τ Persei (tau Persei)

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:

Color of τ Persei ⬤

Magnitude of τ Persei 3.95

Class Giant

VISIBILITY RIGHT NOW τ Persei (tau Persei) is above the horizon from Greenwich, United Kingdom [change]. Altitude: 44°.

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:

Right Ascension J2000 02h 54m 15s

Declination J2000 +52° 45’ 45”

Galactic Longitude 141.02°

Galactic Latitude -5.74°

Constellation Perseus

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

Simplified finder chart for τ Persei (tau Persei).

Visibility of τ Persei from your location

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

τ Persei (tau Persei) is circumpolar and transits at 14:11 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.

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.

Distance (parsec) 76.05 pc

Distance (light year) 247.91 ly

Heliocentric radial velocity 2 km/s

Proper Motion Dec -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.

Absolute magnitude -0.46

Spectral Type G4III

Color Index (B-V) 0.74

Temperature of τ Persei 5468K

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

Main star magnitude 3.95

Secondary star magnitude 12.55

Magnitude difference 8.6

Separation 51.7 arcsec

Alternative designations of τ Persei

Bayer designation τ Persei
(tau Persei)

Flamsteed designation 18 Persei

Henry Draper Catalogue HD17878

SAO Catalogue SAO23685

Hipparcos Catalogue HIP13531

Durchmusterung Catalogue BD+52 641

FK5 Catalogue 103

General Catalogue of Variable Stars Tau Per

Aitken Double Star Catalogue ADS2202

How to support us

In Evidence

Other stars in Perseus