[X] My Assistant

[rogelio]

Long time lurker on this site (msnbc.com alerted me to it over a year ago). I check it several times daily; great job Doug; BruceMoomaw, you are the greatest planetary journalist and I agree with you that expensive manned spaceflight should be suspended until we can get our house in order here on earth... But keep sending out those robots!

A bit of personal back story: I got hooked on planetology in 1961 in first grade with my first look at the fuzzy B & W Lowell observatory photos of Mars, Jupiter, and Saturn in the “planets” article in Encyclopedia Brittanica. In a few years I was painting styrofoam balls to look like these planets and viewing them at night, illuminated by flashlight, at the correct scale distances, from several hundred meters away with my miserable, almost useless 3” department store reflector...

I’ve followed the exploration of the solar system closely ever since, although by profession I am a plant taxonomist involved in cataloguing tropical plant diversity...

So, for fun...Here are some less obvious solar system satellite superlatives... (Wikipedia was the source of the raw data used to calculate these numbers)

Satellite with largest apparent angular diameter as seen from surface/cloud tops of planet:
Charon (11250” = 3.12° in diameter) as seen from Pluto.
Io (2145” in diameter) as seen from Jupiter’s cloud tops.

Largest apparent angular diameter as seen from another satellite:
Possibly Prometheus as seen from Pan (12134” = 3.37°), depending on orbital mechanics...
For “classical” (pre-Voyager) satellites:
Ariel as seen from Miranda (3915” =1.08°).
Dione as seen from Tethys (2790”).

Smallest apparent diameter of planet as seen from satellite:
Neptune from S/2002 N1 would appear to be 325” in diameter at apoapsis.

Closest to planet: Phobos (ca. 5950 km from surface of Mars).

Farthest from planet: S/2003 J2: 39,400,000 km at apoapsis.

Fastest satellite: Metis (Jupiter): 114,000 km/hr.

Slowest satellite: S/2005 P1: 450 km/hr.

Most revolutions around planet per planet’s year:
Naiad (Neptune): ca. 203,000 times in Neptune’s 165 year orbital period.

Fewest revolutions around planet per planet’s year:
S/2003 J2: 4.02

Relatively closest to planet: Metis (0.45 planet radii from cloud tops of Jupiter)

Longest period of revolution: S/2002 N1: 2,870 days (7.86 years).

Longest synodic period with respect to the planet’s day length:
Puck (Uranus): 10.1 days.

Longest synodic period with respect to another satellite: This is tough to calculate due to the varying eccentricities and inclinations of the tiny, outer satellites of the gas giants...

and...

Largest solar transit diameter as seen from another planet:
Jupiter transiting the sun from Saturn would appear ca. 45” in diameter moving across a solar disk ca. 200” in diameter, blocking about 5% of the sun’s light. How often does this happen? (the nominal synodic period is about 20 years, of course) The “dimming” of Saturn and its close-in satellites would certainly be noticeable from earth...

[Toma B]

...Largest solar transit diameter as seen from another planet:
Jupiter transiting the sun from Saturn would appear ca. 45” in diameter moving across a solar disk ca. 200” in diameter, blocking about 5% of the sun’s light.  How often does this happen?  (the nominal synodic period is about 20 years, of course)  The “dimming” of Saturn and its close-in satellites would certainly be noticeable from earth...

Nice calculations... I'm not sure it will actually happen any time soon (or at all)...but it would be great to watch from Saturn...
Welcome rogelio!

[alan]

The most interesting case would be a transit of Jupiter from Saturn. Unfortunately, no such transit occurs between about 1625 and 2475, and according to the calculations of Albert Marth in 1886, no such transit will in fact occur for 2000 years in the past and 2000 years in the future.

http://en.wikipedia.org/wiki/Transit_of_Jupiter_from_Neptune