently, its luminosity will increase due to its expanded size. On the H-R Diagram the Sun moves upward and to the right: cooler and much more luminous. The Red Giant Sun will consume Mercury, Venus and perhaps even Earth. Even if Earth remains outside the Sun, its oceans will have boiled away and its land masses will be nothing more than molten soup.
Life becomes quite interesting for the Sun after it enters this Red Giant phase. As the helium core contracts and also receives heat energy from the hydrogen burning shell, the Sun will experience a helium flash! Literally within minutes, slightly less than ten percent of the core will be converted into carbon. The helium burning phase will then begin. The Sun will shrink back to a size equal to 10 times its present volume and 50 times its current luminosity. Over the following 100 million years the Sun will convert helium into carbon in its core. Once the Sun exhausts its helium reserve, the core will be a mixture of carbon and oxygen. The Sun is not massive enough to produce the pressures and temperatures required to ignite carbon fusion reactions. A helium burning shell will form around it. A helium layer will then separate this shell from the hydrogen burning shell on the outside. The Sun will expand again, this time encompassing Earth and growing even more luminous than it had been during its previous red giant expansion. At this time the Sun will be passing through the Asymptotic Giant Branch phase. Remarkably, the Sun will become 5,000 times more luminous than it is now!
Over the course of the next 20 million years, the Sun will become unstable and will expel much of its material every 100,000 years through a series of violet pulses. After the conclusion of this phase, the Sun will be half as massive as it is today. The outer solar layers will then disperse, at first slowly and then rapidly to form a planetary nebula. The exposed core, more than 30,000 K at its surface will then slowly cool over trillions of years. This stellar remnant is known as a white dwarf. A white dwarf will not collapse in on itself because of electron degeneracy. The electrons within the dwarf will repel each other, preventing any further contraction.
The Ring Nebula in Lyra is a well known example of a planetary nebula. We have no idea how the planetary nebula that will form around the Sun will appear. We do know that the nebula will likely disperse into invisibility within 10,000 years after its formation.
The Sun that is blazing hot outside our windows right now is destined to become a bloated red giant that will cover most of our sky. (Nobody will be around to observe this expansion.) Eventually, the Sun will become an ultra hot white dwarf: a stellar remnant that will slowly cool over trillions of years. So, our Sun will certainly remain in the cosmos for quite a long time. However, it won't always be the same as it is now.
Tomorrow, we discover what happens to stars that are far more massive than the Sun.
To subscribe or unsubscribe from the Daily Astronomer: