The Phoenix Constellation

Phoenix is a minor constellation in the southern sky. Named after the mythical phoenix, it was first depicted on a celestial atlas by Johann Bayer in his 1603 Uranometria. The French explorer and astronomer Nicolas Louis de Lacaille charted the brighter stars and gave their Bayer designations in 1756. The constellation stretches from roughly −39° to −57° declination, and from 23.5h to 2.5h of right ascension. The constellations Phoenix, Grus, Pavo and Tucana, are known as the Southern Birds. Phoenix is bordered by Fornax and Sculptor to the north, Grus to the west, Tucana to the south, touching on the corner of Hydrus to the south, and Eridanus to the east and southeast. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 10 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 23h 26.5m and 02h 25.0m, while the declination coordinates are between −39.31° and −57.84°. This means it remains below the horizon to anyone living north of the 40th parallel in the Northern Hemisphere and remains low in the sky for anyone living north of the equator. It is most visible from locations such as Australia and South Africa during the late Southern Hemisphere spring. Most of the constellation lies within, and can be located by, forming a triangle of the bright stars Achenar, Fomalhaut and Beta Ceti—Ankaa lies roughly in the centre of this.

A curved line of stars comprising Alpha, Kappa, Mu, Beta, Nu and Gamma Phoenicis was seen as a boat by the ancient Arabs. French explorer and astronomer Nicolas Louis de Lacaille charted and designated 27 stars with the Bayer designations Alpha through to Omega in 1756. Of these, he labelled two stars close together Lambda, and assigned Omicron, Psi and Omega to three stars, which subsequent astronomers such as Benjamin Gould felt were too dim to warrant their letters. A different star was subsequently labelled Psi Phoenicis, while the other two designations fell out of use. Ankaa is the brightest star in the constellation. It is an orange giant of apparent visual magnitude 2.37 and spectral type K0.5IIIb, 77 light years distant from Earth and orbited by a secondary object about which little is known. Beta Phoenicis is the second brightest star in the constellation and another binary star. Together the stars, both yellow giants of spectral type G8, shine with an apparent magnitude of 3.31, though the components are of individual apparent magnitudes of 4.0 and 4.1 and orbit each other every 168 years. Gamma Phoenicis is a red giant of spectral type M0IIIa and varies between magnitudes 3.39 and 3.49. It lies 235 light years away.

The constellation does not lie on the galactic plane of the Milky Way, and there are no prominent star clusters. NGC 625 is a dwarf irregular galaxy of apparent magnitude 11.0 and lying some 12.7 million light years distant. Only 24,000 light years in diameter, it is an outlying member of the Sculptor Group. NGC 625 is thought to have been involved in a collision and is experiencing a burst of active star formation. NGC 37 is a lenticular galaxy of apparent magnitude 14.66. It is approximately 42 kiloparsecs (137,000 light-years) in diameter and about 12.9 billion years old. Robert’s Quartet (composed of the irregular galaxy NGC 87, and three spiral galaxies NGC 88, NGC 89 and NGC 92) is a group of four galaxies located around 160 million light-years away which are in the process of colliding and merging. They are within a circle of radius corresponding to about 75,000 light-years. Located in the galaxy, ESO 243-49 is HLX-1, an intermediate-mass black hole—the first one of its kind identified. It is thought to be a remnant of a dwarf galaxy that was absorbed in a collision with ESO 243-49. Before its discovery, this class of black hole was only hypothesised. Lying within the bounds of the constellation is the gigantic Phoenix cluster, which is around 7.3 million light-years wide and 5.7 billion light years away, making it one of the most massive galaxy clusters. It was first discovered in 2010, and the central galaxy is producing an estimated 740 new stars a year. Larger still is El Gordo, or officially ACT-CL J0102-4915, whose discovery was announced in 2012. Located around 7.2 billion light years away, it is composed of two sub-clusters in the process of colliding, resulting in the spewing out of hot gas, seen in X-rays and infrared images.

Phoenix is the radiant of two annual meteor showers. The Phoenicids, also known as the December Phoenicids, was first observed on 3 December 1887. The shower was particularly intense in December 1956 and is thought related to the breakup of the short-period comet 289P/Blanpain. It peaks around 4–5 December, though is not seen every year. A very minor meteor shower peaks around July 14 with around one meteor an hour, though meteors can be seen anytime from July 3 to 18; this shower is referred to as the July Phoenicids. Credit: Wikipedia.