[dramatic percussion music]
- HI, WELCOME TO "NASA LAUNCHPAD."
I'M YOUR HOST, JUSTIN TULLY.
SO WHEN I SAY "KEPLER," WHAT FLASHES IN YOUR MIND?
JOHANNES KEPLER, RIGHT?
GERMAN MATHEMATICIAN, ASTRONOMER, ASTROLOGER,
AND KEY FIGURE
IN THE 17TH-CENTURY SCIENTIFIC REVOLUTION.
HIS LAWS OF PLANETARY MOTION
LED NEWTON TO HIS LAW OF GRAVITATION.
BUT YOU KNEW ALL THAT, RIGHT?
BUT THERE'S A NEW KEPLER IN TOWN.
ACTUALLY, IT'S NAMED AFTER THE OLD KEPLER,
AND ACTUALLY, IT'S NOT IN TOWN ANYMORE
SINCE IT WAS LAUNCHED INTO SPACE ON MARCH 6, 2009.
ANYWAY, IT'S NASA'S NEW KEPLER SPACECRAFT,
AND IT'S NASA'S FIRST MISSION
CAPABLE OF FINDING EARTH-SIZE AND SMALLER PLANETS
AROUND OTHER STARS.
THE KEPLER MISSION WILL BE LOOKING CONTINUOUSLY
AT OVER 100,000 STARS IN ONE REGION OF THE SKY,
IN THE CYGNUS AND LYRA CONSTELLATIONS.
THE FIELD OF VIEW IS EXTREMELY LARGE
FOR AN ASTRONOMICAL TELESCOPE.
MOST TELESCOPES, SUCH AS HUBBLE SPACE TELESCOPE,
ONLY VIEW A SMALL REGION AT ONE TIME.
IT'S ABOUT THE SIZE OF A GRAIN OF SAND HELD AT ARM'S LENGTH.
KEPLER COVERS A MUCH LARGER FIELD,
ABOUT A HAND AT ARM'S LENGTH.
THE FIELD OF VIEW IS OVERHEAD AT MIDNIGHT
IN THE MIDDLE OF SUMMER
FOR THOSE IN THE MID-NORTHERN LATITUDES
AND EARLIER IN THE EVENING IN LATE SUMMER AND FALL.
KEPLER USES THE TRANSIT METHOD
TO DETECT THE EXISTENCE OF A PLANET.
A TRANSIT OCCURS WHEN A PLANET
PASSES IN FRONT OF ITS PARENT STAR
AND BLOCKS A BIT OF STARLIGHT WHILE DOING SO.
WITHIN OUR OWN SOLAR SYSTEM,
WE CAN OBSERVE PLANETARY TRANSITS
OF MERCURY AND VENUS FROM EARTH
WHEN THEY PASS IN FRONT OF THE SUN.
THE PHENOMENON IS MUCH LIKE AN ECLIPSE.
ALTHOUGH THE PLANETS ARE LARGER THAN OUR MOON,
THEY ARE ALSO MUCH FARTHER AWAY,
SO THE TRANSIT JUST LOOKS LIKE A SMALL BLACK DISK
MOVING OVER THE FACE OF THE SUN.
KEPLER WILL OBSERVE THE SAME PHENOMENA
IN ORDER TO DETECT EARTH-SIZE PLANETS
BUT FROM VERY FAR AWAY.
IN FACT, THE DISTANT SUNS THAT KEPLER WILL OBSERVE
ARE SO FAR AWAY THAT THE STARS ARE JUST POINTS OF LIGHT.
DETECTING AN EARTH-SIZE PLANET TRANSITING A DISTANT STAR
IS LIKE OBSERVING A GNAT FLYING IN FRONT OF A CAR'S HEADLIGHT
SEEN FROM MANY MILES AWAY.
THE PROBLEM IS THAT THE ORIENTATIONS
OF PLANET ORBITS IN OTHER SOLAR SYSTEMS
ARE RANDOMLY ALIGNED.
SOME MAY EVEN ORBIT FACE-ON.
ONLY ABOUT 1% OF THE PLANETS ARE ALIGNED
SO THAT THEY CAN BE DETECTED BY THE TRANSIT METHOD.
HENCE, TO DETECT A LARGE NUMBER OF PLANETS,
WE CAN'T JUST LOOK AT A FEW STARS.
HUNDREDS OR EVEN THOUSANDS OF STARS ARE NOT ENOUGH.
WITH KEPLER, THE SCIENTISTS WILL BE OBSERVING
OVER 100,000 STARS AT ONCE TO FIND EARTH-SIZE PLANETS.
KEPLER DOES NOT DIRECTLY OBSERVE THE IMAGE OF A PLANET.
RATHER, IT OBSERVES THE EFFECT THE PLANET HAS
ON ITS PARENT STAR.
IF THE ORBIT OF THE PLANET IS ALIGNED
ALONG KEPLER'S LINE OF SIGHT TO THE STAR,
IT WILL BLOCK A VERY TINY AMOUNT OF LIGHT
COMING FROM THE STAR TO THE KEPLER TELESCOPE.
THE TELESCOPE WILL IMAGE THE LIGHT
FROM MANY STARS AT ONCE.
IT USES 42 CCDs, CHARGE-COUPLED DEVICES,
DETECTORS SIMILAR TO THOSE IN COMMERCIAL DIGITAL CAMERAS.
BUT THESE ARE MUCH LARGER,
HAVING A TOTAL OF 95 MEGAPIXELS.
WITH THE CCDs, KEPLER IS CAPABLE
OF OBSERVING OVER 100,000 STARS ALL AT ONCE
AND MEASURING THEIR BRIGHTNESS TO AN ACCURACY
OF BETTER THAN 1 PART IN 100,000,
OR 10 PARTS PER MILLION.
THIS IS EQUIVALENT TO WATCHING A FOOTBALL GAME
FROM THE CAMERA BLIMP
AND DETECTING EVERY TIME JUST ONE PERSON
WALKS IN OR OUT OF THE STADIUM.
THE RESULTS FROM KEPLER WILL COME
FROM MEASURING THE BRIGHTNESS OF THE STARS.
THE DATA WILL LOOK LIKE AN EKG SHOWING THE HEARTBEAT.
WHENEVER A PLANET PASSES IN FRONT OF ITS PARENT STAR
AS VIEWED FROM OUR SOLAR SYSTEM,
IT PRODUCES A TINY PULSE, OR BEAT.
FROM THE REPEATED BEATS, WE CAN DETECT AND CONFIRM
THE EXISTENCE OF EARTH-SIZE PLANETS
AND LEARN ABOUT THE ORBIT AND SIZE OF THE PLANET.
A HABITABLE PLANET,
ONE THAT CAN HAVE LIQUID WATER ON ITS SURFACE,
MUST BE BETWEEN ABOUT 80% AND 200% THE DIAMETER OF EARTH.
PLANETS THAT ARE SMALLER THAN 8/10 OF AN EARTH DIAMETER
HAVE LESS THAN HALF AN EARTH MASS
AND DO NOT HAVE ENOUGH GRAVITY
TO HOLD ON TO A LIFE-SUSTAINING ATMOSPHERE.
PLANETS THAT ARE MORE THAN TWICE THE DIAMETER OF EARTH
HAVE ABOUT TEN EARTH MASSES
AND ENOUGH GRAVITY TO HOLD ON TO HYDROGEN,
THE MOST ABUNDANT ELEMENT IN THE UNIVERSE.
SUCH LARGE PLANETS TURN INTO GAS GIANTS
LIKE JUPITER AND SATURN.
THE HABITABLE ZONE IS THE DISTANCE FROM A STAR
WHERE ONE CAN HAVE LIQUID WATER ON THE SURFACE OF A PLANET.
IF A PLANET IS TOO CLOSE TO ITS PARENT STAR,
IT WILL BE TOO HOT, AND WATER WOULD HAVE EVAPORATED.
IF A PLANET IS TOO FAR FROM A STAR,
IT'S TOO COLD, AND THE WATER IS FROZEN.
STARS COME IN A WIDE VARIETY
OF SIZES, MASSES, AND TEMPERATURES.
STARS THAT ARE SMALLER, COOLER, AND LOWER MASS THAN THE SUN
HAVE THEIR HABITABLE ZONE
MUCH CLOSER TO THE STAR THAN THE SUN.
STARS THAT ARE LARGER, HOTTER, AND MORE MASSIVE THAN THE SUN
HAVE THEIR HABITABLE ZONE MUCH FARTHER OUT FROM THE STAR.
SO KEEP YOUR EARS AND EYES OPEN FOR NEWS ABOUT KEPLER.
WHO KNOWS?
A FEW YEARS DOWN THE ROAD,
WHEN ALL THAT THOSE LIGHT CURVES ARE PROCESSED,
MAYBE WE'LL HAVE FOUND A FEW PLANETS
THAT ARE SIMILAR TO EARTH.
HOW EXCITING WOULD THAT BE, HUH?
THAT'S IT FOR NOW.
FOR "NASA LAUNCHPAD," I'M JUSTIN TULLY.
WE'LL CATCH YOU NEXT TIME.