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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
north SunriseRise: 7:49  
clear_day Transit: 11:49  
SunsetSet: 15:50 south
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All Constellations » Perseus » 

τ Persei (tau Persei)

Altitude: 14.5°   Azimuth: 5.6°   Direction: North

τ Persei is a variable and multiple giant star in the constellation of Perseus.

τ Persei visual magnitude is 3.95. Because of its moderate brightness, τ Persei 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 Persei:


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

Altitude: 14.5°
Azimuth: 5.6°
Direction: North

Celestial coordinates and finder chart of τ Persei

τ Persei 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 Persei are provided in the following table:

02h 54m 15s
+52° 45’ 45”

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

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

Visibility of τ Persei from your location

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

τ Persei (tau Persei) is circumpolar and transits at 21:48 UTC (altitude: 88.7°)

Digitized Sky Survey image of τ Persei

The image below is a photograph of τ Persei 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 Persei is 0 arcsec per year in Right Ascension and -0.005 arcsec per year in Declination and the associated displacement for the next 100000 years is represented with the red arrow.

Image of τ Persei (tau Persei) star
DSS2 image of τ Persei. The red arrow shows the motion of τ Persei during the next 100000 years (0.00 arcmin in Right Ascension and -8.33 arcmin in declination);

Distance of τ Persei from the Sun and relative movement

τ Persei is distant 247.91 light years from the Sun and it is moving far from the Sun at the speed of 2 kilometers per second.

76.05 pc
247.91 ly
2 km/s
-0.005 arcsec/year

Spectral properties of τ Persei

τ Persei belongs to spectral class G4 and has a luminosity class of III corresponding to a giant star.


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

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

τ Persei star system properties

τ Persei 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 Persei double sysyem:

51.7 arcsec

Alternative designations of τ Persei

τ Persei
(tau Persei)