The Pavo Constellation

Pavo is a constellation in the southern sky whose name is Latin for “peacock.” Pavo first appeared on a 35-cm (14 in) diameter celestial globe published in 1598 in Amsterdam by Plancius and Jodocus Hondius and was depicted in Johann Bayer’s star atlas Uranometria of 1603 and was likely conceived by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. French explorer and astronomer Nicolas-Louis de Lacaille gave its stars Bayer designations in 1756. The constellations Pavo, Grus, Phoenix and Tucana are collectively known as the “Southern Birds.” Pavo is bordered by Telescopium to the north, Apus and Ara to the west, Octans to the south, and Indus to the east and northeast. Covering 378 square degrees, it ranks 44th of the 88 modern constellations in size and covers 0.916% of the night sky. 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 18h 10.4m and 21h 32.4m, while the declination coordinates are between −56.59° and −74.98°. As one of the deep southern constellations, it remains below the horizon at latitudes north of the 30th parallel in the Northern Hemisphere and is circumpolar at latitudes south of the 50th parallel in the Southern Hemisphere.

French explorer and astronomer Nicolas-Louis de Lacaille labelled the stars Alpha to Omega in 1756, but omitted Psi and Xi, and labelled two pairs of stars close together Mu and Phi Pavonis. In 1879, American astronomer Benjamin Gould designated a star Xi Pavonis as he felt its brightness warranted a name, but dropped Chi Pavonis due to its faintness. Lying near the constellation’s northern border with Telescopium is Alpha Pavonis, the brightest star in Pavo. Alpha has an apparent (or visual) magnitude of 1.91 and spectral type B2IV. It is a spectroscopic binary system, one estimate placing the distance between the pair of stars as 0.21 astronomical units or half the distance between Mercury and the Sun. The two stars rotate around each other in a mere 11 days and 18 hours. The star system is located around 180 light years away from Earth. With an apparent magnitude of 3.43, Beta Pavonis is the second-brightest star in the constellation. A white giant of spectral class A7III, it is an ageing star that has used up the hydrogen fuel at its core and has expanded and cooled after moving off the main sequence. It lies 135 light years away from the Solar System. Lying a few degrees west of Beta is Delta Pavonis, a nearby Sun-like but more evolved star; this is a yellow subgiant of spectral type G8IV and apparent magnitude 3.56 that is only 19.9 light years distant from Earth.

The deep-sky objects in Pavo include NGC 6752, the third-brightest globular cluster in the sky, after 47 Tucanae and Omega Centauri. An estimated 100 light years across, it is thought to contain 100,000 stars. Lying three degrees to the south is NGC 6744, a spiral galaxy around 30 million light years away from Earth that resembles the Milky Way, but is twice its diameter. A type 1c supernova was discovered in the galaxy in 2005; known as SN2005at, it peaked at magnitude 16.8. The dwarf galaxy IC 4662 lies 10 arcminutes northeast of Eta Pavonis and is of magnitude 11.62. Located only 8 million light years away, it has several regions of high star formation. The 14th-magnitude galaxy IC 4965 lies 1.7 degrees west of Alpha Pavonis and is a central member of the Shapley Supercluster.

Pavo is the radiant of two annual meteor showers: the Delta Pavonids and August Pavonids. Appearing from 21 March to 8 April and generally peaking around 5 and 6 April, Delta Pavonids are thought to be associated with Comet Grigg-Mellish. The shower was discovered by Michael Buhagiar from Perth, Australia, who observed meteors on six occasions between 1969 and 1980. The August Pavonids peak around August 31 and are thought to be associated with the Halley-type Comet Levy (P/1991 L3). Credit: In The Sky, Wikipedia.