Andromeda:  Princess in Chains

The mythological universe was terrifying.    One could find malevolent spirits lurking within lotus flowers as easily as one could encounter a fell chieftain residing atop a mountain summit.   Divine anger was made manifest in every thunderclap and each volcanic rumble was the tectonic fury of an Earth-imprisoned Titan.   And, yet, the most dreaded regions were those steeped in perpetual darkness, from the deep chasms serving as conduits to the underworld to the unfrequented caverns housing various varieties of fearsome, flesh craving creatures. The most feared of all dark places, however, was the wine-dark sea.  Even the most intrepid divers couldn't venture far down into its waters. Below this razor thin top layer lurked a world far beyond all human fathoming.  Therein dwelt the ancient realm's oldest and most malignant monsters: denizens of the unplumbed ocean depths and home of Cetus the strongest and most loathsome of all sea creatures.      For the moment, we'll leave him to languish in his briny lair as we now turn to Andromeda, the chained princess.

Andromeda's tale begins with her parents: the taciturn King Cepheus and the vain Queen Cassiopeia.     Together they ruled the kingdom of Ethiopia located at the world's far eastern edge.   Though neither were truly beloved, Cassiopeia was the more disagreeable of the two.  She was known to have boasted and bragged quite often to anyone and everyone about anything and everything .  For instance:  Hers was the most spacious and luxurious castle in the kingdom.  (True enough. Very little competition.)  And: She was the wealthiest woman in the kingdom. (Ditto.)  And so forth and so on, ad infinitum.   Though her arrogance won her very few friends, it at least caused her little trouble until she once loudly proclaimed that her only daughter, Andromeda, "was more beautiful than the Nereides!"  Numbering about 50, the Nereides were lovely sea nymphs residing principally in the waters surrounding Greece.     They were uncommonly kind and therefore beloved of the ocean god Poseidon, who wasn't.  On hearing of this boast he resolved to punish Cassiopeia swiftly.  One might wonder why he would have bothered, though.  Mortals, being, well, mortals, were prone to make outlandish statements constantly.   If the gods had punished every faux pas, the world would have been forever consumed in a punitive conflagration.  Poseidon bothered because Cassiopeia and Cepheus were royalty and as such wielded powers over the masses that ordinary mortals didn't possess.  For a queen to assert that any supernatural being was in any measure inferior could imperil the religious order and therefore necessitated prompt retribution.       Poseidon released Cetus from the farthest reaches of the sea.   It arose off the Ethiopian coast and laid siege to Cepheus and Cassiopeia's kingdom.     Having witnessed the creature rising from the waves, the king and queen correctly assumed its arrival to have been the result of divine disfavor.     They quickly consulted the prophet Calchas who explained that Cassiopeia's boast about Andromeda so enraged Poseidon that he summoned forth the monster to destroy the kingdom.  In desperation they asked him if they could do anything to prevent whole scale destruction.  Calchas replied  "You must chain your daughter Andromeda to the rocks by the seashore as an offering to the sea serpent. Only by devouring your daughter will the monster be satiated and Poseidon appeased."   With nothing else for it, Cephus and Cassiopeia locked their only daughter in chains by the seashore and retreated to a nearby promontory to observe her demise.      They watched miserably as Cetus turned away from a throng of fleeing citizens in order to move toward Andromeda. At that very moment,  the warrior Perseus conveniently flew by on the winged sandals of Hermes.   He was returning from the world's end where he had beheaded Medusa at Athena's behest.   All at once Perseus saw a beautiful woman chained to the rocks, a ferocious sea monster approaching her and the two people he rightly assumed to have been her parents looking onto the ghastly scene.     He did not immediately intervene on Andromeda's behalf.  Instead, he flew up to her parents and bluntly said, "If I save her, you will allow me to marry her."    They agreed at once while prudently neglecting to mention that Andromeda was already engaged to her paternal uncle Phineus.     Perseus swooped down on his winged sandals and slew Cetus using the magical sword he had employed to slay Medusa.    It was said that Perseus had to inflict a thousand cuts onto the monster before it fell and the entire seashore was coated red with its blood.    Perseus then unlatched Andromeda and proceeded to the wedding party.  Perseus and many of his friends had gathered for this prenuptial shindig and were enjoying themselves immensely before Phineus -who was curiously absent when his niece/fiancee  was about to be devoured- arrived with his entourage.   Phineus arrived to reclaim Andromeda as his own.  (Here we must interject our regret that Andromeda, herself, was given no say in these arrangements.)   A fierce fight ensued  between the parties.    Despite the unflinching bravery and strength of Perseus and his friends, they were losing to Phineus' vastly larger group of allies.    Perseus then shouted, "Let all who are my friends close their eyes!"   His friends and Phineus shut their eyes at once just as Perseus withdrew the Medusa head.   All of Phineus' friends looked up at the gorgon's severed head and were petrified where they stood.  "Open them now," Perseus said while placing the head back in his satchel.  When Phineus opened his eyes to see his entire entourage turned to stone, he became hysterical and tearfully pleaded with Perseus to spare him.    "Base coward!" Perseus shouted with disgust as he lifted the head back out and shoved it in front of Phineus' face. The uncle was ignominiously petrified in a begging position.    Perseus and Andromeda placed this unsightly statue in the corner of their bedchamber.  [Note:  if you're ever on a blind date in the mythological universe, sprouting an extra head during dinner will merely be a conversation starter.  Behave like a coward and you'll strike out every time.]     Andromeda and Perseus were happily married for many years.  In fact, they remained forever faithful to one another.      The five principal players in this drama:  Andromeda, Cassiopeia, Cepheus, Cetus and Perseus have all been imprinted into the night sky.     While Cassiopeia and Cepheus are circumpolar and consequently always visible, the other three are best seen in the evening skies of autumn which, we're glad to say, is many months in the future.  

THE SOUTHWORTH PLANETARIUM

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2019-2020:  CXLIX

THE DAILY ASTRONOMER

Monday, May 18, 2020

Remote Planetarium 36:  Everything!

Humans have come a long way in the last century.   Slightly more than a century ago  (April 26, 1920), two preeminent astronomers, Harlow Shapley and Heber Curtis, participated in the now famous debate pertaining to the nature of certain "nebulae."  Shapley argued that these nebulae were contained within our Milky Way Galaxy which he assumed encompassed the entire Universe.   Curtis asserted that they were instead individual galaxies well beyond the Milky Way.   Later that decade Edwin Hubble and Vesto Slipher settled the matter by determining that the Andromeda "nebula" was located well outside our home galaxy's well established boundaries. Now we know of literally hundreds of billions of galaxies scattered over a universe so vast in scale as to stagger the imagination.     Today, as we finally prepare to depart the solar system, we will embark on a whirlwind tour of the cosmos to determine our place within it.  

Our home on the "pale blue dot."

On February 14, 1990, while the Voyager 1 spacecraft was racing beyond Neptune, it turned around to capture an image of the home world it had abandoned  almost thirteen years before.   From the Voyager perspective, Earth was almost lost from view: a dim, nearly indiscernible mote against the star adorned firmament.  The rotating stage on which all natural processes and human dramas play out.    We see it above, slightly enhanced for better viewing.   We live on  a planet that is revolving around a dwarf star at speeds far exceeding that of the fastest bullet.          Ours is the third world away from the Sun: the largest of the four inner terrestrial planets and the fifth largest planet over all.    

Except for the many objects in orbit around it, the Sun is truly alone in space.   As the closest star system, Alpha Centauri, is 4.2 light years away, the Sun is the only star within a sphere measuring 310 cubic light years in volume.     Or, by scale, if the Sun were a softball in Portland, Maine, the Alpha Centauri system would be two softballs and an apple in Florida.      Alpha Centauri consists of three stars, two sun-like stars and a red dwarf named "Proxima Centauri."

• Light year:  the distance that a light beam moving through a vacuum covers in one year, equal to about 5.8 trillion miles
• Parsec:  equal to 3.26 light years

Our nearest neighbors

From this perspective, Alpha Centauri seems like an arm's length away from the Sun.     Here we see the closest stars to our solar system.  We recognize some of the star names such as Sirius (Canis Major) and Procyon (Canis Minor).   Others aren't as well known such as Ross 128, Lalande 21185 and Wolf 359.    As is true with seventeen of the twenty closest stars to the Sun, these three aren't visible to the unaided eye and so are named for the catalogs in which they first appeared.  (We'll be returning to these catalogs in another class.)         Even from this perspective we can start to notice the three dimensional nature of our  cosmos.  The stars are not all aligned along the same disc, but appear "above" or "below" the Sun's plane.           As we proceed we'll learn that the concepts of "up" and "down" have little meaning in outer space.

If we expand our view to include all stars within 10 parsecs of the Sun, we find stars in all directions.   The Sun is now almost lost to sight.    It is positioned at the center of this image.

The Galaxy

We now expand our view by many factors to observe the entire Milky Way Galaxy.   Our Sun, located on the Orion Spur with the Orion Cygnus Arm, is labeled.     The Sun is approximately 23,000 light years from the nucleus, concealed within the bar at the galactic center.     To give a perspective on this size contrast, if we could construct a scale model map of the galaxy as large as the North American continent, our solar system would fit neatly inside a coffee cup.   Or, imagine that you drew ten thousand small black dots on a sheet of paper measuring 8.5" by 14."  Let those dots represent all the stars we can see on Earth without a telescope.     In order to draw enough dots to represent all the stars in the Milky Way Galaxy, you would need a sheet of paper measuring 8.5" by 1500 miles: a column of dots nearly connecting Portland Maine and Miami, Florida.     According to recent estimates our one galaxy contains more than 400 billion stars.    A billion, incidentally, is an enormous number that transcends intuition.  If we could go back a billion minutes in time, we'd find ourselves in the year AD 118.   Four hundred billion minutes ago was around 760,800 BCE.  

The Sun is but one of those stars completely lost within the galactic star streams

 The nearest galactic neighbors:

The next step up brings us to the Local Group of Galaxies.     Astronomers believe this group consists of 54 galaxies distributed over a region about 10 million light years in diameter.     The three largest galaxies within this group are the Andromeda Galaxy, the Milky Way and the Triangulum Galaxy.   At a distance of 2.2 million light years, the Andromeda Galaxy is the closest major galaxy to us.  

THE LOCAL SUPERCLUSTER

Yes, we are well outside the range of intuition now.     Increasing our perspective even further we can see that the local group is part of a local supercluster, called the Virgo Supercluster, after the Virgo Group of Galaxies.   Approximately 100,000 galaxies are contained within this cluster that extends over 110 million light years.   From this perspective even our grand Milky Way Galaxy is lost to view.        Astronomers now estimate that this Virgo Super Cluster is just one of 10 million super clusters within the observable Universe!  

PISCES-CETUS SUPERCLUSTER COMPLEX

The Virgo Supercluster contains only about 0.1 percent of all the matter contained within the Pisces-Cetus Supercluster Complex, named for the

Pisces-Cetus cluster, the richest SC within this complex.     One of the largest defined structures within the observable Universe, this complex measures about one billion light years in diameter and is nearly 160 million light years in width.  At this level, the entire local group of 54 galaxies vanishes from view.

OBSERVABLE UNIVERSE:

Would you believe that this "final" stage might just be the beginning?   The "observable Universe" extends 46.5 billion light years in all directions and contains every visible object.  On this scale, galactic superclusters are like sand grains scattered across our viewfield.  The light emitted from any object beyond this boundary has not yet had time to reach us and so is "outside" of our perspective.   Some cosmologists believe that the observable Universe is a small part of the entire Universe, the extent of which is not currently knowable.     Within this universe one would find more than 400 billion galaxies altogether, a number exceeding the number of stars within the Milky Way.          

And, could much more than this Universe even exist?   The concept of parallel universes, those unconnected to our own, was once considered the sole domain of science fiction.  Now, the physics community is seriously considering the existence of myriad other Universes as distinct from our own.     They could number in the trillions and like bubbles in some hyperspatial reality that we might well never understand.

Yes, one could certainly say that humanity has come a long way in the last century.    

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