21 Sagittarii

21 Sagittarii is a double bright giant star in the constellation of Sagittarius.

21 Sagittarii visual magnitude is 4.81. Because of its moderate brightness, 21 Sagittarii 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 21 Sagittarii:

Color of 21 Sagittarii ⬤

Magnitude of 21 Sagittarii 4.81

Class Bright giant

VISIBILITY RIGHT NOW 21 Sagittarii is below the horizon from Greenwich, United Kingdom [change].

Celestial coordinates and finder chart of 21 Sagittarii

21 Sagittarii 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 21 Sagittarii are provided in the following table:

Right Ascension J2000 18h 25m 20s

Declination J2000 -20° 32’ 30”

Galactic Longitude 11.74°

Galactic Latitude -3.75°

Constellation Sagittarius

The simplified sky map below shows the position of 21 Sagittarii in the sky:

Simplified finder chart for 21 Sagittarii.

Visibility of 21 Sagittarii from your location

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

Today's 21 Sagittarii rise, transit and set times from Greenwich, United Kingdom [change] are the following (all times relative to the local timezone Europe/London):

Azimuth: 110.5° RISE 2:28

Max altitude: 18.0° TRANSIT 6:35

Azimuth: 249.5° SET 10:41

RIGHT NOW 21 Sagittarii is below the horizon from Greenwich, United Kingdom

Digitized Sky Survey image of 21 Sagittarii

The image below is a photograph of 21 Sagittarii 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 21 Sagittarii is 0.006 arcsec per year in Right Ascension and -0.025 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

DSS2 image of 21 Sagittarii. The red arrow shows the motion of 21 Sagittarii during the next 10000 years (1.00 arcmin in Right Ascension and -4.17 arcmin in declination);

Distance of 21 Sagittarii from the Sun and relative movement

21 Sagittarii is distant 597.07 light years from the Sun and it is moving towards the Sun at the speed of 12 kilometers per second.

Distance (parsec) 183.15 pc

Distance (light year) 597.07 ly

Heliocentric radial velocity -12 km/s

Proper Motion RA 0.006 arcsec/year

Proper Motion Dec -0.025 arcsec/year

Spectral properties of 21 Sagittarii

21 Sagittarii belongs to spectral class K2 and has a luminosity class of II corresponding to a bright giant star.

Absolute magnitude -1.50

Spectral Type K2II

Color Index (B-V) 1.31

Temperature of 21 Sagittarii 4104K

The red dot in the diagram below shows where 21 Sagittarii is situated in the Hertzsprung–Russell diagram.

H-R diagram showing the position of 21 Sagittarii. Attribution: Richard Powell / CC BY-SA

21 Sagittarii star system properties

21 Sagittarii is a visual double star which can be observed with the help of medium or large telescopes. The table below shows key information about the 21 Sagittarii double sysyem:

Main star magnitude 4.81

Secondary star magnitude 8.41

Magnitude difference 3.6

Separation 1.7 arcsec

Alternative designations of 21 Sagittarii

Flamsteed designation 21 Sagittarii

Henry Draper Catalogue HD169420

SAO Catalogue SAO186794

Hipparcos Catalogue HIP90289

Durchmusterung Catalogue BD-20 5134

Aitken Double Star Catalogue ADS11325

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