IAU designated constellations by area

Last updated July 30, 2024

The International Astronomical Union (IAU) designates 88 constellations of stars. In the table below, they are ranked by the solid angle that they subtend in the sky, measured in square degrees and millisteradians.

These solid angles depend on arbitrary boundaries between the constellations: the list below is based on constellation boundaries drawn up by Eugène Delporte in 1930 on behalf of the IAU and published in Délimitation scientifique des constellations (Cambridge University Press). Before Delporte's work, there was no standard list of the boundaries of each constellation.

Delporte drew the boundaries along vertical and horizontal lines of right ascension and declination; however, he did so for the epoch B1875.0, which means that due to precession of the equinoxes, the borders on a modern star map (e.g., for epoch J2000) are already somewhat skewed and no longer perfectly vertical or horizontal. This skew will increase over the centuries to come. However, this does not change the solid angle of any constellation.

Rank	Abbrev.	Constellation	Solid angle ("Area") (sq. deg.) ^[1]	Solid angle (millisteradians)	Percentage	Right ascension (hours & mins) ^[2]	Declination (degs & mins) ^[3]	Quad ^[4]
01	Hya	Hydra	1302.844	396.869	3.16%	+11 36.73	−14 31.91	SQ2
02	Vir	Virgo	1294.428	394.305	3.14%	+13 24.39	−04 09.51	SQ3
03	UMa	Ursa Major	1279.660	389.807	3.10%	+11 18.76	+50 43.27	NQ2
04	Cet	Cetus	1231.411	375.109	2.99%	+01 40.10	−07 10.76	SQ1
05	Her	Hercules	1225.148	373.201	2.97%	+17 23.16	+27 29.93	NQ3
06	Eri	Eridanus	1137.919	346.630	2.76%	+03 18.02	−28 45.37	SQ1
07	Peg	Pegasus	1120.794	341.413	2.72%	+22 41.84	+19 27.98	NQ4
08	Dra	Draco	1082.952	329.886	2.63%	+15 08.64	+67 00.40	NQ3
09	Cen	Centaurus	1060.422	323.023	2.57%	+13 04.27	−47 20.72	SQ3
10	Aqr	Aquarius	979.854	298.481	2.38%	+22 17.38	−10 47.35	SQ4
11	Oph	Ophiuchus	948.340	288.881	2.30%	+17 23.69	−07 54.74	SQ3
12	Leo	Leo	946.964	288.462	2.30%	+10 40.03	+13 08.32	NQ2
13	Boo	Boötes	906.831	276.237	2.20%	+14 42.64	+31 12.16	NQ3
14	Psc	Pisces	889.417	270.932	2.16%	+00 28.97	+13 41.23	NQ1
15	Sgr	Sagittarius	867.432	264.235	2.10%	+19 05.94	−28 28.61	SQ4
16	Cyg	Cygnus	803.983	244.907	1.95%	+20 35.28	+44 32.70	NQ4
17	Tau	Taurus	797.249	242.856	1.93%	+04 42.13	+14 52.63	NQ1
18	Cam	Camelopardalis	756.828	230.543	1.83%	+08 51.37	+69 22.89	NQ2
19	And	Andromeda	722.278	220.018	1.75%	+00 48.46	+37 25.91	NQ1
20	Pup	Puppis	673.434	205.140	1.63%	+07 15.48	−31 10.64	SQ2
21	Aur	Auriga	657.438	200.267	1.59%	+06 04.42	+42 01.68	NQ2
22	Aql	Aquila	652.473	198.755	1.58%	+19 40.02	+03 24.65	NQ4
23	Ser	Serpens ^[5]	636.928	194.019	1.54%	+16 57.04	+06 07.32	NQ3
24	Per	Perseus	614.997	187.339	1.49%	+03 10.50	+45 00.79	NQ1
25	Cas	Cassiopeia	598.407	182.285	1.45%	+01 19.16	+62 11.04	NQ1
26	Ori	Orion	594.120	180.979	1.44%	+05 34.59	+05 56.94	NQ1
27	Cep	Cepheus	587.787	179.050	1.42%	+02 32.64	+71 00.51	NQ4
28	Lyn	Lynx	545.386	166.134	1.32%	+07 59.53	+47 28.00	NQ2
29	Lib	Libra	538.052	163.900	1.30%	+15 11.96	−15 14.08	SQ3
30	Gem	Gemini	513.761	156.501	1.25%	+07 04.24	+22 36.01	NQ2
31	Cnc	Cancer	505.872	154.097	1.23%	+08 38.96	+19 48.35	NQ2
32	Vel	Vela	499.649	152.202	1.21%	+09 34.64	−47 10.03	SQ2
33	Sco	Scorpius	496.783	151.329	1.20%	+16 53.24	−27 01.89	SQ3
34	Car	Carina	494.184	150.537	1.20%	+08 41.70	−63 13.16	SQ2
35	Mon	Monoceros	481.569	146.694	1.17%	+07 03.63	+00 16.93	NQ2
36	Scl	Sculptor	474.764	144.621	1.15%	+00 26.28	−32 05.30	SQ1
37	Phe	Phoenix	469.319	142.963	1.14%	+00 55.91	−48 34.84	SQ1
38	CVn	Canes Venatici	465.194	141.706	1.13%	+13 06.96	+40 06.11	NQ3
39	Ari	Aries	441.395	134.457	1.07%	+02 38.16	+20 47.54	NQ1
40	Cap	Capricornus	413.947	126.095	1.00%	+21 02.93	−18 01.39	SQ4
41	For	Fornax	397.502	121.086	0.96%	+02 47.88	−31 38.07	SQ1
42	Com	Coma Berenices	386.475	117.727	0.94%	+12 47.27	+23 18.34	NQ3
43	CMa	Canis Major	380.118	115.791	0.92%	+06 49.74	−22 08.42	SQ2
44	Pav	Pavo	377.666	115.044	0.92%	+19 36.71	−65 46.89	SQ4
45	Gru	Grus	365.513	111.342	0.89%	+22 27.39	−46 21.11	SQ4
46	Lup	Lupus	333.683	101.646	0.81%	+15 13.21	−42 42.53	SQ3
47	Sex	Sextans	313.515	95.502	0.76%	+10 16.29	−02 36.88	SQ2
48	Tuc	Tucana	294.557	89.727	0.71%	+23 46.64	−65 49.80	SQ4
49	Ind	Indus	294.006	89.559	0.71%	+21 58.33	−59 42.40	SQ4
50	Oct	Octans	291.045	88.657	0.71%	+23 00.00	−82 09.12	SQ4
51	Lep	Lepus	290.291	88.428	0.70%	+05 33.95	−19 02.78	SQ1
52	Lyr	Lyra	286.476	87.266	0.69%	+18 51.17	+36 41.36	NQ4
53	Crt	Crater	282.398	86.023	0.68%	+11 23.75	−15 55.74	SQ2
54	Col	Columba	270.184	82.303	0.65%	+05 51.76	−35 05.67	SQ1
55	Vul	Vulpecula	268.165	81.688	0.65%	+20 13.88	+24 26.56	NQ4
56	UMi	Ursa Minor	255.864	77.941	0.62%	+15 00.00	+77 41.99	NQ3
57	Tel	Telescopium	251.512	76.615	0.61%	+19 19.54	−51 02.21	SQ4
58	Hor	Horologium	248.885	75.815	0.60%	+03 16.56	−53 20.18	SQ1
59	Pic	Pictor	246.739	75.161	0.60%	+05 42.46	−53 28.45	SQ1
60	PsA	Piscis Austrinus	245.375	74.745	0.59%	+22 17.07	−30 38.53	SQ4
61	Hyi	Hydrus	243.035	74.033	0.59%	+02 20.65	−69 57.39	SQ1
62	Ant	Antlia	238.901	72.773	0.58%	+10 16.43	−32 29.01	SQ2
63	Ara	Ara	237.057	72.212	0.57%	+17 22.49	−56 35.30	SQ3
64	LMi	Leo Minor	231.956	70.658	0.56%	+10 14.72	+32 08.08	NQ2
65	Pyx	Pyxis	220.833	67.270	0.54%	+08 57.16	−27 21.10	SQ2
66	Mic	Microscopium	209.513	63.821	0.51%	+20 57.88	−36 16.49	SQ4
67	Aps	Apus	206.327	62.851	0.50%	+16 08.65	−75 18.00	SQ3
68	Lac	Lacerta	200.688	61.133	0.49%	+22 27.68	+46 02.51	NQ4
69	Del	Delphinus	188.549	57.435	0.46%	+20 41.61	+11 40.26	NQ4
70	Crv	Corvus	183.801	55.989	0.45%	+12 26.52	−18 26.20	SQ3
71	CMi	Canis Minor	183.367	55.857	0.44%	+07 39.17	+06 25.63	NQ2
72	Dor	Dorado	179.173	54.579	0.43%	+05 14.51	−59 23.22	SQ1
73	CrB	Corona Borealis	178.710	54.438	0.43%	+15 50.59	+32 37.49	NQ3
74	Nor	Norma	165.290	50.350	0.40%	+15 54.18	−51 21.09	SQ3
75	Men	Mensa	153.484	46.754	0.37%	+05 24.90	−77 30.24	SQ1
76	Vol	Volans	141.354	43.059	0.34%	+07 47.73	−69 48.07	SQ2
77	Mus	Musca	138.355	42.145	0.34%	+12 35.28	−70 09.66	SQ3
78	Tri	Triangulum	131.847	40.163	0.32%	+02 11.07	+31 28.56	NQ1
79	Cha	Chamaeleon	131.592	40.085	0.32%	+10 41.53	−79 12.30	SQ2
80	CrA	Corona Australis	127.696	38.898	0.31%	+18 38.79	−41 08.85	SQ4
81	Cae	Caelum	124.865	38.036	0.30%	+04 42.27	−37 52.90	SQ1
82	Ret	Reticulum	113.936	34.707	0.28%	+03 55.27	−59 59.85	SQ1
83	TrA	Triangulum Australe	109.978	33.501	0.27%	+16 04.95	−65 23.28	SQ3
84	Sct	Scutum	109.114	33.238	0.26%	+18 40.39	−09 53.32	SQ4
85	Cir	Circinus	93.353	28.437	0.23%	+14 34.54	−63 01.82	SQ3
86	Sge	Sagitta	79.932	24.349	0.19%	+19 39.05	+18 51.68	NQ4
87	Equ	Equuleus	71.641	21.823	0.17%	+21 11.26	+07 45.49	NQ4
88	Cru	Crux	68.447	20.850	0.17%	+12 26.99	−60 11.19	SQ3

Notes

↑ The total solid angle of all constellations is the total solid angle of the sky, which is exactly 4π steradians, or 4π × (180/π)² = 129,600/π square degrees, or approximately 41,252.961 square degrees. The figures in the table do not sum precisely to this number due to rounding errors, which vanish when the areas are rounded instead to one decimal place.
↑ Average of the most eastward and most westward RA.
↑ Average of the most northern and most southern declination.
↑ "Quad" designates the quadrant of the sky as N for North or S for South, Quadrants 1 (0^h–6^h), 2 (6^h–12^h), 3 (12^h–18^h), or 4 (18^h–0^h).
↑ Serpens is divided into two parts:
Serpens Caput ("Serpent's Head"; 428.484 sq. deg.; midpoint: RA: 15 46.49, Dec: +10 58.20), and
Serpens Cauda ("Serpent's Tail"; 208.444 sq. deg.; midpoint: RA: 18 07.60, Dec: -04 51.73)

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A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.

Libra is a constellation of the zodiac and is located in the Southern celestial hemisphere. Its name is Latin for weighing scales. Its old astronomical symbol is (♎︎). It is fairly faint, with no first magnitude stars, and lies between Virgo to the west and Scorpius to the east. Beta Librae, also known as Zubeneschamali, is the brightest star in the constellation. Three star systems are known to have planets.

Ophiuchus is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek ὀφιοῦχος (ophioûkhos), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constellation Serpens. Ophiuchus was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. An old alternative name for the constellation was Serpentarius.

<span class="mw-page-title-main">Right ascension</span> Astronomical equivalent of longitude

Right ascension is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the point in question above the Earth. When paired with declination, these astronomical coordinates specify the location of a point on the celestial sphere in the equatorial coordinate system.

Serpens is a constellation in the northern celestial hemisphere. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations designated by the International Astronomical Union. It is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput to the west and Serpens Cauda to the east. Between these two halves lies the constellation of Ophiuchus, the "Serpent-Bearer". In figurative representations, the body of the serpent is represented as passing behind Ophiuchus between Mu Serpentis in Serpens Caput and Nu Serpentis in Serpens Cauda.

The steradian or square radian is the unit of solid angle in the International System of Units (SI). It is used in three dimensional geometry, and is analogous to the radian, which quantifies planar angles. A solid angle in steradians, projected onto a sphere, gives the area of a spherical cap on the surface, whereas an angle in radians, projected onto a circle, gives a length of a circular arc on the circumference. The name is derived from the Greek στερεός stereos 'solid' + radian.

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Sculptor is a faint constellation in the southern sky. It represents a sculptor. It was introduced by Nicolas Louis de Lacaille in the 18th century. He originally named it Apparatus Sculptoris, but the name was later shortened.

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Reticulum is a small, faint constellation in the southern sky. Its name is Latin for a small net, or reticle—a net of crosshairs at the focus of a telescope eyepiece that is used to measure star positions. The constellation is best viewed between October and December, and save for one main star visible in ideal conditions, cannot be seen from north of the 30th parallel north.

In contemporary astronomy, 88 constellations are recognized by the International Astronomical Union (IAU). Each constellation is a region of the sky bordered by arcs of right ascension and declination, together covering the entire celestial sphere. Their boundaries were officially adopted by the International Astronomical Union in 1928 and published in 1930.

In ancient times, only the Sun and Moon, a few stars, and the most easily visible planets had names. Over the last few hundred years, the number of identified astronomical objects has risen from hundreds to over a billion, and more are discovered every year. Astronomers need to be able to assign systematic designations to unambiguously identify all of these objects, and at the same time give names to the most interesting objects, and where relevant, features of those objects.

Eugène Joseph Delporte was a Belgian astronomer born in Genappe.

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A square degree (deg²) is a non-SI unit measure of solid angle. Other denotations include sq. deg. and (°)². Just as degrees are used to measure parts of a circle, square degrees are used to measure parts of a sphere. Analogous to one degree being equal to ⁠ $π$ /180⁠ radians, a square degree is equal to (⁠ $π$ /180⁠)² steradians (sr), or about ⁠1/3283⁠ sr or about 3.046×10⁻⁴ sr.

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Former constellations are old historical Western constellations that for various reasons are no longer widely recognised or are not officially recognised by the International Astronomical Union (IAU). Prior to 1930, many of these defunct constellations were traditional in one or more countries or cultures. Some only lasted decades but others were referred to over many centuries. All are now recognised only for having classical or historical value. Many former constellations had complex Latinised names after objects, people, or mythological or zoological creatures. Others with unwieldy names were shortened for convenience. For example, Scutum Sobiescianum was reduced to Scutum, Mons Mensae to Mensa, and Apparatus Sculptoris to Sculptor.

The International Astronomical Union (IAU) designates 88 constellations. In the table below, they are listed by geographical visibility according to latitude as seen from Earth, as well as the best months for viewing the constellations at 21:00.

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[1] The total solid angle of all constellations is the total solid angle of the sky, which is exactly 4π steradians, or 4π × (180/π)² = 129,600/π square degrees, or approximately 41,252.961 square degrees. The figures in the table do not sum precisely to this number due to rounding errors, which vanish when the areas are rounded instead to one decimal place.

[2] Average of the most eastward and most westward RA.

[3] Average of the most northern and most southern declination.

[4] "Quad" designates the quadrant of the sky as N for North or S for South, Quadrants 1 (0^h–6^h), 2 (6^h–12^h), 3 (12^h–18^h), or 4 (18^h–0^h).

[5] Serpens is divided into two parts:
Serpens Caput ("Serpent's Head"; 428.484 sq. deg.; midpoint: RA: 15 46.49, Dec: +10 58.20), and
Serpens Cauda ("Serpent's Tail"; 208.444 sq. deg.; midpoint: RA: 18 07.60, Dec: -04 51.73)

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[5]

IAU designated constellations by area

See also

Sources

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