Your Guide to the Solar System and the Night Sky
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public Observing fromLocation: Greenwich, United Kingdom edit_location_alt
north SunriseRise: 4:45  
clear_day Transit: 12:57  
SunsetSet: 21:09 south
wb_twilight Astronomical TwilightWhat's Visible Now
All Constellations » Perseus » 

40 Persei

Altitude: -4.4°   Azimuth: 5.1°   Direction: North

40 Persei is a double hypergiant star in the constellation of Perseus.

40 Persei visual magnitude is 4.97. Because of its moderate brightness, 40 Persei 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 40 Persei:


40 Persei is below the horizon from Greenwich, United Kingdom edit_location_alt.

Altitude: -4.4°
Azimuth: 5.1°
Direction: North

Celestial coordinates and finder chart of 40 Persei

40 Persei is situated north of the celestial equator, as such, it is more easily visible from the northern hemisphere. Celestial coordinates for the J2000 equinox as well as galactic coordinates of 40 Persei are provided in the following table:

03h 42m 22s
+33° 57’ 54”

The simplified sky map below shows the position of 40 Persei in the sky:

Finder chart 40 Persei star
Simplified finder chart for 40 Persei.

Visibility of 40 Persei 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 40 Persei 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: 56.0°
Max altitude: 72.5°
Azimuth: 304.0°
40 Persei is below the horizon from Greenwich, United Kingdom

Digitized Sky Survey image of 40 Persei

The image below is a photograph of 40 Persei 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 40 Persei is -0.005 arcsec per year in Right Ascension and -0.009 arcsec per year in Declination and the associated displacement for the next 100000 years is represented with the red arrow.

Image of 40 Persei star
DSS2 image of 40 Persei. The red arrow shows the motion of 40 Persei during the next 100000 years (-8.33 arcmin in Right Ascension and -15.00 arcmin in declination);

Distance of 40 Persei from the Sun and relative movement

40 Persei is distant 923.51 light years from the Sun and it is moving far from the Sun at the speed of 20 kilometers per second.

283.29 pc
923.51 ly
20 km/s
-0.005 arcsec/year
-0.009 arcsec/year

Spectral properties of 40 Persei

40 Persei belongs to spectral class B0 and has a luminosity class of V corresponding to a hypergiant star.


The red dot in the diagram below shows where 40 Persei is situated in the Hertzsprung–Russell diagram.

HR Diagram
H-R diagram showing the position of 40 Persei. Attribution: Richard Powell / CC BY-SA

40 Persei star system properties

40 Persei 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 40 Persei double sysyem:

20 arcsec

Alternative designations of 40 Persei