21 Cassiopeiae — Variable Star in Cassiopeia
Excellent (60/100)
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1Physical Properties
Magnitude
5.66
Range
5.64 - 6.06
Period
4.5 days
Variable Type
Eclipsing Binary (Algol-type)
Spectral Type
A2IV
subgiant
Star Color
White
(B-V 0.05)
2Position & Identifiers
RA
00h 45m 39.0s
Dec
+74° 59' 17.0"
Constellation
Cassiopeia
(Cas)
HR
192
HIP
3572
HD
4161
SAO
4216
Flamsteed
21 Cas
Variable ID
YZ Cas
Double Cat
624
Querying VizieR catalog...
3How easy to follow?
Magnitude
5.6 – 6.1 mag
Amplitude
0.4 mag
Period
4.47 d
Type
EA/DM
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| Equipment | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| Naked eye Naked eye | V. hard+ | V. hard | V. hard |
| 50 mm finder 50mm finder | Hard+ | Hard+ | Hard+ |
| 150 mm telescope 150mm scope | Hard+ | Hard+ | Hard+ |
Easy
Medium
Hard
Very hard
Impossible
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
Out of reach for typical amateur telescopes, even at Bortle 3.
4Visibility
Set a location in User Settings to see visibility data.
Best season
Aug – Oct
(peak: Sep)
5Survey Image
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6Light Curve
7Comparison Stars for 21 Cas (5.6–6.1)
Nearby stable stars for estimating brightness (AAVSO)
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Explore
8
Size Comparison
Querying VizieR for stellar data…
9
Compare Stars
10
Spectral Classification
11
Hertzsprung-Russell Diagram
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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
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16Stellar Notes
ADS 624A, EA 5.71 - 6.12B, 4.467224d, i 87.95d. Amp. of primary 0.40V, secondary 0.12V.
Physical pair.
4.4672d, K 73.0k/s, V0 +8.1k/s, asini 4.48.
Also classified A2V + F2V.
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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A practical guide to visual observation of variable stars: estimating magnitudes, finding comparison stars, recording data, and contributing to science with AAVSO.
Article
Cassiopeia
Mythology, bright stars, and deep-sky highlights.
Constellation
