Genitive: Piscis Austrini
English: The Southern Fish
Size Ranking: 60th
Area: 245 square degrees
Fully Visible: 53°N-90°S.
Piscis Austrinus is a small constellation of the southern sky that was known to the ancient Greeks. It depicts a fish into whose mouth Aquarius, represented by the neighboring constellation to the north, pours water from his urn. In Greek mythology, this fish is also the parent of the two zodiacal fish, represented by Pisces. The name of the constellation is sometimes given as Piscis Australis.
This constellation contains Fomalhaut, which is the most southerly of the first magnitude stars visible from the latitudes of England, but there are no other stars above the fourth magnitude.
The suggested way of locating Fomalhaut is to find the arrow head shaped pattern of stars, the axis of which comprises Achernar, αEri, and Alnair, αGru.
Achernar forms the point of the arrow head, the Peacock, αPav, in turn forms the southern wing of the shape and, symmetrically situated, forming the northern wing, is Fomalhaut. If the axis of the shape is extended further to the west, the shaft of the arrow is depicted by Altair, αAql, and then Vega, αLyr.
Features of Interest:
αPsA, named Fomalhaut, ‘the fish’s mouth’, which describes the place the star occupies in this celestial pattern, is a blue-white main sequence star 25ly distant. At magnitude 1.2, it is not only the brightest star in this constellation but also ranks amongst the 20 brightest stars in the sky. It is surrounded by a disc of cool dust from which a planetary system may be forming.
βPsA, is a wide double star consisting of a blue-white primary of magnitude 4.3 and a companion of magnitude 7.7, separation 30.3”, PA 172°. It lies 148ly away.
γPsA, is another double star, 222ly distant. The components are of magnitude 4.5 and 8.0, separation 4.2”, PA 262°. The closeness of the components and the magnitude contrast make this star difficult to split.
δPsA, is a further double star with components 4.2 and 9.2, separation 5.0”, PA 244°. It is 160ly away. Similarly, it is difficult to split.
ηPsA, is a close pair of blue-white stars of magnitudes, 5.8 and 6.8, separation 1.7”, PA 115°. High power and aperture is required to effect optical separation.
1. Redshift 2 – Maris Multimedia
2. The Guinness Book of Astronomy – Patrick Moore
3. Stars and Planets – Ian Ridpath and Wil Tirion
4. Sky Charts – Cartes du Ciel V 2.75.
5. Where the Stars Are – Orion..