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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: 7:37  
clear_day Transit: 11:46  
SunsetSet: 15:55 south
wb_twilight Nautical TwilightWhat's Visible Now?
All Constellations » Serpens » 

τ1 Serpentis (tau1 Serpentis)

Altitude: 11.6°   Azimuth: 280.3°   Direction: West

τ1 Serpentis is a variable giant star in the constellation of Serpens.

τ1 Serpentis visual magnitude is 5.17. Because of its reltive faintness, τ1 Serpentis 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 τ1 Serpentis:


τ1 Serpentis (tau1 Serpentis) is above the horizon from Greenwich, United Kingdom edit_location_alt.

Altitude: 11.6°
Azimuth: 280.3°
Direction: West

Celestial coordinates and finder chart of τ1 Serpentis

τ1 Serpentis 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 τ1 Serpentis are provided in the following table:

15h 25m 47s
+15° 25’ 41”

The simplified sky map below shows the position of τ1 Serpentis in the sky:

Finder chart τ1 Serpentis (tau1 Serpentis) star
Simplified finder chart for τ1 Serpentis (tau1 Serpentis).

Visibility of τ1 Serpentis 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 τ1 Serpentis (tau1 Serpentis) 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: 74.6°
Max altitude: 53.9°
Azimuth: 285.4°

Digitized Sky Survey image of τ1 Serpentis

The image below is a photograph of τ1 Serpentis 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 τ1 Serpentis is -0.013 arcsec per year in Right Ascension and -0.007 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

Image of τ1 Serpentis (tau1 Serpentis) star
DSS2 image of τ1 Serpentis. The red arrow shows the motion of τ1 Serpentis during the next 10000 years (-2.17 arcmin in Right Ascension and -1.17 arcmin in declination);

Distance of τ1 Serpentis from the Sun and relative movement

τ1 Serpentis is distant 918.31 light years from the Sun and it is moving towards the Sun at the speed of 20 kilometers per second.

281.69 pc
918.31 ly
-20 km/s
-0.013 arcsec/year
-0.007 arcsec/year

Spectral properties of τ1 Serpentis

τ1 Serpentis belongs to spectral class M1 and has a luminosity class of III corresponding to a giant star.


The red dot in the diagram below shows where τ1 Serpentis is situated in the Hertzsprung–Russell diagram.

HR Diagram
H-R diagram showing the position of τ1 Serpentis. Attribution: Richard Powell / CC BY-SA

Alternative designations of τ1 Serpentis

τ1 Serpentis
(tau1 Serpentis)
9 Serpentis