Q1. A comparison of the Fraunhofer lines allows one to also determine the speed

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Q1. A comparison of the Fraunhofer lines allows one to also determine the speed at which a galaxy is moving relative to the Earth. Using the measured spectrum of the new galaxy,

Calculate its speed (along with its uncertainty), determine if this galaxy is moving towards the Earth or away from the Earth also determine the distance that the galaxy is away from the Earth.

* Please make sure your answers are correct and show all your workings with proper explanations and equations making it clear to understand. It should be in clear handwriting or in word format. Shortcuts will not be accepted.

0 10/2017 The Australian Astronomical Observatory (AAO) is Australia's premier astronomical research facility. The AAO, searches for new distant stars and galaxies. One such new galaxy was recently discovered and has been given the code GENF1102. When new stars or galaxies are found, they are characterised for their composition, and their distance from the Earth. The composition of the galaxy can be determined by using spectroscopy and studying the optical spectrum of the light coming from the galaxy. As the primary source of light in galaxies is from their stars, the optical spectrum of the galaxy light can be compared to a reference light source (our Sun). Using optical absorption spectroscopy, the spectrum of the Sun can be seen in Figure 1 below. The dark lines in the spectrum represent wavelengths of light that are strongly absorbed by certain elements in the Sun (known as the Fraunhofer lines) Figure 1: SPECTRUM OF THE SUN 397 410 393 434 486 518 589 656 400 500 600 700 Wavelength (nm) Figure 2: SPECTRUM OF NEWLY DISCOVERED GALAXY 405 418 401 442 496 528 601 669 400 500 600 700 Wavelength (nm) 1/2

Explanation / Answer

The red shift is:

1+z = lambda(observed)/lambda(emitted) = 669/656 =1.0198

z=.0198

So, the velocity is: .0198*3*1e8= 5.95e6 m/sec (moving away)

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