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Analysis and Interpretation of Astronomical Spectra 68

15.11 The Redshift of the Quasar 3C273

The above listed, very low -values, clearly show, that Messier’s world of galaxies just be-
longs to our "backyard" of the universe. As a contrast the following graph shows the im-
pressively red-shifted H-emission lines of the apparently brightest quasar 3C273 in the
constellation Virgo. Thanks to advances, particularly in camera technology, also amateur
astronomers have nowadays the pleasure to deal with cosmologically relevant distance
ranges. We must therefore be aware of the effects of the STR, as well as of the cosmologi-
cal models, which are still under debate. 3C273 demonstrates, that the above presented
formulas have a practical use and are more than just “gimmicks at an academic level”.

uUsnetDQdilA)DurOetarSca:seGnranasttrminlyg3i2ss0Csu0iLco2mhn7mfg-31a,r5i,an0tμtiRmnosgeblistjd,er[esc4coht8srdi0efwdt]m.eoaNryef2o6gwt,he2a0ne1d2eaHrwyaisytlhlydiAttrirkceo3ag1gn4aLer+bdne-e10rdB°eCaac, 5solxmr1td2h0eee0drsdmLoimuncaehinsboeftttehrew(sitlhitlaeslosw

resoThleuitnidoicnatiosnliotf tshpe weacvterleonggthr,adpetherm–ineddewtiathiVlsspesceaet G[a3us5sfi]t.s, is provided red shifted on the original scale
The profile is normalised to the continuum Ic = 1, the intensity on the level of the wavelength axis is Ic = 0.6.

Hα 7580

Δλ≈1017Å

I Hβ 5632

Δλ≈771Å

Hγ 5023

Δλ≈683 Å

Hδ 4748

Δλ≈646 Å

1.0

0.6

Red shifted, calibrated original scale

©Richard Walker 2012/06

The splitting of the Hα line is caused here by the superposition with the intense Fraunhofer

A-band (O2). Therefore the evaluation of this line was omitted in the following table. The -

values have been measured at Gaussian fitted lines and calculated with formula {17}. The
individual amounts of shift are rounded to 1Å. They vary in size, but behave strictly propor-

tional to their according rest wavelengths . Therefore, the calculation of the -values for

all evaluated lines must yield almost the same amounts. This is also a good final test for the
quality of the wavelength calibration. The obtained values are consistent here up to almost
three decimal places with the accepted value , [100], [101].

5632 4861 771 0.1586
5023 4340 683 0.1574
4748 4102 646 0.1574

With the distance to 3C273 is already so large, that cosmological models and ap-

propriately chosen parameters should be applied. Nevertheless, with the measured -value

and applying a "classical" approach, the apparent radial velocity and the distance to

3C273, shall here roughly be estimated. Considering this enormous distance, the kinematic
peculiar motion of 3C273 can be neglected and therefore the measured apparent radial ve-