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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: 7:48  
clear_day Transit: 11:49  
SunsetSet: 15:50 south
sleep NighttimeWhat's Visible Now?
All Constellations » Hydra » 


Altitude: -19.9°   Azimuth: 85.7°   Direction: East

HR3991 is a main-sequence star in the constellation of Hydra.

HR3991 visual magnitude is 5.31. Because of its reltive faintness, HR3991 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 HR3991:


HR3991 is below the horizon from Greenwich, United Kingdom edit_location_alt.

Altitude: -19.9°
Azimuth: 85.7°
Direction: East

Celestial coordinates and finder chart of HR3991

HR3991 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 HR3991 are provided in the following table:

10h 10m 05s
-12° 48’ 57”

The simplified sky map below shows the position of HR3991 in the sky:

Finder chart HR3991 star
Simplified finder chart for HR3991.

Visibility of HR3991 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 HR3991 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: 102.8°
Max altitude: 25.7°
Azimuth: 257.2°

Digitized Sky Survey image of HR3991

The image below is a photograph of HR3991 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 HR3991 is -0.125 arcsec per year in Right Ascension and -0.113 arcsec per year in Declination and the associated displacement for the next 1000 years is represented with the red arrow.

Image of HR3991 star
DSS2 image of HR3991. The red arrow shows the motion of HR3991 during the next 1000 years (-2.08 arcmin in Right Ascension and -1.88 arcmin in declination);

Distance of HR3991 from the Sun and relative movement

HR3991 is distant 89.05 light years from the Sun and it is moving far from the Sun at the speed of 23 kilometers per second.

27.31 pc
89.05 ly
23 km/s
-0.125 arcsec/year
-0.113 arcsec/year

Spectral properties of HR3991

HR3991 belongs to spectral class F5 and has a luminosity class of V corresponding to a main-sequence star.


The red dot in the diagram below shows where HR3991 is situated in the Hertzsprung–Russell diagram.

HR Diagram
H-R diagram showing the position of HR3991. Attribution: Richard Powell / CC BY-SA

Alternative designations of HR3991