Virgo the Maiden
As with other ancient constellations, there are many classical traditions surrounding the constellation. For example, the early Greeks saw Virgo as Dike, the goddess of moral justice in the Golden Age. In later ages, as the human race deteriorated, she retreated to the sky.
However one of the best known stories identifies Virgo as Demeter (Roman Ceres), the goddess of agriculture. She was the mother of Persephone (Roman Proserpina) whose beauty so entranced Hades (Roman Pluto) that he carried her off to the underworld to be his queen. Demeter was distraught and refused to look after the crops. Zeus (Roman Jupiter) intervened, but Persephone had eaten something in the underworld, so she was partly bound to to it. Nonetheless Persephone was allowed to spend half the year with her mother.
In the northern hemisphere, the constellation appears from March through August. Demeter's daughter is with her and the crops grow. But when Persephone returns to the underworld, Virgo disappears as Demeter mourns. In this representation you can see Virgo with a wheat sheaf in her left hand.
In yet another story Virgo is Persephone, which I think is a better fit to the representation of a maiden.
There is a skywatcher's mnemonic for finding Virgo. You begin with the Big Dipper (in Britain called the Plough). Then “follow the arc to Arcturus, and speed on to Spica.” This reminds you to follow the curve of the dipper's handle to the bright yellow star Arcturus. If you then continue in the same arc, you'll see Virgo's brightest star Spica.
Let's now look at some of the interesting objects in this Zodiac constellation.
Stars and planets
Spica, also known as Alpha Virginis, isn't a solitary star. There are at least two stars there, and they're much bigger and hotter than the Sun. They orbit each other every four days. However specialized observations seem to show four stars, and there may even be a fifth.
Virgo's other stars are considerably dimmer than Spica, even those sufficiently visible to have traditional names. For example, Eta Virginis, known as Zaniah, appears as a fourth magnitude star, even though it's a triple star system. (The dimmer the star the higher the magnitude number.) The three stars are so close together that special equipment is needed to show them as separate bodies. They're all brighter than the Sun, but are quite distant from us, about 265 light years away.
There are around three dozen known planets in Virgo. Three of the planets circle the sunlike star 61 Virginis. The smallest of the three is a super-Earth, the first to be discovered orbiting a sunlike star. A super-Earth is smaller than a giant planet, but nonetheless larger than Earth.
Another three-planet system discovered in Virgo orbits PSR B1257+12, a pulsar. A pulsar is the remains of a massive star whose life has ended in a supernova explosion. Interestingly, the very first extrasolar planets discovered were orbiting a pulsar.
The planet GJ 504b was discovered in 2013, using direct imaging, by a team at NASA's Goddard Space Center. It's about four times as massive as Jupiter and orbits a sunlike star. The star system is much younger than the Solar System, for a member of the discovery team described the planet as "still glowing from the heat of its formation . . . a dull magenta.”
Deep sky objects
Virgo is exceptionally rich in deep sky objects. It contains not only galaxies, but several clusters of galaxies. One of them – the Virgo cluster – has well over a thousand galaxies in it.
M84 is a lenticular galaxy. An unusual feature is that it shows a large blueshift. Most of the galaxies we observe have redshifts, because they are moving away from us as space expands. However M84 is on the opposite side of the Virgo cluster from the Milky Way. Since it's moving towards the center of the cluster, it's also moving towards us. This causes its light to be shifted towards the blue.
One of the best-known galaxies in Virgo is the spiral galaxy M104, popularly known as the Sombrero Galaxy because of its unusual shape. Not so well known to the general public, but of great use to astronomers, is NGC 4639. It has an unusually large number of Cepheid variables in it. As discovered by American astronomer Henrietta Leavitt, this kind of star can be used to measure distances on a cosmic scale.
The biggest galaxy that we know of in the Universe is IC 1101, a supergiant elliptical galaxy in the Abell 2029 galaxy cluster. It's over fifty times the size of the Milky Way. That is impressive.
We'll end the tour with 3C 273. The first quasar ever found was 3C 273, and it was discovered in Virgo. A quasar is the brightest object in the Universe, releasing energy equivalent to a hundred billion stars. Quasars are powered by supermassive black holes. Many other galaxies in Virgo – and elsewhere – have supermassive black holes at the center. However most of them are no longer very active, including the one at the heart of our own Galaxy.
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