τ Ophiuchi (tau Ophiuchi)

τ Ophiuchi is a variable and multiple main-sequence star in the constellation of Ophiuchus.

τ Ophiuchi visual magnitude is 5.24. Because of its reltive faintness, τ 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 τ Ophiuchi:

Color of τ Ophiuchi ⬤

Magnitude of τ Ophiuchi 5.24

Class Main-sequence

VISIBILITY RIGHT NOW τ Ophiuchi (tau Ophiuchi) is below the horizon from Greenwich, United Kingdom [change].

Celestial coordinates and finder chart of τ Ophiuchi

τ 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 τ Ophiuchi are provided in the following table:

Right Ascension J2000 18h 03m 04s

Declination J2000 -08° 10’ 50”

Galactic Longitude 20.06°

Galactic Latitude 6.87°

Constellation Ophiuchus

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

Finder chart τ Ophiuchi (tau Ophiuchi) star

Simplified finder chart for τ Ophiuchi (tau Ophiuchi).

Visibility of τ Ophiuchi from your location

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

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

Azimuth: 98.2° RISE 1:13

Max altitude: 30.3° TRANSIT 6:29

Azimuth: 261.8° SET 11:46

RIGHT NOW τ Ophiuchi (tau Ophiuchi) is below the horizon from Greenwich, United Kingdom

Digitized Sky Survey image of τ Ophiuchi

The image below is a photograph of τ 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 τ Ophiuchi is 0.028 arcsec per year in Right Ascension and -0.037 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

DSS2 image of τ Ophiuchi. The red arrow shows the motion of τ Ophiuchi during the next 10000 years (4.67 arcmin in Right Ascension and -6.17 arcmin in declination);

Distance of τ Ophiuchi from the Sun and relative movement

τ Ophiuchi is distant 169.61 light years from the Sun and it is moving towards the Sun at the speed of 40 kilometers per second.

Distance (parsec) 52.03 pc

Distance (light year) 169.61 ly

Heliocentric radial velocity -40 km/s

Proper Motion RA 0.028 arcsec/year

Proper Motion Dec -0.037 arcsec/year

Spectral properties of τ Ophiuchi

τ Ophiuchi belongs to spectral class F2 and has a luminosity class of V corresponding to a main-sequence star.

Absolute magnitude 1.66

Spectral Type F2V

Color Index (B-V) 0.38

Temperature of τ Ophiuchi 6989K

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

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

τ Ophiuchi star system properties

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

Main star magnitude 5.24

Secondary star magnitude 5.94

Magnitude difference 0.7

Separation 1.9 arcsec

Alternative designations of τ Ophiuchi

Bayer designation τ Ophiuchi
(tau Ophiuchi)

Flamsteed designation 69 Ophiuchi

Henry Draper Catalogue HD164765

SAO Catalogue SAO142050

Durchmusterung Catalogue BD-08 4549

Gliese Catalogue Gl 700.1A

General Catalogue of Variable Stars 10073

Aitken Double Star Catalogue ADS11005

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Other stars in Ophiuchus