Your guide to the Solar System and the night sky
By donating now you help keep this site alive and free from ads. Please consider supporting this project.
🌎  Observing from: Greenwich, United Kingdom [change]
🌅 Sunrise: 6:01  ☀️ Transit: 12:06  🌅 Sunset: 18:11

Diadem - α Comae Berenices (alpha Comae Berenices)

Diadem, also designated as α Comae Berenices (alpha Comae Berenices), is a variable and multiple main-sequence star in the constellation of Coma Berenices.

Diadem visual magnitude is 5.22. Because of its reltive faintness, Diadem 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 Diadem:

Diadem - α Comae Berenices (alpha Comae Berenices) is above the horizon from Greenwich, United Kingdom [change]. Altitude: 12°.

Celestial coordinates and finder chart of Diadem

Diadem 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 Diadem are provided in the following table:

13h 09m 59s
+17° 31’ 45”
Coma Berenices

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

Finder chart Diadem - α Comae Berenices (alpha Comae Berenices) star
Simplified finder chart for Diadem - α Comae Berenices (alpha Comae Berenices).

Visibility of Diadem from your location

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

Today's Diadem - α Comae Berenices (alpha Comae Berenices) rise, transit and set times from Greenwich, United Kingdom [change] are the following (all times relative to the local timezone Europe/London):

Azimuth: 72.5°
Max altitude: 56.0°
Azimuth: 287.5°
Diadem - α Comae Berenices (alpha Comae Berenices) is above the horizon from Greenwich, United Kingdom

Digitized Sky Survey image of Diadem

The image below is a photograph of Diadem 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 Diadem is -0.431 arcsec per year in Right Ascension and 0.136 arcsec per year in Declination and the associated displacement for the next 1000 years is represented with the red arrow.

Image of Diadem - α Comae Berenices (alpha Comae Berenices) star
DSS2 image of Diadem. The red arrow shows the motion of Diadem during the next 1000 years (-7.18 arcmin in Right Ascension and 2.27 arcmin in declination);

Distance of Diadem from the Sun and relative movement

Diadem is distant 46.70 light years from the Sun and it is moving towards the Sun at the speed of 18 kilometers per second.

14.32 pc
46.70 ly
-18 km/s
-0.431 arcsec/year
0.136 arcsec/year

Spectral properties of Diadem

Diadem 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 Diadem is situated in the Hertzsprung–Russell diagram.

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

Diadem star system properties

Diadem 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 Diadem double sysyem:

0.2 arcsec

Alternative designations of Diadem

α Comae Berenices
(alpha Comae Berenices)
42 Comae Berenices
Gl 501 A