Virgo

Virgo


Transit Date of principal star:
13 April


Virgo is the second largest constellation (after Hydra). As a member of the Zodiac, Virgo has a number of ancient myths and tales. The Sun passes through Virgo in mid-September, and is therefore the constellation that announces the harvest.

Virgo is often represented as a "maiden" (as its name indicates). In antiquity, she may have been Isis, the Egyptian protectress of the living and the dead and the principal mother goddess.

She was also Ishtar of the Sumerian-Chaldean civilisations, or "Inanna", meaning Queen of Heaven. Inanna is described by Kramer (The Sumerians) as an ambitious, aggressive, and demanding goddess of love.

In Roman times the goddess Ceres was depicted: the goddess of the growth of food plants and harvests, and particularly corn. Her festival was in the second week of April, the same time that the constellation appears in the Spring skies.

The Romans had simply adopted an earlier Greek goddess, Demeter. This goddess of agriculture was of the highest birth: born to Cronus and Rhea, she was the sister of Zeus. As evidence of her antiquity in Greek lore, her name has been found on a tablet from Pylos dating to the thirteenth century B.C.

Demeter was said by Homer to have "lain with Iasion in a thrice-plowed field", the result of which was the birth of Plutus, whose name translates as "riches from the soil" (perhaps "cornucopia" would be an appropriate description).

The goddess was depicted then, as now, as carrying a sheaf of wheat. But her influence carried not only to cereal crops, but to all kinds of food crops. Not surprisingly, perhaps, she was also the goddess of health, and of births and marriages.

A ceremony held in her honour in ancient Greece was called Proarktouria, which possibly indicates that the festivities were held just before the rising of Arcturus. However the name may instead make reference to the constellation Virgo, which in fact rises just before the star Arcturus.

Virgo is unique in that it is the only constellation containing all the Bayer stars with no additional superscript letters or numbers: just the Greek alphabet from alpha to omega.


Alpha Virginis is known as Spica: the "ear of wheat" that the goddess is carrying.
Spica is a blue-white eclipsing binary with a period of just over four days. The star is about twice the size of the Sun, but with a luminosity of about 2000 times the Sun.

Gamma Virginis carries the name of the Roman goddess of prophecy: Porrima.

Porrima is a notable binary of twin stars (see below). It's 32.9 light years distant and has the diameter of 1.5 Suns.


Double stars in Virgo:

[NOTE: See the Binocular link at the bottom of this page for updated data.]

Gamma Virginis is a splendid binary of similar 3.5 magnitude stars, with a recently revised orbit of 168.8 years. The 2000.0 values are PA 260º and separation 1.5".

Theta Virginis is a white star with two companions, both rather faint: AB: 4.4, 9.4; PA 343, separation 7.1"; AC: 4.4, 10.4; PA 298º, separation 70".

Phi Virginis is a fixed binary: 4.8, 9.3; PA 110º, separation 4.8". The primary is a delicate yellow.

Struve 1719 is a striking binary of nearly equal stars: 7.3, 7.8; PA 1º, separation 7.5".

The star is located exactly midway between zeta and gamma Virginis, north about two degrees from a line joining these two stars. Another way to find it would be to form a triangle with zeta, gamma, and delta Virginis. The star is at the centre of this triangle.
Struve 1833 is even more attractive: 7.0, 7.0; PA 172º, separation 5.7".

This system is located 2.5º SE of iota Virginis. If using Tirion's SkyAtlas, you'll find two binaries in this region. Struve 1833 is the northern one. (The other is a triple system called b939. See Burnham for its details.)
Struve 1869 is the third of our trio of Struve binaries. Another lovely sight, but a bit of a challenge: 8.0, 9.0; PA 133º, separation 26".

To find this one, move southeast of mu Virginis two degrees.

Variable stars in Virgo:

A number of stars show very slight variability, such as alpha Virginis, an "Ell." type variable: 0.95 to 1.05 ever four days and rho Virginis is a delta Scuti variable: 4.86-4.88.

R Virginis is a long-period variable with a range from 6.2 to 12.1 every 145.63 days, exceptionally short for a Mira type variable. In 2000 the maximum should occur in the first week of June.


Deep Sky Objects in Virgo:

Virgo has some exceptional deep sky objects: the Virgo Galaxy Cluster, which contains eleven Messier Objects, more than any other constellation except Sagittarius (which has 15). There are also many fine NGC objects in the same vicinity, some just as splendid as the Messiers (such as NGC 5364 and the Siamese Twins: NGC 4567 and 4568).

Then there is the quasar 3 C 273, thought to be from two to three billion light years away.


The region from Coma Berenices down through Virgo is renowned for its galaxies: the Virgo Galaxy Cluster, considered to be about 42 million light years distant. In the midst of dozens of bright galaxies are eleven chosen by Messier for his catalogue.

It is impossible to is give specific directions to locate each Messier object in an extremely rich field. Burnham (p. 2075) gives a useful grid to assist in their location, and recommends at least a six inch telescope. You may find that an even larger scope is necessary to get the most out of this region.

M49: a bright elliptical found between two six magnitude stars.

M58: bright compact barred spiral, but it takes a good night and at least a medium sized telescope to see the central bar.

The Siamese Twins (NGC 4567 and NGC 4568) are 0.5 degree southwest: two faint galaxies seemingly joined in the middle.
Also in the same vicinity are M59 and M60: two small but bright ellipticals.

M61: armed spiral seen face-on, very bright. This is one of the largest galaxies associated with the Virgo Cluster, and may have a mass of fifty billion Suns. Three supernovae have occurred in M61, the last in 1964.

M84, M86, and M87: three more ellipticals, in a very rich region. M87 is the centre of the Virgo Cluster, and is one of the most luminous galaxies known.

M89: small elliptical, resembling M87 but fainter.

M90: nice spiral in same region as M89.

M104: The Sombrero Galaxy. Truly magnificent, this galaxy is isolated from the rest (although apparently is still a member of the Virgo Cluster).

Seen edge-on, the huge luminous nucleus is surrounded by a dark dust lane, which should be visible even in smaller telescopes (depending on the quality of the night sky).


The quasar 3 C 273 has a variable magnitude, roughly from 12 to 13. Its exact 2000 epoch location is: right ascension 12h29.1m, declination +2 degrees, 3.2'; or about 3.5 degrees northeast of eta Virginis.
The name comes from "quasi-stellar object". A single quasar can emit more energy than a hundred galaxies, emitted (in the most part) in the form of infared radiation.

It was this object in Virgo, 3 C 273, that was first identified as a non-stellar object, by Maarten Schmidt, from the analysis of its redshift.

Quasars are perhaps the most luminous object known; some (including 3 C 273) are known to have absolute magnitudes as great as -27.

Burnham (p. 2101) gives an identification chart, as well as a detailed discussion on the phenomenon of quasars.



For a closer look at Virgo visit the Binocular Section.


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