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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: 6:59  
clear_day Transit: 12:12  
SunsetSet: 17:25
sleep NighttimeWhat's Visible Now?
All Constellations » Hydra » 

21 Hydrae

Altitude: -0.1°   Azimuth: 258.7°   Direction: West-South-West

21 Hydrae is a variable giant star in the constellation of Hydra.

21 Hydrae visual magnitude is 6.11. Because of its reltive faintness, 21 Hydrae should be visible only from locations with dark skyes, while it is not visible at all from skyes affected by light pollution.

The proper motion of 21 Hydrae is -0.016 arcsec per year in Right Ascension and 0.019 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

Image of 21 Hydrae star
DSS2 image of 21 Hydrae. The red arrow shows the motion of 21 Hydrae during the next 10000 years (-2.67 arcmin in Right Ascension and 3.17 arcmin in declination);

Key facts about 21 Hydrae


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

Altitude: -0.1°
Azimuth: 258.7°
Direction: West-South-West

Celestial coordinates and finder chart of 21 Hydrae

21 Hydrae 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 Hydrae are provided in the following table:

09h 12m 25s
-07° 06’ 34”

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

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

Visibility of 21 Hydrae 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 Hydrae 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: 97.1°
Max altitude: 31.4°
Azimuth: 262.9°

Distance of 21 Hydrae from the Sun and relative movement

21 Hydrae is distant 269.42 light years from the Sun and it is moving towards the Sun at the speed of 4 kilometers per second.

82.64 pc
269.42 ly
-4 km/s
-0.016 arcsec/year
0.019 arcsec/year

Spectral properties of 21 Hydrae

21 Hydrae belongs to spectral class A3 and has a luminosity class of III corresponding to a giant star.


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

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

Alternative designations of 21 Hydrae