Article View: sci.physics.relativity
Article #7554Re: Absorption lines are unaffected by Doppler shift.
From: Mike Williams
Date: Sat, 15 Oct 2005 19:37
Date: Sat, 15 Oct 2005 19:37
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3736 bytes
Wasn't it Androcles who wrote: > >Assistant Professor "Paul B. Andersen" <paul.b.andersen@hia.no> of : >Agder University College (HiA) >Serviceboks 422, N-4604 Kristiansand, NORWAY Tel (+47) 38 14 10 00 Fax >(+47) 38 14 10 01 >has executed the biggest fumble ever seen in the history of >sci.physics.relativity >in message > news:dir555$965$1@dolly.uninett.no... > >"The spectral class [of stars] is determined by the relative positions >and intensities > of the absorption lines, and these are unaffected by a Doppler shift." I can't see anything wrong with that. For distant very stars that have spectra strongly affected by red shift, you can't classify them by how red or blue they are, because the colour has been shifted by an unknown amount. What you have to do is look for the patterns formed by the absorption lines. The lines may be shifted down the spectrum, but the positions of the lines relative to each other doesn't change, and allows you to recognise the patterns and identify which line is caused by which element. What you could then do is to compare the positions of those lines to a reference spectrum, calculate the red shift, and work out what colour the star actually would be if there were no red shift. But that's not what they actually do in practice, once they've worked out which line corresponds to which element, they compare the relative intensities of those lines. The strongest lines in O type stars correspond to ionized helium. For B type stars its neutral helium. A type stars have neutral hydrogen as the strongest line. F: Calcium II in a singly ionized state. G: neutral Calcium II and other neutral metals. K: Calcium and Iron and some faint molecular lines. M: lines corresponding to molecules like Titanium Oxide. -- Mike Williams Gentleman of Leisure
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X-Google-Thread: 10f545,2dbfbfa79603a5b5 X-Google-Thread: 10b271,d45805f30d16221d X-Google-Thread: fdc67,d45805f30d16221d X-Google-Thread: 10cf28,d45805f30d16221d X-Google-Thread: f871d,d45805f30d16221d X-Google-Attributes: gid10f545,gid10b271,gidfdc67,gid10cf28,gidf871d,public X-Google-Language: ENGLISH,ASCII-7-bit Path: arc1-ca.pugleaf.net!g2news1.google.com!news1.google.com!newsfeed.gamma.ru!Gamma.RU!newsfeed.icl.net!newsfeed.fjserv.net!newsfeed00.sul.t-online.de!newsfeed01.sul.t-online.de!t-online.de!newsfeed.vmunix.org!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!econym.demon.co.uk!nospam From: Mike Williams <nospam@econym.demon.co.uk> Newsgroups: sci.physics.relativity,sci.physics,alt.astronomy,alt.binaries.astronomy,uk.sci.astronomy,gac.physics.astronomy Subject: Re: Absorption lines are unaffected by Doppler shift. Date: Sat, 15 Oct 2005 20:37:53 +0100 Lines: 44 Message-ID: <qCfJvGARqVUDFwDT@econym.demon.co.uk> References: <dhhek9$cbg$1@dolly.uninett.no> <dHX_e.10800$VI6.6668@fe1.news.blueyonder.co.uk> <dhk566$5lg$1@dolly.uninett.no> <P_g%e.19914$iW5.309@fe3.news.blueyonder.co.uk> <i8crj11j03i6vq329stackled162skji23@4ax.com> <1128330387.104120.20430@g44g2000cwa.googlegroups.com> <4o02k1do899k3hmmovmmpieojgqv9aa5lm@4ax.com> <1128424624.429266.186850@g47g2000cwa.googlegroups.com> <kuv5k15e65jjb9f44egkok6qht68k537c0@4ax.com> <1129067309.314427.64350@z14g2000cwz.googlegroups.com> <2ikok1p9ttrd0nifufenuflm2hkh2h5uv7@4ax.com> <dir555$965$1@dolly.uninett.no> <wHb4f.34240$U9.16999@fe3.news.blueyonder.co.uk> NNTP-Posting-Host: econym.demon.co.uk Mime-Version: 1.0 X-Trace: news.demon.co.uk 1129405284 23593 83.104.52.64 (15 Oct 2005 19:41:24 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Sat, 15 Oct 2005 19:41:24 +0000 (UTC) X-Newsreader: Turnpike Integrated Version 4.02 S <y6w6i7iXF7su4e1qhLHXuschMm>