Ibd database investigation Astrophysics




Дата канвертавання24.04.2016
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IBD Database investigation - Astrophysics

You will complete all three parts of the investigation.

Part A is about the Hertzsprung Russell diagram (E2.11)

Part B is about Cepheid variables (E3.13)

Part C is about Hubble’s Law (E6.4)

You must present your results so that you can be assessed as follows:

Correct plot of HR diagram 4

Labelled classifications/stars 5

Calculated radius of red giant/white dwarf 4

Straight line graph of cepheids 5

Plot of apparent magnitude 4

Calculate Absolute magnitude 3

Calculate distance 3

Plot graph 4

Find Hubble constant 2

Estimate age of universe 2

Total /36

Part A – Hertzsprung Russell

The purpose of this investigation is to construct parts of the Hertzprung-Russell diagram using a spreadsheet. It is best to plot the absolute magnitude of luminosity by using the command ‘=log10’ (with the relevant cell to be used).


NAME TEMPERATURE K LUMINOSITY LO

Sun 5860 1

Proxima Centauri 3240 0.00006

α - Centauri A 5860 1.5

α - Centauri B 5250 0.43

Barnard’s star 3240 0.00044

Wolf 359 2640 0.00002

BD +36o 2147 3580 0.0055

Luyten 726-8A 3050 0.00006

UV Ceti 3050 0.00004

Sirius A 9230 24

Sirius B 9000 0.002

Ross 154 3240 0.00048

Ross 248 3050 0.00011

ε - Eri 4900 0.30

Sun 5860 1

Sirius A 9230 23.5

Canopus 7700 1500

Rigil Kentaurus 5860 1.5

Arcturus 4420 104

Vega 9520 55

Capella 5200 150

Rigel 11200 59700

Procyon 6440 7.2

Betelguese 3450 19700

Achernar 15400 655

Hadar 24000 8630

Altair 7850 11

α - Crucis 25400 3200

Aldebaran 15400 180


1. Use the data above to plot a Herzsprung Russell diagram.

2. Label the horizontal axis further on your print out with the spectral type classifications

O 52000-33000 K B 30000-11000 K A 9500-7600 K

F 7200-6200 K G 6000-5600 K K 5200-4100 K

M 3900-2600 K

3. Identify main sequence stars, red giants and white dwarfs on your plot.

4. Given that the radius of a star is approximately equal to L01/2T2, estimate the radius of one selected red giant and one selected white dwarf.
Part B - Cepheid Variables

The table below gives the absolute magnitude and the period in days for a small number of Cepheid variable stars in the Milky Way galaxy.



ABSOLUTE MAGNITUDE PERIOD IN DAYS

-1.72 1.95

-2.41 3.63

-2.81 4.36

-2.98 5.37

-3.42 4.90

-3.51 6.76

-3.72 7.94

-4.08 10.96

-4.49 14.79

-5.61 21.88

-6.38 44.67

Use the data provided to plot a graph that will produce a straight line.
The following data is for three Cepheid variables in the Large Magellanic Cloud (LMC).

HV 2063 HV 843 HV 837

Apparent Period/days Apparent Period/days Apparent Period/days

Magnitude Magnitude Magnitude

14.2 5 14.35 5 13.68 5

14.8 10 14.8 10 13.1 10

14.1 15 15.28 15 12.7 15

14.2 20 14.35 20 12.85 20

14.8 25 14.8 25 13.0 25

14.1 30 15.28 30 13.1 30

14.2 35 14.35 35 13.2 35

14.8 40 14.8 40 13.35 40

14.1 45 15.28 45 13.6 45

14.2 50 14.35 50 13.4 50

14.8 55 14.8 55 12.8 55

14.1 60 15.28 60 12.8 60

14.2 65 14.35 65 13.05 65


On the same set of axes, plot the variation in apparent magnitude for the three Cepheid variable stars. Use the information from your graph to calculate the absolute magnitude of each star, and then their distance from the Earth.
Part C – Hubble’s Law

The table below gives the distances in megaparsecs and the recessional velocities in kilometres per second of various galaxies in the Universe.


NAME OF GALAXY DISTANCE / MPC RECESSIONAL VELOCITY / KM/S

NGC 3198 14.4 663

NGC1433 12.3 1075

M107 12.6 1048

M82 3.68 203

NGC157 21.5 1652

NGC720 27.6 1745

SCULPTOR 0.08 243

SMC 0.06 158

LMC 0.05 278

LEO 1 0.25 285

M95 10.1 778

M96 10.1 897

NGC891 9.81 528

NGC908 18.4 1509

NGC936 23 1430

UGC4305 3.68 142

M74 7.36 657

NGC55 1.99 129

NGC2841 12.3 638


1. Plot a graph of the recessional velocity against the distance to the galaxy.

2. From the graph, determine a value of the Hubble constant.



3. Use the value obtained and other relevant information to estimate the age of the Universe.


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