Figure 4a (next page) shows a part of the spectrum of the star Vega (in blue),...

  

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Figure 4a (next page) shows a part of the spectrum of the star Vega (in blue), compared to the sun. The spectrum from Vega shows distinct absorption lines – four of them from a very abundant element in this (and all other) stars. a) Determine what element it is and identify theses four lines! (1 p) b) If you know that the wavelength of the resonance line in this spectra is at 121.567 nm, determine as accurately as you can the excitation energies of as many levels you can from the Vega-spectrum. (2 p) c) Figure 4b shows a spectra of quasar, i.e. a vey distant object, where the right- most line in the series we observe in Vega is shown in emission (as indicated by the right-most vertical line in the spectra and the red arrow), but for a completely different wavelength. Why is the wavelength in the quasar so much larger? Determine one property of the quasar relative to us from this shifted wavelength! (2 p) Spectra of two stars Vega Sun 1.5 0.5 -0.5 400 450 500 550 600 650 700 750 800 Wavelength (nm) Figure 4a. Spectra of Vega and the sun. 10-17 4 1.5 2 Observed A (u. m) 2.5 Figure 2. spectra from a quasar, showing same line as in Figure 4a. F, (erg s cm2 A) Log (flux per unit wavelength) (arb scale) Figure 4a (next page) shows a part of the spectrum of the star Vega (in blue), compared to the sun. The spectrum from Vega shows distinct absorption lines – four of them from a very abundant element in this (and all other) stars. a) Determine what element it is and identify theses four lines! (1 p) b) If you know that the wavelength of the resonance line in this spectra is at 121.567 nm, determine as accurately as you can the excitation energies of as many levels you can from the Vega-spectrum. (2 p) c) Figure 4b shows a spectra of quasar, i.e. a vey distant object, where the right- most line in the series we observe in Vega is shown in emission (as indicated by the right-most vertical line in the spectra and the red arrow), but for a completely different wavelength. Why is the wavelength in the quasar so much larger? Determine one property of the quasar relative to us from this shifted wavelength! (2 p) Spectra of two stars Vega Sun 1.5 0.5 -0.5 400 450 500 550 600 650 700 750 800 Wavelength (nm) Figure 4a. Spectra of Vega and the sun. 10-17 4 1.5 2 Observed A (u. m) 2.5 Figure 2. spectra from a quasar, showing same line as in Figure 4a. F, (erg s cm2 A) Log (flux per unit wavelength) (arb scale)

Answer rating: 100% (QA)

a The abundant element is hydrogen H The lines from the bigger to smaller wavelengths are given by ... View the full answer