ETA CARINAE – NATURE’S OWN HADRON COLLIDER We still do not know one thousandth of one percent of what nature has revealed to us. - Albert Einstein -

ARTIST DRAWING

ETA CARINAE IS ONE OF THE MOST MASSIVE STARS KNOWN. IT IS AROUND 100 SOLAR MASSES. THE UPPER LIMIT OF STAR SIZE IS THOUGHT TO BE AROUND 150 SOLAR MASSES. BECAUSE OF ITS SIZE, AND THE HIGH ENERGIES PRODUCED BECAUSE OF GRAVITY, IT IS UNSTABLE. IN AN EVENT THAT WAS OBSERVED IN 1843, IT SHED MASS EQUIVALENT TO 10 SOLAR MASSES AND WAS THE SECOND BRIGHTEST STAR NEXT TO SIRUS IN THE NIGHT SKY. IT IS CURRENTLY SHEDDING AROUND SOLAR MASSES EACH YEAR. IN CONTRAST, OUR SUN SHEDS ONLY AROUND SOLAR MASSES PER YEAR. AS A RESULT, ETA CARINAE HAS FORMED ITS OWN SURROUNDING NEBULAE. IT IS 5 MILLION TIMES AS BRIGHT AS OUR SUN.

THERE ARE MANY LARGE CLOUDS OF GAS AND DUST IN SPACE CALLED NEBULAE. NEBULAE ARE NURSERYS FOR STAR FORMATION. EVENTS IN SPACE CAN CAUSE AN AREA OF GAS AND DUST TO COMPRESS, SUCH AS A GRAVITY WAVE. IF ONE AREA DEVELOPS MORE MASS THAN SURROUNDING AREAS, THE INCREASE IN GRAVITY CAN CAUSE ADDITIONAL MASS TO COLLECT, AND STAR FORMATION CAN BEGIN.

H-R DIAGRAM FOR CLASSIFICATION OF STARS

MAIN SEQUENCE STARS ARE STARS IN THEIR NORMAL LIFE TIME. INTERACTIVE GUIDE TO STELLAR EVOLUTION INTERACTIVE GUIDE TO STELLAR EVOLUTION – CHANDRA SITE THE TYPE OF FUSION THAT CAN OCCUR IN A STAR DEPENDS ON ITS CORE TEMPERATURE. THE CORE TEMPERATURE, IN TURN, DEPENDS ON ITS MASS. SMALLER STARS ARE ONLY ABLE TO FUSE HYDROGEN TO HELIUM. AS THE MASS INCREASES, FUSION OF HEAVIER ELEMENTS IS ABLE TO OCCUR. THE HEAVIEST ELEMENT THAT CAN BE FORMED IN NORMAL FUSION REACTIONS IN A STAR IS IRON.

ELEMENTS HEAVIER THAN IRON ARE FORMED WHEN LARGE STARS GO SUPERNOVAE. THIS IS BECAUSE OF THE BINDING ENERGY.

MASSES OF MOST STARS LIE WITHIN 0.3 TO 3 SOLAR MASSES. THE LARGEST STAR KNOWN IS R136A1 AT 265 SOLAR MASSES. THE THEORETICAL LOWER LIMIT IS SOLAR MASSES. ANYTHING SMALLER THAN THIS WOULD NOT HAVE ENOUGH GRAVITY TO GENERATE TEMPERATURES NECESSARY FOR HYDROGEN FUSION. THE HIGHER THE MASS, THE MORE GRAVITY, AND THE HIGHER THE INTERIOR TEMPERATURE. TEMPERATURE WILL AFFECT HOW LONG A STAR CAN LIVE AND WHAT FUSION REACTIONS CAN OCCUR, E.G., WHAT ELEMENTS CAN BE FORMED.

A STAR WITH THE MASS OF THE SUN WILL LAST ABOUT 10 BILLION YEARS. AT TWICE THE MASS OF THE SUN ABOUT 3 BILLION YEARS. AT 10 SOLAR MASSES, LIFE WOULD BE MEASURED IN 10’S OF MILLIONS OF YEARS. STARS HAVING FRACTIONS OF THE SUN’S MASS COULD LAST A TRILLION YEARS – LONGER THAN THE CURRENT LIFE OF THE UNIVERSE.

BROWN DWARF STARS ARE INTERMEDIATE BETWEEN PLANETS AND STARS. THEY EMIT A SMALL AMOUNT OF LIGHT – MOSTLY IN THE INFRARED DUE TO A LIMITED AMOUNT OF DEUTERIUM FUSION AND THERMAL ENERGY FROM SLOW GRAVITATIONAL CONTRACTION. THE SIZE LIMIT RANGE IS FROM ABOUT SOLAR MASSES TO SOLAR MASS (ABOUT 13 TIMES THE SIZE OF JUPITER). THE FIRST ONE DISCOVERED WAS IN 1995.

INTERACTIVE GUIDE TO STELLAR EVOLUTION INTERACTIVE GUIDE TO STELLAR EVOLUTION – CHANDRA SITE FOR A STAR THE SIZE OF THE SUN, WHEN ABOUT 10 PERCENT OF THE STAR’S MASS OF HYDROGEN HAS BEEN CONSUMED, ITS STRUCTURE CHANGES. THE INERT HELIUM ACCUMULATES IN THE CORE, AND HYDROGEN FUSION MOVES TO LAYERS OUTSIDE OF THE CORE. THIS HEATS UP THE OUTER LAYERS AND CAUSES THEM TO SWELL OUTWARD. THE STAR BECOMES A RED GIANT. WHEN THIS HAPPENS TO OUR SUN, THE OUTER LAYER WILL BE ABOUT WHERE EARTH’S ORBIT IS NOW. FOR STARS FROM ABOUT HALF TO 3 TIMES THE SIZE OF THE SUN, AS MORE HELIUM IS PRODUCED, THE CORE SHRINKS AND BECOMES HOTTER.

THE CORE TEMPERATURE RISES TO AROUND 120,000,000 o K, AND HELIUM FUSION BEGINS, MAKING ELEMENTS IN THE CNO CYCLE. THIS OCCURS MUCH FASTER THAN THE HYDROGEN BURNING PHASE – ABOUT 1/100 TH OF THE TIME. THE END OF THIS PROCESS WILL BE A SWOLLEN OUTER SHELL WITH DIMENSIONS ABOUT THE SIZE OF THE SOLAR SYSTEM AND A CORE OF CARBON ASH – WHITE DWARF. THIS IS KNOWN AS A PLANETARY NEBULA.

IN MORE MASSIVE STARS, THE FUSION CYCLES CAN CONTINUE TO HEAVIER ELEMENTS AS THE CORE TEMPERATURES REACH EVEN HIGHER VALUES. BEYOND IRON, NO ENERGY IS RELEASED IN THE FUSION REACTION, SO THERE IS NO THERMAL ENERGY TO BALANCE THE GRAVITATIONAL ENERGY. AT THIS POINT, THE STAR WILL COLLAPSE AND EXPERIENCE A SUPERNOVA EXPLOSION. ELEMENTS BEYOND IRON CAN BE PRODUCED IN THE SUPERNOVA EXPLOSION. MUCH GAS AND DUST WILL BE DISPERSED TO FORM A NEBULA. A CENTRAL CORE WILL REMAIN AS EITHER A NEUTRON STAR OR A BLACK HOLE DEPENDING ON THE MASS OF THE STAR.

CRAB NEBULA

CASSIOPEIA A NASA FALSE COLOR IMAGE – IR IN RED, VISIBLE IN YELLOW, AND X-RAY IN GREEN AND BLUE. STAR WENT SUPERNOVA ABOUT 325 YEARS AGO. LOCATED ABOUT 10,000 LIGHT YEARS AWAY.

A TYPICAL NEUTRON STAR WOULD HAVE A MASS OF ABOUT 1.44 TO 2 TIMES THE MASS OF OUR SUN, BUT WITH A DIAMETER OF ABOUT 12 KM. OUR SUN HAS A DIAMETER OF 60,000 TIMES THAT. MUCH BELOW 1.44 SOLAR MASSES AND A WHITE DWARF WOULD BE CREATED. ABOVE 10 SOLAR MASSES, AND A BLACK HOLE WOULD EXIST. WHITE DWARF STARS RADIATE BECAUSE OF STORED THERMAL ENERGY. NO FUSION CAN TAKE PLACE. OVER A VERY LONG PERIOD OF TIME, A WHITE DWARF WILL LOSE THERMAL ENERGY THROUGH RADIATION AND BECOME A BLACK DWARF.

THIS RADIATIVE COOLING WILL TAKE A VERY LONG TIME, LONGER THAN THE AGE OF THE UNIVERSE, SO SCIENTISTS THINK NO BLACK DWARF STARS EXIST.