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June is Saturn Month at Lowell

Image credit: jpl/NASA

One of the more familiar and alluring features of the night sky is now well-positioned to wow observers through a telescope.  While it will remain visible until lost in November’s setting Sun, now is an ideal time to view it because of its relatively close approach to Earth.  The farthest planet easily visible with the unaided eye, this jewel of the solar system has no problem showing off its bling, capturing the imagination of viewers young and old.

For centuries, Saturn has been referred to as the “ringed planet” because of the brilliant bands circling it.  Jupiter, Uranus, and Neptune, which with Saturn comprise the solar system’s four “gas giants,” also have rings, but the tenuous nature and dusty composition of these features obscured their presence until the 1970s-80s.

The discovery of Saturn’s rings, on the other hand, dates back to 1610, when Galileo first observed and documented Saturn through a telescope.  Using a crude, 1 ½ -inch-diameter instrument that magnified only about 20 times, Galileo noted “to my very great amazement Saturn was seen by me to be not a single star, but three together, which almost touch each other.  They are completely immobile and are situated in this manner, the one in the middle rather larger than the lateral ones.”

Galileo figured the two smaller bodies to be satellites orbiting Saturn, but when he revisited Saturn through the telescope two years later, the “satellites” were gone.  Galileo concluded that the features he saw were some sort of arms.  Not until the 1650s did Christian Huygens, using a much better telescope than Galileo’s and one that magnified 50 times, realize that the satellites were, in fact, a system of rings, and that the appearance of these rings changed regularly (Saturn does have moons, with the current count standing at 62).

Spacecraft in the 20th century revealed that what astronomers thought of as a few major rings around Saturn is actually thousands of thin, tenuous ones.  While political satirist Mark Russell supported the hypothesis that the rings “are composed entirely of lost airline luggage,” astronomers know now that water ice is the main ingredient.

Saturn is named after the Roman god of agriculture and is the namesake of Saturday.  Like Jupiter, Saturn is comprised of about 75 per cent hydrogen, 25 per cent helium, and only some traces of other elements.  Its core is solid and perhaps the size of Earth.  The rotation of this core creates a strong magnetic field that, like Earth’s magnetic field, interacts with charged particles emanating from the Sun to create aurorae.

Due to intense heat created in Saturn’s interior, the planet radiates more energy into space than it receives from the Sun, which is about 885 million miles away—over nine times the distance from Earth to the Sun.  Because of this distance, sunlight that takes eight minutes to reach Earth needs another hour and ten minutes to arrive at Saturn. Its greater distance from the Sun also means that one Saturn year equals 29 ½ Earth years (nearly 11,000 Earth days).

Saturn is easily visible as a point of light to the unaided eye; a magnified view through a telescope will reveal its rings, atmospheric features, and several moons.  Saturn will be the featured object to view at Lowell Observatory during June.