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!