Zeta Herculis — Double Star in Hercules
About Zeta Her
Description
Zeta Herculis is a yellow subgiant of spectral type G0IV at magnitude 2.81 in Hercules. Located only about 35 light-years from Earth, it is one of the nearest bright stars and is a well-studied binary system with a G-type primary and a faint K-type companion orbiting every 34.5 years.
Observing Tips
Zeta Her lies at the southeastern corner of the Keystone asterism in Hercules. The binary companion can be resolved in a moderate telescope when near maximum separation. Best observed May through September when Hercules is high overhead.
History
Zeta Herculis has no widely used traditional proper name. Its proximity (35 light-years) and binary nature have made it a frequent target for high-resolution studies. It is also a prime example of a star that is evolving off the main sequence into a subgiant.
Fun Facts
At only 35 light-years, Zeta Her is one of the nearest binary star systems that can be visually resolved in a small telescope. Its primary is slightly more evolved than the Sun, giving astronomers a preview of the Sun's future evolution.
Observe
1Physical Properties
2Position & Identifiers
3How easy to split?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | V. hard+ | V. hard+ | V. hard+ |
| 150 mm Newton 150mm Newt. | Hard+ | Hard+ | Hard+ |
| Celestron C8 (203 mm SCT) C8 203mm | Medium | Medium | Medium |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
Set a location in User Settings to see visibility data.
5Multiple Star System
Separation over time
Apparent separation over time, computed from ORB6 orbital elements. Steep curves indicate fast-changing pairs — catch them while they're splittable.
Eyepiece View
A: 2.8 · B: 5.4 · Sep: 1.6″ · PA: 110° · N up, E right
Unresolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″
Explore
7
Size Comparison
8
Compare Stars
9
Spectral Classification
10
Hertzsprung-Russell Diagram
11
Stellar Lifecycle
12
Blackbody Spectrum
13
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
14
Stellar Fusion
Discover
15Stellar Notes
16
Light Travel Time Machine
17
Relativistic Travel
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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