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CSUSB NSCI 314 - drake equation

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Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Slide 54Slide 55Slide 56Slide 57Slide 58Slide 59Slide 60Slide 61Slide 62Slide 63Slide 64Slide 65Slide 66Slide 67NSCI 314LIFE IN THE COSMOS14 -EXTRASOLAR PLANETS (CONTINUED)AND THE DRAKE EQUATIONDr. Karen KolehmainenDepartment of Physics, CSUSBhttp://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.htmDOPPLER 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 CARDOPPLER 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 DETECTIONStar Moves Toward ObserverLIGHT FROM STAR IS BLUE SHIFTEDUnseen Planet Moves Away From ObserverSTELLAR DOPPLER SHIFT DETECTIONStar Moves Away From ObserverLIGHT FROM STAR IS RED SHIFTEDUnseen Planet Moves Towards ObserverDOPPLER 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 AGAINDOPPLER 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 WAYWHAT 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 MASSRESULTS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 PLANETSMERCURY VENUS EARTH0.5 A.U. 1.0 A.U.MARS1.0 A.U. 2.0 A.U.2.3 A.U.2.5 A.U.2.5 A.U.3.3 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 STAREXPLANATION??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 NEARBYMIGRATING 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 SYSTEMEXTRASOLAR 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 JUPITER-LIKE 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 HIERARCHYSTARS 0.08 TO 20 SOLAR MASSESBROWN DWARFS0.013 TO 0.08 SOLAR MASSES13 - 80 JUPITER MASSESMASSES IN BETWEEN THOSE OF PLANETS AND STARSGAS GIANT PLANETS 0.04(?) - 13 JUPITER MASSESROCKY (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


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CSUSB NSCI 314 - drake equation

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