ANDROMEDAS FATHER!
JAMES:
WELCOME TO STAR GAZERS.
I'M JAMES ALBURY, DIRECTOR OF THE KIKA SILVA
PLA PLANETARIUM IN GAINESVILLE FLORIDA.
DEAN:
AND I'M DEAN REGAS, ASTRONOMER FROM THE CINCINNATI
OBSERVATORY.
WE'RE HERE TO HELP YOU FIND YOUR WAY AROUND
THE NIGHT SKY.
THIS WEEK, WE'RE GOING TO TALK ABOUT A CONSTELLATION
THATS PART OF AN ANCIENT CELESTIAL STORY.
JAMES:
AND MORE EXCITINGLY, ONE OF IT'S STARS HELPED
ASTRONOMERS DETERMINE THE SIZE AND SHAPE OF
OUR OWN GALAXY AND THE DISTANCES TO NEARBY
GALAXIES.
WONDERING WHAT WERE TALKING ABOUT?
LETS SHOW YOU!
JAMES:
OK, WE HAVE OUR SKIES SET FOR AN HOUR AFTER
SUNSET, ANY NIGHT THIS WEEK, FACING NORTH.
OFF TO THE NORTHEAST YOU'LL SEE THE FAMILIAR
W-SHAPED PATTERN OF CASSIOPEIA THE QUEEN.
THE STARS THAT MARK THIS CONSTELLATION, STARTING
FROM THE TOP DOWN ARE CAPH, SHEDAR, TSIH,
RUCHBAH AND SEGIN.
DEAN:
IF YOU DRAW A STRAIGHT LINE FROM SHEDAR TO
CAPH AND KEEP ON GOING, YOU'LL RUN
SMACK DAB INTO A CONSTELLATION THAT LOOKS
LIKE AN
UPSIDE-DOWN HOUSE.
THIS IS CEPHEUS THE KING.
CEPHEUS WAS THE HUSBAND OF CASSIOPEIA AND
FATHER OF ANDROMEDA.
JAMES:
THE BRIGHTEST STAR IN CEPHEUS IS ALDERAMIN
AND ITS 49 LIGHT YEARS AWAY FROM US.
IT'S BAYER DESIGNATION IS ALPHA CEPHEII, SO
NAMED BY GERMAN ASTRONOMER JOHANN BAYER, WHO
NAMED THE STARS WITH A GREEK LETTER (BASED
ON THEIR BRIGHTNESS) AND THE LATINIZED NAME
OF THE CONSTELLATION.
BEING THE BRIGHTEST STAR IN CEPHEUS, IT WAS
NAMED ALPHA CEPHEII.
DEAN:
ALDERAMIN LIES VERY CLOSE TO A REGION OF THE
NORTHERN SKY CALLED THE PRECESSION CIRCLE.
OVER A PERIOD OF 26,000 YEARS, EARTHS ROTATIONAL
AXIS PASSES THROUGH SEVERAL CONSTELLATIONS,
TRACING A GIANT CIRCLE IN THE SKY.
RIGHT NOW, OUR ROTATIONAL AXIS IS POINTING
TOWARD POLARIS; OUR CURRENT NORTH STAR.
HOWEVER IN 7500 AD, ALDERAMIN WILL BE OUR
NORTH STAR.
JAMES:
TRAVELING COUNTER CLOCKWISE FROM ALDERAMIN,
WE HAVE ALFIRK, ALSO KNOWN AS BETA CEPHEII.
ALFIRK IS A MULTIPLE STAR SYSTEM APPROXIMATELY
690 LIGHT YEARS FROM EARTH.
ALFIRK WILL BE OUR NORTH STAR BETWEEN 5200
AD AND 7500 AD.
DEAN:
THE NEXT STAR IN CEPHEUS IS ERRAI;
ALSO KNOWN AS GAMMA CEPHEII.
ERRAI MARKS THE POINT ON THE ROOF OF THIS
HOUSE-SHAPED CONSTELLATION AND IS A BINARY
STAR SYSTEM APPROXIMATELY 45 LIGHT YEARS AWAY.
ERRAI WILL BECOME OUR NORTH STAR IN LESS THAN
A THOUSAND YEARS,
AND IT WILL RETAIN THE TITLE OF NORTH STAR
FOR OVER 2000 MORE.
IN 5200 AD IT WILL HAVE
TO RELINQUISH THE TITLE TO BOTH ALFIRK AND
THE NEXT STAR IN CEPHEUS, IOTA CEPHEII.
JAMES:
IN 6000 AD, THE EARTHS AXIS WILL POINT SMACK
DAB IN THE MIDDLE - BETWEEN ALFIRK AND IOTA
CEPHEII; AND FOR ALMOST 2000 YEARS,
THEY WILL SEEM TO PERFORM A NIGHTLY WALTZ
AROUND OUR NORTH CELESTIAL POLE.
DEAN:
IOTA CEPHEII IS A SINGLE STAR, APPROXIMATELY
206 LIGHT YEARS AWAY FROM US.
ITS OVER TWICE THE MASS AND OVER 57 TIMES
AS BRIGHT AS OUR SUN.
JAMES:
THE FIFTH STAR IN CEPHEUS IS ZETA CEPHEII;
AN ORANGE SUPERGIANT STAR OVER 830 LIGHT YEARS
AWAY AND OVER
8 TIMES THE MASS OF
OUR SUN.
THE MASS VALUE IS IMPORTANT, BECAUSE ITS VERY
LIKELY, FROM WHAT WE KNOW ABOUT THE PROCESSES
THAT HAPPEN WITHIN A STAR, THAT ZETA CEPHEII
HAS A ENOUGH MASS TO ULTIMATELY
GO SUPERNOVA, PRODUCING A VERY DENSE WHITE
DWARF
AS A RESULT.
DEAN:
THE LAST STAR WE'LL TALK ABOUT IS ONE OF
MY FAVORITES.
IT'S DELTA CEPHEII AND ITS JUST UP AND TO
THE RIGHT OF ZETA.
THIS STAR IS SPECIAL BECAUSE ITS THE PROTOTYPE
FOR A CLASS OF STARS THAT ASTRONOMERS CALL
CEPHEID VARIABLES,
AND ITS BECAUSE OF THIS STAR THAT WE KNOW
THE DISTANCES TO NEARBY GALAXIES.
JAMES:
IN 1784 A YOUNG ENGLISH ASTRONOMER NAMED JOHN
GOODRICKE BEGAN OBSERVING DELTA CEPHEII AND
NOTICED THAT IT VARIED IN BRIGHTNESS AT REGULAR
INTERVALS.
THIS DISCOVERY LAID THE GROUND WORK FOR MEASURING
DISTANCES
IN THE UNIVERSE.
DEAN:
IN 1908, ASTRONOMER HENRIETTA LEVITT WAS STUDYING
THOUSANDS OF VARIABLE STARS IN THE MAGELLANIC
CLOUDS AND SHE NOTICED THAT MANY STARS WERE
FOUND TO HAVE THIS SAME RELATIONSHIP.
JAMES:
ONCE THE PULSATION PERIOD FOR A PARTICULAR
CEPHEID VARIABLE WAS DETERMINED, ASTRONOMERS
COULD GET AN ACCURATE MEASUREMENT OF THE STARS
DISTANCE, BY COMPARING THE STARS KNOWN LUMINOSITY
TO ITS OBSERVED BRIGHTNESS.
DEAN:
THIS RELATIONSHIP WAS SO STRONG THAT IT ALLOWED
ASTRONOMERS TO ESTABLISH THE SIZE AND SHAPE
OF OUR GALAXY.
JAMES:
ISNT ASTRONOMY WONDERFUL?
AND ITS ALL WAITING FOR YOU WHEN YOU
BOTH: KEEP LOOKING UP!