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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: 7:03  
clear_day Transit: 12:12  
SunsetSet: 17:22
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All Constellations » Boötes » 

τ Boötis (tau Boötis)

Altitude: 19.1°   Azimuth: 85.7°   Direction: East

τ Boötis is a variable and double sub-giant star in the constellation of Boötes.

τ Boötis visual magnitude is 4.5. Because of its moderate brightness, τ Boötis 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 proper motion of τ Boötis is -0.482 arcsec per year in Right Ascension and 0.041 arcsec per year in Declination and the associated displacement for the next 1000 years is represented with the red arrow.

Image of τ Boötis (tau Boötis) star
DSS2 image of τ Boötis. The red arrow shows the motion of τ Boötis during the next 1000 years (-8.03 arcmin in Right Ascension and 0.68 arcmin in declination);

Key facts about τ Boötis

4.5
Sub-giant

τ Boötis (tau Boötis) is above the horizon from Greenwich, United Kingdom edit_location_alt.

Altitude: 19.1°
Azimuth: 85.7°
Direction: East

Celestial coordinates and finder chart of τ Boötis

τ Boötis 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 Boötis are provided in the following table:

13h 47m 15s
+17° 27’ 24”
358.95°
73.88°
Boötes

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

Finder chart τ Boötis (tau Boötis) star
Simplified finder chart for τ Boötis (tau Boötis).

Visibility of τ Boötis 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 τ Boötis (tau Boötis) 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: 72.5°
Max altitude: 56.0°
Azimuth: 287.5°

Distance of τ Boötis from the Sun and relative movement

τ Boötis is distant 50.84 light years from the Sun and it is moving towards the Sun at the speed of 16 kilometers per second.

15.60 pc
50.84 ly
-16 km/s
-0.482 arcsec/year
0.041 arcsec/year

Spectral properties of τ Boötis

τ Boötis belongs to spectral class F6 and has a luminosity class of IV corresponding to a sub-giant star.

3.53
F6IV
6481K

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

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

τ Boötis star system properties

τ Boötis 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 Boötis double sysyem:

4.5
12
7.5
5 arcsec

Alternative designations of τ Boötis

τ Boötis
(tau Boötis)
SAO100706
SAO100706
Gl 527 A