>> THE EARTH IS OUR HOME, BUT IT'S JUST ONE OF THE PLANETS IN OUR SOLAR SYSTEM.

WHAT'S OUT THERE?

HOW DO SCIENTISTS LEARN ABOUT THE PLANETS?

AND WHY IS IT IMPORTANT TO FIND OUT?

SCIENTISTS ARE HERE TO ANSWER YOUR QUESTIONS ABOUT THE PLANETS.

STAY TUNED.

"D4K" IS NEXT.

>> THANK YOU FOR JOINING US HERE ON IDAHO PUBLIC TELEVISION AND ON THE WORLDWIDE WEB.

>>> ASTRONOMY IS THE BRANCH OF SCIENCE THAT STUDIES THE SUN, THE MOON, THE STARS, AND THE PLANETS.

WE LIVE ON THE EARTH.

IT'S ONE OF THE PLANETS IN OUR SOLAR SYSTEM.

SOLAR MEANS CONNECTED TO THE SUN.

AND THE SUN IS THE CENTER OF OUR NEIGHBORHOOD.

THE SUN ISN'T A PLANET, IT'S ACTUALLY A STAR.

AND STARS ARE BASICALLY BIG BALLS OF BURNING GAS.

THE CENTER OF THE SURNTION OR ITS CORE, IS LIKE AN ENORMOUS FURNACE, LIKE A BOMB THAT NEVER STOPS EXPLODING.

THE HEAT SPREADS OUT AND WARMS THE REST OF THE SOLAR SYSTEM.

GASES LEAP UP AND BRIGHT BURSTS CALLED SOLAR FLARES.

THERE ARE NINE PLAN NETS OUR SOLAR SYSTEM.

THEY EACH REVOLVE AROUND THE SUN IN WHAT'S CALLED AN ORBIT.

AN ORBIT IS THE PATH A PLANET TAKES AROUND THE SUN.

EVERYTHING IS HELD IN PLACE BY A FORCE CALLED GRAVITY.

GRAVITY IS ALSO WHAT MAKES SOMETHING FALL WHEN IT DROPS HERE ON EARTH.

NOW LET'S LOOK AT OUR NEIGHBORS.

THE PLANET NEAREST TO THE SUN IS MERCURY.

NEAREST DOESN'T MEAN CLOSE.

MERCURY IS ABOUT 36 MILLION MILES FROM THE SUN.

THE NEXT PLANET IS VENUS.

IT'S ABOUT 67 MILLION MILES FROM THE SUN.

VENUS IS ABOUT THE SAME SIZE AS THE EARTH, BUT ITS ATMOSPHERE, OR THE BLANKET OF GAS THESE SURROUND THE PLANET, IS MADE UP OF POISONOUS GASSES, IT'S NOT AT ALL A FRIENDLY PLACE.

IT'S COVERED WITH SIX CLOUDS -- THICK CLOUDS, WHICH REFLECT A LOT OF LIGHT.

THAT'S WHY VENUS IS THE EASIEST PLANET TO SEE IN THE NIGHT SKY.

THE EARTH IS THE THIRD PLANET FROM THE SUN.

93ILLION MILES AWAY, IT'S JUST THE RIGHT DISTANCE FROM THE SUN TO BE WARM ENOUGH AND COOL ENOUGH FOR LIFE.

IT HAS ENOUGH GRAVITY TO HOLD ON TO ITS ATMOSPHERE.

THE EARTH HAS ONE MOON.

MOONS ARE OBJECTS THAT ORBIT A PLANET THE WAY A PLANET ORBITS THE SUN.

THE NEXT PLANET IS MARS.

MARS IS ABOUT HALF THE SIZE OF THE EARTH AND IS ABOUT 141 MILLION MILES AWAY FROM THE SUN.

IT HAS A THIN ATMOSPHERE AND IS KNOWN AS THE RED PLANET.

MARS HAS TWO SMALL MOONS.

A PROBE FIND GIANT FROZEN SEA OF WATER THERE AND SCIENTISTS BELIEVE THERE MIGHT BE SOME KIND OF MICROBES LIVING IN THE SOIL.

THESE FOUR PLANETS, MERCURY, VENUS, EARTH, AND MARS, ARE KNOWN AS THE INNER PLANETS.

NEXT COMES A BIG GAP CALLED THE STEROID BELT.

STEROIDS ARE CHUNKS OF ROCK, SOME AS SMALL AS PEBBLES, SOME AS BIG AS MOUNTAINS, ORBIT THE SUN.

AFTER THIS GAP COMES A FIVE OUTER PLANETS.

JUPITER IS ABOUT 483 MILLION MILES FROM THE SUN.

IT IS HUGE.

THE LARGEST PLANET IN THE SOLAR SYSTEM.

1300 EARTH DOES FIT INSIDE THIS ONE PLANET.

NEXT COMES SATURN.

IT'S 887 MILLION MILES FROM THE SUN AND IS KNOWN FOR ITS RINGS.

THE SEVENTH PLANET IS URANUS, ABOUT 1.8 BILLION MILES FROM THE SUN.

TIPPED OVER ON ITS SIDE.

NEPTUNE IS THE EIGHTH PLANET IN THE SYSTEM, AND POLLUTE 0 IS THE NINTH.

SORT OF.

PLUTO IS NOW CLASSIFIED AS A DWARF PLANET.

BOTH NEPTUNE AND PLUTO ARE SMALLER AND VERY COLD.

ABOUT 11 TIMES COLDER THAN YOUR HOME'S FREEZER.

SO WHAT'S BEYOND OUR SOLAR SYSTEM?

MORE STARS AND MORE PLANETS.

OUR SYSTEM IS PART AFTER BIGGER GALAXY, OR GROUP OF STARS.

WHEN YOU LOOK INTO THE SKY AT NIGHT, JUST THINK WHAT IS OUT THERE TO BE DISCOVERED.

AND JOINING ME NOW TO ANSWER YOUR QUESTIONS ABOUT THE PLANETS ARE TWO SCIENTISTS.

IN OUR MOSCO STUDIO IS JASON BARNS, PROFESSOR OF ASTRO PHYSICS AT THE UNIVERSITY OF IDAHO.

THANK YOU FOR JOINING US.

I APPRECIATE IT.

AND JOININGES HERE IN OUR BOISE STUDIO IS GEORGE BENNETT, A RETIRED NASA SCIENTIST.

AND OF COURSE WE WANT TO HEAR FROM YOU.

CALL US HERE TOLL-FREE AT 1-800-973-9800 OR EMAIL ME AT D4K@IDAHOPTV.ORG.

REMEMBER, WHEN YOU SEND IN A QUESTION OR ANSWER ONE OF OUR QUESTIONS, YOU AND YOUR CLASS WILL HAVE A CHANCE TO WAYNE D.V.D.

PLAYER AND OTHER PRIZES.

THE FIRST QUESTION IS ABOUT PLUTO.

LET ME ASK YOU ABOUT PLUTO.

THIS COMES FROM JESSE IN BLACKFOOT.

HE'D LIKE TO KNOW WHY IS PLUTO NOT A PLANET ANYMORE?

>> WELL, IT TURNS OUT WHEN WE FIRST DISCOVERED PLUTO IN 1930, WE THOUGHT IT WAS A PLANET BECAUSE IT WAS THE BRIGHTEST THING WE FOUND IN THAT ORBIT.

AND IT TURNS OUT IN 1993 WE STARTED FINDING OTHER -- WHAT SEEMED TO BE PLANETS, ABOUT THE SAME TIES AS PLUTO IN SIMILAR ORBITS TO PLUTO.

INSTEAD OF PLUTO BEEGHT ONLY PLAN NET ITS PART OF THE SOLAR SYSTEM, IT TURNS OUT TO BE HUNDREDS OF ICY PLANETS IN A BIG SWARM.

SO LIKE THE STEROID BELT, WHEN THE FIRST STEROID WAS FOUND, IT WAS CALLED A PLANET AS WELL.

BUT THEN AS WE FOUND MORE AND MORE PLANETS THAT WERE IN THE SAME ORBIT OR SIMILAR ORBITS, IT -- WE REALIZED IT WASN'T A FULL PLANET ITSELF, ONLY A MEMBER OF A SWARM OF MINOR PLANETS.

SO NOW WE FIND THE SAME THING IS TRUE FOR PLUTO.

IT'S ONLY THE LARGEST AND BRIGHTEST ELEMENT OF A LARGER SWARM OF WHAT WE CALL CORPORATE BELT OBJECTS.

>> FROM JENNINGS IN MRS.

CAMERON'S CLASS, IN THERE ARE OTHER GALAXIES, ARE THERE OTHER PLANETS THAT SUSTAIN LIFE?

>> THERE MAY VERY WELL BE.

WHAT WE DO KNOW RIGHT NOW IS THAT THERE ARE AT LEAST 300 PLANETS OUTSIDE OF OUR OWN SOLAR SYSTEM.

ASTRONOMERS HAVE DETECTED THESE BY VARIOUS MECHANISMS, PRIMARILY LOOKING AT THE WOBBLE OF THE PARENT SUN.

MOST OF THESE PLANETS ARE WHAT HAVE BEEN DESCRIBED AS SUPER JUPITERS.

THEY'RE MUCH LARGER THAN OUR OWN PLANET JUPITER, AND MANY OF THEM ARE IN WEIRD POSITIONS, VERY CLOSE TO THEIR PARENT STAR.

WE'RE STILL LOOKING FOR EARTH-TYPE PLANETS, AND WITH THE DUST CLOUDS THAT HAVE BEEN SEEN AROUND SOME STARS PLUS THESE PLANETS THAT HAVE BEEN FOUND, THE ODDS ARE PRETTY GOOD THAT WE'RE GOING TO FIND PLANETS THAT ARE LIKE THE EARTH.

AS TO OTHER GALAXIES, THOSE ARE A BIT TOO FAR AWAY FOR US TO REALLY TELL ANYTHING.

BUT THEY'RE AT LEAST 300 EXTRA SOLAR PLANETS THAT HAVE BEEN DISCOVERED.

>> WE'RE HOPING -- >> LET ME ASK YOU, WE'LL HAVE YOU -- TRY AGAIN.

WE'RE HAVING AUDIO PROBLEMS.

>> I'M INVOLVED IN A MISSION WHERE WE'RE GOING TO LAUNCH A TELESCOPE INTO SPACE TO FIND EARTH-SIZED PLANETS FOR THE FIRST TIME.

WE'RE GOING TO LAUNCH NEXT APRIL, AND IT WILL TAKE A COUPLE YEARS TO FIND PLANETS, BUT HOPEFULLY WITHIN A COUPLE YEARS WE'LL BE ABLE TO TELL IF YOU THEY'RE EARTH-SIZE PLANETS AT THE RIGHT DISTANCE FROM THEIR SCARCE TO HAVE -- STARS AND LIQUID WATER.

WE WON'T KNOW JUST YET, THOUGH.

>> LET'S GET TO OUR FIRST CALLER.

ANDREW IN TWIN FALLS.

ARE YOU THERE?

>> Caller: YEAH.

>> WHAT'S YOUR QUESTION?

>> Caller: WHAT COLOR ARE THE PLANETS?

>> WHAT COLOR ARE THE PLANETS?

OK.

>> MERCURY LOOKS A LOT LIKE THE MOON, BASED ON THE IMA LITTLE THAT HAVE BEEN TAKEN BY THE TWO SPACECRAFT THAT HAVE VISITED MERCURY.

MERCURY BEING THE CLOSEST PLANET TO THE SUN.

VENUS, AT LEAST IN SOME OF THE IMAGES THAT CAME BACK FROM SPACECRAFT ACTUALLY HAS A YELLOWISH CAST.

THAT COULD BE AN ARTIFACT OF HOW THEY PROCESSED THE IMAGES, BECAUSE OTHER IMAGES SHOW IT NOT QUITE LOOKING LIKE THAT.

I THINK THEY DID IT TO SHOW THAT IT'S GOT SUR FEAR I CAN ACID IN THE ATMOSPHERE.

OUR OWN PLANET IS A BEAUTIFUL BLUE AND WHITE.

MARS HAS AN ORANGISH RED COLOR.

JUPITER AND SATURN HAVE GOT BANDS, VERY COLORFUL BANDS, AND THEY'RE DIFFERENT COLORS.

SATURN TENDS MORE YELLOW, JUPITER LOOKS GRAY WITH THAT GIANT RED SPOT.

URANUS AND NEPTUNE ARE IN THE BLUISH RANGE.

NEPTUNE IS A BEAUTIFUL BLUE, URANUS IS A GREENISH-BLUE, AND PLUTO, WE'LL FIND OUT WHEN THE NEW HORIZON SPACECRAFT GETS THERE.

IT MAY JUST BE COVERED WITH ICE.

>> CARL WOULD LIKE TO KNOW, HOW IS A PLANET FORMED?

>> PLANETS ARE THOUGHT TO BE FORMED AT THE SAME TIME THAT STARZ STARS ARE FORMED.

OUR SUN WAS FORMED 4.5 BILLION YEARS AGO FROM THE COLLAPSE OF A GIANT CLOUD OF GAS AND DUST.

AND AS THE GAS AND DUST COLLAPSED UNDER ITS OWN GRAVITY, THE PLANETS FORMED OUT OF A DISK, A FLAT PART OF THE FORMATION PROCESS THAT'S ORBITING THE SUN AND IS VERY THIN, AND COMPOSED OF DUST AND ROCKS.

SLOWLY THE DUST AND ROCKS GREW ON TO BIGGER AND BIGGER OBJECTS THAT BECAME ROCKY PLANETS LIKE THE EARTH AND MARS.

>> LET'S GO TO JAMES IN MIDDLETON.

ARE YOU THERE?

>> Caller: YEAH.

>> GO AHEAD.

>> Caller: HOW HOT IS THE SUN?

>> HOW HOT IS THE SUN?

>> I THINK THE TEMPERATURE, AND I SHOULD REFER TO PROFESSOR BARNS, BUT IT'S ON THE ORDER OF 6,000 ON THE SURFACE.

BUT AT THE CENTER IT'S ON THE ORDER OF 15 PERHAPS 20 MILLION DEGREES ON THE METRIC SCALE.

VERY HOT, BUT AT THOSE TEMPERATURES IT ALLOWS THE NUCLEAR FUSION TO OCCUR, WHICH GIVES US THE LIGHT AND THE WARMTH THAT WE NEED.

>> OK.

LET'S GO TO MOLLY.

ARE YOU THERE?

>> Caller: YES.

>> WHERE ARE YOU CALLING FROM?

>> Caller: IDAHO.

>> WHEREABOUTS IN IDAHO?

>> Caller: BOISE.

>> WHAT'S YOUR QUESTION?

>> Caller: WELL, CAN ASTRONAUTS SURVIVE ON THE MOON?

>> CAN ASTRONAUTS SURVIVE ON THE MOON?

>> Caller: YEAH.

>> OK.

>> WITH SPACE SUITS AND HABITATS, THEY CAN.

WE SAW THAT WITH THE APOLLO ASTRONAUTS WHO WENT TO THE MOON BEGINNING IN JULY OF 1969.

IF YOU LOOK AT THE OLD VIDEOS, THEY ALL WORE SPACE SUITS, AND THEY HAD THE LUNAR MODULE WHERE THEY COULD REPAIR AFTER THEY HAD BEEN OUT ON THE SURFACE OF THE MOON.

AS LONG AS YOU TAKE YOUR OWN SPACE SUIT, YOUR OWN AIR AND WATER AND FOOD, YES.

>> BUT WITHOUT THAT -- >> WITHOUT THAT, YOU ARE IN TROUBLE.

>> OK.

LET'S GO TO TIMER FROM MRS.

SCHWEITZER'S CLASS AT RIVERSIDE ELEMENTARY IN BOISE.

WHAT IS A METEOR?

>> A METEOR IS AN STEROID, AND AS STEROIDS ARE FLYING AROUND THE INNER SOLAR SYSTEM, THEY'RE ON CRAZY, RANDOM ORBITS.

SOMETIMES AN STEROID FLIES INTO -- CRASHES INTO EARTH, AND AS IT'S FLYING THROUGH THE ATMOSPHERE IT BURNS UP ON THE WAY THROUGH.

WHEN YOU LOOK UP AND SEE A BIG FLASH OF LIGHT, THAT'S THIS LITTLE STEROID BURNING UP IN EARTH'S ATMOSPHERE, AND THAT'S A METEOR.

>> HOW DID THE PLANETS GET UP INTO SPACE?

>> WELL, AS PROFESSOR RNS POINTED OUT, IT ALL BEGAN WITH A CLOUD OF GAS, PROBABLY LEFT OVER FROM STARS WHICH IT EXPLODED BILLIONS OF YEARS AGO, AND DUE TO RANDOM MOTIONS, PERHAPS TRIGGERED BY OTHER NEARBY STAR EXPLOSIONS, PERHAPS BY ELECTROMAGNETIC AND GRAVITATIONAL EFFECTS, SOME OF THE GAS BEGAN TO COALESCE, AND WE BEGAN TO GET THE TINY PARTICLES THAT EVENTUALLY THROUGH COLLISIONS AND OTHER PROCESSES GREW TO BE THE PLANETS.

AND THAT'S BASICALLY HOW THEY GOT THERE.

WE DON'T REALLY HAVE FRICTION TO SPEAK OF IN SPACE, SO THEY CAN KEEP ORBITING AS LONG AS WE'VE GOT THE CENTRAL SUN.

>> CALLEN LEWISTON.

ARE YOU THERE?

GO AHEAD.

>> Caller: IS PLANET X8 A PLANET OR A MOON?

WHY OR WHY NOT?

>> PLANET X.

>> WE DON'T KNOW ANYTHING ABOUT PLANET X. IN FACT, AT ONE POINT IT WAS THOUGHT THAT PERHAPS THERE WAS ANOTHER ADTIONAL PLANET BEYOND NEPTUNE.

THIS WAS IN THE EARLY -- ABOUT 100 YEARS AGO.

AND SO PEOPLE LOOKED FOR THAT PLANET AND FOUND PLUTO.

AND SO MAYBE -- THERE'S AN IDEA MAYBE THERE ARE ADDITIONAL PLANETS FURTHER OUT IN OUR SOLAR SYSTEM, BUT BY LOOKING AT THE ORBITS OF THE PLANETS WE DO KNOW ABOUT, IF THERE WERE ONE OUT THERE, WE'D BE ABLE TO SEE IT BECAUSE THE MOTION OF THE OTHER PLANETS WOULD CHANGE JUST SLIGHTLY.

IN FACT, THE PLANET NEPTUNE WAS FOUND, WAS PREDICTED, PEOPLE SAW THE ORBIT OF URANUS CHANGE, AND THEY KNEW NEPTUNE WAS THERE BEFORE THEY EVEN SAW IT.

NOW WE DON'T THINK THERE WAS A PLANET X. IT WAS AN IDEA WE THOUGHT MIGHT BE THERE, BUT WE NO LONGER THINK THAT'S TRUE.

>> BEN IN -- MR.

HARVEY'S CLASS WOULD LIKE TO KNOW, WHY IS THERE NO AIR IN OUTER SPACE?

>> WELL, THERE IS ONLY SO MUCH GAS TO GO AROUND, AND THE PLANETS BASICALLY GRABBED THE GASSES THAT WERE IN THE ORIGINAL SOLAR NEBULA.

THAT IS, THE GASSES THAT WEREN'T BLOWN AWAY BY THE SUN WHEN ITS NUCLEAR REACTIONS FINALLY WERE TRIGGERED.

BASICALLY WE ON EARTH PLUS MARS, VENUS, JUPITER, SAN TURN -- THEY'VE ALL GRABBED ALL THOSE GASSES.

>> RACHEL IN MRS.

HUNT'S CLASS AT CYNTHIA MANN ELEMENTARY WOULD LIKE TO KNOW, WHAT IS THE COLDEST PLANET?

>> THE COLDEST PLANET IS -- WOULD BE URANUS OR NEPTUNE.

THEY'RE ABOUT THE SAME TEMPERATURE.

THEY'RE SO FAR OUT, THEY ONLY RECEIVE ABOUT 11,000th OF THE LIGHT WE GET ON EARTH.

SO CRER VERY COLD.

>> LET'S GO TO ZACH LEWISTON.

ARE YOU THERE?

>> Caller: YEAH.

WHEN WAS SATURN DISCOVERED?

>> SATURN IS ONE OF THE PLANETS THAT GO BACK IN HISTORY.

THERE ARE FIVE PLANETS WHICH THE ANCIENTS KNEW ABOUT, MERCURY, VENUS, MARS, JUPITER, AND SATURN, AS WELL AS THEY TALKED ABOUT THE MOON AND THE SUN POSSIBLY ORBITING THE EARTH, THAT WAS THE EARLY CONCEPTION GOING BACK TO THE ANCIENT GREEKS.

BUT SATURN WAS KNOWN TO THE ANCIENTS.

>> MYA FROM MR.

HARVEY'S CLASS WOULD LIKE TO KNOW, HOW CLOSE CAN YOU GET TO THE SUN BEFORE YOU BURN UP?

>> WELL, IT DEPENDS ON WHAT YOU'RE MADE OUT OF.

IF YOU'RE MADE OUT OF WATER, IF YOU HAVE A PLANET MADE OF WATER, YOU CAN'T GET ANY CLOSER TO THE SUN THAN EARTH BEFORE THE WATER BOILS AWAY.

BUT IF YOU'RE MADE OF ROCK OR METAL YOU CAN GET IN MUCH CLOSER, UP CLOSER TO MAYBE 50 TIMES CLOSER TO THE SUN THAN THE EARTH IS, AND YOU COULD STILL SURVIVE.

>> LET'S GO TO TENNYSON.

DWEAD.

-- GO AHEAD.

>> Caller: MY QUESTION IS, WHAT WOULD HAPPEN IF OUR SUN WASN'T A REGULAR STAR AND IT WAS A BLUE STAR?

>> PERHAPS YOU COULD DESCRIBE THE DIFFERENCE BETWEEN A YELLOW SUN AND A BLUE STAR?

>> THAT MAY BE A GOOD ASTROPHYSICS QUESTION.

>> WELL, THERE ARE A LOT OF DIFFERENT COLORS OF STARS.

THE SUN IS IN THE MIDDLE RANGE.

THERE ARE RED STARS THAT ARE VERY SMALL, AND DIM, AND THEN THERE ARE BLUE STARS THAT ARE VERY BIG AND VERY BRIGHT.

SO IF OUR SUN WERE BLUE, FIRST OF ALL IT WOULD BE UP TO A MILLION TIMES BRIGHTER THAN IT IS NOW.

AND FURTHERMORE, THOSE BIG STARS, IT'S SORT OF LIKE THEY -- THEY'RE BURNING SO FAST, THEY ACTUALLY DON'T LIVE VERY LONG.

THOSE STARS ONLY LIVE A THOUSAND TIMES LESS LONG THAN OUR SUN DOES.

SO IF OUR SON WERE A -- SUN WERE A BLUE STAR, WE WOULD NEVER BE HERE.

THE STAR WOULD HAVE BURNED UP AND EXPLODED IN THE TIME THAT IT TOOK THE EARTH TO FORM.

SO THERE NEVER WOULD HAVE BEEN AN EARTH, THERE NEVER WOULD HAVE BEEN WATER OR LIFE.

SO WE'RE ALL THANKFUL THAT OUR SUN IS A YELLOW STAR AND NOT A BLUE STAR.

>> AUDREY AT HAYDEN MEADOWS ELEMENTARY WOULD LIKE TO KNOW, WHY DOES SATURN HAVE RINGS AROUND IT?

IT'S NOT JUST SATURN.

>> WE FOUND RINGS AROUND JUPITER, SATURN, URANUS AND NEPTUNE.

THERE'S EVEN SPECULATION THAT EARTH MAY HAVE EARLY IN ITS HISTORY HAVE HAD A RING.

THE RINGS APPEAR TO BE A COMBINATION OF THINGS, DEBRIS WHICH THE PLANETS HAVE COLLECTED, AND MANY CASES IT MAY SIMPLY BE THE RESULT OF VERY SMALL SATELLITES THAT WERE IN ORBIT AROUND THE PLANET, SUCH AS SATURN, AND THEY COLLIDED AND BROKE APART, AND THEN THE DUST JUST GOT SPREAD OUT AND RINGS AROUND THE PLANET.

SATURN'S GOT ON THE ORDER OF 19 RINGS AROUND.

AND WE HAVE A SPACECRAFT THERE RIGHT NOW WHICH IS LOOKING AT THE RINGS AMONG OTHER THINGS.

>> LET'S GO TO AUDREY LEWISTON.

>> Caller: [INAUDIBLE] I WAS WONDERING HOW FARTHER IS THE SUN -- AND THE MOON AWAY FROM EARTH?

>> THE MOON IS ABOUT 250,000 MILES FROM THE EARTH.

IF YOU WERE TO WALK AROUND THE EARTH, THAT WOULD BE ABOUT 25,000 MILES.

SO IF YOU HAVE TO WALK AROUND THE EARTH 10 TIMES -- THE SUN IS FARTHER AWAY STILL.

THE SUN IS 93 MILLION MILES AWAY.

IT'S ALMOST 400 TIMES FARTHER AWAY THAN THE MOON IS.

>> A QUESTION FROM RYAN, A HOME-SCHOOLER.

HE'D LIKE TO KNOW, WHAT IS AN ORBIT AND HOW DOES AN ORBIT WORK?

>> AN ORBIT DESCRIBES THE PATH THAT, FOR EXAMPLE, A PATH IT TAKES AROUND ITS PARENT STAR.

THE EARTH IS IN AN ORBIT THAT TAKES IT ABOUT 365-PLUS DAYS TO TRAVEL AROUND THE SUN.

YOU CAN THINK OF IT BASICALLY AS A PATH THAT -- AND IT'S A CLOSED LOO IT'S ACTUALLY AN ELLIPSE.

IT'S NOT QUITE CIRCULAR.

AND THE EARTH AND THE SUN CAN BE THOUGHT OF AS ORBITING AROUND THEIR COMMON CENTERS OF MASS.

BUT IT'S JUST BASICALLY THE PATH THAT THE PLANET TAKES AROUND THE SUN.

AND THE MOON HAS AN ORBIT AROUND THE EARTH.

>> WHAT KEEPS EVERYTHING SWIRLING AROUND?

>> IT'S GRAVITY.

WE ALL OWE IT TO SIR ISAAC NEWTON FOR BEGINNING TO EXPLAIN IT, AND ALBERT EINSTEIN FOR UPDATING IT.

IT'S A POLE, IF YOU WILL, THAT ALL BODIES WITH MASS EXERT ON EACH OTHER.

AND THE SUN IS PULLING ON THE EARTH, THE EARTH IS ACTUALLY PULLING BACK ON THE SUN, BUT OUR MASS IS PRETTY SMALL COMPARED TO THE SUN'S.

>> FROM MRS WALKER'S CLASS, DYLAN WOULD LIKE TO KNOW, DOES THE SOLAR SYSTEM END, AND HOW BIG IS IT?

>> THAT'S A VERY GOOD QUESTION.

THAT'S A TOPIC THAT PEOPLE ARE STUDYING RIGHT NOW.

SO THERE'S A STUDENT WHO I GUESS THESE ARE STUDENTS THAT ARE ABOUT 25 YEARS OLD, BUT SHE WAS STUDYING WHERE THE SOLAR SYSTEM ENDS, AND SHE WAS LOOKING FOR OBJECTS LIKE PLUTO THAT ORBIT AROUND FARTHER AWAY.

SO THE END OF OUR SOLAR SYSTEM AS WE KNOW IT IS ABOUT 50 TIMES FARTHER FROM THE SUN THAN THE EARTH ARE.

THERE'S A COUPLE SMALL BITS OF DEBRIS THAT CONTINUE OUT FARTHER, BUT ESSENTIALLY THE END IS A LITTLE BIT BEYOND NEPTUNE AT 50IMES THE DISTANCE FROM THE EARTH TO THE SUN.

>> LET'S GO TO JACK IN MIDDLETON.

JACK?

ARE YOU THERE, JACK?

>> Caller: YEAH.

>> GO AHEAD.

>> Caller: HOW LONG, APPROXIMATELY, WOULD IT TAKE YOU TO TRAVEL AROUND THE SUN?

>> HOW LONG WOULD IT TAKE TO TRAVEL AROUND THE SUN?

I GUESS IF YOU'RE ON THE EARTH?

>> IF WE'RE ON THE EARTH, IT'S 365 AND A FOURTH DAYS TO TRAVEL AROUND THE SUN.

AS PROFESSOR BARNS SAID, IF YOU START GETTING CLOSER, I'M NOT SURE YOU COULD SURVIVE WITHOUT PROTECTION.

PEOPLE HAVE LOOKED AT BUILDING SPACECRAFT THAT COULD ORBIT VERY CLOSE TO THE SUN, AND THEY WOULD HAVE PROTECTIVE SHIELDS, HEAT SHIELDS TO PROTECT THE SCIENTIFIC INSTRUMENTS.

BUT AFTER THAT, IT JUST BECOMES A QUESTION OF HOW CLOSE ARE YOU AND HOW FAST YOU'RE MOVING.

BUT CERTAINLY FOR US 365 DAYS DOES IT.

>> LET'S GO TO JOSHUA.

ARE YOU THERE?

WE MAY HAVE LOST HIM.

THE QUESTION WAS, WHAT PLANET WAS CREATED FIRST?

DO WE KNOW WHAT PLANET WAS CREATED FIRST?

>> GO AHEAD.

>> THAT'S A GREAT QUESTION.

THEY WERE CREATED AT THE SAME TIME.

THIS ISN'T SOMETHING THAT WAS OBVIOUS TO SCIENTISTS BEFORE ABOUT 100 YEARS AGO.

THE WAY WE KNOW HOW LONG AGO IT WAS CREATED IS FROM -- WHEN PEOPLE LANDED ON THE MOON THEY BROUGHT BACK ROCKS, AND BY LOOKING AT THE CHEMISTRY OF THE ROCKS YES ABLE TO FIGURE OUT HOW OLD THEY ARE.

THAT'S HOW WE KNOW THE SOLAR SYSTEM IS 4.5 BILLION YEARS OLD, AND ALL THE PLANETS WERE FORMED AT THAT TIME.

>> LET'S GO TO KEISHA.

>> Caller: HELLO?

>> KEISHA?

>> Caller: YEAH?

>> GO AHEAD.

>> Caller: I WAS CURIOUS WHY, AFTER ALL THESE YEARS, PLUTO ISN'T A PLANET ANYMORE.

>> WE TALKED A LITTLE BIT ABOUT THAT AT THE BEGINNING.

A LOT OF PEOPLE ARE UPSET ABOUT PLUTO GETTING DOWNGRADED TO A DWARF PLANET.

>> PROFESSOR BARNS EXPLAINED THAT, AND THE INTERNATIONAL ASTRONOMICAL UNION, WHICH CONSISTS ABOUT 10,000 ASTRONOMERS, DEBATED THAT, AND AS PROFESSOR BARNS SAID, THE ISSUE THAT CAME UP WAS FINDING OBJECTS BEYOND NEPTUNE, THE TRANSNEPTUNAN OBJECTSES, SOME OF WHICH ARE LARGE OR LOARNLG THAN -- LARGER THAN PLUTO.

WHAT THEY WERE FACED WITH, DO THEY START CALLING THESE OTHER THINGS PLANETS AS WELL, OR JUST CHANGE THE DEFINITION?

AND THAT THAT EXCLUDES PLUTO.

THEY OPTED TO CHANGE THE DEFINITION, SO PLUTO BECOMES A DWARF PLANET.

ONE CAN ARGUE ABOUT THAT.

MY PERSONAL VIEW, FOR HISTORICAL REASONS, LET'S GRANDFATHER IT AND CALL IT A PLANET AND CHANGE EVERYTHING ELSE, BUT THAT'S A PERSONAL VIEW.

>> DO YOU THINK THEY'LL CHANGE THEIR MINDS, THAT THE SCIENTISTS WILL GET TOGETHER AND DECIDE MAYBE IT'S A PLANET AFTER ALL?

>> THAT MAY HAPPEN, BUT I KIND OF HOPE IT DOESN'T HAPPEN.

THERE ARE ALL THESE PLANETS BEYOND PLUTO, AND WE DEMOTED A PLANET BEFORE.

SO I THINK IT'S BETTER TO UNDERSTAND THE SOLAR SYSTEM AS IT IS AND MOVE ON FROM THERE, RATHER THAN GO BACK AND TRY TO RESUSCITATE PLUTO.

>> CHELSEA FROM MRS.

AMBER'S CLASS WOULD LIKE TO KNOW, HOW MANY SOLAR SYSTEMS HAVE BEEN FOUND AND WHAT ARE SOME OF THEIR NAMES?

>> WELL, AS I MENTIONED, THERE ARE ASTRONOMERS THAT FOUND OVER 300 EXTRA SOLAR PLANETS.

WE'RE LOOKING AT POTENTIALLY HUNDREDS OF EXTRA SOLAR SYSTEMS, AND THE NAMES RIGHT NOW ARE BASICALLY BASED ON WHATEVER THE STAR'S NAME HAPPENS TO BE.

THEY USUALLY IDENTIFY THIS SOLAR SYSTEM BASED ON THE NAME OF THE STAR ITSELF.

>> THE NAME OF THE STARS ARE ACTUALLY PRETTY OBSCURE, SO AS DR.

BENNETT SAID, THEY'RE NAMED AFTER THE STARS THEMSELVES, AND THE STARS DON'T HAVE VERY CREATIVE NAMES.

SO MY FAVORITE PLANETS ARE THE PLANETS HD 209458D AND HD 80606B, AND ANOTHER NICE PLANET IS HD 28185V, IN ORBIT JUST SIMILAR TO THE EARTH, EVEN THOUGH IT'S JUPITER SIZE.

SO THESE ARE ALL NAMED AFTER A CATALOG BY A MAN NAMED HENRY DRAPER, THAT'S WHERE THE H.D.

CAME FR.

HE NUMBERED ALL THE STARS UP TO ABOUT A MILLION, SO THAT'S -- THE STARS HAVE -- THE PLANETS HAVE THESE VERY CREATIVE NAMES WITH A NUMBER BETWEEN 1 AND 1,.

>> WE'RE ALMOST OUT OF TIME.

LIBERTY?

GO AHEAD.

ARE YOU THERE?

>> Caller: YEAH.

>> GO AHEAD.

>> Caller: UM, WHAT'S A BLACK HOLE?

>> WHAT'S A BLACK HOLE?

>> IT'S A GRAVITATIONALLY COLLAPSED STAR.

IT WAS SO MASSIVE, IT BEGAN AS A SUPER NOVA AND COLLAPSED ON ITSELF.

THE SPACE, IF YOU WILL, IS SO TINY AND THE MASS IS SO CONCENTRATED, LIGHT CANNOT ESCAPE FM IT, AND THAT'S WHY IT'S REFERRED TO AS A BLACK HOLE.

THE CENTER OF OUR GALAXY MAY HAVE AIANT BLACK HOLE THAT'S STILL FEEDING.

>> WE'RE JUST ABOUT TO RUN OUT OF TIME.

IF YOU'RE ON THE PHONES, STAY ON THE PHONES AND WE'LL TAKE YOUR QUESTIONS WHEN WE RECORD OUR WEB-ONLY PROGRAM.

SO IF YOU'RE ON THE PHONES NOW, GO AHEAD AND STAY ON THE PHONE AND WE'LL GET TO YOU IN JUST A COUPLE OF MINUTES.

I WANT TO GET A QUICK QUESTION TO THE TWO OF YOU.

WHY DID YOU WANT TO STUDY THE STARS?

>> JUST FASCINATING.

I DON'T WANT TO JUST STUDY THEM, I'D LIKE TO FIND A WAY TO GET THE HUMAN RACE OUT THERE.

>> HOW ABOUT YOU?

>> WELL, WHEN I WAS LITTLE MY MOM TAUGHT ME HOW TO COUNT, AND THEN SHE TAUGHT ME THE ALPHABET, AND SHE WAS LOOKING FOR SOMETHING ELSE TO TEACH ME, SO SHE TAUGHT ME THE NAMES OF THE PLANETS.

SO I WAS BRAINWASHED FROM BERTH.

>>IF YOU'RE IN SCHOOL NOW AND WANTS TO BECOME AN ASTRO PHYSIST OR WANTS TO WORK AT NASA, WHAT SHOULD YOU DO?

>> WELL, IT'S A LONG PROCESS.

UNFORTUNATELY THERE'S A LOT OF SCHOOL INVOLVED, SO YOU NEED TO STUDY YOUR SCIENCE AND MATHEMATICS AND GO TO COLLEGE, AND MAJOR IN SOMETHING LIKE PHYSICS OR CHEMISTRY, OR MAYBE BIOLOGY OR SOMETHING LIKE THAT.

>> OK.

>> AND THEN GO TO EVEN MORE SCHOOL.

>> STAY IN SCHOOL.

WE'VE GOT A LOT OF SHOWS NEXT MONTH, WE HAVE OUR FIVE SENSES PROGRAM, IT'S GOING TO BE A WEEK EARLIER THAN OUR USUAL DATE.

SO LOOK FOR THAT ON JANUARY 13th.

OUR CONTEST WINNER LAST MONTH WAS TROY.

SO CHECK OUT THE WEBSITE AND BE SURE EACH WEEK TO CHECK OUT MY BLOG.

AND THANK YOU VERY MUCH, I APPRECIATE YOU BOTH BEING HERE.

CHECK OUT OUR WEBSITE, IDAHOPTV.ORG.

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