DEAN: WELCOME TO STAR GAZERS!
I'M DEAN REGAS, ASTRONOMER FROM THE CINCINNATI OBSERVATORY.
JAMES: AND I'M JAMES ALBURY, DIRECTOR OF THE KIKA SILVA PLA PLANETARIUM IN GAINESVILLE,
FLORIDA.
JUPITER IS ABOUT TO LEAVE OUR EVENING SKIES ONCE AGAIN, SO DEAN AND I THOUGHT WE'D SHARE
ONE OF OUR FAVORITE WAYS TO REMEMBER THE ORDER OF JUPITER'S FOUR LARGEST MOONS!
DEAN: THAT'S RIGHT, JAMES.
I HATE TO SAY IT, BUT LET'S GO EAT SOME GREEN CATERPILLARS!
DEAN: JUPITER IS THE LARGEST PLANET IN OUR SOLAR SYSTEM AND IT'S THE FIFTH ONE FROM THE
SUN.
EARTH IS, ON AVERAGE, 93 MILLION MILES AWAY FROM THE SUN, WHEREAS JUPITER'S AVERAGE DISTANCE
IS 484 MILLION MILES.
BUT BECAUSE JUPITER IS A MUCH SLOWER MOVING PLANET THAN OUR EARTH, JUPITER AND EARTH CONSTANTLY
VARY THEIR DISTANCE FROM EACH OTHER.
JAMES: ONCE EACH YEAR, EARTH AND JUPITER LINE UP ON THE SAME SIDE OF THE SUN AND ARE MANY
MILLIONS OF MILES CLOSER TO EACH OTHER.
WHENEVER THIS HAPPENS WE SAY JUPITER IS AT OPPOSITION BECAUSE JUPITER IS OPPOSITE THE
SUN IN THE SKY AS SEEN FROM EARTH.
DEAN: JUPITER WAS AT OPPOSITION BACK ON APRIL 7TH, AND WAS ONLY 400 MILLION MILES AWAY.
WHEN JUPITER IS NEAR OPPOSITION ITS GREAT TO LOOK AT BECAUSE IT'S AT ITS CLOSEST AND
BRIGHTEST.
JAMES: WHEN JUPITER IS AT ITS FARTHEST DISTANCE FROM US AND IS ON THE OTHER SIDE OF THE SUN
AS SEEN FROM EARTH, IT CAN BE AS FAR AS 593 MILLION MILES AWAY.
THAT IS GOING TO HAPPEN LATER AT THE END OF OCTOBER, AND JUPITER WILL BE AT WHAT WE ASTRONOMERS
CALL SUPERIOR CONJUNCTION.
DEAN: THEREFORE, THIS WEEK IS YOUR LAST CHANCE TO VIEW JUPITER BEFORE IT GETS CAUGHT IN THE
GLARE OF THE SUN.
IF YOU GET TO LOOK AT JUPITER THROUGH A TELESCOPE, YOU CAN SEE ITS FOUR LARGEST MOONS.
HERE'S WHERE THE "I EAT GREEN CATERPILLARS" COMES IN.
DEAN: O.K., WE'VE GOT OUR SKIES SET UP FOR JUST AFTER SUNSET ANY NIGHT THIS WEEK FACING
WEST.
JUST ABOVE THE WEST-SOUTHWESTERN HORIZON YOU MAY SEE TWO FAIRLY BRIGHT OBJECTS.
THE LOWER ONE IS THE BLUE GIANT STAR SPICA, THE BRIGHTEST STAR OF VIRGO THE MAIDEN.
THE BRIGHT OBJECT ABOVE IT WILL BE JUPITER.
JAMES: AS YOU LOOK THROUGH YOUR TELESCOPE, YOU'LL ALSO NOTICE SOMETHING THAT ATTRACTED
THE ATTENTION OF GALILEO, THE FIRST PERSON WHO EVER LOOKED AT JUPITER THROUGH A TELESCOPE.
HE SAW FOUR TINY PINPOINTS OF LIGHT, WHICH SEEM TO EXTEND OUT FROM JUPITER'S EQUATOR.
IF YOU OBSERVE JUPITER EACH NIGHT, YOU'LL NOTICE THAT THESE FOUR LIGHTS CONSTANTLY CHANGE
THEIR POSITION FROM NIGHT TO NIGHT.
JAMES: SOMETIMES YOU'LL SEE TWO MOONS LINED UP ON ONE SIDE AND TWO ON THE OTHER.
SOMETIMES YOU'LL SEE THREE AND ONE, SOMETIMES FOUR LINED UP ON ONE SIDE AND SO ON.
THESE ARE JUPITER'S FOUR LARGEST MOONS AND THEY'RE CALLED THE GALILEAN SATELLITES BECAUSE
THEY WERE FIRST DISCOVERED BY GALILEO IN 1610.
DEAN: NOW, ALTHOUGH JUPITER (AS OF TODAY) IS KNOWN TO HAVE 67 MOONS, THESE FOUR MOONS
ARE THE BIGGIES!
AND IN FACT ALL BUT ONE OF THESE FOUR IS LARGER THAN OUR MOON.
THEIR NAMES, IN ORDER, OUTWARD FROM JUPITER, ARE IO, EUROPA, GANYMEDE AND CALLISTO.
EACH OF THESE MOONS HAS UNIQUE CHARACTERISTICS.
FOR EXAMPLE, IO HAS VOLCANOES THAT ERUPT MOLTEN SULFUR AND EUROPA HAS A LIQUID OCEAN OF WATER
BENEATH AN ICY CRUST.
JAMES: GANYMEDE IS THE LARGEST MOON IN THE SOLAR SYSTEM, AND IT'S EVEN LARGER THAN THE
PLANET MERCURY, AND CALLISTO IS ONE OF THE MOST HEAVILY CRATERED OF ALL THE LARGE MOONS
IN OUR SOLAR SYSTEM.
SURPRISINGLY, SOME PEOPLE HAVE A DIFFICULT TIME REMEMBERING THEIR CORRECT ORDER, BUT
A WHILE BACK, JACK HORKHEIMER AND ONE OF THE SHOWS PRODUCERS, BILL DISHONG, SHARED HOW
THEY REMEMBERED THEM.
DEAN: THEY DECIDED TO TAKE THE FIRST LETTER OF EACH MOON'S NAME AND THOUGHT OF A CATCHY
PHRASE THAT THEY WOULD NEVER FORGET.
THEY CAME UP WITH "I" FOR IO,
JAMES: "EAT" FOR EUROPA,
DEAN: "GREEN" FOR GANYMEDE
JAMES: AND "CATERPILLARS" FOR CALLISTO.
YUM!
DEAN: DOING THAT, WE'VE NEVER FORGOTTEN THEIR CORRECT ORDER SINCE.
JAMES: SO JUST REMEMBER "I EAT GREEN CATERPILLARS" AND IMPRESS YOUR FRIENDS!
DEAN: AND CHECK OUT JUPITER ONE LAST TIME IN THE EVENING SKY.
JAMES: IT'S EASY TO DO IF YOU…
BOTH: KEEP LOOKING UP!