τ Herculis (tau Herculis)

τ Herculis is a variable and double sub-giant star in the constellation of Hercules.

τ Herculis visual magnitude is 3.89. Because of its moderate brightness, τ Herculis should be easily visible from locations with dark skyes, while it can be barely visible, or not visible at all, from skyes affected by light pollution.

The table below summarizes the key facts about τ Herculis:

Color of τ Herculis ⬤

Magnitude of τ Herculis 3.89

Class Sub-giant

VISIBILITY RIGHT NOW τ Herculis (tau Herculis) is above the horizon from Greenwich, United Kingdom edit_location_alt. Altitude: 18°.

Celestial coordinates and finder chart of τ Herculis

τ Herculis is situated north of the celestial equator, as such, it is more easily visible from the northern hemisphere. Celestial coordinates for the J2000 equinox as well as galactic coordinates of τ Herculis are provided in the following table:

Right Ascension J2000 16h 19m 44s

Declination J2000 +46° 18’ 47”

Galactic Longitude 72.48°

Galactic Latitude 45.04°

Constellation Hercules

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

Finder chart τ Herculis (tau Herculis) star

Simplified finder chart for τ Herculis (tau Herculis).

Visibility of τ Herculis from your location

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

τ Herculis (tau Herculis) is circumpolar and transits at 23:50 UTC (altitude: 84.8°)

Digitized Sky Survey image of τ Herculis

The image below is a photograph of τ Herculis 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 Herculis is -0.011 arcsec per year in Right Ascension and 0.04 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

DSS2 image of τ Herculis. The red arrow shows the motion of τ Herculis during the next 10000 years (-1.83 arcmin in Right Ascension and 6.67 arcmin in declination);

Distance of τ Herculis from the Sun and relative movement

τ Herculis is distant 314.37 light years from the Sun and it is moving towards the Sun at the speed of 14 kilometers per second.

Distance (parsec) 96.43 pc

Distance (light year) 314.37 ly

Heliocentric radial velocity -14 km/s

Proper Motion RA -0.011 arcsec/year

Proper Motion Dec 0.04 arcsec/year

Spectral properties of τ Herculis

τ Herculis belongs to spectral class B5 and has a luminosity class of IV corresponding to a sub-giant star.

Absolute magnitude -1.03

Spectral Type B5IV

Color Index (B-V) -0.15

Temperature of τ Herculis 12489K

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

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

τ Herculis star system properties

τ Herculis 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 τ Herculis double sysyem:

Main star magnitude 3.89

Secondary star magnitude 14.59

Magnitude difference 10.7

Separation 6.7 arcsec

Alternative designations of τ Herculis

Bayer designation τ Herculis
(tau Herculis)

Flamsteed designation 22 Herculis

Henry Draper Catalogue HD147394

SAO Catalogue SAO46028

Hipparcos Catalogue HIP79992

Durchmusterung Catalogue BD+46 2169

FK5 Catalogue 608

General Catalogue of Variable Stars 7641

Aitken Double Star Catalogue ADS10010

In Evidence

Other stars in Hercules