A closeup screenshot of a double shadow transit in 2017.
What’s new under the Sun? There’s certainly no shortage of astronomy apps out there competing for your hard-earned cyber dollar. Increasingly, these pocket planetarium sky programs are also showing up at public star parties, as glowing mobile phones now punctuate the darkness, waving at the night sky.
One great observational tool that has come to our attention recently is JoveMoons Pro. Developed by Yeudy Blanco and TuanisApps and available both for Android and Iphone, this simple yet elegant application displays the current positions of the four major Jovian moons (Io, Europa, Ganymede and Callisto) as well as the orientation of the Great Red Spot.
We recently had a chance to put the App through its paces, and we liked what we saw. The App also simulates the view from different angles in space and time as well, displaying the Jovian system from 2014 up through 2020. This is a wise idea, as things not only get a bit chaotic over time, but the Great Red Spot also tends to drift a bit in terms of longitude. The GRS has been shrinking over recent years, appearing more pale-salmon than red. Still, many planetarium programs fail to incorporate the true rotational position of the GRS, a great added feature in JoveMoons Pro.
A wide view of the JoveMoons simulator app screen interface.
We also put the program through its paces as we edit our upcoming Guide to Astronomy for 2017. We’re always on the hunt for double shadow transit events for Jupiter’s moons, and can happily report that JoveMoons Pro jibes well with other big league programs such as Stellarium and Starry Night Pro. It even displays how the size and shape of each individual moons’ shadow differs.
JoveMoons Pro is not only a handy educational resource, but is a great tool to plan that next observing session of the largest planet in the solar system. One minor quibble: when zoomed in, the app gives the impression of hurdling through space, past the Jovian moons, complete with photo- realistic surface features… this is great, but (there’s always a ‘but’,) this doesn’t really represent the view at the eyepiece, with the moons as tiny unresolved dots. A minor fact, I know, but it’s hard to have a large disk of Jove zoomed in and see just what moon is casting a shadow at the same time.
Triple shadow transits of moons are rarer still, but JoveMoons Pro does indeed see the 2015 event as forcasted by Jean Meeus, another great test. Quadruple transits of Jupiter’s moons aren’t currently possible as seen from our Earthly vantage point in our current epoch… it should, however, be possible to simulate that ‘sweet spot’ vantage point in space to find out just where they can be seen from… plus, it’s just plain fun the see a ‘half quarter Jove,’ a view only witnessed by NASA spacecraft such as Galileo or Juno.
In fact, triple play transits need to involve outermost Callisto, the only moon that can miss on occasion. The innermost Galilean moons are in a 1:2:4 resonance. App developer Yeudy Blanco mentioned that one thing they learned while developing JoveMoons Pro was just how infrequent Callisto shadow transits are.
Be sure to add JoveMoons Pro to your astronomical toolkit of essential apps.