Virgo 5

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:

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 little variablility, 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.