Distances to nearby stars are determined by parallax. This is similar to triangulation techniques used by surveyors but uses the Earth's revolution to create a baseline of up to <1>. The parallax of a nearby star is then measured relative to distant stars which would not appear to move on a series of CCD frames taken over many years. The distance to a star in parsecs is inversely proportional to the parallax angle in arcseconds. Thus, a star with a parallax angle of $par" must be at a distance of <2> parsecs. Hipparcos has measured the parallax for most of the stars within <3> parsecs -- about 1 million stars.
Astronomers also make use of pulsating variable stars to determine distances. These are stars that function as <4> because astronomers have some method of determining their absolute magnitude. RR Lyraes all have absolute magnitudes of MV = <5>. Thus, astronomers can observe the apparent magnitude mV and then use the distance modulus to determine the distance. Cepheid variables stars function in a similar manner in that they obey a(n) <6> relationship. One can simply observe the pulsational period of the star and look up the corresponding absolute magnitude. The apparent magnitude is once again observed and the distance modulus applied.
Spectroscopic pararallax is also used to determine the distances to stars. It uses the spectral features of a star to determine its location on the HR Diagram so that its MV can be read off. One can determine the spectral classification of a star by noting the <7> of absorption lines in its spectrum. The luminosity class of the star can also be determined by noting the <8> of absorption lines in its spectrum. For example, a $star star would be luminosity class <9>. The intersection of the spectral type and luminosity class uniquely determines a location on the HR Diagram and MV can be determined. The distance modulus can then be used once again to get the distance.
@ qu.1.1.blank.1=2 AU,1 AU,3 AU,4 AU@ qu.1.1.blank.2=$paranswer,$badchoice1,$badchoice2,$badchoice3@ qu.1.1.blank.3=500,100,250,1000@ qu.1.1.blank.4=standard candles,signposts,golden arches,calibrators@ qu.1.1.blank.5=0.5,1.0,1.5,2.0,0.0@ qu.1.1.blank.6=period-luminosity,calibrated-distance,magnitude-normal,average-magnitude@ qu.1.1.blank.7=types,thicknesses,wavelengths,frequencies,doppler shifts@ qu.1.1.blank.8=thicknesses,types,wavelengths,frequencies,doppler shifts@ qu.1.1.blank.9=$answerclass,$badclass,III@ qu.1.1.algorithm= $num = rint(4); $par=switch($num,"0.5","0.25","0.2","0.1"); $paranswer=switch($num,"2","4","5","10"); $badchoice1=switch($num,"4","5","10","2"); $badchoice2=switch($num,"5","10","2","4"); $badchoice3=switch($num,"10","2","4","5"); $num2=rint(2); $star=switch($num2,"main sequence","supergiant"); $answerclass=switch($num2,"V","I"); $badclass=switch($num2,"I","V"); @ qu.1.1.grader.1=menu@ qu.1.1.grader.2=menu@ qu.1.1.grader.3=menu@ qu.1.1.grader.4=menu@ qu.1.1.grader.5=menu@ qu.1.1.grader.6=menu@ qu.1.1.grader.7=menu@ qu.1.1.grader.8=menu@ qu.1.1.grader.9=menu@ qu.1.2.mode=Blanks@ qu.1.2.editing=useHTML@ qu.1.2.name=Stellar Parameters4 - Distances@ qu.1.2.question=Distances to nearby stars are determined by parallax. This is similar to triangulation techniques used by surveyors but uses the Earth's revolution to create a baseline of up to <1>. The parallax of a nearby star is then measured relative to distant stars which would not appear to move on a series of CCD frames taken over many years. The distance to a star in parsecs is inversely proportional to the parallax angle in arcseconds. Thus, a star with a parallax angle of $par" must be at a distance of <2> parsecs. Hipparcos has measured the parallax for most of the stars within <3> parsecs -- about 1 million stars.
Astronomers also make use of pulsating variable stars to determine distances. These are stars that function as <4> because astronomers have some method of determining their absolute magnitude. RR Lyraes all have absolute magnitudes of MV = <5>. Thus, astronomers can observe the apparent magnitude mV and then use the distance modulus to determine the distance. Cepheid variables stars function in a similar manner in that they obey a(n) <6> relationship. One can simply observe the pulsational period of the star and look up the corresponding absolute magnitude. The apparent magnitude is once again observed and the distance modulus applied.
Spectroscopic pararallax is also used to determine the distances to stars. It uses the spectral features of a star to determine its location on the HR Diagram so that its MV can be read off. The luminosity class of the star can be determined by noting the <7> of absorption lines in its spectrum. For example, a $star star would be luminosity class <8>. One can also determine the spectral classification of a star by noting the <9> of absorption lines in its spectrum. The intersection of the luminosity class and spectral type uniquely determines a location on the HR Diagram and MV can be determined. The distance modulus can then be used once again to get the distance.
@ qu.1.2.blank.1=2 AU,1 AU,3 AU,4 AU@ qu.1.2.blank.2=$paranswer,$badchoice1,$badchoice2,$badchoice3@ qu.1.2.blank.3=500,100,250,1000@ qu.1.2.blank.4=standard candles,signposts,golden arches,calibrators@ qu.1.2.blank.5=0.5,1.0,1.5,2.0,0.0@ qu.1.2.blank.6=period-luminosity,calibrated-distance,magnitude-normal,average-magnitude@ qu.1.2.blank.7=thicknesses,types,wavelengths,frequencies,doppler shifts@ qu.1.2.blank.8=$answerclass,$badclass,III@ qu.1.2.blank.9=types,thicknesses,wavelengths,frequencies,doppler shifts@ qu.1.2.algorithm= $num = rint(4); $par=switch($num,"0.5","0.25","0.2","0.1"); $paranswer=switch($num,"2","4","5","10"); $badchoice1=switch($num,"4","5","10","2"); $badchoice2=switch($num,"5","10","2","4"); $badchoice3=switch($num,"10","2","4","5"); $num2=rint(2); $star=switch($num2,"main sequence","supergiant"); $answerclass=switch($num2,"V","I"); $badclass=switch($num2,"I","V"); @ qu.1.2.grader.1=menu@ qu.1.2.grader.2=menu@ qu.1.2.grader.3=menu@ qu.1.2.grader.4=menu@ qu.1.2.grader.5=menu@ qu.1.2.grader.6=menu@ qu.1.2.grader.7=menu@ qu.1.2.grader.8=menu@ qu.1.2.grader.9=menu@