THE BRIGHTEST BODIES OF THE SOLAR SYSTEM

 The table at right provides the magnitudes of the brightest bodies of the solar system sorted by the maximal visual magnitudes.Only the bodies brightest than m_v = 10 are provided. The table provides also the absolute magnitudes of these bodies. The Near-Earth objects are excluded from this list. 

Magnitude definition:

The brightness of the solar system bodies depend, except for the Sun, to the capacity of the surface of the objects to reflect or diffuse the light of the Sun. For an observer on Earth, it depends also on the distance to the object. 

The magnitude allows to quantify this brightness: the apparent magnitude provides the apparent brightness for an observer and depends on the distance. one defines the magnitude m of a celestial body which has a brightness L by :  
  
m = -2.5 log (L/L₀)  
  
where L₀ is a constant defining the brightness of a body having a magnitude 0 (case of the star Vega). Two bodies the brightness of which are in a ratio 100 to 1, will have a difference of 5 magnitudes. The high values for the magnitude correspond to faint objects less bright. The brightest objects may have a negative magnitude (for example the Sun, -27, the Full Moon, -12, Venus, -4, Jupiter at opposition, -2 and Sirius, -1.4). 

The visual magnitude corresponds to a detector which has the same sensitivity than eyes. The naked eye may detect objects until magnitude 6. 

The photographic magnitude corresponds to a detector which has a maximal sensitivity in blue or violet. The difference between the visual and photographic magnitudes is the color index. For the Sun or for the bodies reflecting the solar light, this index is +0,8. It varies with the spactral type of the stars. 

The absolute magnitude measures the intrinsic brightness. For objects outside the solar system, it corresponds to the brightness of a body measured from a distance of 10 parsecs (one parsec is the distance from where the Earth-Sun angle is one arcsec, i.e. 206265 astronomical units astronomiques). We have the relationship :  

M = m + 5 - 5 log D 

where m is the visual magnitude, M the absolute magnitude, D the distance to the object in parsecs.   

For the bodies of the solar system, we use a different definition for the absolute magnitude. Asteroids and comets are characterized by their absolute magnitude corresponding to the magnitude of the object at the distance of one astronomical unit. We have the relationship : 

H = m - 5 log(rD) + g 

where m est is the visual magnitude, H the absolute magnitude, D the distance of the object to the Earth and r its distance to the Sun in astronomical units. g is a complementary term for the phase effects.    

Above the double star m Bootis. This shows the difficulty to observe objects with very different magnitudes: the star at the center has a magnitude 4.5 and the second star a magnitude 7.2. The faint stars in the background have a magnitude from 15 to 18.

For the correspondance between absolute magnitude and size for the asteroids : click here.

Click on the title of the columns in order to sort the list.