Home > Ephemeris Program, Jupiter > 04/12/2016 – Ephemeris – Can you tell the Jovian moons apart without a program?

04/12/2016 – Ephemeris – Can you tell the Jovian moons apart without a program?

April 12, 2016

Ephemeris for Yuri’s Night, Tuesday, April 12th.  The Sun will rise at 7:02.  It’ll be up for 13 hours and 21 minutes, setting at 8:24.   The Moon, 1 day before first quarter, will set at 2:22 tomorrow morning.

It’s the 55th anniversary of Yuri Gagarin’s flight as first human to orbit the Earth.  Speaking of orbits, we can see Jupiter’s 4 largest moons orbit that planet in small telescopes.  Their orbits are nearly edge on to us, so they seem to move back and forth from one side to the other of the planet in pretty much a straight line.  So how can you tell them apart without a reference?  The four moons from Jupiter in order are Io, Europa, Ganymede, and Callisto.  They are not normally arranged like that.  Ganymede is the brightest and Callisto the dimmest, and is usually the farthest away.  Io is usually the closest appearing and has a slight reddish hue due to its sulfurous volcanic surface, and Europa is the dimmer moon close in to Jupiter.  Io also can be seen to noticeably move in an hour.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


Jupiter's moons

One of my old pictures of Jupiter. Callisto is obvious from its far left position and dimmer brightness. On the right, the farthest is Ganymede due to its brightness and position. Inside of it is Europa, again, dimmer than Ganymede and inside position is probably Europa. That leaves Io, which may be trying to duck behind Jupiter, as a bump in the left edge of the planet.

Jupiter and moons tonight

Jupiter and its moons as simulated by Cartes du Ciel for tonight, 10 p.m. April 12, 2016. The bodies, from let to right are Ganymede, Callisto. a background star, Jupiter, Io, and Europa.

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