Stories in the Sky: Andromeda, the Chained Lady
February 2016 :
I’m sure many of you can recognize more than just a handful of constellations. Even in moderately light polluted skies a knowledgeable observer can easily locate and identify Ursa Major (Big Dipper asterism), Orion or Scorpius. Many of our northern hemisphere star patterns owe their existence to classical Greek mythology, though in some instances their origins date back even further to at least 6000 years ago. With incredibly dark skies and no distractions like television or smart phones, the starry heavens were our ancestors’ entertainment. They connected the dots (stars) to form sky pictograms and created intriguing stories to account for their appearance.
And when you become familiar with even a few of these great sky myths, you’ll see that human nature hasn’t changed for millennia. Just as William Shakespeare incorporated every human condition into his works, the ancients likewise portrayed the best and worst of humanity in their sky lore. And that “tradition,” if you will, continues right up to present day with soap operas and reality television, though we will never see a Kardashian constellation!
Today we are going to explore the mythology behind the constellation Andromeda. Then I will highlight two beautiful objects you should attempt to view with either your own telescope or through any of the local observatories’ fine instruments.
Each constellation has numerous mythological stories associated with their star pattern. The more well known one associated with Andromeda involves your typical Greek hero, Perseus. Our story begins with Queen Cassiopeia of Ethiopia being overheard boasting she was even more beautiful than the Nereids, sea nymphs famous for their beauty. They complained to Poseidon who was so angry he sent a sea monster (now recognized as the whale Cetus) to destroy the country. Cetus was in the process of laying waste to Ethiopia when King Cepheus consulted the Oracle of Zeus looking for help. The solution presented to Cepheus was to sacrifice his daughter Andromeda to the sea monster to appease the wrath of Poseidon. (That’s a common theme in most mythologies…the gods using proxies to do their bidding.) Andromeda was thusly chained to a rock on the shoreline to be devoured by Cetus.
Well, as luck would have it, Perseus was flying by on his winged horse Pegasus just after slaying the Gorgon Medusa, that creature with hair of snakes whose stare could turn anything that gazed upon her into stone. Perseus saw Andromeda’s predicament and also noticed how beautiful she was. Since he was still carrying the severed head of the Medusa in a sack, Perseus had a big advantage. He plucked it from the bag for the sea monster to see and Cetus immediately turned to stone. And as most stories of this nature go, Andromeda and Perseus lived happily ever after.
All the constellations associated with this mythological story can be found surrounding Andromeda in the northern hemisphere sky. While Andromeda is an autumn constellation, it can still be seen into mid-March, low above the northwestern horizon. I suggest observing the star pattern and the objects I will be describing during early February with the constellation around 53 degrees high in the sky at 7:00 p.m., though even by the end of the month Andromeda will still be about 34 degrees above the horizon after evening twilight.
While Andromeda ranks 19th in size among the official 88 constellations, it can be challenging to identify, as it does not contain the brightest stars in the sky. Use the accompanying star map for reference. Locate the sideways “M” or “W” shaped group of stars which form much of Cassiopeia in the west-northwest sky. To the left is Andromeda. Look just a short distance in this direction and you should notice a fuzzy path. This object is the Great Andromeda Galaxy, the nearest spiral galaxy to our own Milky Way. It is also known by the designation M31, the 31st entry in a catalog of 110 objects compiled by French astronomer and comet hunter Charles Messier (1730-1817).
It was once called a nebula and was thought to be part of the Milky Way until 1923 when Edwin Hubble determined it to be an “island universe” well beyond the confines of our home galaxy. Later research determined it to be about 2.2 million light years distant, and research in recent years has refined it to be 2.5 million light years away. Imagine, the light entering your eye has been travelling through space for 2.5 million years. How’s that for an eye test?
This vast system of stars comprising M31 is easy to see with your naked-eye. Its magnitude (brightness) of 3.4 is almost identical to Megrez, the star marking the junction of the handle and bowl of the Big Dipper asterism of Ursa Major. Also, to the naked-eye the galaxy covers an area of sky equal to about three full moon diameters. (Long exposure photographs reveal it to be twice that apparent size across.) So, if you can see Megrez when Andromeda is above the horizon, then it’s time to grab a pair of binoculars to enhance the view. Good 7 X 50 binoculars will reveal a little more of the elongated shape of this fuzzy patch of light.
Telescopes of increasing aperture will reveal more of the structure of our galactic neighbor. The Andromeda Galaxy is a barred spiral like the Milky Way, containing about 400 billion stars. It wasn’t until 1887 that it was first photographed, revealing its spiral structure. Astronomers now know that M31 has at least two spiral arms that extend outward from the central bulge of the galaxy and are tightly wound around it. Many years ago, when Skyscrapers first obtained a 16-inch Meade Cassegrain telescope, I remember observing the Andromeda Galaxy and detecting the spiral arms and dust lanes. The view was quite impressive. If clear skies prevail during the open nights at the local observatories, ask one of the volunteer sky interpreters to show you the Great Andromeda Galaxy.
The four brightest stars in order of brightness in Andromeda are Alpheratz, Mirach, Almach and Delta Andromeda. Alpheratz marks one corner of the Square of Pegasus, and in fact until 1930 was part of that constellation. A favorite target for amateur astronomers is the double star Almach. While you can see this second magnitude star with your naked-eye (it’s as bright as the stars defining the Big Dipper asterism), a telescope will be necessary to observe its fifth magnitude companion. Almach is a golden yellow sun and its companion is indigo blue. However, there is more to this system than “meets the eye.” The blue companion itself has another star orbiting it, and that star also has a star revolving around it as well. So in fact, the Almach star system is comprised of 4 stars. But you’ll only be able to see the primary and secondary. The contrasting colors look fine in even small telescopes, rivaling Cygnus’ Alberio.
The Chained Lady was placed in the sky for everyone to revere, so it is your obligation on the next clear night to give her the recognition she deserves. Examine the multiple star system Almach 350 light years from the Earth, and explore the Great Andromeda Galaxy, one of approximately 54 island universes in the local group of galaxies that includes our own Milky Way.
In conclusion, please take advantage of the observing opportunities provided by the local observatories during their public observing nights, which do continue during the winter months, weather dependant of course. These facilities are unheated, so dress warmly. Seagrave Memorial Observatory in North Scituate is open every clear Saturday night. Ladd Observatory in Providence is open every Tuesday night. The Margaret M. Jacoby Observatory at the CCRI Knight Campus in Warwick is open every clear Wednesday night. Frosty Drew Observatory in Charlestown is open every clear Friday night. Snow or ice can force closures, so please check the respective websites for any cancellation notices before venturing out for a visit. Currently the winter hours for Seagrave and Ladd are 7:00-9:00 p.m., while Frosty Drew begins at 6:00 p.m. with no set end time.
Keep your eyes to the skies.
