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public LocationGreenwich, UK
TimezoneEurope/London
Sunrise: 5:00 
Transit: 13:04 
Sunset: 21:07
wb_twilight   (Nautical Twilight)   What's Visible Now?
All Constellations » Ophiuchus » 

21 Ophiuchi

Above the horizon.  Rise: 16:11 | Tran: 22:15 | Set: 4:23
Alt: 39.57°   Az: 174.61°   Direction: South

21 Ophiuchi is a double main-sequence star of spectral class A2 in the constellation of Ophiuchus.

21 Ophiuchi visual magnitude is 5.51. Because of its faintness, 21 Ophiuchi is visible to the naked eye only from locations with very dark skies, while it is not visible at all from skies affected by light pollution.

21 Ophiuchi is situated close to the celestial equator, as such, it is at least partly visible from both hemispheres in certain times of the year.

Image of 21 Ophiuchi star
DSS2 image of 21 Ophiuchi. The red arrow shows the motion of 21 Ophiuchi during the next 10000 years (-3.83 arcmin in Right Ascension and -0.83 arcmin in declination);

Celestial Coordinates

Apparent

16h 52m 39s
+01° 10’ 34”
23h 43m 23s
16h 36m 03s

J2000

16h 51m 24s
+01° 12’ 57”

Galactic Coordinates

19.35°
27.04°

Finder Chart

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

Magnitude, Color, Spectral Class

5.51
Main-sequence

0.39
A2V
9542K

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

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

Star System Properties

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

5.51
7.01
1.5
0.4 arcsec

Distance, Radial Speed, Proper Motion

21 Ophiuchi is distant 344.97 light years from the Sun and it is moving towards the Sun at the speed of 26 kilometers per second.

105.82 pc
344.97 ly
-26 km/s
-0.023 arcsec/y
-0.005 "/y

Alternative Designations

21 Ophiuchi
SAO121911
SAO121911

Visibility from Your Location

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

Azimuth: 88.8°
Max altitude: 39.7°
Azimuth: 271.2°