With an estimated age of seven to nine million years, Rigel has exhausted its core hydrogen fuel, expanded, and cooled to become a supergiant.

It is classified as an Alpha Cygni variable due to the amplitude and periodicity of its brightness variation, as well as its spectral type.

Rigel and the triple system orbit a common center of gravity with a period estimated to be 24,000 years.

The system is listed variously in historical astronomical catalogs as H II 33, Σ 668, β 555, or ADS 3823.

The "beta" designation is usually given to the second-brightest star in each constellation, but Rigel is almost always brighter than α Orionis (Betelgeuse).

[23] However, closer examination of Bayer's method shows that he did not strictly order the stars by brightness, but instead grouped them first by magnitude, then by declination.

The star is a vertex of the "Winter Hexagon", an asterism that includes Aldebaran, Capella, Pollux, Procyon, and Sirius.

[39] Variations in the spectrum have resulted in the assignment of different classes to Rigel, such as B8 Ia, B8 Iab, and B8 Iae.

[15][40] As early as 1888, the heliocentric radial velocity of Rigel, as estimated from the Doppler shifts of its spectral lines, was seen to vary.

The small amplitude of Rigel's brightness variation requires photoelectric or CCD photometry to be reliably detected.

Observations over 18 nights in 1984 showed variations at red, blue, and yellow wavelengths of up to 0.13 magnitudes on timescales of a few hours to several days, but again no clear period.

[45] From analysis of Hipparcos satellite photometry, Rigel is identified as belonging to the Alpha Cygni class of variable stars,[46] defined as "non-radially pulsating supergiants of the Bep–AepIa spectral types".

[53] It is estimated that Rigel has lost about three solar masses (M☉) since beginning life as a star of 24±3 M☉ seven to nine million years ago.

[54] The 2007 Hipparcos new reduction of Rigel's parallax is 3.78±0.34 mas, giving a distance of 863 light-years (265 parsecs) with a margin of error of about 9%.

Most notable of these is the 5°-long IC 2118 (Witch Head Nebula),[56][57] located at an angular separation of 2.5° from the star,[56] or a projected distance of 39 light-years (12 parsecs) away.

[8] Friedrich Georg Wilhelm von Struve first measured the relative position of the companion in 1822, cataloguing the visual pair as Σ 668.

[12] Burnham listed the Rigel multiple system as β 555 in his double star catalog[65] or BU 555 in modern use.

[8] Component B is a double-lined spectroscopic binary system, which shows two sets of spectral lines combined within its single stellar spectrum.

[63] Rigel is a blue supergiant that has exhausted the hydrogen fuel in its core, expanded and cooled as it moved away from the main sequence across the upper part of the Hertzsprung–Russell diagram.

[5][68] When it was on the main sequence, its effective temperature would have been around 30,000 K.[69] Rigel's complex variability at visual wavelengths is caused by stellar pulsations similar to those of Deneb.

Further observations of radial velocity variations indicate that it simultaneously oscillates in at least 19 non-radial modes with periods ranging from about 1.2 to 74 days.

[17] Estimation of many physical characteristics of blue supergiant stars, including Rigel, is challenging due to their rarity and uncertainty about how far they are from the Sun.

[72] Due to their closeness to each other and ambiguity of the spectrum, little is known about the intrinsic properties of the members of the Rigel BC triple system.

[12] Stellar evolution models suggest the pulsations of Rigel are powered by nuclear reactions in a hydrogen-burning shell that is at least partially non-convective.

The surface abundances of carbon, nitrogen, and oxygen seen in the spectrum are compatible with a post-red supergiant star only if its internal convection zones are modeled using non-homogeneous chemical conditions known as the Ledoux Criteria.

[11] It is one of the closest known potential supernova progenitors to Earth,[17] and would be expected to have a maximum apparent magnitude of around −11 (about the same brightness as a quarter Moon or around 300 times brighter than Venus ever gets).

[81] The Wardaman people of northern Australia know Rigel as the Red Kangaroo Leader Unumburrgu and chief conductor of ceremonies in a songline when Orion is high in the sky.

[82] The Māori people of New Zealand named Rigel as Puanga, said to be a daughter of Rehua (Antares), the chief of all-stars.

[83] Its heliacal rising presages the appearance of Matariki (the Pleiades) in the dawn sky, marking the Māori New Year in late May or early June.

The Moriori people of the Chatham Islands, as well as some Māori groups in New Zealand, mark the start of their New Year with Rigel rather than the Pleiades.