>> HELLO AND WELCOME TO A
SPECIAL EPISODE OF NASA SCIENCE
LIVE.
I'M JOY.
I'M GLAD YOU ARE JOINING US TO
TALK ABOUT COMET NEOWISE.
THIS THREE MILE WIDE COMET IS
GOING THROUGH THE NIGHT SCHOOL.
YOU CAN LOOK UP, IF YOU ARE
LUCKY, YOU CAN SEE IT WITH THE
NAKED I'M.
IT WAS AT 4:00 A.M. IN THE
CHESAPEAKE BAY IN MARYLAND.
YOU GET A CHANCE TO SEE IT IN
THE EVENING JUST AFTER SUNSET.
WE HAVE RECEIVED AMAZING IMAGES.
WE'LL FEATURE THEM THROUGHOUT
THE SHOW.
COMET NEOWISE WAS DISCOVER IN
MARCH OF THIS YEAR.
IT'S BEEN PUTTING ON A GRAND
SHOW AT DOWN AND NOW AT DUSK.
IT'S THE FORMATION FROM OUR
SOLAR SYSTEM ABOUT 4 BILLION
YEARS AGO.
THEY HAVE GASSES AND DUST IN A
GLOWING HEAD.
THIS FORMS THE TAIL YOU SEE
STRETCHING ACROSS THE SKY.
TODAY WE HAVE TWO NASA EXPERTS
THEY'RE ANSWER KEY QUESTIONS
ABOUT THIS FASCINATING OBJECT.
PLEASE SEND YOUR QUESTIONS USING
THE #ASKNASA OR WRITE IN THE
COMMENTS.
LET'S GET STARTED.
EMILY IS THE COINVESTIGATOR AND
JAMES IS THE DEPUTY INVESTIGATOR
FROM NASA.
THANK YOU FOR JOINING US.
>> THANKS FOR HAVING US.
>> GREAT TO BE HERE.
>> SO WE ARE ALL EXCITED ABOUT
THE OPPORTUNITY TO SEE COMMENT
NEOWISE IN THE SKY.
I'M CURIOUS, WHAT IS THE
DIFFERENCE BETWEEN A COMET AND
AN ASTEROID?
>> THEY ARE BOTH OBJECTS IN OUR
SOLAR SYSTEM THAT ORBIT THROUGH
THE DIFFERENT AREAS.
THE ASTEROIDS ARE BETWEEN MARS
AND JUPITER AND THE COMETS ARE
IN A WIDER AREA.
ASTEROIDS ARE ROCKY AND COMETS
ARE ICY MUD BALLS, A COMBINATION
OF WATER, ICE, CARBON DIOXIDE
AND DUST AS WELL.
>> HOW WAS COMET NEOWISE FIRST
DISCOVERED?
>> COMET NEOWISE WAS PICKED UP
BY THE SURVEY AT THE END OF
MARCH.
NEOWISE STANDS FOR THIS.
SO THIS COMMENT WAS FIRST PICKED
UP AT THE END OF MARCH AS PART
OF OUR AUTOMATED PROCESSING.
IT GOES THROUGH A SYSTEM THAT
TRIES TO IDENTIFY MOVING
OBJECTS.
SO AS PART OF THAT REVIEW WE
WERE LOOKING AT, THIS LOOKS LIKE
A COMET.
WE CAN SEE A CLEAR, FUZZY CLOUD
AROUND IT.
HERE'S A NEW OBJECT, IT LOOKS TO
BE COMETARY.
IT WAS GOING AROUND THE SUN AND
THERE WAS A CHANCE IT COULD
BECOME VERY BRIGHT.
WE WERE CROSSING OUR FINGERS AND
WE GOT LUCKY THAT IT TURNED OUT
TO BE A SPECTACULAR SIGHT.
>> IT'S REALLY, REALLY STUNNING.
SO WHY IS IT NAMED NEOWISE?
>> SO THIS IS A TRADITION IN
ASTRONOMY THAT GOES BACK
CENTURIES.
THEY ARE NAMED AFTER THEIR
DISCOVERER OR FIRST PERSON WHO
REPORTED IT IN THE JOURNALS OR
LETTERS TO COLLEAGUES.
NOW THAT MOST OF THE DISCOVERIES
ARE DONE BY SURVEYS, THE RULES
ARE IF IT'S FOUND BY THE SURVEY,
IT'S NAMED AFTER THE SURVEY.
SINCE OUR SURVEY IS NEOWISE, THE
COMET IS NEOWISE.
>> IS THERE ANYTHING THAT MAKES
THIS COMMENT UNIQUE?
>> THE FACT WE CAN SEE IT IS
WHAT MAKES IT UNIQUE.
IT'S QUITE RARE FOR A COMET TO
BE BRIGHT ENOUGH THAT WE CAN SEE
IT WITH THE NAKED EYE.
THE LAST TIME WAS BACK IN 1995
TO 1996.
IT'S BEEN QUITE A WHILE.
IT'S EXCITING TO SEE THIS NOW.
>> WHY IS IT THAT WE CAN SEE
COMET NEOWISE NOW?
I UNDERSTAND IT WILL DISAPPEAR
AT THE END OF THE MONTH.
>> SO, WHEN IT CAME BY THE CLOSE
PASS OF THE SUN JULY 3, THAT'S
WHEN IT GETS THE HOTTEST.
THE SUN BAKES OFF THESE ICES
THAT EMILY SPOKE ABOUT AND TURNS
THEM INTO A GAS THAT MAKES THIS
CLOUD.
THAT'S A COMBINATION OF MELTING
GASSES AND DUST.
WHETHER YOU CAN SEE A COMET OR
NOT AND HOW BRIGHT IT APPEAR A
FUNCTION OF GEOMETRY.
IF ALL THE THINGS LINE UP RIGHT,
THEN THE COMET REFLECTS ENOUGH
OF THE SUN'S LIGHT TO SEE IT
WITH THE NAKED EYE.
>> WE HAVE HAD A FEW NASA
SATELLITES THAT HAVE CAPTURED
COMET IMAGES.
WHAT CAN WE LEARN?
>> SATELLITES CAN PROVIDE US
WITH INTERESTING INFORMATION WE
ARE NOT ABLE TO GET FROM THE
GROUND.
FOR EXAMPLE, WITH THE NEOWISE
SPACECRAFT, THE ONE WE USED TO
DISCOVER THE COMET, WE ARE ABLE
TO DETECT CARBON MONOXIDE AND
CARBON DIOXIDE.
WE ARE ABLE TO GET INFORMATION
WE WOULDN'T BE ABLE TO DO
OTHERWISE.
WITH OTHER SPACECRAFT SUCH AS
HUBBLE SPACE TELESCOPE OR SOHO
OR A FEW OTHERS, WE ARE ABLE TO
SEE THE COMET WITHOUT THE
EARTH'S ATMOSPHERE OBSCURING IT
TO GET A MORE DETAILED PICTURE
OF WHAT'S GOING ON.
>> THAT'S INTERESTING.
LET'S ANSWER QUESTIONS FROM
#ASKNASA.
SEND US YOUR QUESTIONS.
SO ONE QUESTION WE HAVE BEEN
GETTING FROM A LOT OF YOU IS HOW
DO I CAPTURE COMET NEOWISE IN
PHOTOS?
NASA SOCIAL MEDIA SPECIALIST
CAPTURED SOME PHOTOS LAST YEAR
AND SHARED A FEW OF HIS TIPS.
>> I'M BILL.
IN MY SPARE TIME I LOVE TO TAKE
PICTURES OF THE NIGHT SKY.
I DO THIS USING A CAMERA MOUNTED
TO A TRI-POD IN MANUAL MODE SO I
CAN LEAVE THE SHUTTER OPEN TO
LET IN LOTS OF LIGHT.
I CAPTURED THESE IMAGES OF COMET
NEOWISE.
I WENT TO A LOCATION FAR FROM
CITY LIGHTS THAT HAD A GOOD VIEW
OF THE NORTHEAST HORIZON.
I COULD SEE THE COMET WITH THE
NAKED EYE.
SO I ZOOMED IN AND EXPOSED EACH
SHOT FOR FOUR SECONDS.
I DID A LITTLE POST PROCESS CAN.
HERE'S AN ORIGINAL PHOTO OUT OF
THE CAMERA.
I WAS ABLE TO BRIGHTEN IT AND
CLEAN UP SOME NOISE.
THE END RESULT WAS HOW IT LOOKED
IN PERSON, WHICH I HAVE TO TELL
YOU IS BEAUTIFUL.
SO I HOPE YOU GET A CHANCE TO
SEE COMET NEOWISE AND ALL OF THE
OTHER WONDERS OF THE NIGHT SKY.
>> SO WE HAVE ANOTHER QUESTION
FROM SOCIAL MEDIA.
TWITTER USER FRAN ASKS WILL THE
COMMENT KEEP MOVING HIGHER AWAY
FROM THE HORIZON EVERY NIGHT?
WILL IT BE OVER MY HEAD AND CAN
I SEE IT ANY TIME AFTER DARK?
>> RIGHT NOW IT'S MOVING FROM
THE MORNING SKY INTO THE EVENING
SKY.
IT WILL BE COMING UP IN THE
EVENING SKY AS THIS NEXT WEEK OR
TWO GO ON.
IT'S GOING TO BE MOVING FURTHER
FROM THE SUN AT THE SAME TIME.
SO THERE IS A CHANCE IT COULD BE
GETTING FAINTER OR IF THERE IS
EXTRA ACTIVITY, IT COULD BE
GETTING BRIGHTER.
WE DON'T KNOW WHAT THE
BRIGHTNESS CHANGE WILL BE OVER
TIME.
IT'S GOING TO BE AFTER A MONTH
GOING TO GET FAINTER RAPIDLY.
IT WON'T BE OVER YOUR HEAD
UNLESS YOU ARE PRETTY FAR NORTH.
>> OKAY.
AND TWITTER USER BOB ASKS NOW
THAT THE COMMENT IS MORE VISIBLE
IN THE EVENING, WILL IT NO
LONGER BE VISIBLE IN THE
MORNING?
>> YES.
AS JOE WAS SAYING, AS THE COMET
MOVES IN THE SOLAR SYSTEM, WE'LL
ONLY BE ABLE TO SEE IT IN THE
EVENING FROM AFTER A FEW DAYS
FROM NOW.
YOU CAN SEE FROM THIS PICTURE
HOW IT WILL MOVE IN THE SKY AS
THE TIME PROGRESSES.
>> FANTASTIC.
TWITTER USER ANDREW ASKS HOW
FAST IS COMET NEOWISE TRAVELING
THROUGH SPACE?
>> AS EMILY MENTIONED, COMETS
FOLLOW THESE ELLIPTICAL ORBITS.
WHEN IT'S FARTHEST FROM THE SUN,
IT'S AT A STAND STILL.
RIGHT NOW IT'S MOVING AT AROUND
40 MILES EVERY SECOND.
TWICE AS FAST AS EARTH'S SPEED
AROUND THE SUN.
AS IT GOES FARTHER FROM THE SUN,
IT WILL SLOW DOWN AS IT CLIMBS
BACK UP.
>> RICKY ASKS WHAT IS COMET
NEOWISE'S TAIL MADE OF?
>> RIGHT.
SO THERE'S USUALLY TWO DIFFERENT
COMET TAILS.
YOU CAN SEE THE BROAD DUST TAIL
WHICH HAS THIS PAIL YELLOW ISSUE
GRAY COLOR AND YOU WILL ALSO SEE
THE ION TAIL WHICH IS MADE OF
IONIZED GASSES.
BOTH OF THESE COME FROM THE
COMET'S NUCLEUS THAT ARE LISTED
OFF AS THE COMET GETS CLOSER TO
THE SUN.
BECAUSE THEY HAVE DIFFERENT
COMPOSITIONS, THEY REACT
DIFFERENTLY TO THE SOLAR
RADIATION PRESSURE, THAT IS TO
SAY THE SUN -- HOW THE SUN
INTERACTS THROUGH THE PARTICLES.
THE TWO DIFFERENT KIND OF
PARTICLES GET SPREAD OUT.
THE OTHER PART OF THE QUESTION
WAS ABOUT HOW MUCH WATER IS IN A
COMET.
THIS COMET IS ABOUT THREE MILES
ACROSS.
AND MOST COMETS ON AVERAGE ARE
ABOUT HALF WATER AND HALF DUST.
TO A QUICK BACK OF THE ENVELOPE
CALCULATION ON AN ACTUAL
ENVELOPE, MY QUICK CAL LOCATION
IS IT'S PROBABLY ABOUT
13 MILLION OLYMPIC SWIMMING
POOLS WORTH OF WATER, SO THAT'S
A LOT OF WATER.
>> THAT IS.
THANK YOU FOR DOING THAT
CALCULATION.
HOW FAST CAN THE COMET BE SEEN
MOVING TO THE HUMAN EYE?
>> YOU CAN'T SEE IT WITH THE
HUMAN EYE, ALTHOUGH YOU MIGHT
NOTICE WITH THE BACKGROUND STARS
AND YOU ARE TAKING IMAGES.
MINUTE TO MINUTE, IT'S NOT
MOVING FAST.
IF YOU TAKE TWO IMAGES NIGHT TO
NIGHT, YOU CAN SEE IT.
YOU CAN'T SEE THAT MOTION EVEN
OVER JUST ONE DAY.
>> SO WE HAVE ANOTHER QUESTION
FROM TWITTER.
WILL I BE ABLE TO SEE IT FROM
THE U.K.?
>> YEAH, YOU SHOULD BE ABLE TO
SEE IT FROM MOST PLACES IN THE
NORTHERN HEMISPHERE AS LONG AS
YOU HAVE A REASONABLY DARK SKY
AND A CLEAR VIEW OF THE
NORTHWESTERN HORIZON.
I KNOW THAT SOME FOLKS IN THE
NORTHERN HEMISPHERE ARE, WE ARE
IN SUMMER, IF YOU ARE
PARTICULARLY FAR NORTH, YOU
DON'T GET A LOT OF DARK TIME.
STILL TRY TO GO FOR IT, YOU NEED
TO SEE IF THAT WOULD WORK.
>> OKAY.
SO WE HAVE ANOTHER QUESTION.
THEY ASK HOW IS NEOWISE FORMED?
>> I WILL TAKE THAT ONE.
SO COMETS WERE FORMED IN THE
EARLY DAYS OF OUR SOLAR SYSTEM,
WHEN EVERYTHING WAS THIS BIG
DISK OF GAS AND DUST, WE DIDN'T
HAVE THE PLANETS OR ANYTHING
FORMED.
WE HAD THE STARS, EARLY SUN IN
THE MIDDLE AND A BIG DISK OF GAS
AND DUST.
THINGS STARTED COLLECTING INTO
WHAT BECAME THE COMETS AND THE
ASTEROIDS AND PLANETS.
THE ASTEROIDS STAYED IN THE
MIDDLE OF THE SOLAR SYSTEM, MOST
OF THE COMETS TEND TO GET FAR
AWAY.
LIKE A COLD STORAGE FOR MOST OF
THE AGE OF THE SOLAR SYSTEM.
THAT'S WHY THEY HAVE THESE ICES
ON BOARD WHICH HELP TO FORM
THESE TAILS YOU SEE LIKE WITH
COMET NEOWISE.
>> THE NUMBER ONE QUESTION WE
ARE GETTING FROM SOCIAL MEDIA IS
CAN I SEE IT FROM MY PART OF THE
WORLD AND CAN YOU EXPLAIN WHERE
COMET NEOWISE IS VISIBLE ACROSS
THE GLOBE?
>> IF YOU ARE IN THE NORTHERN
HEMISPHERE, YOU CAN SEE IT.
AS THE NEXT COUPLE DAYS
PROGRESS, YOU WANT TO LOOK TO
THE NORTHWEST.
YOU CAN SEE WHERE IT WAS WITH
RESPECT TO THE BIG DIPPER.
SO THAT WILL BE MOVING UP AND
THIS IMAGE TO THE LEFT A LITTLE
BIT.
SO GETTING MORE UNDERNEATH THE
BIG DIPPER.
YOU WANT TO GO OUT AROUND THE
TIME THAT THE FIRST STARS START
TO SHOW UP.
YOU ARE NOT GOING TO BE ABLE TO
SEE BEFORE THAT, IT'S ABOUT AS
BRIGHT AS THE STARS IN THE BIG
DIPPER.
FIND OUT WHAT TIME YOUR LOCAL
SUNSET IS, GO OUT ABOUT 45
MINUTES AFTER THAT, WAIT UNTIL
THE FIRST STARS START TO APPEAR.
THAT'S WHEN YOU LOOK.
>> IS IT VISIBLE FROM THE
SOUTHERN HEMISPHERE AT ALL?
>> UNFORTUNATELY, NO, NOT NOW.
>> THAT'S A SHAME.
WHAT IS THE DIAMETER OF COMET
NEOWISE, AND IS IT AN
INTERSTELLAR OBJECT?
>> SO FROM OUR INITIAL DATA WITH
THE NEOWISE SPACECRAFT, WE CAN
MAKE A PRELIMINARY MEASUREMENT.
IT'S ABOUT THREE MILES ACROSS OR
5 KILOMETERS FOR OTHER FOLKS WHO
MIGHT USE THE METRIC SYSTEM.
IT'S NOT AN INTERSTELLAR OBJECT.
BY WATCHING ITS MOTION, WE CAN
SEE THAT IT'S BOUND TO THE SUN'S
GRAVITY.
IT'S COMING IN VERY RAPIDLY AND
THEN IT'S GOING TO GO FAR BACK
OUT AGAIN.
BUT THEN IT SHOULD COME BACK
AGAIN IN ABOUT 6,800 YEARS.
>> FANTASTIC.
TWITTER USER ASKS I WOULD LIKE
TO KNOW IF COMETS HAVE REGULAR
ORBIT, AND I WOULD LIKE TO KNOW
IF THE FORMATION OF COMET TAILS
LEADS TO THE REDUCTION IN THE
MASS.
IS IT REPLENISHED WHEN THE COMET
IS FARTHER AWAY FROM THE SUN?
>> COMETS DO HAVE REGULAR
ORBITS.
THIS IS AN ELLIPTICAL ORBIT.
EACH TIME IT GOES AROUND THE
SUN, IT LOSES SOME OF ITS MASS.
THERE IS NOTHING OUT THERE TO
REPLENISH IT.
ALL THE GASSES AND DUST ARE NO
LONGER THERE.
THEY ARE BEEN BLOWN OUT BY THE
SOLAR WIND OVER THE PAST
BILLIONS OF YEARS.
EACH TIME IT GOES BY, IT WILL
LOSE A LITTLE MORE UNTIL ONE DAY
IT DISSINTY GREATS.
>> HOW LONG DOES THAT PROCESS
TAKE?
>> NO, GO AHEAD.
>> THAT PROCESS, DEPENDS ON THE
COMET.
SOME LOSE MASS QUICKLY.
IF THIS IS THE FIRST TIME IN THE
SOLAR SYSTEM AND NOT MUCH IN THE
WAY AND THERE IS A LOT OF ICE ON
THE SURFACE, IT CAN LOSE THAT
QUICKLY.
AS IT GETS OLDER, THE ICE HAS
BEEN BLOWN OFF AND THE DUST
REMAINS T GETS THIS CRUST THAT
SHIELDS IT.
THEY ARE EXPECTED TO GET WEAKER,
A LITTLE LESS POWERFUL IN TERMS
OF THE AMOUNT OF MATERIAL BEING
SHED OFF.
THEY MIGHT STILL HAVE EYES ON
THE SURFACE, IT'S JUST THAT
THERE IS A THICK LAYER OF RUBBLE
THAT PROTECTS THEM FROM THE HEAT
OF THE SUN.
>> KATE FROM TWITTER ASKS WHY IS
THERE A PUBLIC CONFERENCE
TOMORROW WHERE THE NASA DEFENSE
OFFICES.
WHAT ARE THE POTENTIALS RISKS
FOR OUR PLANET?
>> I WOULD LIKE TO TAKE THIS
ONE.
>> OKAY.
>> THERE IS NO RISK.
THIS IS THREE QUARTERS OF AN
ATRY NO MY CAL UNIT FROM US.
THIS IS VERY FAR AWAY FROM US.
IT'S NOT COMING ANYWHERE NEAR
US.
THE REASON THE COORDINATION
OFFICE IS HAVING A PRESS
CONFERENCE IS BECAUSE NEOWISE IS
UNDER THE UMBRELLA OF THE
PLANETARY DEFENSE OFFICE.
WE FIND ALL KINDS OF THINGS LIKE
COMET NEOWISE.
BECAUSE THIS IS THE OFFICE THAT
IS ALLOWING NEOWISE TO OPERATE
AND GIVING US OUR GUIDANCE, THEY
ARE GOING TO BE TALKING ABOUT
WHAT WE FOUND AND ALL THE COOL
STUFF THAT COMES OUT OF IT.
>> THERE IS ANOTHER QUESTION ON
TWITTER.
ARE THERE ANY CHANCES OF NEOWISE
BECOMING A GREAT COMET AND
TURNING IT EXCEPTIONALLY BRIGHT?
IF YES, WHAT ARE THE CHANCES?
>> SO COMETS ARE NOTORIOUSLY
HARD TO PREDICT IN TERMS OF HOW
GREAT THEY WILL BE.
EVEN FOR COMETS WE HAVE SEEN
BEFORE, THIS IS A CHALLENGE.
BUT FOR COMET NEOWISE, THE FIRST
TIME WE ARE SEEING IT, WE DON'T
KNOW FOR SURE.
BECAUSE IT'S ALREADY PASSED ITS
CLOSEST POINT TO THE SUN, WHERE
IT'S GOTTEN THE MOST HEAT, IT'S
UNLIKELY TO BECOME MUCH BRIGHTER
THAN IT IS.
BUT THEY SURPRISE US.
KEEP A LOOK OUT.
WHO KNOWS, WE MIGHT SEE IT
BECOME A GREAT COMET, BUT IT
MIGHT FADE AWAY.
YOU NEVER KNOW.
>> AND WE ARE ALL IN THIS
TOGETHER RIGHT NOW.
>> IT'S TRUE.
>> Facebook ASKS WHY ARE THERE
TWO OR EVEN THREE TAILS WITH
COMETS?
>> YEAH.
SO AS I EXPLAINED BEFORE, COMET
TAILS ARE MADE UP OF DUST AND
IONS, IONIZED GASSES.
SO THAT BROAD TAIL YOU SEE IS
THE DUST AND IT INTERACTS WITH
THE SUN'S SOLAR WIND DIFFERENT
THAN THE IONIZED GASSES.
THE THIRD TAIL, THE SODIUM TAIL,
YOU HAVE A COMET THAT HAS A LOT
OF DUST AND GAS COME OFF THE
SURFACE.
MOST THE TIME THEY ARE TOO FAR
OR TO FAINT TO SEE THAT THIRD
TAIL.
SO IT'S EXCITING WHEN WE GET A
CHANCE TO SEE THAT THIRD TAIL.
>> WE HAVE A COUPLE OF QUESTIONS
ABOUT WHEN WAS THE LAST TIME
COMET NEOWISE APPEARED OR IS
THIS THE FIRST TIME IT'S VISITED
US?
>> SO, IT'S ORBITAL PERIOD IS
AROUND 6,800, 6,900 YEARS.
THAT WOULD MEAN IT WAS HERE LAST
ABOUT 7,000 YEARS AGO.
AS THE COMET IS OUT, MATERIAL IS
KICKED OFF, THEY ARE LIKE
THRUSTER JETS.
SOMETIMES THEY CHANGE FROM ONE
PASS OF THE SUN TO THE NEXT.
WE CAN SAY IT WAS HERE AROUND
7,000 YEARS AGO.
WE ARE NOT SURE IF IT WAS HERE
FROM MANY MORE PASSES BEFORE
THAT.
OR IF IT HAS CHANGED BECAUSE OF
THE OUT-GASSING OF THE DUST.
>> WHAT IS THE AVERAGE
TEMPERATURE OF A COMET?
>> SO COMETS ARE PRETTY COLD
COMPARED TO WHAT WE HAVE HERE ON
EARTH.
THEY ARE RELATIVELY WARM
COMPARED TO THE BACKGROUND OF
SPACE.
FOR AN EXACT NUMBER, I HAVE TO
PASS IT OVER TO JOE.
I CAN'T DO THESE CALCULATIONS ON
MY HEAD.
>> THE TEMPERATURE IS JUST A
FUNCTION OF HOW FAR IT IS FROM
THE SUN, THAT'S WHERE IT'S
GETTING ITS HEAT FROM.
BECAUSE THIS COMMENT IS PASSING
ABOUT THE SAME DISTANCE FROM THE
SUN IS, IT'S GOING TO HAVE ABOUT
THE SAME TEMPERATURE.
IF YOU WERE STANDING ON THE
SURFACE, PROBABLY CLOSE TO ROOM
TEMPERATURE.
AS IT GOES FURTHER OUT, IT WILL
COOL OFF.
SO IT'S GOING TO GET LIQUID
NITROGEN AND THEN LIQUID HELIUM
TEMPERATURES BEFORE IT GOES OUT.
>> YOU SAID THEY CAN CHANGE
TRAJECTORY.
WHEN THEY CHANGE MASS, DO THEIR
ORBITS CHANGE?
>> YES, ABSOLUTELY, THE ORBITS
CAN CHANGE.
IT DEPENDS ON WHERE THE THRUSTER
IS COMING OUT FROM.
WE THOUGHT OF THEM AS SNOWBALLS
LOSING MASS EVERYWHERE.
FROM THE MISSIONS, WE SAW IT
CAME OUT IN THESE NARROW JETS
FROM CERTAIN PARTS ON THE
COMET'S SURFACE.
THEY CAN EACH CAUSE A PUSH AND
CAN CHANGE HOW IT SPINS OR
CHANGE THE ORBIT AROUND THE SUN.
IT DEPENDS ON WHERE THAT JET IS
AND WHERE IT IS WHEN IT FIRES
OFF.
>> IS THIS COMET DISINTEGRATING
AS SEEN BY SOME OF THE PHOTOS?
>> I TOOK A LOOK AT A FEW OF
THOSE FROM A COUPLE OF DAYS AGO.
WHAT I THINK WE ARE SEEING IN
THOSE IMAGES IS NOT NECESSARILY
THE COMET BREAKING UP, BUT A
JITTER IN THE WAY THE CAMERA IS
SET UP.
IF YOU HAVE A CAMERA THAT'S VERY
STABLE, YOU WILL GET A NICE
CLEAR PICTURE.
IF IT SHAKES A LITTLE, IT WILL
LOOK LIKE THE COMET IS SPLITTING
UP.
THIS IS A COMMON THING THAT
PROFESSIONAL ASTRONOMERS HAVE TO
DEAL WITH.
IF YOU SEE A LITTLE JITTER IN
YOUR OBJECT OR IMAGES, THAT'S
NORMAL.
IT MEANS THAT YOU MIGHT NEED TO
TRY TO SECURE YOUR CAMERA A
LITTLE MORE TIGHTLY BEFORE
TRYING TO TAKE ANOTHER LONG
EXPOSURE.
>> A QUESTION FROM SOCIAL MEDIA.
WHAT DOES THE COLOR OF NEOWISE
GASSES TELL US ABOUT ITS
CHEMICAL MAKEUP?
>> EMILY, YOU CAN TAKE THIS ONE.
>> SURE.
YEAH, SO WE CAN USE SPECTRA TO
HELP US UNDERSTAND THE
COMPOSITION OF COMETS.
BY THE COLOR OF THE LIGHT WE CAN
TELL WHAT IT'S MADE OF WITHOUT
HAVING TO TOUCH IT.
WHAT WE KNOW FROM COMETS IS THAT
GENERALLY THESE ION TAILS ARE
MADE OF HYDROGEN CYANIDE AND A
FEW OTHER WHAT WE CALL
CARBON-BEARING MOLECULES.
HYDROGEN CYANIDE IS ONE OF THE
BIGGEST ONE.
YOU WOULDN'T WANT TO BREATHE IT
IN IF YOU WERE STANDING ON THE
COMET.
>> WE HAVE LEARNED A LOT ABOUT
COMMENT NEOWISE TODAY.
THANK YOU FOR JOINING US.
>> YOU ARE VERY WELL COME.
>> YES, A LOT OF FUN.
>> AND THANK YOU FOR JOINING US
FROM HOME.
IF YOU WITH A TONIGHT LEARN MORE
OR TAKE A CLOSER LOOK AT VIEWING
TIPS, VISIT GO.NASA.GOV.
WE'LL END WITH A VIDEO ABOUT
WHAT YOU NEED TO KNOW ABOUT
NEAR-EARTH OBJECTS AND NASA'S
MISSION TO MONITOR THEM.
UNTIL NEXT TIME, HAPPY SKY
WATCHING.
♪