Pisces

Article written: 30 Dec , 2008
Updated: 24 Dec , 2015
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Located on the ecliptic plane, Pisces is a constellation of the zodiac and one of the 48 original constellations listed by Ptolemy. Spanning approximately 889 square degrees of sky, Pisces ranks 14th in constellation size, despite its faint stars. It contains 21 main stars in its asterism and has 86 Bayer Flamsteed designated stars within its confines. Pisces is bordered by the constellations of Triangulum, Andromeda, Pegasus, Aquarius, Cetus and Aries. It can be seen by all observers located at latitudes between +90° and ?65° and is best seen at culmination during the month of February.

There is one annual meteor shower associated with Pisces which peaks on or about October 7 of each year. The Piscid meteor shower has a radiant near the Aries constellation and produces an average of 15 meteors per hour which have been clocked at speeds of up to 28 kilometers per second. As always, the meteoroid stream can begin a few days earlier and end a few days later than the expected peak and success on viewing depends on dark sky conditions.

In mythology, the constellation of Pisces is represented by two fish bound together with a piece of string. According to one Greek myth, Pisces represents the fish into which Aphrodite and her son Eros transformed in order to escape the monstrous Typhon; they are tied together with a cord on their tails, to make sure they do not lose one another! Even more mythology states that Pan changed himself into a goat-fish (Capricorn) and jumped into the river to save them… Or perhaps it was a pair of fish which rescued them from the reeds along the river banks… Or maybe they were turned into eggs that were saved by the fish… One thing is for certain, somewhere along the line, the translation got lost – but the twin fish got left in the sky!

Let’s begin our tour of Pisces with binoculars as we take a look at it’s Alpha star – the “a” symbol on our map. Crowned with the traditional name of Alrischa – “Knot In The Rope” – 139 light year distant Alpha Piscium surely isn’t the brightest in the sky, nor the easiest to find. However, once located, take the time to power up in a telescope because Alrischa is a close binary star with angular separation of presently 1.8″ between the components. While the secondary star is separated from the primary by about one stellar magnitude, take note of their soft color. Both are A type stars, but many observers have reported seeing them as white and pale blue. What’s more, each of the chemically peculiar components might also be spectroscopic binary stars, too!

Now, let’s take a look at Beta Piscium in binoculars – the “B” symbol on our map. Located 495 light years from Earth, Samakah, the “Fish’s Mouth”, is a B-class hydrogen fusing dwarf star. It produces 750 times more light than our own Sun and rotates fully on its axis in about 2 days. At 60 million years old, one day Samakah will become a giant star, losing 80% of its mass in its high velocity solar winds and eventually become a white dwarf star.

Time to have a look at the brightest star – Eta – the “n” symbol. This unusual, bright class B star is located 294 years away from our solar system and has the unique distinction of being one of the few of its class to have had its angular diameter measured. It is about 26 times larger than Sol and shines almost 316 times brighter! However, Eta is a dying star… reduced to internal helium fusion. If you power up in a telescope, perhaps you’ll catch a glimpse of this binary star’s small, disparate companion located about a second of arc away.

Now aim binoculars towards Gamma – the “Y” symbol on our chart. Gamma is a yellow-orange giant star located about 130 light years distant. Oddly enough for a giant, it only puts out about 61 times more light than our Sun – but with good reason… it’s currently fusing it’s core to carbon. Right now, it is waiting to become a white dwarf, but that’s not what distinguishes Gamma – it is its speed. Apparently Gamma came from outside our Milky Way Galaxy altogether! According to its low metal content and cyanogen-weak spectral signature, Gamma had to have originated outside the galactic disc and it is still traversing the sky at over three-quarters of a second of arc per year!

For a very nice optical double star in binoculars, take a look at Kappa – the “K” symbol… or better yet, turn a telescope towards TX Piscium. It’s a gorgeous carbon variable star, which shines a deep, ruby red and varies by about a magnitude with time.

Now, let’s talk some deep sky and a Messier catalog object. Located about about 1/2 degree North and 1 1/2 degree East of Eta Piscium (RA 01 : 36.7 Dec +15 : 47), grand design spiral galaxy, Messier 74 isn’t always an easy object for small telescopes and will require dark skies and good viewing conditions to be seen in binoculars. Discovered 1780 by Pierre Méchain, and later cataloged by Charles Messier, this 95,000 light year distant island of light is about the same size as our Milky Way galaxy. When viewing M74 is smaller optics, be sure to look for a very precise, almost stellar nucleus and faded, wispy spiral galaxy structure.

For a big telescope challenge, try your luck with NGC 676 (RA 01h 48m 57.3s Dec +05° 54′ 25.8″). It is also a spiral galaxy with a bright, sharp nucleus, but seen more edge on. At magnitude 11 and about 4 arc minutes in size, it isn’t going to be easy – but what challenge is?

Perhaps you’d like to try NGC 474 (RA 1 : 20.1 Dec +03 : 25), too. It’s a huge elliptical galaxy with tidally disrupted tails from galaxy interactions with nearby NGC 470. While NGC 474 is billed at magnitude 11, you’ll find its stellar bright nucleus so distracting that magnitude 12 NGC 470 will at first appear to be the brighter of the two. While averting your vision, see if you can catch magnitude 13 NGC 467 to the north as well. It is by far the smallest of this galaxy group!

As a curious note, the Vernal Equinox is currently located in Pisces and, due to the precession of the equinoxes, is slowly drifting below the western fish towards Aquarius. In astronomy, equinox is a moment in time at which the vernal point, celestial equator, and other such elements are taken to be used in the definition of a celestial coordinate system. The position at other equinoxes can be computed by taking into account precession, nutation and aberration, which directly affect e.g. right ascension and declination.

Sources:
SEDS
Chandra Observatory
Chart courtesy of Your Sky.


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