Fawaris — Double Star in Cygnus
HIP 97165; Delta Cygni; 18 Cygni
About Fawaris
Description
Delta Cygni is a binary star system at magnitude 2.87 in Cygnus, consisting of a blue-white subgiant (B9.5IV) and a yellow-white companion (F1V). Located about 165 light-years from Earth, the pair orbits every 780 years. It marks the western wing of the Swan.
Observing Tips
Delta Cyg lies at the western wing-tip of Cygnus, part of the Northern Cross. A moderate telescope can resolve the pair when seeing is steady. The constellation Cygnus is one of the best for exploring the summer Milky Way. Best observed June through November.
History
Delta Cygni has no traditional proper name. Cygnus the Swan is one of the most prominent summer constellations, identified with the mythological swan into which Zeus transformed himself. The Milky Way runs directly through the constellation.
Fun Facts
Delta Cyg will become the north pole star around AD 11,250 as Earth's axis precesses. It will be one of the brighter pole stars in the precession cycle, comparable in brightness to Polaris.
Observe
1Physical Properties
2Position & Identifiers
3How easy to split?
| 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 | 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 Triple F: optical
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: 2.9 · B: 6.3 · Sep: 2.8″ · PA: 214° · N up, E right
Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″
Explore
7
Size Comparison
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Compare Stars
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Spectral Classification
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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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