Gamma Cassiopeiae — Double Star in Cassiopeia
About Gamma Cas
Description
Gamma Cassiopeiae is a blue emission-line star of spectral type B0IVe at magnitude 2.47 (variable between 1.6 and 3.0) in Cassiopeia. Located about 550 light-years from Earth, it is the prototype 'Gamma Cassiopeiae variable' — a rapidly rotating Be star that occasionally ejects shells of gas, causing dramatic brightness changes. Its luminosity is roughly 34,000 times solar.
Observing Tips
Gamma Cas is the central star of Cassiopeia's W-shape. Its brightness varies unpredictably over months and years — sometimes it is the brightest star in the W, other times one of the faintest. Compare it regularly with the other W stars to track its changes. Best observed year-round from mid-northern latitudes.
History
Gamma Cas was first noted as variable in 1937 when it unexpectedly brightened to magnitude 1.6. It has undergone multiple shell-ejection episodes since. The star defines an entire class of variable stars (Gamma Cassiopeiae variables) — Be stars that undergo episodic mass loss from their rapidly spinning equators.
Fun Facts
Gamma Cas is also a powerful and unusual X-ray source, much brighter in X-rays than a typical Be star. The origin of these X-rays is debated — possibilities include magnetic interactions, accretion onto a white dwarf companion, or wind-collision effects.
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. | V. hard | V. hard | V. hard |
| Celestron C8 (203 mm SCT) C8 203mm | V. hard | V. hard | V. hard |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
Set a location in User Settings to see visibility data.
5Light Curve
6Multiple Star System Triple C: optical
Separation over time
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
A: 2.5 · B: 10.9 · Sep: 2.1″ · PA: 259° · N up, E right
At limit · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″
Explore
8
Size Comparison
9
Compare Stars
10
Spectral Classification
11
Hertzsprung-Russell Diagram
12
Stellar Lifecycle
13
Blackbody Spectrum
14
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
15
Stellar Fusion
Discover
16Stellar Notes
17
Light Travel Time Machine
18
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.
Explore Nightbase
Related knowledge, tools, and stories — no observation planning required.
