Diagram caption: The constellation Centaurus with its bright stars and surrounding constellations. Centaurus is surrounded by (going clockwise from the top): Hydra, Antlia, Vela, Carina, Musca, Crux, Circinus, Lupus and Libra. Centaurus is a large constellation most notable for its brightest star Alpha Centauri. Alpha Centauri is a triple star system and is the nearest star system to the Solar System. When viewed with the naked eye, the two brightest components of Alpha Centauri appear as one star. The combined light from these two stars makes Alpha Centauri appear as the third brightest star in the night sky. The third component of the Alpha Centauri system Proxima Centauri, the nearest star to the Sun, is too faint to be viewed with the naked eye.

Centaurus is a southern constellation and thus the whole constellation is visible from the southern hemisphere at some point in the year. The whole constellation is also visible from equatorial regions of the northern hemisphere with parts of the constellation visible from temperate northern regions. The constellation is best viewed in the evening in the late northern hemisphere spring and late southern hemisphere autumn.

The globular cluster Omega Centauri, also known as NGC 5319, lies in Centaurus. Bright enough to be seen with the naked eye, this cluster was initially given a designation as a star in the constellation before its true nature was realised. It is marked here with a yellow circle with a plus sign superimposed on it. As is the globular cluster NGC 5286. The open cluster NGC 3766 is marked here with a yellow circle. NGC 5128, also known as Centaurus A, is the closest active galaxy to Earth. The supermassive black hole at the heart of this galaxy has launched two huge jets of matter which emit in many different wavelengths including x-ray and radio emission. NGC 5128 is marked with a red ellipse here, as is the edge-on spiral galaxy NGC 4945.

The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the lines joining the stars appear on the sky. The blue line in the top left is the ecliptic.

Diagram credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope. Credit Link

Related glossary terms: Alpha Centauri , Apparent Magnitude , Celestial Coordinates , Constellation , Declination , Globular Cluster , Open Cluster , Right Ascension (RA)
Categories: Naked Eye Astronomy

Diagram license: Creative Commons Attribution 4.0 International (CC BY 4.0) Creative Commons Attribution 4.0 International (CC BY 4.0) icons