The night sky has captivated humanity for millennia. Ancient civilizations observed patterns in the stars, connecting them to their myths, stories, and daily lives. These celestial groupings, known as constellations, served as fundamental tools for navigation, agricultural planning, and understanding the passage of time.
Understanding the Altar Constellation
The Altar constellation is officially known as Ara, a Latin name meaning “the altar.” This small constellation, ranking 63rd in size among the 88 modern constellations, primarily resides in the southern celestial hemisphere. Greek mythology often associates Ara with the altar where Zeus and other Olympian gods swore an oath before their battle against the Titans. Another connection links it to the altar of King Lycaon of Arcadia, who tested Zeus’s omnipotence. Visually, Ara is often depicted as a compact classical altar, with its stars forming an uneven quadrilateral or an ‘H’ shape.
Locating and Observing the Altar Constellation
Ara is predominantly a Southern Hemisphere constellation, fully visible to observers south of 22° North latitude and not visible north of 45° North. Its celestial coordinates place its center around 17 hours 18 minutes right ascension and approximately -56° 30′ declination. The best time to observe Ara is during July and August, when it reaches its highest point in the sky around 9 PM.
To locate Ara, use the prominent constellation Scorpius as a guide, as Ara lies just south of Scorpius’s distinctive tail. Neighboring constellations include Norma and Triangulum Australe to its west, Apus to the south, and Pavo and Telescopium to the east. Under clear, dark skies, Ara’s main stars are discernible without optical aid, appearing as a faint but discernible pattern.
Celestial Highlights within Ara
The Altar constellation, despite its modest size, hosts several intriguing celestial objects. Beta Arae is the brightest star in Ara, an orange K-type supergiant located approximately 603 light-years away with an apparent magnitude of 2.84. Alpha Arae, the second brightest, is a variable blue-white Be star, whose brightness fluctuates slightly between magnitudes 2.76 and 2.90. Other notable stars include Gamma Arae, a blue-white supergiant, and Zeta Arae, an orange giant.
Ara is also home to a variety of deep-sky objects, offering rewarding targets for observers with telescopes. One prominent example is NGC 6397, a globular cluster containing around 400,000 stars, positioned about 7,200 to 7,800 light-years from Earth. It is one of the two nearest globular clusters to our solar system and can be faintly seen with the naked eye under exceptionally dark conditions, becoming easily visible with binoculars. The constellation also contains the open cluster NGC 6193 and the Stingray Nebula, one of the youngest known planetary nebulae. The Milky Way crosses the northwestern part of Ara, contributing to rich star fields within the constellation’s boundaries.