Monday, October 10, 2011

Last Two Jovian Dual-Transits for the 2011 Season

Although it is rather sad, the last two Jovian dual-transits will take place respectively on October 24 and 31, 2011; always a sempiternal treat! Apparently, the Jovian moons are falling back to imperfect resonance (to cause them not to be aligned perfectly), but the orbits are never too imperfect; more than likely, their orbital Saros has ended. It is a misconception to think that only earth's moon has a Saros, but indeed other moons do as well. For eclipsing (or transiting, respectively!) all moons need a Saros pattern, and even though one hasn't been established (that I am aware of), it still follows this Saros.

Figure 1 - The Orbital Resonance of the Jovian moons.

A Jovian dual-transit is a rare and exciting phenomena that occurs when two (or more) of the Jovian moons pass in front of Jupiter, passing together and usually casting shadows. Below is such an example, and below that is a picture of a Jovian triple-transit; quite an event.

May 7, 2011 dual transit provided by the transits page.

March 28, 2004 triple Jovian transit. The fourth black dot is actually a moon itself, casting a shadow.

As we begin to wait for the moons to dual-transit one last time in 2011, let us make known the occurrence of such events. In the Dual-Transits Ephemeris provided by the transits-page, in 2011, eighteen dual transits occur, but twenty dual-shadow-transits occur. This is important to note: the difference between the dual-shadow transit and the plain dual-transit.

Jovian dual-transit - the transit of two or more Jovian moons across the face of Jupiter, usually very long due to the fact of their shadows

Jovian dual-shadow transit - the transit of two or more Jovian moons across the face of Jupiter, with shadows, so the length would be shorter

According to these definitions, if two moons transit, with two shadows transiting as well as moons (Jovian dual-shadow transit) four spots may appear on the planet (Jupiter), though most of the time it's just the shadows that occur. You can read more at the link provided above. More information will be provided in the coming days - ON THIS SITE. Thank you!

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Credit: NASA