The Last Newt; and Eclipses on Jupiter (Shallow Thoughts)

The Last Newt; and Eclipses on Jupiter

We went for a "mander meander" up at Montebello this afternoon, curious how late in the season the California Newts hang around the newt pond. A month ago, the pond was full of newts, but today, only one was left. The rest must be migrating to wherever they go in winter. We didn't see any migrators.

Interestingly, the poison oak disappears at the same time as the newts: a month ago the trail was full of poison oak, but today, nearly all of it was gone.

Having nothing to do with newts, my fun project last night concerned an article in New Scientist about a new Hubble photo of a triple shadow transit on Jupiter. (They make it sound like a much more unusual event than it is; amateur astronomers get to see Jupiter double transits pretty much every year, and triple transits every few years, weather permitting, of course.) The article comments that the moons would look to an observer on Jupiter about the same as our moon looks to us, and that these eclipses as viewed from Jupiter would be similar to an earth eclipse.

That seemed unlikely -- that all four Galilean satellites would just coincidentally have the same size as each other and as the sun, just like our moon does from here -- so I wrote a little program to calculate the apparent sizes in arcseconds, and came up with:

       Sun : 6.1
        Io : 35.6
    Europa : 18.0
  Ganymede : 18.1
  Callisto : 9.1

So a Callisto eclipse might be somewhat like an earth eclipse, with Callisto being one and a half the sun's apparent size, but the other moons appear much much larger than the sun. And Io is about the same apparent size in Jupiter's sky as our moon is here (about half a degree).

Tags: nature
[ 21:00 Nov 07, 2004    More nature | permalink to this entry | ]