Distant Nature: Astronomy Exercises


Objectives

After Edwin Hubble’s work using Cepheid variable stars to measure distance to the “Spiral Nebulae”, he embarked on a quest to understand the velocity, if any, that theses galaxies were moving with respect to ourselves. In this experiment, we will trace through the steps similar to Hubble’s work. These steps eventually led Hubble to the observation that the farther away a galaxy was, the greater was its recessional velocity. His insights led him to the constant H0, called the Hubble constant, which directly relates to the expansion rate of the universe.

Equipment/Materials Needed

Stellarium, Calculator, Graph Paper.

Subject Introduction

Hubble examined the spectra of many galaxies, looking for the red or blue shifts in the spectra which would indicate relative motion. To his surprise, not only did all of the galaxies appear to be moving, but all were moving away from us, no matter the direction of the galaxy. He measured the spectral shifts for many galaxies and found them to all exhibit a redshift. He used Equation 1 to quantify the redshift (z) values for each galaxy. Figure 1, represents Hubble’s original findings, of H0 =68 (km/s)/Mpc. 

z=(\lambda_{obs}-\lambda_0)/\lambda_0


Equation 1.

Where: z = the redshift, lobs = the observed wavelength, l0 = the un-shifted wavelength.

Figure 1.
HubbleConst_01.jpgFigure 1.

Figure 1.



Download Exercise Here:


Download: Expansion_ofthe_Universe_ExerciseForm.pdf


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