[image: Frederic_Leighton.jpg]
*Orpheus and Eurydice:* an hour of wedded bliss
A particularly pessimistic poet once proposed that every person has his or
her perfect partner. Called a "soul mate" by the sweetly sentimental, or
"the love of your life," by those who don't believe in do-overs, this
embodiment of all things exquisite, melodious, and captivating is
everywhere in mythological circles. Mythology also abounds, quite
naturally, in those who lament the loss of these loves. You know, the
sorry sort who waste the rest of their lives languishing in a state of
excruciating torment. One can't swing a sacrificial fish in the ancient
realm without scraping at least half a dozen faces of these forlorn lovers.
Well, that is the point, isn't it? One falls desperately in love with that
space-time transfiguring specimen of earthly loveliness and then the
latter flits away to some twilight-tinctured horizon. Because of this
precipitous departure, the love remains lovely, fresh and ever-present.
The abandoned admirer then enjoys hours of melancholy pleasure strumming on
strings, composing verse, or staring morosely at the vibrant foliage under
overcast skies. Mythogophers certainly understood that love's most
beautiful element was often absence and tragedy. Hence, the divinely
beautiful and, of course, tragic tale of Orpheus.
Orpheus was the gifted son of King Oeagrus and the muse Calliope. Even as a
child, he developed unrivaled musical skills. Apollo presented him with a
lyre, on which Orpheus produced tones so beautiful that its sounds were
said to have enchanted every human and animal within listening range. Some
poets claimed that Orpheus' music could animate trees, shift hedges and
levitated rocks. It is safe to say that Orpheus was loved by everybody,
save, perhaps, professional landscapers. Along with bouncing rocks and
sprinting trees, Orpheus was followed by a mesmerized procession of adoring
females. Their ardent love was, alas, unrequited. Orpheus only wanted
Eurydice, a lovely dryad who loved him with equal intensity. They wed soon
after he returned from his adventures with the argonauts (a topic for
another day.) During the ceremony, Orpheus did not say a single world,
opting instead to express his devotion musically. All the attendees and
even the gods who observed the wedding were reduced to tears. Never before
or after had such joyous music been performed on Earth. Orpheus and
Eurydice were a deliriously happy married couple...for one hour. Their
wedded bliss ended just after the ceremony when Eurydice was stung by a
serpent that had been concealed within the meadow where their wedding had
been performed. She died instantly. Orpheus quickly found her body and was
devastated by the deepest grief from which anyone has ever suffered.
Inconsolable, Orpheus vowed to devote his life to composing melodies in
Eurydice's honor. Those unfortunate enough to listen to this music
literally felt Orpheus' heart wrenching torment. Having noticed how
profoundly people were being affected by his melodies, Orpheus devised a
mad scheme: He resolved to venture into the underworld to retrieve
Eurydice. Nobody had ever thought of such a rescue before, let alone
attempted it. Yet, Orpheus was both determined to liberate his wife and
confident that, aided by his beguiling music, he could persuade Hades
to relinquish her. Traveling to the underworld after you die is easy,
considering that you are conveyed there at once after your material death.
A mortal who goes to the underworld has to follow a secret passageway in
Aornum. Orpheus used this route and after a few harrowing encounters, soon
encountered Cerberus, the three-headed hell-hound who guarded the
underworld entrance. Usually, anybody confronted by the ghastly Cereberus
would beat a hasty retreat in the opposite direction. Undaunted by the
dog's ferocity, Orpheus drew near him while strumming the lyre and
singing. Cerberus was quickly soothed and soon after fell asleep. On
entering the underworld, Orpheus quickly enchanted the dead shades as he
had the living mortals. Every phantom stood enraptured as he passed.
Even Tantalus momentarily stopped reaching desperately for food while
Sisyphus suspended his rock moving labors. The three judges of the dead,
usually an austere lot, sobbed helplessly and permitted Orpheus to proceed
to Hades' lair. When he stood before the god of the underworld, he begged
him to release Eurydice's shade to his care. Orpheus acknowledged that all
souls ultimately belonged to Hades in the end, but Eurydice died far too
young and deserved to live again. It was said that Hades wept tears of iron
and assented to Orpheus' request. He called Eurydice forth and gave her
permission to follow Orpheus back to the living world. He did, however,
impose one condition. Orpheus was to leave at once and not look back to
ensure that Eurydice was following him until he had reached his home in
Thrace. Orpheus agreed to this condition and immediately left. He had
almost reached home when, as you already know, he yielded to temptation and
turned around, hoping to see Eurydice behind him. Indeed, he did see
Eurydice for a moment before she vanished forever. Orpheus had broken the
pact and lost her forever. He was barred from entering the underworld ever
again. (It was said that Hades inserted wax into Cerberus' ears to prevent
him from hearing Orpheus' music.) Orpheus grew even more despondent than he
had been originally. His grief was double itself for he knew that it was
his own caprice that sent her back to the underworld for the second and
last time. His legion of female admirers sought this opportunity to woo
him knowing that he could never again be with Eurydice. He was having none
of it and angrily repelled their repeated attempts to seduce him. Finally
driven to madness by Orpheus' continued rejections, his suitors conspired
to kill him. At first, he protected himself effectively with his music. As
soon as the enraged women heard the enchanting sounds, they abandoned the
assault and wept. Eventually, however, the women clogged their ears with
wax and launched another attack. Unable to hear Orpheus' music, they
managed to wrest the lyre from his grasp. They then proceeded to literally
rip Orpheus into pieces which they cast into a river. Orpheus' head
continued singing as it floated to the island of Lesbos. Once there,the
head began speaking prophetically. Apollo, fearing that Orpheus'
posthumous oracles would cause people to abandon his own temple at Delphi,
conveyed the head to Olympus where nobody by the gods could hear it .
While Orpheus' head was heaven bound, his shade descended into the
underworld where it was reunited with the shade of Eurydice. They were said
to have loved each other with an unbounded passion of which ghosts were
thought incapable. The lyre, itself, was hoisted up into the night sky and
became the summer constellation Lyra.
THE SOUTHWORTH PLANETARIUM
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Julian Date: 2458991.16
2019-2020: CLII
THE DAILY ASTRONOMER
Thursday, May 21, 2020
Remote Planetarium 39: The Closest Stars
[image: FG17_02.jpg]
We now begin our journey through the Universe outside the solar system.
Above us we see the names and positions of the stars closest to the Sun.
Although in this graphic they seem quite close to each other, vast
distances separate the Sun and the nearest stars. The closest star system,
Alpha Centauri, is 4.2 light years away: equal to nearly 25 trillion
miles. To give one an appreciation of this distance, let's try a
demonstration. Read the following line.
*Oh, snap!*
Well done! Now, during the time you needed to read that sentence, an
immense number of photons escaped the three stars comprising the Alpha
Centauri system. By the time you finish reading this sentence, those
photons will have already traveled more than a million miles from these
stars. Every second of everyday, those photons will move at 186,290 miles
per second through space. A small amount of those photons will reach
Earth around *August 1, 2024! *Every so often during the next four
years, think about these photons en route to our solar system. Although
they're moving at the highest attainable velocity, they need so much time
to reach us. And that is from the nearest star!
Although the focus of today's article will be on the means by which
astronomers determined this distance and those of the surrounding stars, we
wanted to explain some of the strange names assigned to some of these stars.
- *Alpha Centauri; Epsilon Eridani: *a few weeks ago we introduced
the *Bayer
Nomenclature system*. This system assigned Greek letters to stars
within each constellation. By this scheme, the brightest star was called
"alpha," the second brightest "beta," the third "gamma," and so on through
to the last letter "omega." The star's name begins with the Greek letter
and ends with the Latin genitive (possessive) form of the host
constellation name. Hence, *Alpha Centauri *is the brightest star
belonging to the constellation Centaurus. Epsilon Eridani (which is also
now called Ran after the Egyptian sea goddess), is one of the dimmer stars
within the constellation Eridanus. (Also *Tau Ceti* in the
constellation Cetus and *Epsilon Indi* in the constellation Indus.)
- *Ross 148; Ross 154; Ross 248 *Stars featured in a catalog compiled
by American astronomer Frank Elmore Ross (1874-1960). Working on the
staff of the Yerkes Observatory, he devised a catalog of stars that
exhibited high *proper motions*. Many of these stars, naturally, are
quite close, such as Ross 148, Ross 154 and Ross 248.
- *Wolf 359 * German astronomer Maximilian Wolf (1863-1932) also
published a catalog of stars with high proper motion. Wolf 359 is one of
these stars and the closest one to the Sun.
- *Lalande 21185 * One of the stars that still retains the name of
French astronomer Jerome Lalande (1732-1807). These stars appeared in
his 1801 catalog "Histoire Celeste Francaise"
- *Lacaille 8760; Lacaille 9352* Notice the positions of these two
stars. "South" Nicolas-Louis de Lacaille (1713-1762) cataloged many
stars within the southern hemisphere. Lacaille 8760 and Lacaille 9352
were two stars featured in the catalog that he compiled; one that was
published after his death. We met Lacaille before when we discussed the
constellations: he named fourteen of them. Lacaille was well known for
having observed the southern sky when he worked at the observatory at the
Cape of Good Hope in southern most part of Africa.
- *61 Cygni * A Flamsteed number. John Flamsteed (1646-1719) was the
first Astronomer Royal. He developed a system by which stars were
numbered by right ascension: angular distance from the vernal equinox
point. (See more below about 61 Cygni in the parallax section.)
- *Grm 34 Groombridge 34. *Notice the position of this star "North."
Groombridge 34 British astronomer Stephen Groombridge (1755-1832) compiled
a catalog of circumpolar stars, those high northern stars that do not set.
Curiously, this catalog was also published after its author died.
- *S2398 Struve 2398* Friedrich Georg Wilhelm von Struve (1793-1864)
published a catalog of double stars. (We'll be discussing those in greater
detail later in the course) S2398 the 2,398th entry in this catalog and
the closest Struve star to us. However, it is not the closest multiple
system star to us.
- *UV Ceti *The UV Ceti is a variable star designation. (We will be
discussing variables and their nomenclature in much greater detail, as
well.)
Very few of these stars have proper names because most are not visible to
the unaided eye. The only properly named stars are Sirius, Procyon and
Alpha Centauri, properly known as Rigel Kentaurus. *Barnard's star *has
a proper name, even though it isn't visible to the unaided eye. The star
is named for American astronomer Edward Emerson Barnard (1857-1923) who
first measured the star's proper motion. Barnard's star, incidentally,
has the highest proper motion of any star in our sky. (10.3" per year.
More about these motions on Tuesday.)
*PARALLAX*
Stellar parallax illustrates how a branch of mathematics as terrestrial as
'geometry,' can be used in the service of celestial science. We'll begin
with a famous illustration. Find an object that won't move, such as a tree,
stop sign, cooperative spouse or northern New England economy. Close one
eye and extend an index finger out in front of your face. Align the finger
with the chosen background object. While keeping the finger steady, close
the open eye and open the closed eye. You might notice that the finger's
position relative to the background object shifted. If you extend the
finger out to its maximum extent and repeat the demonstration,* you'll
observe the shift is small. If you hold the index finger just in front of
your face and repeat the demonstration, the shift will be quite large.
[image: unnamed.jpg]
*Parallax is the apparent shift in an object's position relative to a more
distant object resulting from a change in the observer's perspective.*
The apparent shift of an observed object's position resulting from a change
of perspective is called "parallax." With the previous demonstration, we've
established an inverse relationship. The closer the object, the greater the
parallax angle.
We can apply the same principle to the stars. Astronomers can measure the
position of a star relative to the background stars at one moment and then,
in six months - when Earth is as far from its original orbital position as
possible - the astronomers measure the star's location again. Provided the
star is sufficiently close,** its parallax angle will yield its distance.
[image: Stellar parallax]
Without delving into all the delicious details pertaining to right angle
trigonometry, we can share a simple equation relating the parallax angle
and the distance. If the distance is expressed in parsecs - one parsec
equals 3.26 light years - and the parallax angle is expressed in
arc-seconds,*** the star's distance is 1 divided by the parallax angle.
*For instance, let's say a star's parallax angle is 0.5." Its distance
would therefore be 1/0.5" = 2.0 parsecs, or about 6.52 light years. *
In 1838, Friedrich Wilhelm Bessel estimated the distance to the star 61
Cygni based on the observed parallax angle. Though his calculation of 10.3
light years was about ten percent less than the currently accepted value of
11.4 light years, Bessel was the first to successfully employ stellar
parallax to measure a star's distance.
The Hipparcos satellite, launched by the European Space Agency in 1997,
catalogued about 118,000 stars and their distances. The GAIA probe,
launched in 2013, will calculate distances and positions of more than 1
billion stars within our region of the Milky Way Galaxy.
The parallax method, valid out to about 500 parsecs, is but one of the many
celestial distance determination methods astronomers have developed. As
we will discover, they now confidently know distances out to billions of
light years. Throughout the remainder of this course we will be learning
many of them.
Before we end today, let's address one immensely important question.
[image: unnamed (1).jpg]
*How did astronomers know which stars to choose as foreground objects
before they knew the distances to any of the stars?*
That seems like a perfect example of placing the cart in front of the
flying horse. One would think that they could have chosen the brightest
stars under the assumption that the bright ones were the closest. That
assumption, however, is based on the incorrect belief that the stars are of
equal brightness. They certainly aren't. If they were, selecting the
foreground stars would have been a trivial matter. Instead, astronomers
correctly assumed that the closest stars would exhibit the highest proper
motions! All stars move very rapidly. However, those closest to us would
tend to appear to move more quickly through the sky than more distant
stars. As an analogy, imagine your watching a car speed down the
freeway. If you're standing close to the freeway, the car will appear to
move very quickly. If you're far away from the freeway, the car will seem
to move more slowly across your viewfield.
Just another example of the human ingenuity that has enabled astronomers to
discover so much about the Universe without setting foot off this planet.
Quiz tomorrow.
Much more about stars next week.
*We could have referred to this exercise as a 'experiment,' except that it
was nothing of the sort. Any exercise that will yield a known result is a
demonstration. An exercise that will lead to a result that, though
predicted, isn't certain, is an experiment.
**For ground based observations, the range has been about 500 parsecs. (A
parsec equals about 3.26 light years.)
***One degree can be equally sub-divided into 60 arc-minutes. One
arc-minute can be equally sub-divided into 60 arc-seconds. An arc-second is
a particularly small angle.
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