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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: 6:40  
clear_day Transit: 12:10  
SunsetSet: 17:41
wb_twilight Nautical TwilightWhat's Visible Now?
All Constellations » Cancer » 

21 Cancri

Altitude: -11.5°   Azimuth: 303.9°   Direction: North-West

21 Cancri is a double giant star in the constellation of Cancer.

21 Cancri visual magnitude is 6.08. Because of its reltive faintness, 21 Cancri 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 Cancri is 0.004 arcsec per year in Right Ascension and -0.023 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

Image of 21 Cancri star
DSS2 image of 21 Cancri. The red arrow shows the motion of 21 Cancri during the next 10000 years (0.67 arcmin in Right Ascension and -3.83 arcmin in declination);

Key facts about 21 Cancri


21 Cancri is below the horizon from Greenwich, United Kingdom edit_location_alt.

Altitude: -11.5°
Azimuth: 303.9°
Direction: North-West

Celestial coordinates and finder chart of 21 Cancri

21 Cancri is situated close to the celestial equator, as such, it is at least partly visible from both hemispheres in certain times of the year. Celestial coordinates for the J2000 equinox as well as galactic coordinates of 21 Cancri are provided in the following table:

08h 23m 55s
+10° 37’ 54”

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

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

Visibility of 21 Cancri from your location

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

Today's 21 Cancri rise, transit and set times from Greenwich, United Kingdom edit_location_alt are the following (all times relative to the local timezone Europe/London):

Azimuth: 79.4°
Max altitude: 49.2°
Azimuth: 280.6°

Distance of 21 Cancri from the Sun and relative movement

21 Cancri is distant 1,112.63 light years from the Sun and it is moving far from the Sun at the speed of 3 kilometers per second.

341.30 pc
1,112.63 ly
3 km/s
0.004 arcsec/year
-0.023 arcsec/year

Spectral properties of 21 Cancri

21 Cancri belongs to spectral class M2 and has a luminosity class of III corresponding to a giant star.


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

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

21 Cancri star system properties

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

1 arcsec

Alternative designations of 21 Cancri