When is the best time to observe Zeta Persei?

Zeta Persei is best observed from October through December, with peak visibility during November when it transits around midnight in the Northern Hemisphere.

Where is Zeta Persei located in the sky?

Zeta Persei lies in the constellation Perseus at right ascension 03h 54m and declination +31° 53′.

What telescope do I need to split Zeta Persei?

Splitting Zeta Persei requires an aperture of roughly 60 mm or larger — the components are separated by about 12.8″ at magnitudes near 2.9. The companion is about 6.3 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Zeta Persei — Double Star in Perseus

Magnitude 2.8–2.9^m DoubleStar Perseus (Per) Visible

Star Map + List + Plan

About Zeta Per

Description

Zeta Persei is a blue supergiant of spectral type B1Ib at magnitude 2.85 in Perseus. Located about 750 light-years from Earth, it has a luminosity of roughly 47,000 times solar. It is a member of the Perseus OB2 association, a group of young, massive stars in the Perseus arm of the Milky Way.

Observing Tips

Zeta Per lies in the main body of Perseus, south of Mirfak and the Alpha Persei Cluster. It is a blue-white star in a rich Milky Way field. A faint companion (magnitude 9.2) is visible in a small telescope. Best observed October through February.

History

Zeta Persei has no widely used traditional name. Perseus is one of the most prominent winter constellations, representing the Greek hero who slew Medusa and rescued Andromeda. Zeta Per's membership in the Perseus OB2 association connects it to ongoing star formation in the Perseus spiral arm.

Fun Facts

Zeta Per illuminates a nearby reflection nebula, visible in long-exposure photographs. Its intense ultraviolet radiation also ionizes surrounding gas, contributing to the rich emission nebulae found throughout the Perseus arm of the Milky Way.

Observe

1Physical Properties

Magnitude 2.85

Range 2.80 - 2.93

Variable Type ACYG

Spectral Type B1Ib supergiant

Star Color White (B-V 0.12)

Distance 878 ly

2Position & Identifiers

RA 03h 54m 07.9s

Dec +31° 53' 01.0"

Constellation Perseus (Per)

HR 1203

HIP 18246

HD 24398

SAO 56799

Bayer Zeta

Flamsteed 44 Per

Double Cat 2843

SIMBAD

3How easy to split?

Primary 2.9 mag Companion 9.2 mag Separation 12.8″

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Hard+	Hard+	Hard+
150 mm Newton 150mm Newt.	Medium+	Medium+	Medium+
Celestron C8 (203 mm SCT) C8 203mm	Easy	Easy	Easy

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

Set a location in User Settings to see visibility data.

Best season Oct – Dec (peak: Nov)

5Multiple Star System Quintuple D: optical

Components 5 (quintuple)

Component IDs AB

Separation 12.8″

Companion Mag 9.2

Companion Sp B8V

Position Angle 208°

Star Colors A: White B: Blue-white

Discoverer STF 464

Notes

AB CPM, B 9.16V B8IV; C, 9.12V at 33" optical; D, 10.35V, +0.713(B-V), +0.20(U-B), at 92" optical; E, 9.90V, A2V, | +0.33(B-V), +0.17(U-B), at 120" physical.

Separation over time

Measured 1824 → 2020 (196 y)

Separation drift 13.3" → 12.8" (-0.50")

Rate -0.0026" / y

PA drift 205° → 208° (+3°, +0.015°/y)

Essentially fixed on human timescales — the same view your grandchildren will see.

Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.

Eyepiece View

Telescope Eyepiece

80x Dawes: 1.9″ TFOV: 0.6°

Seeing

Scale Realistic = true angular size

A: 2.9 · B: 9.2 · Sep: 12.8″ · PA: 208° · N up, E right

Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″

Explore

Size Comparison

Querying VizieR for stellar data…

Compare Stars

Compare with another star

Spectral Classification

Hertzsprung-Russell Diagram

Loading HR diagram…

Read: The Hertzsprung-Russell Diagram — Reading Stars Like a Map

Stellar Lifecycle

Blackbody Spectrum

Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

Stellar Fusion

Discover

15Stellar Notes

Variable Star

2.80 - 2.93V.

Spectroscopic Binary

1.765d, K 6.0k/s, V0 +22.2k/s.

Color

Reddened star. Color excess E(B-V) = +0.33.

Group/Cluster

IC 348; Per OB2.

Spectral

Interstellar CH detected optically. COPERNICUS data used to analyze the chemical abundances in line of sight to | Zeta Per: CO, HD, and OH. About 60% of the hydrogen in front of the star is molecular.

Dynamical

0.012".

Radial Velocity

Comp. B +20.8k/s.