Largest Constellations

The largest constellations in the sky are Hydra, Virgo, Ursa Major, Cetus and Hercules. The largest northern constellations are Ursa Major, Hercules, Pegasus, Draco and Leo, and the southern ones are Hydra, Virgo, Cetus, Eridanus and Centaurus.

Largest constellations, image: Wikisky

All these are Greek constellations, listed by Ptolemy in his Almagest in the 2nd century AD. They have been known since ancient times. The largest constellation that has not been known since antiquity is Lynx, which was created by the Polish astronomer Johannes Hevelius in the 17th century. Lynx is the 28th constellation in size with an area of 545 square degrees.

Hydra, the largest of the 88 modern constellations, measures 1303 square degrees and has the shape of a twisting snake that stretches from Cancer in the north to Libra and Centaurus in the south. In spite of its size, Hydra is not particularly prominent or easily recognizable. Its brightest star, the orange giant Alphard, has an apparent magnitude of 2.0, which makes it only moderately bright.

brightest star in hydra

Alphard in Hydra and other bright stars in the vicinity, image: Wikisky

Virgo is much easier to find than Hydra because it is home to Spica, the 16th brightest star in the sky. Spica can be located by following the arc of the Big Dipper‘s handle. After Arcturus, it is the first bright star along the imaginary line.

Ursa Major, the largest northern constellation, is one of the most recognizable constellations in the sky. The Big Dipper asterism makes it easy for northern observers to find at any time of year. Six of the stars that form the asterism are of second magnitude and easily seen even in less than ideal conditions. Ursa Major is circumpolar to northern observers, which means that it never sets below the horizon. However, it remains mostly invisible to observers living south of latitude 30°S.

Finding Arcturus and Spica using the bright stars of the Big Dipper, image: Wikisky

Like Hydra, Cetus is large, but not particularly prominent. Its brightest star, the orange giant Diphda (also known as Deneb Kaitos), has a visual magnitude of 2.02, which makes it slightly fainter than Alphard.

Hercules, the second largest northern constellation, is considerably easier to spot, as some of its stars form an asterism known as the Keystone, which marks Hercules’ torso. However, the constellation does not have any first or second magnitude stars. Its brightest star, Kornephoros, is a yellow giant with an apparent magnitude of 2.8.

Eridanus, the sixth largest constellation, is home to Achernar, the ninth brightest star in the sky. Achernar marks the end of the celestial river and is located at the southern end of Eridanus. The constellation’s northern end borders with Orion and Taurus.

Pegasus is easy to recognize because it is dominated by a prominent asterism known as the Great Square. The Great Square of Pegasus is formed by three bright stars in Pegasus and Alpheratz, the brightest star in the neighbouring Andromeda.

great square of pegasus,circlet of pisces, water jar

The Great Square of Pegasus, the Circlet of Pisces and the Water Jar, image: Wikisky

Draco is located in the far northern sky. Like Ursa Major, it is circumpolar and never sets for northern observers. It is not a particularly bright constellation, but it can be found between the more recognizable Ursa Major, Ursa Minor, Hercules and Cygnus. The brightest star in Draco, the orange giant Eltanin, has an apparent magnitude of 2.23.  The constellation is mostly invisible to observers south of latitude 15°S.

Centaurus, the ninth largest constellation, is located in the southern sky and cannot be seen from locations north of latitude 25°N. It is one of the brightest and most recognizable southern constellations. Its brightest stars – Alpha and Beta Centauri – are the 3rd and 11th brightest stars in the sky. The stars are known as the Southern Pointers because they help observers find Crux and true south.

The Southern Pointers Alpha and Beta Centauri and the constellation Crux, the Southern Cross

Aquarius is relatively faint – its brightest star, Sadalsuud, a class G supergiant, has a visual magnitude of 2.87 – but can be spotted on a clear night near Pegasus and Pisces. Like other zodiac constellations, Aquarius lies on the ecliptic. It contains an asterism known as the Water Jar, from which the mythical Water Bearer pours water in a stream of stars that ends with Fomalhaut, the brightest star in the constellation Piscis Austrinus, the Southern Fish, and 18th brightest star in the sky.

Ophiuchus and Leo, the 11th and 12th largest constellations, also lie on the ecliptic. Ophiuchus, the Serpent Bearer, borders Hercules on the northern end and Sagittarius and Scorpius on the southern. Its brightest star, Rasalhague, is a binary system with an apparent magnitude of 2.07. Ophiuchus divides the constellation Serpens into two parts – Serpens Caput and Serpens Cauda – representing the Serpent‘s head and tail.

Leo, the fifth largest northern constellation, is much easier to identify, with the bright Regulus (mag. 1.39) marking the Lion’s heart, Denebola (mag. 2.11) its tail and an asterism known as the Sickle representing its mane and shoulders. The Sickle looks like a backward question mark and is quite prominent in the spring sky. Regulus, located at the base of the question mark, is part of the Spring Triangle, a large spring asterism also formed by the bright stars Arcturus and Spica, which makes it even easier to locate Leo in the evening sky.

Below is the list of all 88 modern constellations ordered by size, from largest to smallest.

Constellation Size (area in square degrees) Quadrant
1.       Hydra 1302.844 SQ2
2.       Virgo 1294.428 SQ3
3.       Ursa Major 1279.660 NQ2
4.       Cetus 1231.411 SQ1
5.       Hercules 1225.148 NQ3
6.       Eridanus 1137.919 SQ1
7.       Pegasus 1120.794 NQ4
8.       Draco 1082.952 NQ3
9.       Centaurus 1060.422 SQ3
10.   Aquarius 979.854 SQ4
11.   Ophiuchus 948.340 SQ3
12.   Leo 946.964 NQ2
13.   Boötes 906.831 NQ3
14.   Pisces 889.417 NQ1
15.   Sagittarius 867.432 SQ4
16.   Cygnus 803.983 NQ4
17.   Taurus 797.249 NQ1
18.   Camelopardalis 756.828 NQ2
19.   Andromeda 722.278 NQ1
20.   Puppis 673.434 SQ2
21.   Auriga 657.438 NQ2
22.   Aquila 652.473 NQ4
23.   Serpens 636.928 NQ3
24.   Perseus 614.997 NQ1
25.   Cassiopeia 598.407 NQ1
26.   Orion 594.120 NQ1
27.   Cepheus 587.787 NQ4
28.   Lynx 545.386 NQ2
29.   Libra 538.052 SQ3
30.   Gemini 513.761 NQ2
31.   Cancer 505.872 NQ2
32.   Vela 499.649 SQ2
33.   Scorpius 496.783 SQ3
34.   Carina 494.184 SQ2
35.   Monoceros 481.569 NQ2
36.   Sculptor 474.764 SQ1
37.   Phoenix 469.319 SQ1
38.   Canes Venatici 465.194 NQ3
39.   Aries 441.395 NQ1
40.   Capricornus 413.947 SQ4
41.   Fornax 397.502 SQ1
42.   Coma Berenices 386.475 NQ3
43.   Canis Major 380.118 SQ2
44.   Pavo 377.666 SQ4
45.   Grus 365.513 SQ4
46.   Lupus 333.683 SQ3
47.   Sextans 313.515 SQ2
48.   Tucana 294.557 SQ4
49.   Indus 294.006 SQ4
50.   Octans 291.045 SQ4
51.   Lepus 290.291 SQ1
52.   Lyra 286.476 NQ4
53.   Crater 282.398 SQ2
54.   Columba 270.184 SQ1
55.   Vulpecula 268.165 NQ4
56.   Ursa Minor 255.864 NQ3
57.   Telescopium 251.512 SQ4
58.   Horologium 248.885 SQ1
59.   Pictor 246.739 SQ1
60.   Piscis Austrinus 245.375 SQ4
61.   Hydrus 243.035 SQ1
62.   Antlia 238.901 SQ2
63.   Ara 237.057 SQ3
64.   Leo Minor 231.956 NQ2
65.   Pyxis 220.833 SQ2
66.   Microscopium 209.513 SQ4
67.   Apus 206.327 SQ3
68.   Lacerta 200.688 NQ4
69.   Delphinus 188.549 NQ4
70.   Corvus 183.801 SQ3
71.   Canis Minor 183.367 NQ2
72.   Dorado 179.173 SQ1
73.   Corona Borealis 178.710 NQ3
74.   Norma 165.290 SQ3
75.   Mensa 153.484 SQ1
76.   Volans 141.354 SQ2
77.   Musca 138.355 SQ3
78.   Triangulum 131.847 NQ1
79.   Chamaeleon 131.592 SQ2
80.   Corona Australis 127.696 SQ4
81.   Caelum 124.865 SQ1
82.   Reticulum 113.936 SQ1
83.   Triangulum Australe 109.978 SQ3
84.   Scutum 109.114 SQ4
85.   Circinus 93.353 SQ3
86.   Sagitta 79.932 NQ4
87.   Equuleus 71.641 NQ4
88.   Crux 68.447 SQ3