31 Orionis

31 Orionis is a variable and double giant star in the constellation of Orion.

31 Orionis visual magnitude is 4.71. Because of its moderate brightness, 31 Orionis 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 31 Orionis:

Color of 31 Orionis ⬤

Magnitude of 31 Orionis 4.71

Class Giant

VISIBILITY RIGHT NOW 31 Orionis is above the horizon from Greenwich, United Kingdom edit_location_alt. Altitude: 13°.

Celestial coordinates and finder chart of 31 Orionis

31 Orionis 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 31 Orionis are provided in the following table:

Right Ascension J2000 05h 29m 44s

Declination J2000 -01° 05’ 31”

Galactic Longitude 204.31°

Galactic Latitude -18.62°

Constellation Orion

The simplified sky map below shows the position of 31 Orionis in the sky:

Simplified finder chart for 31 Orionis.

Visibility of 31 Orionis 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 31 Orionis 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: 91.1° RISE 8:09

Max altitude: 37.4° TRANSIT 14:02

Azimuth: 268.9° SET 19:55

RIGHT NOW 31 Orionis is above the horizon from Greenwich, United Kingdom

Digitized Sky Survey image of 31 Orionis

The image below is a photograph of 31 Orionis 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 31 Orionis is 0.004 arcsec per year in Right Ascension and -0.023 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

DSS2 image of 31 Orionis. The red arrow shows the motion of 31 Orionis during the next 10000 years (0.67 arcmin in Right Ascension and -3.83 arcmin in declination);

Distance of 31 Orionis from the Sun and relative movement

31 Orionis is distant 455.94 light years from the Sun and it is moving far from the Sun at the speed of 8 kilometers per second.

Distance (parsec) 139.86 pc

Distance (light year) 455.94 ly

Heliocentric radial velocity 8 km/s

Proper Motion RA 0.004 arcsec/year

Proper Motion Dec -0.023 arcsec/year

Spectral properties of 31 Orionis

31 Orionis belongs to spectral class K5 and has a luminosity class of III corresponding to a giant star.

Absolute magnitude -1.02

Spectral Type K5III

Color Index (B-V) 1.57

Temperature of 31 Orionis 3691K

The red dot in the diagram below shows where 31 Orionis is situated in the Hertzsprung–Russell diagram.

H-R diagram showing the position of 31 Orionis. Attribution: Richard Powell / CC BY-SA

31 Orionis star system properties

31 Orionis is a visual double star which can be observed with the help of small or medium telescopes. The table below shows key information about the 31 Orionis double sysyem:

Main star magnitude 4.71

Secondary star magnitude 10.11

Magnitude difference 5.4

Separation 12.5 arcsec

Alternative designations of 31 Orionis

Flamsteed designation 31 Orionis

Henry Draper Catalogue HD36167

SAO Catalogue SAO132176

Hipparcos Catalogue HIP25737

Durchmusterung Catalogue BD-01 913

General Catalogue of Variable Stars CI Ori

Aitken Double Star Catalogue ADS4097

In Evidence

Other stars in Orion