Pisces
Pisces is an autumn constellation showing two fish tied together by a cord. Its stars are faint, but it matters to astronomers because it's where the vernal equinox point lies today.
| Latin name | Pisces |
|---|---|
| Abbreviation | Psc |
| Brightest star | Alpherg (mag 3.6) |
| Best seen | Autumn–early winter evenings (Northern Hemisphere) |
| Astrological dates | February 19 – March 20 |
| Sun actually passes | March 12 – April 18 |
| Stars used by Planetica | 1,880 |
How to find it
Pisces is well placed in the evening sky from October to December and climbs high in the south in the early evening in November. Even its brightest star is only magnitude 3.6, so look on a moonless night from somewhere with little light pollution.
Your signpost is the Great Square of Pegasus. Pisces spreads out in a big V shape that wraps around the Square's south and east sides. First look just below the south side of the Square. Five or six stars of 4th–5th magnitude form a small ring called the "Circlet," which is the body of the western fish.
From the Circlet, a line of faint stars runs east, bends at Alrescha, the point of the V, and climbs north. This line of stars is the cord tying the two fish together. The northern fish, at the north end of the cord, sits just south of Andromeda. Following the line star by star with binoculars makes the figure much easier to trace.
The myth: two fish bound by a cord
In Greek and Roman mythology, Pisces tells the story of Aphrodite (Venus to the Romans), goddess of love and beauty, and her son Eros (Cupid). One day, as the two gods were by a river, the terrifying monster Typhon appeared. Startled, they turned into fish and dove into the water, tying their tails together with a cord so they wouldn't lose each other in the chaos. In some versions, two fish appeared and carried the gods to safety on their backs, and those fish were placed in the sky.
The two fish swim in different directions yet stay joined by the cord, a reminder of bonds that hold even across distance. The star at the knot is Alrescha, whose name means "the cord" in Arabic. This myth also links to Ganymede's Aquarius and to Capricornus, Pan turned sea-goat while fleeing Typhon, so the "water" constellations of the autumn sky form one family of stories.
Main stars
| Name | Apparent magnitude | Distance (approx., ly) | Notes |
|---|---|---|---|
| Alpherg (Eta) | 3.6 | ~350 | The brightest star in Pisces, a yellow giant on the northern part of the cord. |
| Gamma Piscium | 3.7 | ~140 | The brightest star of the Circlet, an orange giant. |
| Alrescha (Alpha) | 3.8 (combined) | ~150 | A binary at the knot of the cord that ties the fish together. It's the Alpha star, but not the brightest. |
| Iota Piscium | 4.1 | ~45 | A star of the Circlet; a yellowish-white star a bit larger and hotter than the Sun. |
Near Alpherg is the spiral galaxy M74, about 32 million light-years away. It shows beautiful face-on spiral arms, but its low surface brightness makes it known as a hard galaxy to find with a small telescope. Also in Pisces, though invisible to the naked eye, is van Maanen's Star, a white dwarf about 14 light-years away. Discovered in 1917, it's the closest solitary white dwarf to Earth.
Birthday sign dates: two different answers
In astrology, Pisces runs from February 19 to March 20. But in the first part of that period, the real Sun is in Aquarius. The Sun actually passes through the Pisces constellation from about March 12 to April 18, a long stay of about 38 days.
The first reason is precession. Earth's axis slowly wobbles like a spinning top over a cycle of about 26,000 years, so the vernal equinox point moves west along the ecliptic by about 1 degree every 72 years. The astrological signs were set based on the time, about 2,000 years ago, when the equinox point was in Aries. Since then the equinox point has moved into Pisces, which is why on today's March equinox (around March 20) the Sun is in Pisces, not Aries.
The second reason is the constellation boundaries set by the International Astronomical Union (IAU) in 1930. Real constellations differ in size, so they don't divide evenly into 30-degree slices the way astrology does. The dates can vary by about a day from year to year.
In Planetica
If your birthday's astrological sign is Pisces, Planetica places your planetary system next to a real star inside the Pisces constellation. The candidates are the 1,880 stars in the HYG catalog that lie within about 3,000 light-years of Earth and inside the IAU boundaries of Pisces.
One of them is picked at random, and your system settles about 1–6 light-years from it. Like the two fish tied by a cord, "twin systems" from people with the same name and birthday share Pisces, but each sits next to a different star.
Planetica also shows which constellation the Sun was really in on your birthday. For example, someone born on March 5 is a Pisces in astrology, but on that day the Sun was actually in Aquarius.
Fun facts
- The vernal equinox point, the reference point astronomers use for positions in the sky, lies in Pisces today. So the zero point of sky coordinates sits inside this constellation.
- The equinox point keeps moving and will cross into Aquarius around the year 2600.
Other constellations
Create your own planetary system
Enter a name and a birthday to get a one-of-a-kind planetary system, placed next to a real star in your birthday constellation.