David Aguilar (617) 495-7462
Christine Pulliam (617) 495-7463

What's New: How Big do the Planets Appear to Us On Earth?

With some of the planets appearing at their maximum possible sizes as seen from Earth this month, it might be a good time to compare their relative apparent diameters. For comparison, the diameter of Venus, below, is roughly one minute of arc - very close to the best theoretical resolution of the unaided human eye.

Venus, seen here on the first of the month, shows mostly its dark hemisphere facing Earth but unilluminated by the Sun, except for the thin crescent visible here round its edge. (Actually, Venus gets even larger in diameter during its inferior conjunction on January 11, but it is then only a black silhouette with no discernible lighting) (Click image to enlarge*.)

Here's Jupiter, during its opposition evening of January 5. Notice that the planet is flattened and has an equatorial bulge caused by its rapid rotation. (Click image to enlarge*.)

Saturn and its beautiful rings fit comfortably into the width of Jupiter's disk (above), but nevertheless display impressive detail on in both the ring system and the planet's disk itself. (Click image to enlarge*.)

Mars can be a frustrating target, given its tiny diameter. Yet many eyes are on the planet when its times of opposition - or nearest passes to Earth - occur. (Click image to enlarge*.)

Mercury can be small and difficult to see due to its proximity to the Sun; however, as here, it can reveal phases. (Click image to enlarge*.)

Uranus can just barely be made out to be a sphere in a small backyard telescope, but little more detail is visible. (Click image to enlarge*.)

Finally, distant Neptune can reveal its non-stellar aspect through a backyard telescope, but don't expect to see much more than that. (Click image to enlarge*.)


Section Photo