[dramatic percussion music]
- HEY, WELCOME TO "NASA LAUNCHPAD."
I'M YOUR HOST, SCOTT BEDNAR.
WE'VE TALKED ABOUT SOME AWESOME NASA RESEARCH
USING TRANSIT METHODS TO STUDY EXOPLANETS,
YOU KNOW, EXOPLANETS,
THE PLANETS THAT ARE OUTSIDE OUR SOLAR SYSTEM.
NASA'S KEPLER MISSION AND THE OBSERVATIONS DONE
BY DR. DEMING AT KITT PEAK NATIONAL OBSERVATORY
ARE BOTH LOOKING AT REALLY FARAWAY WORLDS
TO SEE JUST WHAT THEY CAN LEARN ABOUT THESE PLACES.
BUT THE USE OF THE TRANSIT METHOD
DOESN'T JUST SERVE SCIENTISTS LOOKING SO FAR AWAY FROM HOME.
IN FACT, OUR CLOSEST PLANETARY NEIGHBOR, VENUS,
COMPLETES TRANSITS ACROSS OUR SUN.
FOR MORE INFORMATION ON THESE VENUS TRANSITS,
LET'S CHECK IN WITH DR. JANET LUHMANN,
A SCIENTIST AT THE UNIVERSITY OF CALIFORNIA
SPACE SCIENCES LAB.
- A VENUS TRANSIT OCCURS
WHEN VENUS CROSSES THE DISK OF THE SUN
AS SEEN BY AN OBSERVER.
IT'S LIKE A SOLAR ECLIPSE
IN THAT VENUS IS LOCATED ON THE LINE
BETWEEN THE SUN AND THE EARTH
AND THEREFORE BLOCKS SOME OF THE SUN'S LIGHT.
HOWEVER, IN A VENUS TRANSIT,
THE AMOUNT OF SUNLIGHT BLOCKED IS VERY SMALL
COMPARED TO A SOLAR ECLIPSE,
AND SO THE OBSERVER WHO IS UNAWARE WILL NEVER NOTICE IT.
VENUS' CIRCULAR SHADOW IS MUCH, MUCH SMALLER
THAN OUR MOON'S SHADOW.
EVEN THOUGH VENUS IS NEARLY THE SIZE OF THE EARTH,
IT IS MUCH FARTHER AWAY THAN THE MOON.
IN CLEAR WEATHER, VENUS TRANSITS ARE VISIBLE WITH THE NAKED EYE
OR WITH A SMALL TELESCOPE,
WHICH IS WHY THEY BECAME POPULAR IN THE 1600s.
- SO UNLIKE THE TRANSITS OBSERVED BY THE KEPLER MISSION
OR BY OBSERVERS USING HUGE ASTRONOMICAL TELESCOPES,
THE VENUS TRANSIT IS ONE
THAT YOU CAN ACTUALLY SEE FOR YOURSELF.
NOW, REMEMBER, YOU SHOULD NEVER LOOK AT THE SUN DIRECTLY.
SO IN ORDER TO OBSERVE THE VENUS TRANSIT,
YOU NEED TO USE A SAFE VIEWING TECHNIQUE
EITHER WITH PROTECTION, SOLAR FILTERS, OR PROJECTORS.
FOR MORE INFORMATION ON THESE SAFE VIEWING TECHNIQUES,
GO TO NASA'S SUN-EARTH DAY WEBSITE AT SUNEARTHDAY.NASA.GOV.
THE MOST RECENT VENUS TRANSIT
ACTUALLY TOOK PLACE ON JUNE 8, 2004.
AND AT THAT TIME,
RESEARCHERS WERE ABLE TO GATHER A LOT OF INFORMATION.
FOR STARTERS, THEY WERE ABLE TO VERIFY THE DISTANCE IN AU,
OR ASTRONOMICAL UNITS,
WITH GLOBALLY ORGANIZED EFFORTS
AND 21ST-CENTURY TECHNOLOGY LOOKING AT PARALLAX.
WHAT'S PARALLAX?
WELL, LET'S HEAR FROM DR. STEN ODENWALD,
NASA ASTRONOMER AT NASA GODDARD SPACE FLIGHT CENTER.
- THE ANSWER IS THAT ASTRONOMERS
USED A GEOMETRIC TECHNIQUE CALLED PARALLAX
TO DETERMINE THE DISTANCE BETWEEN THE EARTH AND THE SUN.
PARALLAX IS THE APPARENT CHANGE IN POSITION OF AN OBJECT
WHEN YOU LOOK AT IT FROM TWO DIFFERENT STATIONS
OR POINTS OF VIEW.
IT SOUNDS MYSTERIOUS,
BUT YOU USE THIS TECHNIQUE ALL THE TIME.
FOR EXAMPLE,
LET ME SHOW YOU HOW PARALLAX WORKS BY USING MY THUMB
AND THAT ROCKET IN THE BACKGROUND.
FIRST, HOLD YOUR THUMB OUT AT ARM'S LENGTH.
NOW LOOK AT YOUR THUMB WITH YOUR LEFT EYE OPEN
AND YOUR RIGHT EYE CLOSED.
WHAT DO YOU NOTICE ABOUT THE POSITION OF YOUR THUMB?
THERE SEEMS TO BE AN APPARENT CHANGE IN POSITION OF YOUR THUMB
FROM TWO POINTS OF VIEW,
YOUR LEFT EYE AND YOUR RIGHT EYE.
YOUR BRAIN USES THIS INFORMATION
TO FIGURE OUT HOW FAR AWAY THINGS ARE FROM YOU.
BY OBSERVING THE APPARENT SHIFTING POSITION OF VENUS
AGAINST THE BACKGROUND OF THE SOLAR DISK
AS SEEN FROM TWO DIFFERENT PLACES ON EARTH,
ASTRONOMERS WERE ABLE TO USE THIS PARALLAX SHIFT
TO DETERMINE THE DISTANCE FROM THE EARTH TO THE SUN.
- BUT THAT'S NOT ALL.
ASIDE FROM EARTH-BASED OBSERVATIONS,
THE TRACE SATELLITE WAS ABLE TO OBSERVE THE VENUS TRANSIT,
AND IT CAPTURED AMAZING IMAGES AND VIDEOS
OF THAT JUNE 2004 TRANSIT.
TAKE A LOOK AT A FEW OF THESE.
WAIT A MINUTE. THAT LAST ONE'S NOT VENUS.
IT'S ACTUALLY THE TRANSIT OF MERCURY
ACROSS THE SUN IN 2003.
THAT'S RIGHT.
MERCURY TRANSITS ACROSS THE SUN JUST LIKE VENUS.
BUT MERCURY TRANSITS MUCH MORE OFTEN,
IN PART BECAUSE MERCURY IS CLOSER TO THE SUN
AND IT ORBITS IT MORE RAPIDLY.
WHILE TRANSITS OF MERCURY HAPPEN ABOUT 13 OR 14 TIMES A CENTURY,
A TRANSIT OF VENUS ONLY HAPPENS FOUR TIMES EVERY 243 YEARS.
AND RESEARCHERS CAN PREDICT ALL OF THESE EVENTS
BECAUSE PLANETS MOVE IN VIRTUALLY FIXED ORBITS,
SO THE PATTERNS OF THE ORBITS CAN BE MAPPED.
IT'S SORT OF LIKE WATCHING THE TURN SIGNALS ON TWO CARS
SITTING AT A STOPLIGHT.
THE BLINK TIMING FOR EACH VEHICLE IS DIFFERENT,
AND THEY PROBABLY STARTED AT DIFFERENT TIMES.
BUT USUALLY, THE PATTERN WILL LINE UP FOR ONE PERFECT BLINK
AND THEN OFF AGAIN.
SIMILAR IDEA.
AND IN FACT, THE TRANSITS OF MERCURY AND VENUS
DO LINE UP SO THEY TAKE PLACE AT THE SAME TIME.
THE NEXT TIME THAT WILL HAPPEN?
TRY JULY 26TH OF THE YEAR 69,163.
SO I THINK YOU'RE KIND OF OUT OF LUCK FOR SEEING THAT ONE.
BUT YOU DON'T HAVE TO WAIT THAT LONG
TO CATCH A SINGLE TRANSIT.
THE NEXT VENUS TRANSIT
WILL TAKE PLACE ON JUNE 5TH AND 6TH OF 2012,
SO YOU SHOULD BE ABLE TO CATCH A GLIMPSE FOR YOURSELF.
MAKE SURE YOU DON'T MISS IT, THOUGH,
BECAUSE THE NEXT ONE WON'T BE AROUND
TILL DECEMBER OF 2117.
I GUESS WE'LL HAVE TO LEAVE THAT ONE
FOR THE NEXT GENERATION OR TWO OF NASA SCIENTISTS.
AND MARK YOUR CALENDARS NOW.
THE NEXT TRANSIT OF MERCURY WILL TAKE PLACE MAY 8, 2016.
WELL, THAT'S IT FOR NOW.
UNTIL NEXT TIME, I AM SCOTT BEDNAR,
AND THANK YOU FOR WATCHING "NASA LAUNCHPAD."
TAKE IT EASY.