CSUSB NSCI 314 - drake equation (67 pages)

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drake equation



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drake equation

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Pages:
67
School:
California State University, San Bernardino
Course:
Nsci 314 - Life in the Cosmos
Life in the Cosmos Documents
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NSCI 314 LIFE IN THE COSMOS 14 EXTRASOLAR PLANETS CONTINUED AND THE DRAKE EQUATION Dr Karen Kolehmainen Department of Physics CSUSB http physics csusb edu karen METHODS FOR DETECTING EXTRASOLAR PLANETS DIRECT OBSERVATION TRANSITS GRAVITATIONAL LENSING ASTROMETRY DOPPLER EFFECT MOST SUCCESSFUL DOPPLER EFFECT A SHIFT IN THE WAVELENGTH OF A WAVE DUE TO RELATIVE MOTION OF THE SOURCE AND THE OBSERVER IF THE SOURCE AND OBSERVER ARE MOVING TOWARDS EACH OTHER THE WAVELENGTH IS SHORTENED IF THE SOURCE AND OBSERVER ARE MOVING AWAY FROM EACH OTHER THE WAVELENGTH IS LENGTHENED THE FASTER THE RELATIVE MOTION THE MORE THE WAVELENGTH CHANGES SEE DEMONSTRATION JAVA APPLET AT http lectureonline cl msu edu mmp applist doppler d htm DOPPLER EFFECT FOR SOUND WAVES A CHANGE IN WAVELENGTH IS A CHANGE IN PITCH THE SOUND IS HIGHER PITCHED IF THE SOURCE AND OBSERVER ARE MOVING TOWARDS EACH OTHER THE SOUND IS LOWER PITCHED IF THE SOURCE AND OBSERVER ARE MOVING AWAY FROM EACH OTHER EXAMPLE SIREN ON A MOVING CAR DOPPLER EFFECT FOR LIGHT WAVES A CHANGE IN WAVELENGTH IS A CHANGE IN COLOR THE LIGHT IS BLUER IF THE SOURCE AND OBSERVER ARE MOVING TOWARDS EACH OTHER BLUESHIFT THE LIGHT IS REDDER IF THE SOURCE AND OBSERVER ARE MOVING AWAY FROM EACH OTHER REDSHIFT EXAMPLE LIGHT COMING FROM DISTANT GALAXIES IS REDSHIFTED DUE TO THE EXPANSION OF THE UNIVERSE STELLAR DOPPLER SHIFT DETECTION Star Moves Toward Observer Unseen Planet Moves Away From Observer LIGHT FROM STAR IS BLUE SHIFTED STELLAR DOPPLER SHIFT DETECTION Unseen Planet Moves Towards Observer Star Moves Away From Observer LIGHT FROM STAR IS RED SHIFTED DOPPLER EFFECT DETECTION OF PLANETS PLANET AND STAR ORBIT AROUND THEIR COMMON CENTER OF MASS SINCE THE STAR IS MUCH HEAVIER IT MOVES IN A SMALLER CIRCLE OR ELLIPSE THE PLANET IS UNSEEN BUT LIGHT FROM STAR IS ALTERNATELY BLUESHIFTED AND REDSHIFTED DUE TO THE MOTION OF STAR CYCLE REPEATS OVER AND OVER AGAIN DOPPLER EFFECT DETECTION OF PLANETS WORKS ONLY IF ORBIT IS SEEN NEARLY EDGE ON EASIEST TO DETECT IF PLANET IS MORE MASSIVE PLANET CLOSER TO STAR CLOSE TO 300 PLANETS DISCOVERED SINCE 1995 VIA THIS TECHNIQUE OVER 90 OF EXTRASOLAR PLANETS DISCOVERED THIS WAY WHAT CAN WE DETERMINE ORBITAL PERIOD TIME NEEDED FOR ONE ORBIT AVERAGE DISTANCE OF PLANET FROM STAR ECCENTRICITY SHAPE OF ORBIT LOWER LIMIT ON PLANET S MASS RESULTS OVER 300 EXTRASOLAR PLANETS HAVE BEEN DISCOVERED SINCE 1995 MOST USING THE DOPPLER EFFECT TECHNIQUE AT LEAST 20 STARS HAVE BEEN FOUND TO HAVE TWO OR MORE PLANETS MOST PLANET MASSES ARE IN JUPITER RANGE MANY ARE EVEN HEAVIER THE LIGHTEST PLANET FOUND SO FAR IS 4 EARTH MASSES MANY PLANETS ARE VERY CLOSE TO STAR HALF OF ALL DISCOVERED PLANETS ARE CLOSER IN THAN 0 5 AU MANY ARE CLOSER TO THEIR STARS THAN MERCURY IS TO OUR SUN MOST ORBITS ARE VERY ECCENTRIC HIGHLY ELLIPTICAL FAR FROM CIRCULAR DISTRIBUTION OF PLANETS MERCURY VENUS 0 5 A U EARTH 1 0 A U 2 3 A U 2 5 A U 2 5 A U MARS 1 0 A U 3 3 A U 2 0 A U THE PROBLEM IN UNDERSTANDING THIS OUR MODELS OF SOLAR SYSTEM FORMATION PREDICT SMALL ROCKY PLANETS CLOSE TO STAR AND MASSIVE GAS GIANTS FARTHER AWAY 5 AU AS IN OUR SOLAR SYSTEM BUT MANY OBSERVED SOLAR SYSTEMS HAVE MASSIVE PLANETS PROBABLY GAS GIANTS CLOSE TO STAR EXPLANATION OBSERVED MASSIVE PLANETS WERE FORMED FARTHER OUT FROM STAR 5 AU WHERE GAS GIANTS ARE EXPECTED TO FORM AFTER FORMATION THE PLANETS MIGRATED TO NEW ORBITS DUE TO GRAVITATIONAL INTERACTIONS WITH OTHER PLANETS MATERIAL IN THE SOLAR DISK NEAR THE END OF SOLAR SYSTEM FORMATION OTHER STARS PASSING NEARBY MIGRATING PLANETS COMPUTER MODELING INDICATES PLANETS ARE MORE LIKELY TO MIGRATE INWARD THAN OUTWARD NEW ORBIT IS USUALLY HIGHLY ECCENTRIC WHEN A LARGE PLANET MIGRATES SMALLER PLANETS ARE PROBABLY THROWN INTO THE STAR OR OUT OF THE SOLAR SYSTEM BY GRAVITY OF MIGRATING MASSIVE PLANET HENCE THERE ARE PROBABLY NO SUITABLE PLANETS IN THE SYSTEM EXTRASOLAR PLANETS DO MOST SOLAR SYSTEMS HAVE MASSIVE PLANETS GAS GIANTS CLOSE TO THE STAR IF SO PLANETS THAT ARE SUITABLE FOR LIFE MAY BE RARE BUT KEEP IN MIND THAT MASSIVE PLANETS CLOSE TO THEIR STARS ARE EASIEST TO DETECT LARGEST DOPPLER EFFECT THEREFORE OBSERVATIONAL BIAS IS PRESENT OUR SAMPLE OF KNOWN EXTRASOLAR PLANETS IS NOT REPRESENTATIVE OR TYPICAL EXTRASOLAR PLANETS OUR CURRENT TECHNOLOGY CANNOT DETECT EARTH LIKE PLANETS WE ARE JUST BEGINNING TO BE ABLE TO DETECT JUPITER LIKE PLANETS AT JUPITER S DISTANCE FROM THE STAR A FEW SUCH PLANETS HAVE BEEN FOUND SOLAR SYSTEMS THAT CONTAIN JUPITER LIKE PLANETS AT JUPITERLIKE DISTANCES FROM THE STAR ARE MORE LIKELY TO HAVE EARTH TYPE PLANETS CLOSER IN TO THE STAR EXTRASOLAR PLANETS WE HAVE FOUND EXTRASOLAR PLANETS ORBITING ABOUT 10 OF STARS EXAMINED MAYBE THE OTHER 90 OF STARS OR MANY OF THEM AT LEAST MAY HAVE PLANETARY SYSTEMS MORE LIKE OURS WHICH WE CANNOT YET DETECT IMPROVED TECHNOLOGY WILL ANSWER THIS PROBABLY WITHIN THE NEXT DECADE NASA IS PLANNING A TERRESTRIAL PLANET FINDER STELLAR PLANETARY HIERARCHY STARS 0 08 TO 20 SOLAR MASSES BROWN DWARFS 0 013 TO 0 08 SOLAR MASSES 13 80 JUPITER MASSES MASSES IN BETWEEN THOSE OF PLANETS AND STARS GAS GIANT PLANETS 0 04 13 JUPITER MASSES ROCKY TERRESTRIAL PLANETS 0 04 JUPITER MASSES OR 13 EARTH MASSES 1 EARTH MASS 0 003 JUPITER MASSES THE DRAKE EQUATION THIS EQUATION IS USED TO ESTIMATE THE NUMBER OF TECHNOLOGICAL CIVILIZATIONS IN THE MILKY WAY GALAXY WE DEFINE A TECHNOLOGICAL CIVILIZATION AS ONE THAT IS CAPABLE OF AND INTERESTED IN ENGAGING IN INTERSTELLAR COMMUNICATIONS WITH OTHER CIVILIZATIONS NOTE WE ARE ONLY MAKING THIS ESTIMATE FOR OUR GALAXY BUT THE NUMBER SHOULD BE ABOUT THE SAME FOR ANY SIMILAR SPIRAL GALAXY THIS IS THE NUMBER OF CIVILIZATIONS THAT COULD BE SENDING OUT RADIO OR OTHER SIGNALS THAT WE MIGHT BE ABLE TO RECEIVE THE DRAKE EQUATION WHY TRY TO ESTIMATE THE NUMBER OF TECHNOLOGICAL CIVILIZATIONS IF THE ESTIMATED NUMBER IS VERY SMALL SEARCHES FOR SIGNALS FROM ALIEN CIVILIZATIONS MIGHT NOT BE WORTH THE TIME EFFORT AND EXPENSE IF THE ESTIMATED NUMBER IS LARGE SEARCHES ARE MORE LIKELY TO BE SUCCESSFUL THEREFORE IT S EASIER TO ARGUE THAT THE TIME MONEY AND EFFORT ARE WORTH IT KEEP IN MIND THAT WE CAN T MAKE AN EXACT CALCULATION OF THE NUMBER OF CIVILIZATIONS ONLY A VERY ROUGH ESTIMATE OUR ESTIMATE WILL APPLY ONLY TO LIFE THAT IS SIMILAR TO TERRESTRIAL LIFE IF EXOTIC LIFE EXISTS CIVILIZATIONS MAY BE MORE COMMON DRAKE EQUATION N N fs n p fl fi fc fL N Number of civilizations in the MW galaxy capable of communication what we d like to find N Number of stars in the MW galaxy fs fraction of stars


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