Eridanus

Eridanus (abbreviation: Eri), the River, is a very large southern constellation that starts near the southwest corner of Orion and meanders down to the region of the south pole. Although one of Ptolemy's original constellations, its southernmost extension, including its brightest star, was added later.

The two Omicrons, Omicron¹ (Beid) and Omicron² (Keid), are not physically connected. Beid is giant F star 125 light-years distant, while Keid is a multiple system, a mere 16 light-years away. Keid contains an easy, wide binary, the secondary of which is itself a binary made up of a red dwarf and the brightest (in terms of apparent magnitude) white dwarf in the sky. See below for details of the constellation's brightest stars.

Stars brighter than magnitude 4.0
star	vis mag	abs mag	spec type	distance (ly)	RA (h m s)	Dec (° ' ")
Alpha (Achernar)	0.45	-2.77	B3Vpe	144	01 37 43	-57 14 12
Beta (Cursa)	2.78	0.60	A3III	89	05 07 51	-05 05 11
Theta (Acamar)	2.88	-0.59	A4III+A1V	161	02 58 16	-40 18 17
Gamma (Zaurak)	2.97	-1.19	M0.5IIICa-ICr	221	03 58 02	-13 30 31
Delta (Rana)	3.52	3.74	K0IV	29	03 43 15	-09 45 48
Upsilon⁴	3.55	-0.15	B9V	178	04 17 54	-33 47 54
Phi	3.56	0.17	B8IV	155	02 16 31	-51 30 44
Tau⁴ (Angetenar)	3.70	-0.79	M3.5IIIaCa	258	03 19 31	-21 45 28
Chi	3.69	2.47	G8IIIbCN	57	01 55 58	-51 36 32
Epsilon Eridani	3.72	6.18	K2V	10.5	03 32 56	-09 27 30
Upsilon² (Theemini)	3.81	-0.22	G8III	209	04 35 33	-30 33 45
53 (Sceptrum)	3.86	1.23	K1IIIb	109	04 38 11	-14 18 15
Eta (Azha)	3.89	0.83	K1IIIbBa0.2	133	02 56 26	-08 53 54