Rigel is the brightest star in Orion and usually the seventh-brightest star in the night sky. It is a blue supergiant about 860 light-years away that shines with roughly 100,000 times the Sun’s light. Look for it at Orion’s foot, diagonally opposite orange Betelgeuse.
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Rigel at a glance
| Other names | Beta Orionis |
|---|---|
| Constellation | Orion (the Hunter) |
| Brightness | Magnitude about +0.13, usually seventh-brightest star |
| Distance | About 860 light-years |
| Type | Blue supergiant (B8Ia) |
| Mass | About 20 Suns |
| Size | About 75–80 times the Sun’s diameter |
| Luminosity | Roughly 100,000 times the Sun |
| Temperature | About 12,000 K |
| Best time to see it | Evenings around January (highest at about 9 p.m.) |
| Where on Earth | Visible from everywhere south of about 82°N |
A true giant among stars
Rigel looks only slightly brighter than its Orion neighbour Betelgeuse, but it is much farther away, about 860 light-years, so it must be extraordinarily powerful. Rigel is a blue supergiant of around 20 solar masses that gives out roughly 100,000 times the Sun’s light. If it were as close as Sirius, it would shine about as brightly as a quarter Moon. Its surface, at about 12,000 K, is twice as hot as the Sun’s, which gives it its icy blue-white colour.
Rigel is young, only around 8 million years old, but massive stars burn through their fuel fast. It has already left the main sequence and will probably end its life as a supernova, although not for a very long time.
Rigel and Betelgeuse: two opposite giants
Orion is a perfect place to see how colour reveals temperature. Betelgeuse, at Orion’s shoulder, is a cool red supergiant at about 3,500 K; Rigel, at the opposite corner, is a hot blue supergiant. Both are massive stars near the ends of their lives, but at different stages. Rigel is officially “Beta” Orionis, even though it is normally brighter than “Alpha” Betelgeuse; the Greek letters were assigned centuries ago, and Betelgeuse varies in brightness.
Rigel’s companions
Rigel is a multiple-star system. A small telescope at about 100× shows a faint companion, Rigel B, about 9 arcseconds away, a challenge because Rigel is about 500 times brighter. Rigel B is itself a close pair of blue-white stars, and there may be more members, making Rigel a system of at least three or four stars.
How to find Rigel
Find Orion’s Belt, the three stars in a short straight line. From the Northern Hemisphere, Rigel is the bright blue-white star below and to the right of the belt; Betelgeuse is above and to the left. In the Southern Hemisphere the picture is upside down. Rigel lies just south of the celestial equator, so it is visible from almost the whole world, except the far Arctic and Antarctic. It rises in the mid-evening in November and is best placed on evenings from December to March. The nearby Orion Nebula (M42), in Orion’s sword, is a wonderful binocular target on the same nights.
Rigel also helps mark the giant Winter Hexagon, a ring of bright stars formed by Rigel, Aldebaran, Capella, Pollux, Procyon and Sirius, with Betelgeuse near its centre.
Where does the name come from?
The name Rigel comes from the Arabic phrase rijl al-jabbār, “the foot of the great one”, referring to the giant figure the constellation represented.
Rigel’s light in the nebulae around Orion
Rigel is bright enough to light up clouds of dust around it. The faint Witch Head Nebula (IC 2118), a reflection nebula about 2.5 degrees from Rigel, glows blue because it reflects Rigel’s light; it is a favourite target for long-exposure astrophotography. Rigel is probably related to the large family of young, massive stars in Orion, although it is somewhat closer to us than the Orion Nebula, which lies about 1,340 light-years away.
Rigel is also one of the traditional navigational stars listed in nautical almanacs, used by sailors to fix their position at sea, because it is bright, easy to identify and visible from both hemispheres. For new stargazers it is a perfect first “blue star” to learn: compare it with Betelgeuse on the same night and the difference in colour is unmistakable, even from a bright city.
Frequently asked questions about Rigel
How far away is Rigel?
Rigel is about 860 light-years away, though estimates range from roughly 800 to 900 light-years.
Is Rigel brighter than Betelgeuse?
Usually, yes. Rigel shines at about magnitude 0.1; Betelgeuse varies between about 0.0 and 1.6, so most of the time Rigel is the brighter of the two.
What colour is Rigel?
Rigel is blue-white, because its surface is hot, about 12,000 K.
Will Rigel go supernova?
Probably, at the end of its life. Rigel is massive enough to die as a supernova, but not for a long time; it is not expected soon.
When can I see Rigel?
Rigel is best on evenings from December to March. In November it rises in the mid-evening.
Sources: Rigel overview and references. Star data from standard catalogues; positions and rise/set times are calculated by SpaceTracker.live with the Astronomy Engine library.