5 Largest Star Constellations in the Sky

Hydra Constellation
Hydra Constellation by Babak Tafreshi/Dreamview.net

Even professional astronomers sometimes admit to having difficulty recognizing all of the 88 modern constellations, as most constellations are marked out by some stars that are not that visible to the naked eye, except under exceptionally good seeing conditions. Regardless of the difficulties, recognizing star constellations can fill one with a sense of both satisfaction and humbling awe, and so to help you on you way, here is a list of the five biggest constellations in the night sky, as well as some of their main Messier objects (nebulae, star clusters, and galaxies). Why not go out tonight and see how many of them you can find!

1) Hydra

Hydra, (“Water Snake”) takes up 3.158% of the sky, and has a head located just to the south of Cancer, with the rest of its twisting body stretching all the way to a point between Centaurus and Libra, where its tail terminates. Hydra is a southern hemisphere constellation that can be seen from latitudes between +54° and -83°, and covers a surface area of 102.5° making it the largest star constellation in the night sky. While Hydra contains around 238 stars, it consists primarily of an asterism of 17 stars, the brightest of which is Alphard, an orange giant of magnitude 2 located 177 light-years distant. In Greek mythology, Hydra is associated with the Lernaean Hydra from the Twelve Labours of Heracles.

Notable Deep Sky Objects:

Hydra contains three main Messier objects, namely M68 (globular cluster), M83 (Southern Pinwheel Galaxy), and M48 (open cluster). Other objects of interest include Tombaugh’s Globular Cluster (NGC 5694), and a planetary nebula called the Ghost of Jupiter (NGC 3242).

2) Virgo

5 Largest Star Constellations in the SkyVirgo (“Virgin”) is one of the 12 Zodiacal Constellations, takes up 3.138% of the Southern hemisphere sky, and can be seen from latitudes between +80° and -80°. It contains around 169 stars, of which only Spica is of first magnitude, and the constellation also currently contains the autumn equinox point, where the sun’s ecliptic crosses the celestial equator on Sept 23rd, marking the start of autumn in the Northern Hemisphere, and the beginning of spring in the Southern Hemisphere. In mythology, the constellation Virgo represents Persephone, Queen of the Underworld, and the daughter of Demeter, the harvest and fertility goddess.

Notable Deep Sky Objects:

Virgo contains the galaxies Messier 49, Messier 58, Messier 59, Messier 60, and Messier 87, as well as the Sombrero Galaxy (M104), the Eyes Galaxies, the Siamese Twins, and the quasar 3C 273.

3) Ursa Major

Ursa Major (“Big Bear”) takes up 3.102% of the sky, and is a northern hemisphere constellation that can be seen from latitudes between +90° and -30°. It is one of the most recognisable constellations in the sky, with its seven most luminous stars forming an asterism known as the Big Dipper, although the constellation itself actually contains around 209 stars, the brightest of which is Alioth, a white star 81 light-years from Earth. As well as containing one of the most recognizable asterism, together with Orion and the Southern Cross, Ursa Major is also one of the oldest constellations, and features prominently in all major cultures and mythologies.

Notable Deep Sky Objects:

Ursa Major contains a number of notable galaxies, such as the Pinwheel Galaxy (M101), Bode’s Galaxy (M81), and the Cigar Galaxy (M82), while the planetary Owl Nebula (M97) is also situated in Ursa Major, 1,630 light-years away.

4) Cetus

Cetus takes up 2.985% of the sky, and is a northern hemisphere that can be viewed from latitudes between +70° and -90°. This constellations name is Latin for “Whale” and is located in a celestial region known as “The Water”, together with other constellations whose names also evoke images of water, such as Aquarius (Water Bearer), Pisces (the Fish), and Eridanus (The River). In mythology, Cetus is associated with the princess Andromeda, who was sacrificed to the Whale in retribution for her mother, Cassiopeia’s tendency to be boastful and vain. Cetus was also one of the constellations first cataloged by Ptolemy in the early 2nd century.

Brightest amongst Cetus’ 189 or so stars is Deneb Kaitos (Beta Ceti), an orange giant of 2.02 apparent magnitude located 96.3 light-years distant. Other stars of note include Menkar (Alpha Ceti), Tau Ceti and the variable star Mira (Omicron Ceti), all of which are well known for various reasons.

Notable Deep Sky Objects:

Amongst the notable deep sky objects in Cetus is Messier 77, a barred spiral galaxy 50 million light-years from Earth, and the planetary nebula NGC 246, also known as the Cetus Ring or “Pac-Man Nebula” because like the video game character, it seems to be chomping down on its surrounding star field.

5) Hercules

Hercules takes up 2.97% of the sky, and is a northern hemisphere constellation that can be seen from latitudes between +90° and -50°. In mythology, the constellation Hercules is most often associated with Heracles’ Twelve Labors, of which the penultimate was the killing of the guardian of the Garden of the Hesperides, the dragon Ladon. The luckless dragon is associated with the constellation Draco.

The constellation contains around 245 stars, none of which are particularly luminous, with its most notable stars including the red giant Ras Algethi (Alpha Herculis), a third to fourth magnitude star which marks the head of Hercules, and four stars known as the Keystone asterism, which represent the legendary hero’s chest, as he stand over the slain dragon, Draco.

Notable Deep Sky Objects:

Hercules is home to the brightest globular cluster in the northern hemisphere, namely the Great Globular Cluster (M13), which is 25,200 light-years away and contains over 300,000 stars. M92 is another bright globular clusters in this constellation, and holds the distinction of being the oldest globular cluster yet discovered at 14 billion years old. The planetary nebulae Abell 39 and NGC 6210 can be found in Hercules, as well as the Hercules Cluster (Abell 2151) of galaxies, and a Galaxy cluster (Abell 2199). Last, but not least, the night sky’s 5th largest constellation contains the largest known super-structure in the universe, the Hercules–Corona Borealis Great Wall, which is a massive group of galaxies 7.2 billion light-years across, 10 billion light-years long, and around 1 billion light-years in depth.

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