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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: 7:47  
clear_day Transit: 11:49  
SunsetSet: 15:50 south
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All Constellations » Hercules » 

Rasalgethi - α1 Herculis (alpha1 Herculis)

Altitude: 0.8°   Azimuth: 292.4°   Direction: West-North-West

Rasalgethi, also designated as α1 Herculis (alpha1 Herculis), is a variable and multiple supergiant star in the constellation of Hercules.

Rasalgethi visual magnitude is 3.48. Because of its moderate brightness, Rasalgethi 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 Rasalgethi:


Rasalgethi - α1 Herculis (alpha1 Herculis) is above the horizon from Greenwich, United Kingdom edit_location_alt.

Altitude: 0.8°
Azimuth: 292.4°
Direction: West-North-West

Celestial coordinates and finder chart of Rasalgethi

Rasalgethi 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 Rasalgethi are provided in the following table:

17h 14m 38s
+14° 23’ 25”

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

Finder chart Rasalgethi - α1 Herculis (alpha1 Herculis) star
Simplified finder chart for Rasalgethi - α1 Herculis (alpha1 Herculis).

Visibility of Rasalgethi 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 Rasalgethi - α1 Herculis (alpha1 Herculis) 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: 75.6°
Max altitude: 52.9°
Azimuth: 284.4°

Digitized Sky Survey image of Rasalgethi

The image below is a photograph of Rasalgethi 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 Rasalgethi is -0.006 arcsec per year in Right Ascension and 0.036 arcsec per year in Declination and the associated displacement for the next 10000 years is represented with the red arrow.

Image of Rasalgethi - α1 Herculis (alpha1 Herculis) star
DSS2 image of Rasalgethi. The red arrow shows the motion of Rasalgethi during the next 10000 years (-1.00 arcmin in Right Ascension and 6.00 arcmin in declination);

Distance of Rasalgethi from the Sun and relative movement

Rasalgethi is distant 382.18 light years from the Sun and it is moving towards the Sun at the speed of 33 kilometers per second.

117.23 pc
382.18 ly
-33 km/s
-0.006 arcsec/year
0.036 arcsec/year

Spectral properties of Rasalgethi

Rasalgethi belongs to spectral class M5 and has a luminosity class of I corresponding to a supergiant star.


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

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

Rasalgethi star system properties

Rasalgethi 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 Rasalgethi double sysyem:

4.9 arcsec

Alternative designations of Rasalgethi

α1 Herculis
(alpha1 Herculis)
64 Herculis