Zeta Persei (ζ Per)
Zeta Persei (ζ Per) is a star in the constellation Perseus, magnitude 2.9.
A blue supergiant blowing itself away — and the namesake of a family of massive stars travelling together.
Imagine losing a whole Sun’s worth of gas every 4.3 million years. That is the rate at which a fierce wind is stripping Zeta Persei away. This blue-white star is a supergiant some 26 times the Sun’s width, 13 to 16 times its mass and about 47,000 times as luminous, with a surface of 20,800 kelvins. Its spectrum shows unusually high levels of carbon.
It does not travel alone. Zeta Persei belongs to the Perseus OB2 association, also called the Zeta Persei association: 17 massive, highly luminous blue stars moving through space on similar paths. They probably formed together from the same cloud of gas, and they are about the same age.
Zeta Persei (ζ Per) is 1,300 light-years away: the light we see from it set off around AD 730, 75 years before Charlemagne was crowned emperor.
Did you know?
- The collarbone of the Pleiades. Zeta and its neighbour Omicron Persei once shared the Arabic name Atik, ‘the collarbone of the Pleiades’. The IAU gave the name to Omicron, so Zeta goes by its Greek letter.
- A partner on the move. A 9th-magnitude star beside Zeta Persei drifts across the sky at the same rate and in the same direction. The two may be a true pair, though a very wide one.
A 3rd-magnitude blue-white supergiant in southern Perseus, about eight degrees north of the Pleiades. A small telescope shows a 9th-magnitude companion 13 arcseconds away — a fine test of contrast.
When and where to see it
It is best placed in the evening sky around December, when it crosses the meridian at about 10 pm local time (around midnight in November). It can be seen from everywhere north of 58°S and never sets north of 58°N.
At its highest it stands 72° up from 50°N, 87° up from 35°N, 58° up from the equator, 23° up from 35°S.
Facts
- Type
- Star
- Constellation
- Perseus
- Designations
- ζ Per, 44 Per, HR 1203, HD 24398, HIP 18246
- Magnitude
- 2.9
- Position
- RA 3h 54.1m, Dec +31° 53′ (J2000)
- Spectral type
- B1Ib
- Colour
- white (B−V 0.12)
- Distance
- 1,300 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Zeta Persei (ζ Per) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.