Your guide to the Solar System and the night sky
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🌎  Observing from: Greenwich, United Kingdom [change]
🌅 Sunrise: 5:59  ☀️ Transit: 12:05  🌅 Sunset: 18:13

21 Ophiuchi

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

21 Ophiuchi visual magnitude is 5.51. Because of its reltive faintness, 21 Ophiuchi 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 Ophiuchi:

21 Ophiuchi is below the horizon from Greenwich, United Kingdom [change].

Celestial coordinates and finder chart of 21 Ophiuchi

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. Celestial coordinates for the J2000 equinox as well as galactic coordinates of 21 Ophiuchi are provided in the following table:

16h 51m 24s
+01° 12’ 57”

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

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

Visibility of 21 Ophiuchi from your location

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

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

Azimuth: 88.8°
Max altitude: 39.7°
Azimuth: 271.2°
21 Ophiuchi is below the horizon from Greenwich, United Kingdom

Digitized Sky Survey image of 21 Ophiuchi

The image below is a photograph of 21 Ophiuchi 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 Ophiuchi is -0.023 arcsec per year in Right Ascension and -0.005 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

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);

Distance of 21 Ophiuchi from the Sun and relative movement

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/year
-0.005 arcsec/year

Spectral properties of 21 Ophiuchi

21 Ophiuchi belongs to spectral class A2 and has a luminosity class of V corresponding to a main-sequence star.


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

21 Ophiuchi 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:

0.4 arcsec

Alternative designations of 21 Ophiuchi

21 Ophiuchi