Fang (Pi Scorpii)
Fang (Pi Scorpii) is a star in the constellation Scorpius, magnitude 2.9.
A star with a Chinese name: a tight, egg-shaped pair of hot stars at the Scorpion’s head.
Unusually for an official star name, Fang is Chinese. Fáng Xiù, ‘the Room’, is one of the lunar mansions of Chinese astronomy, made from the stars of the Scorpion’s head, and Fang is its first star.
Look closer and it becomes three stars. Two hot, blue-white stars race round each other every 1.57 days, so close that their centres are only about 15 times the Sun’s radius apart. Gravity stretches each one out of round, and the light of the pair wobbles slightly as they turn. A faint third star keeps its distance. The brighter of the inner pair has 12 to 13 times the Sun’s mass and shines like about 22,000 Suns.
Harvard’s Edward Pickering announced the pair in 1899. Two years later Solon Bailey found their 1.57-day period, and in 1927 Otto Struve and Christian Elvey worked out the precise orbit of this double that no telescope can split.
Fang (Pi Scorpii) is 590 light-years away: the light we see from it set off around 1435, around the time Gutenberg printed his Bible.
Did you know?
- Born with the Scorpion’s stars. Fang belongs to the Upper Scorpius group, part of the Scorpius–Centaurus association of thousands of young stars. It is only 12 to 14 million years old.
- Spinning as well as orbiting. Both stars of the inner pair spin quickly — at least 87 and 108 kilometres a second — while they circle each other on a circular orbit.
The southernmost of the three bright stars that mark the Scorpion’s head — Acrab, Dschubba and Fang — about three and a half degrees south of Dschubba. Compare the two: Fang is a little fainter, and just as blue-white.
When and where to see it
It is best placed in the evening sky around June, when it crosses the meridian at about 10 pm local time (around midnight in May). It can be seen from everywhere south of 64°N and never sets south of 64°S.
At its highest it stands 14° up from 50°N, 29° up from 35°N, 64° up from the equator, 81° up from 35°S.
Facts
- Type
- Star
- Constellation
- Scorpius
- Designations
- Pi Scorpii, π Sco, 6 Sco, HR 5944, HD 143018, HIP 78265
- Magnitude
- 2.9
- Position
- RA 15h 58.9m, Dec −26° 7′ (J2000)
- Spectral type
- B1V+B2:V:
- Colour
- blue-white (B−V -0.20)
- Distance
- 590 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Fang (Pi Scorpii) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.