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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
north SunriseRise: 7:51  
clear_day Transit: 11:50  
SunsetSet: 15:49 south
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All Constellations » Eridanus » 

21 Eridani

Altitude: 16.4°   Azimuth: 237.8°   Direction: West-South-West

21 Eridani is a main-sequence star in the constellation of Eridanus.

21 Eridani visual magnitude is 5.96. Because of its reltive faintness, 21 Eridani should be visible only from locations with dark skyes, while it is not visible at all from skyes affected by light pollution.

The table below summarizes the key facts about 21 Eridani:


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

Altitude: 16.4°
Azimuth: 237.8°
Direction: West-South-West

Celestial coordinates and finder chart of 21 Eridani

21 Eridani 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 Eridani are provided in the following table:

03h 39m 01s
-05° 37’ 33”

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

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

Visibility of 21 Eridani 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 Eridani 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: 95.6°
Max altitude: 32.9°
Azimuth: 264.4°

Digitized Sky Survey image of 21 Eridani

The image below is a photograph of 21 Eridani from the Digitized Sky Survey 2 (DSS2 - see the credits section) taken in the red channel. The area of sky represented in the image is 0.5x0.5 degrees (30x30 arcmins). The proper motion of 21 Eridani is -0.015 arcsec per year in Right Ascension and -0.205 arcsec per year in Declination and the associated displacement for the next 1000 years is represented with the red arrow.

Image of 21 Eridani star
DSS2 image of 21 Eridani. The red arrow shows the motion of 21 Eridani during the next 1000 years (-0.25 arcmin in Right Ascension and -3.42 arcmin in declination);

Distance of 21 Eridani from the Sun and relative movement

21 Eridani is distant 114.63 light years from the Sun and it is moving far from the Sun at the speed of 40 kilometers per second.

35.16 pc
114.63 ly
40 km/s
-0.015 arcsec/year
-0.205 arcsec/year

Spectral properties of 21 Eridani

21 Eridani belongs to spectral class K1 and has a luminosity class of V corresponding to a main-sequence star.


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

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

Alternative designations of 21 Eridani