θ Hydrae (theta Hydrae)

θ Hydrae is a variable and multiple main-sequence star in the constellation of Hydra.

θ Hydrae visual magnitude is 3.88. Because of its moderate brightness, θ 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 θ Hydrae:

Color of θ Hydrae ⬤

Magnitude of θ Hydrae 3.88

Class Main-sequence

VISIBILITY RIGHT NOW θ Hydrae (theta Hydrae) is below the horizon from Greenwich, United Kingdom [change].

Celestial coordinates and finder chart of θ Hydrae

θ 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 θ Hydrae are provided in the following table:

Right Ascension J2000 09h 14m 21s

Declination J2000 +02° 18’ 51”

Galactic Longitude 228.77°

Galactic Latitude 32.53°

Constellation Hydra

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

Finder chart θ Hydrae (theta Hydrae) star

Simplified finder chart for θ Hydrae (theta Hydrae).

Visibility of θ Hydrae from your location

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

Today's θ Hydrae (theta Hydrae) rise, transit and set times from Greenwich, United Kingdom [change] are the following (all times relative to the local timezone Europe/London):

Azimuth: 87.7° RISE 15:44

Max altitude: 40.8° TRANSIT 21:54

Azimuth: 272.3° SET 4:07

RIGHT NOW θ Hydrae (theta Hydrae) is below the horizon from Greenwich, United Kingdom

Digitized Sky Survey image of θ Hydrae

The image below is a photograph of θ 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 θ Hydrae is 0.129 arcsec per year in Right Ascension and -0.31 arcsec per year in Declination and the associated displacement for the next 1000 years is represented with the red arrow.

DSS2 image of θ Hydrae. The red arrow shows the motion of θ Hydrae during the next 1000 years (2.15 arcmin in Right Ascension and -5.17 arcmin in declination);

Distance of θ Hydrae from the Sun and relative movement

θ Hydrae is distant 128.65 light years from the Sun and it is moving towards the Sun at the speed of 10 kilometers per second.

Distance (parsec) 39.46 pc

Distance (light year) 128.65 ly

Heliocentric radial velocity -10 km/s

Proper Motion RA 0.129 arcsec/year

Proper Motion Dec -0.31 arcsec/year

Spectral properties of θ Hydrae

θ Hydrae belongs to spectral class B9 and has a luminosity class of V corresponding to a main-sequence star.

Absolute magnitude 0.90

Spectral Type B9V

Color Index (B-V) -0.06

Temperature of θ Hydrae 10941K

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

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

θ Hydrae star system properties

θ Hydrae 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 θ Hydrae double sysyem:

Main star magnitude 3.88

Secondary star magnitude 11.58

Magnitude difference 7.7

Separation 27.1 arcsec

Alternative designations of θ Hydrae

Bayer designation θ Hydrae
(theta Hydrae)

Flamsteed designation 22 Hydrae

Henry Draper Catalogue HD79469

SAO Catalogue SAO117527

Hipparcos Catalogue HIP45336

Durchmusterung Catalogue BD+02 2167

FK5 Catalogue 347

General Catalogue of Variable Stars 4425

Aitken Double Star Catalogue ADS7253

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