Ask A Scientist© Astronomy Archive

Author:      rachael mccullough  and  wildman jackson
In my magazine Natural History, it said that it is possible to see Saturn,
Jupiter, and Mars.  I have seen Venus, and is very easy to spot.  Do you
have any tips on spotting the others without a telescope?  Do you know when
the next blue moon will occur?

Response #:  1 of 3
Author:      hawley
WHERE IS JACK HORKHEIMER WHEN WE NEED HIM?!?!?!
Sorry about that.  Jack does a 5 minute fill spot for amateur astronomers
that is broadcast on many PBS TV stations; he lives for questions like
these.  As for observing the planets, look for bright stars that do not
twinkle, also, Mars is reddish.  (extra-credit:  Why do stars twinkle but
not planets?) 

Response #:  2 of 3
Author:      rcwinther
Check out Astronomy and Sky & Telescope magazines (often available at the
public library) for directions on where to look for the planets month-by--
month.  Mercury is currently in the glare of the Sun, so it cannot be seen
with the naked eye.  It is seldom easy to spot anyway; you usually have to
know just where to look.  
The expression "once in a blue moon" means "very seldom".  It is not a
regular occurrence.  According to Jearl Walker's book "The Flying Circus of
Physics", the Moon can appear bluish when the upper atmosphere contains dust
from a volcanic eruption, or smoke from a forest fire, with particles of a
size that preferentially scatter light from the red end of the spectrum,
leaving the remaining light relatively enriched in blue.  

Response #:  3 of 3
Author:      unterman
The dictionary definition of blue moon is when two full moons occur in a
single solar (secular) calendar month.  This periodically occurs every 4 or
so years.