# Solar System by apparent size [Image.] Solar eclipses are possible because (by coincidence) the apparent sizes of Sol and Luna are approximately equal.  When Luna passes in front of Sol, if Luna appears smaller than Sol, then an annular Solar eclipse occurs, and if Luna appears larger than Sol, then a total Solar eclipse occurs.  Photograph shows an Annular Solar Eclipse displaying the relative angular sizes of Luna and Sol.

Solar System objects sorted by apparent angular diameter.  

## list

1. Planet Terra: (3.1415926535897932384626433832795 = π) rad = 180 deg (12.74M / 0)
2. Star Sol: 9.3099381622456608377567028963016 mrad = 32.005209853467492394412374774496 arcmin (1.393G / 149.6G) 
3. Terran Satellite Luna: 9.1924733415766236658905126057414 mrad = 31.601395545531677869275770447370 arcmin (3.475M / 384.4M) 
4. Planet Jupiter: 176.38342059183204249972698706792 µrad = 36.381692073574341769062888511907 arcsec (139.8M / 778.5G) 
5. Planet Saturn: 80.804366614590771015035932939646 µrad = 16.667097023677906623999609656452 arcsec (116.5M / 1.434T) 
6. Planet Venus: 65.557754895471439224993918452156 µrad = 13.522257611509048977196601587376 arcsec (12.1M / 149.6G) 
7. Planet Mercury: 30.418531890520777418473660749422 µrad = 6.2742725867193897525492834124436 arcsec (4.879M / 149.6G) 
8. Planet Mars: 24.864310071007387989563198840282 µrad = 5.1286320992640655002603020583460 arcsec (6.779M / 227.9G) 
9. Planet Uranus: 17.643986266660484646561759683674 µrad = 3.6393334087191538304117174747131 arcsec (50.72M / 2.871T) 
10. Planet Neptune: 10.940951094337036545922443091756 µrad = 2.2567331576323856791155130374892 arcsec (49.24M / 4.498T) 
11. Jovian Satellite Ganymede: 6.6457516559391904488160888324418 µrad = 1.3707846776786168771797746278470 arcsec (5.268M / 778.5G) 
12. Jovian Satellite Callisto: 6.0810996708582598711685808110014 µrad = 1.2543168453788603898364781318473 arcsec (4.821M / 778.5G) 
13. Jovian Satellite Io: 4.5958431873590778175870863250252 µrad = 0.94796070458265793885064096711556 arcsec (3.643M / 778.5G) 
14. Jovian Satellite Europa: 3.9378516100190881273980359335144 µrad = 0.81224019937040364887742618540130 arcsec (3.122M / 778.5G) 
15. Saturnian Satellite Titan: 3.5727667268260305440699972133520 µrad = 0.73693603667484382194570809689712 arcsec (5.149M / 1.434T) 
16. Minor Planet Ceres: 2.1340634690465546941919479637938 µrad = 0.44018218796189391383987453951568 arcsec (939.4k / 414G) 
17. Minor Planet Vesta: 1.3693765737543177734686736150136 µrad = 0.28245419366474700741821944755938 arcsec (525.4k / 353.3G) 
18. Minor Planet Pallas: 1.1631259273490422140561661172389 µrad = 0.23991194404562446380404693996124 arcsec (512k / 414G) 

## calculation

The angular diameter (δ) of a sphere is equal to twice the arcsine of the ratio between the object's radius (r) and the distance to the object (D):

δ = 2arcsin(r/D) 

The simplest approximation of the mean distance (D) from an observer in a heliocentric orbit to an astronomical object in the same solar system as the observer is as the orbital semimajor axis (a) of the observed object if the observed object is superior or as the orbital semimajor axis of the observer if the observed object is inferior.  For observers on Terra, the Terran orbital semimajor axis (a🜨) can be approximated as one astronomical unit (lA).  For these calculations, satellites in orbit around the observer should be considered as superior objects and satellites not in orbit around the observer should use the satellite's heliocentric semimajor axis.

• Dsuperioraobject
• Dinferioraobserver

For small angles, the mean angular diameter (δ) can be approximated as the ratio between the observed object's mean diameter (d = 2r) and the observed object's mean distance.  The dimensionless ratio can be expressed in radians (θI) without an arcsine:

δ ≈ (d/a)θI

• `Solar System`
• `Solar System by orbit`
• `Solar System by size`
• `Solar System by mass`