Your Guide to the Solar System and the Night Sky
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public Observing fromLocation: Greenwich, United Kingdom edit_location_alt
north SunriseRise: 6:49  
clear_day Transit: 12:50  
SunsetSet: 18:50 south
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All Constellations » Hydra » 

τ1 Hydrae (tau1 Hydrae)

Altitude: -37.0°   Azimuth: 31.7°   Direction: North-North-East

τ1 Hydrae is a double main-sequence star in the constellation of Hydra.

τ1 Hydrae visual magnitude is 4.6. Because of its moderate brightness, τ1 Hydrae 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 τ1 Hydrae:


τ1 Hydrae (tau1 Hydrae) is below the horizon from Greenwich, United Kingdom edit_location_alt.

Altitude: -37.0°
Azimuth: 31.7°
Direction: North-North-East

Celestial coordinates and finder chart of τ1 Hydrae

τ1 Hydrae 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 Hydrae are provided in the following table:

09h 29m 08s
-02° 46’ 08”

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

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

Visibility of τ1 Hydrae 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 Hydrae (tau1 Hydrae) 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: 92.8°
Max altitude: 35.8°
Azimuth: 267.2°

Digitized Sky Survey image of τ1 Hydrae

The image below is a photograph of τ1 Hydrae 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 Hydrae is 0.13 arcsec per year in Right Ascension and -0.015 arcsec per year in Declination and the associated displacement for the next 1000 years is represented with the red arrow.

Image of τ1 Hydrae (tau1 Hydrae) star
DSS2 image of τ1 Hydrae. The red arrow shows the motion of τ1 Hydrae during the next 1000 years (2.17 arcmin in Right Ascension and -0.25 arcmin in declination);

Distance of τ1 Hydrae from the Sun and relative movement

τ1 Hydrae is distant 55.75 light years from the Sun and it is moving far from the Sun at the speed of 10 kilometers per second.

17.10 pc
55.75 ly
10 km/s
0.13 arcsec/year
-0.015 arcsec/year

Spectral properties of τ1 Hydrae

τ1 Hydrae belongs to spectral class F6 and has a luminosity class of V corresponding to a main-sequence star.


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

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

τ1 Hydrae star system properties

τ1 Hydrae is a visual double star which can be observed with binoculars or small telescopes. The table below shows key information about the τ1 Hydrae double sysyem:

65.7 arcsec

Alternative designations of τ1 Hydrae

τ1 Hydrae
(tau1 Hydrae)
Gl 348 A