Four-in-one: Hubble has snapped a remarkabe close-up of four of Saturn's moons all in one go.
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
SYDNEY: In late February NASA's Hubble Space Telescope captured a remarkable close-up image of four of Saturn's moons simultaneously passing in front of the gas giant.
To the top of the image you can see Saturn's largest moon Titan, which appears orange, casting a large shadow onto the planet's northern polar region (this would be visible as an eclipse from Saturn).
Edge-on
Below Titan, to the left, near the plane of Saturn's rings and the equator you can see the tiny white moon Mimas and it's equally small shadow on the cloud tops (difficult to see at this scale, find a larger version of the image here).
Farther to the left, and off Saturn's disk, are the bright moon Dione and the fainter moon Enceladus.
These rare moon transits only happen when the tilt of Saturn's ring plane is nearly 'edge on' as seen from the Earth, said experts at the U.S. Space Science Telescope Institute in Baltimore, Maryland. Saturn's rings will be perfectly edge on to our line of sight on August 10, 2009, and September 4, 2009.
Unfortunately, Saturn will be too close to the Sun (as seen from Earth) to be seen by telescopes here at that time. These ring plane crossings occurs just every 14 to 15 years.
1.25 billion kilometres
Between 1995/96 Hubble witnessed a previous ring plane crossing event, as well as many moon transits, and even helped discover several new moons of Saturn.
Early 2009 was a favourable time for viewers with small telescopes to watch moon and shadow transits crossing the face of Saturn. Titan, Saturn's largest moon, crossed Saturn on four separate occasions, although not all events were visible from all locations on Earth.
These pictures were taken with Hubble's Wide Field Planetary Camera 2 on February 24, 2009, when Saturn was at a distance of roughly 1.25 billion kilometres from Earth. Hubble can see details that are as small as 300 kilometres wide on Saturn.
With the Space Science Telescope Institute.
