lab 6

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San Jacinto Community College *

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Course

1301

Subject

Astronomy

Date

Dec 6, 2023

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pdf

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Uploaded by ProfessorTarsierMaster1091

Pleiades 6-1 Lab 6 D ETERMINING THE D ISTANCE TO THE P LEIADES CLUSTER P ART I: P LOTTING THE HR D IAGRAM FOR A C LUSTER : Q1: Is the relationship between a main sequence star’s temperature and luminosity a direct or inverse relationship? direct What about the relationship between (B-V) and luminosity? inverse Temperature and absolute magnitude? direct (B-V) and absolute magnitude? direct Q2: If a star has an absolute magnitude of -4.0, what would you expect its (B-V) to be? What are you assuming about the star? -.28, We would assume it is small and hot Q3: If you find that a star has an APPARENT magnitude of 1.2 and a (B-V) of - 0.25, it is [circle one] (closer than/exactly/farther than) 10 parsecs.

Pleiades 6-2 P ART II: D ETERMINING THE D ISTANCE TO THE P LEIADES : Q4: If the V magnitude represents the apparent magnitudes of the Pleiades stars, how is it that we can use their apparent magnitudes, when an HR diagram typically plots the luminosities or absolute magnitudes of stars? Because comparing apparent magnitude is basically comparing their intrinsic brightness luminosity. So, we can plot the apparent magnitudes of the stars versus their temperatures, and the temperature is related to the color index Q5: Why do we want to plot the largest V magnitudes at the bottom of the graph and the smallest V magnitudes at the top? Because the lower the magnitude the brighter the star/ the bluer the star is. B-V V (Pleiades MS) M (Standard MS) V-M 0.1 7.45 2 5.45 0.3 7.02 3 4.02 0.62 10.75 5 5.75 Average -> 5.07 Q6: Based ONLY on this information, would you expect the Pleiades to be closer than 10 pc to earth? Why or why not? No, because the average is positive and if the value is positive than it is farther than 10 parsecs

Pleiades 6-3 Q7: Based on your average value of V-M, what is the distance to the Pleiades? Show your work below. 5.07=5log(d/10pc) d(pc)=10 x 10 (5.07/5) d(pc) = 10 x 10 1.014 d(pc) = 10 x 10.33= 103.28 Q8: What is the accepted value for the distance to the Pleiades (you can find it either on the internet or in your textbook)? Compare your results and comment on any possible discrepancies. 135 parsecs Q9: How many of the 25 brightest Pleiades stars are apparently HOTTER than 10,000 degrees C? (Hint: What B-V value does this correspond to?) 5

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Pleiades 6-4 What is the approximate absolute magnitude (M) of a 10,000K star (look at the standard main sequence)? 1.527 P ART III: D ETERMINING THE A GE OF THE P LEIADES : Q10: At what spectral type is the Pleiades main-sequence turnoff point located? B5 Q11: Using the information in table 3, what is the age of the Pleiades cluster? (NOTE: You may have to interpolate between values if your answer to the previous question is not listed in the table.) 100 million years old Q12: What is the accepted value for the age of the Pleiades (you can find it either on the internet or in your textbook)? Compare your results and comment on any possible discrepancies. 410 light years

Pleiades 6-5 Lab Report: (Make sure you also include your HR Diagram graph on a separate page.) In this lab I continued to work with HR diagrams to determine different aspects of the Pleiades cluster including how far away it is, Its age, and where its main sequence turnoff point is. I learned stars don’t form on their own but instead of binary pairs or large groups called clusters. used the H-R diagram technique and plotted the intrinsic brightness of several stars versus their spectral type to determine the properties and characteristics of an open star cluster. By plotting the apparent magnitudes of the stars versus their temperature I was also able to use the color index of the star

Pleiades 6-6

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lab 6

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