Sigma Cygni — Star in Cygnus
Observe
1Physical Properties
Magnitude
4.23
Range
4.19 - 4.26
Period
120 days
Variable Type
ACYG
Spectral Type
B9Iab
supergiant
Star Color
White
(B-V 0.12)
Distance
297 ly
2Position & Identifiers
RA
21h 17m 25.0s
Dec
+39° 23' 41.0"
Constellation
Cygnus
(Cyg)
HR
8143
HIP
105102
HD
202850
SAO
71165
Bayer
Sigma
Flamsteed
67 Cyg
Querying VizieR catalog...
3How easy to spot?
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| Equipment | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| Naked eye Naked eye | Medium+ | Medium+ | Medium |
| 50 mm finder 50mm finder | Easy | Easy | Easy |
| 150 mm telescope 150mm scope | 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
Jul – Sep
(peak: Aug)
5Survey Image
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Explore
7
Size Comparison
Querying VizieR for stellar data…
8
Compare Stars
9
Spectral Classification
10
Hertzsprung-Russell Diagram
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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
H alpha profile varies.
11.043d?
Cyg OB4; embedded in dust.
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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The Hertzsprung-Russell Diagram — Reading Stars Like a Map
The HR diagram turns the night sky into a physics map: every named star has a spot, every spot tells you mass, age, and fate. A guide for amateur observers.
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