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A Complete Guide to the Solar System and the Night Sky
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public Observing fromLocation: Greenwich, United Kingdom edit_location_alt
SunriseRise: 5:43  
clear_day Transit: 12:56  
SunsetSet: 20:10
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All Constellations » Cassiopeia » 

21 Cassiopeiae

Altitude: 56.5°   Azimuth: 335.8°   Direction: North-North-West

21 Cassiopeiae is a variable and double sub-giant star in the constellation of Cassiopeia.

21 Cassiopeiae visual magnitude is 5.66. Because of its reltive faintness, 21 Cassiopeiae should be visible only from locations with dark skies, while it is not visible at all from skies affected by light pollution.

The proper motion of 21 Cassiopeiae is -0.018 arcsec per year in Right Ascension and -0.026 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

Image of 21 Cassiopeiae star
DSS2 image of 21 Cassiopeiae. The red arrow shows the motion of 21 Cassiopeiae during the next 10000 years (-3.00 arcmin in Right Ascension and -4.33 arcmin in declination);

Key facts about 21 Cassiopeiae


21 Cassiopeiae is above the horizon from Greenwich, United Kingdom edit_location_alt.

Altitude: 56.5°
Azimuth: 335.8°
Direction: North-North-West

Celestial coordinates and finder chart of 21 Cassiopeiae

21 Cassiopeiae is situated close to the northern celestial pole and, as such, it is visible for most part of the year from the northern hemisphere. Celestial coordinates for the J2000 equinox as well as galactic coordinates of 21 Cassiopeiae are provided in the following table:

00h 45m 38s
+74° 59’ 17”

The simplified sky map below shows the position of 21 Cassiopeiae in the sky:

Finder chart 21 Cassiopeiae star
Simplified finder chart for 21 Cassiopeiae.

Visibility of 21 Cassiopeiae from your location

Location: Greenwich, United Kingdom edit_location_alt
Latitude: 51° 28’ 47” N
Longitude: 0° 00’ 00” E
Timezone: Europe/London

21 Cassiopeiae is circumpolar and transits at 10:29 UTC (altitude: 66.5°)

Distance of 21 Cassiopeiae from the Sun and relative movement

21 Cassiopeiae is distant 290.04 light years from the Sun and it is moving far from the Sun at the speed of 9 kilometers per second.

88.97 pc
290.04 ly
9 km/s
-0.018 arcsec/year
-0.026 arcsec/year

Spectral properties of 21 Cassiopeiae

21 Cassiopeiae belongs to spectral class A2 and has a luminosity class of IV corresponding to a sub-giant star.


The red dot in the diagram below shows where 21 Cassiopeiae is situated in the Hertzsprung–Russell diagram.

HR Diagram
H-R diagram showing the position of 21 Cassiopeiae. Attribution: Richard Powell / CC BY-SA

21 Cassiopeiae star system properties

21 Cassiopeiae is a visual double star which can be observed with the help of small or medium telescopes. The table below shows key information about the 21 Cassiopeiae double sysyem:

36 arcsec

Alternative designations of 21 Cassiopeiae

21 Cassiopeiae