Virgo and Galaxies

Posted in: astronomy, Constellations, Deep Sky Objects, Galaxies, MsGalaxy, Virgo

There is a ring of constellations that circles the sky all the way around the Earth that is sometimes called the “circle of life”. This ring contains all 12 zodiac constellations. They are among the oldest of the constellations and were extremely important to early cultures. When a certain star picture rose in the sky, people knew it was time to prepare the soil for planting. A different constellation would remind them to prepare for harvest, and another would warn them that soon the Nile river would flood. One of the most important, and oldest, of these zodiac constellations was Virgo, the Virgin. This constellation is thought to date back at least 15,000 years. She had several names, depending on the culture. To the Egyptians she was Isis and to the Greeks she was Ceres, goddess of the harvest, in particular goddess of the grains. She is usually shown in the sky holding a sheaf of wheat in her hand.

Ceres had a beautiful daughter named Persephone (Per-SE-fon-ee). Hades, the god of the underworld, also known as Pluto, fell in with Persephone. Against her mother’s wishes, he took Persephone away to live with him in his underworld as his queen. This left Ceres distraught. She fell into a deep depression, and ignored her duty as goddess of the harvest. The world turned cold; famine threatened. The king of the gods, Zeus, saw what was happening. He convinced Hades to allow Persephone to come back to the Earth for six months out of each year to visit her mother, then return to Hades for six months. Now, while Persephone visits her mother, the Earth enjoys a warm growing and harvest season (spring and summer, with Virgo in the night sky), then, when Persephone returns to the underworld, her mother mourns again for six months (fall and winter, when Virgo is not visible).

Virgo is one of many constellations that looks nothing like what it represents. In fact, Virgo has only one bright star, Spica. Spica means “ear of wheat.” To find the star, begin at the handle of the Big Dipper. Follow the curve of the handle down to a bright red star, Arcturus, or “arc to Arcturus”. Then continue on this path until you reach the bright blue star Spica (“spike to Spica”). It is the only bright star in this area of the sky, even though Virgo covers twice as much area of sky as does her neighbor to the west, Leo. Spica is quite an interesting star. It is called a spectroscopic binary star. By a method called spectroscopy, astronomers found that Spica is actually two stars orbiting around a common center of gravity. The primary star is about 2,300 times more luminous than our Sun and almost eleven times more massive. The smaller star is about half the size of the primary star. In addition, the primary star is a “pulsating variable” star; it grows and shrinks several times a day!

 

Look for Saturn in Virgo, visible until late July. This naked eye planet will be the steady-light object, as opposed to the twinkle from stars like Spica. In small telescopes Saturn is truly one of the most spectacular visions for backyard astronomers!

Even though there is not much to see by the naked eye in Virgo besides Saturn, it is by no means an empty area of sky. In fact, the apparent barrenness of stars belies the incredible telescopic objects visible in very deep space. This is home of the famous Virgo Cluster of Galaxies, an immense group of more than a thousand galaxies!

A galaxy is an enormous swirl of billions upon billions of stars spiraling around a massive black hole at the heart of the galaxy. Galaxies come in several sizes and shapes: pinwheel, fried egg, spherical, irregular, elliptical and many more. We live in the Milky Way Galaxy, which is shaped like a flattened pinwheel. The Virgo Cluster of Galaxies contains galaxies of almost every imaginable shape and size. One of the most famous, and one of my personal favorites, is M104, the Sombrero Galaxy. It has a very bright central bulge and a prominent dark lane cutting across its outer edge nearest us, giving it the appearance of a sombrero hat. Even though this distant galaxy is about 40 million light years away it, and in fact all the galaxies of the cluster, are considered near neighbors of ours. We are part of what is called a supercluster of galaxies, Mind-boggling stuff, this! Caution: astronomy is addicting! Clear skies!

2 Comments on “Virgo and Galaxies”

  1. I once had the opportunity to observe M104 through the 36″ refractor at Lick Observatory. What a treat!

    M104 is actually a rare example of a ring galaxy. It’s not easy to make out the ring structure in a “visible light” photo like the one above because it’s obscured by the stars in the halo. But take a gander at how it looks in infrared, courtesy of the Spitzer Space Telescope…

    http://tinyurl.com/m104spitzer

    Enjoy!

  2. Don Walton says:

    Thanks for reminding me how amazing astronomy is! Well written, clear and clean.
    Spica rules.

Posted on Tuesday, May 24th, 2011.

Category: astronomy, Constellations, Deep Sky Objects, Galaxies, MsGalaxy, Virgo | Tags: , , , ,

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