*Xanthus and Balius:  Immortal Horses*
They are the four Anemoi, or wind gods, each one associated with a
cardinal direction.   *Boreas*, the north wind, brings the deep winter
chill.  (It will arrive here tomorrow morning.)  The south wind *Notus* conveys
the violent storms of late summer and autumn.  *Eurus*, the east wind,
though not generally associated with a specific season, conjures the
assailing ocean gusts. The west wind *Zephyrus*,  the gentlest of the four,
delivers the gentle spring breezes.     Though his winds are soft, Zephyrus
is himself, often fierce.    For instance, he and Apollo were once rivals
for the love of the youth Hyacinthus.  When Apollo prevailed in this
rivalry, Zephyrus crafted a strong wind so that a discus thrown by Apollo
struck and killed his young lover.  On another occasion, when the Harpy
Podarge ("fleet footed") assumed the form of a filly grazing by the sea,
Zephyrus rapidly approached and coupled with her to sire Xanthus and
Balius, two immortal horses.   Though incapable of flight, they were both
as swift as the wind.  Being perpetually youthful, these two steeds roamed
over the world while being careful to not venture into any human habitation
where they might be saddled and locked in a stable.  Eventually, Zeus
captured them both and presented them as gifts to Peleus and the nymph
Thetis on their wedding day.       Curiously, at that time he bestowed on
Xanthus prophetic abilities while Hera gifted the horses with the ability
to speak in human language, though only with their rightful owners and then
only when the speech served their owners' interests.      Unable to tame
the horses himself, Peleus confined them to stables until his son, the
famous warrior Achilles, prepared to join the Trojan War.  Achilles brought
the horses with him to the conflict and found them quite useful. Toward the
end of the war, Achilles lent them to his first cousin Patroclus to aid him
in his battle with the Myrmidons.   (Achilles, himself, withdrew from
the Trojan War for awhile due to a conflict with Agamenon.)    During the
battle, Hector slew Patroclus.  Achilles, always ill-tempered, became so
enraged by his cousin's death that he set aside his dispute with Agamenon
and re-entered the War.  First, though, he chastised the two horses for not
protecting Patroclus.   Xanthus then spoke in their defense by explaining
that Apollo, himself, had ordained that Hector would slay Patroclus.    He
added that Achilles was also fated to die soon, as well* and nobody's
intervention would prevent this death.    Immediately, the Furies, known
principally for avenging murders, struck Xanthus dumb for having revealed
the prophecy.    Achilles, never bashful, screamed at the Furies for having
forever deprived Xanthus of speech.  "I knew the prophecy already!"  he
yelled. "Restore his voice at once!"   However, the Furies departed without
a word.        Little remains known about Xanthus and Balius following the
Trojan War.  Achilles released them from his service and presumably they
continue to roam the wild places so as to avoid humans.     Although
Xanthus retains his prophetic abilities, he lacks any ability to
communicate his prophecies to others.   Since he prefers to remain apart
from people, this inability to speak human languages hardly matters at
all,



*When quite young, Achilles was given a choice by the three Fates: to
either die young in a glorious manner and become immortalized in legend or
to lead a life without distinction and die an old man.  Achilles chose the
former option.

THE SOUTHWORTH PLANETARIUM
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2020-2021:  XXXV



THE DAILY ASTRONOMER
Thursday, October 29, 2020
Remote Planetarium 113:   Nearby Superclusters

Unfathomable!
Here we are on Earth:

[image: drawings_spring_12key6.jpg]

A terrestrial planet more than 90 million miles away from its parent star.
From a cosmic perspective, Earth is negligibly small.  Yet, to us it is
inconceivably huge.   How huge?    If hollowed out,
2,000,000,000,000,000,000,000
people could fit inside it.        That number is approximately equal
to 256,410,256,410
times the current world population of 7.8 billion!

When compared to the Sun, Earth doesn't seem quite as immense:

[image: 8abfff6877581a5a006d032ea6df2f52.png]
1.2 million Earths could fit inside the Sun.

The Sun is but one of 300 billion stars within the Milky Way Galaxy.   A
number that is so large as to be beyond intuition and therefore
unimpressive.     However, if we drew a scale model map of the Milky Way
Galaxy that could cover the entire North American continent,  our entire
solar system -Sun included, of course- would fit neatly inside a coffee
cup.  The Milky Way Galaxy, itself, is but a part of the Local Group of
Galaxies: a collection consisting of more than 80 galaxies, most of which
are dwarfs.  The Andromeda and Milky Way Galaxies are the two largest
members.

The Local Group comprises just a small part of the Virgo Supercluster:

[image: Local_supercluster-ly.jpg]

The volume of the Virgo Supercluster is 7000 that of the Local Group and
100 billion times that of the Milky Way Galaxy!        We can see that at
this level, our galaxy becomes comparatively minuscule.

Now, we learn that our Universe contains 10 million Superclusters!     Yet
again we encounter an intuition-defying number.    Think of that value this
way:  Ten million minutes equals approximately 19 years!  Below we see an
image of the local Superclusters:  those in "close" proximity to the Virgo
Supercluster of which we are a part.

[image: Pavo-Indo_Supercluster.jpg]

Each of those "smudges" contains a collection of groups consisting of
galaxies.  At this level, even the vast Milky Way appears to be little more
than a pinpoint light source.

Notice that the vast "voids" separate Superclusters.      As their name
suggests, these voids consist of large swaths of emptiness, save for errant
stars and planets that might have been expelled from their host galaxies.
   Yet, these isolated bodies are likely few and far between.   Mostly,
innumerable light years of nothing keep Superclusters apart.

Superclusters generally consist of dozens of galaxy groups, each consisting
of 10,000,000,000,000 - 100,000,000,000,000 solar masses worth of
material.   Superclusters tend to be distributed over millions of light
years of space.

The next question, which we will address next week, is how can astronomers
determine the sizes and distances of these structures that are so massive,
immense, and far away?      After all, we are confined to this minuscule
planet within a small spur inside a galaxy that is mote-like when compared
to its Supercluster.     As we shall learn, the techniques astronomers use
to make these determinations are of relatively recent origin.
More on the Cosmic Distance Ladder next week.

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