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Quasar 3C-273 - Measuring the redshift!


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Hi all,

Last evening (or should I say this morning) I set about capturing a spectrum of quasar 3C-273 (in Virgo). Rather that write a lengthy post about it here, I wrote it all up including how the spectrum was used to calculate its redshift and thus provide an approximation as to its distance. Please see here for the article.

Quasar 2C-374 - Measuring the Redshift

Best Wishes,

Dave.

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It's sobering to realise that it's only 14 years since the very first amateur astronomer achieved this type of observation.

Maurice Gavin first measured the redshift of 3C273 in 1998 (he measured z=0.16)

You've joined a very Élite club!

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I concur with the others. Very well done. I actually tried this last night and failed miserably with a slitless SA100 improvisation. Havent given up yet though.

cheers

John

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Very interesting and very impressive work, with a result very closed to the published figure. I don't know much about the conventions for these published redshift figures: does your result need to be corrected to remove solar system or local group motion (though maybe that wouldn't make much difference), or otherwise adjusted to give a figure relative to the cosmic microwave background? Just wondering if it might get you even nearer to the published figure.

Well done!:D

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Truly stunning work. One day, when we retire to St Helena, and I can afford a 14" scope, I hope I can do the same. Until then, wow.

@acey, I'm no astrophysicist, but going out on a limb, I think it doesn't matter, since, between two bodies, as far as redshift is concerned, it doesn't matter who's moving, i.e whether it's us, or 3C-273, or both. Or it's equally correct to say any of the above; since what matters is the relative motion of the two bodies. The measured redshift already contains all the relative motion.

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No, some correction is going to be necessary in general (you'd get a different red-shift depending on the time of year, if Earth happened to be moving towards or away from the object while orbiting the sun). My guess is that for large redshifts this isn't going to make a significant difference but you never know. Maybe not relevant in this case, but there's stuff on redshift correction (and a calculator) here:

Calculator

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Very impressive. What you Spectro guys are able to achieve is fascinating. However can i just point out something and thats is that the distance arrived at of 2.06 billion years is the distance to 3C-273 2.06 billion years ago and not a reflection its true present distance. For that surely you would need to adjust distance by 75kms over the 2.06 billion year period.

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acey - thanks for the link. i was thinking of the motion of the solar system as a whole (is this called proper motion?), but of course, i forgot that there would be a slight blue shift for 6 months of our orbit and a red shift for the other half a year. thanks.

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Nice work David - well done :) Have you tried 3C273 H-beta redshift from your data? The apparent redshift is progressively compressed for ever shorter wavelengths :(

acey - thanks for the link. i was thinking of the motion of the solar system as a whole (is this called proper motion?), but of course, i forgot that there would be a slight blue shift for 6 months of our orbit and a red shift for the other half a year. thanks.
Beauty of quasars [if you can record 'em :)] are twofold...

1] redshifts are so huge that solar and earthly motions can largely be discounted in amateur work.

2] bright emission lines [unlike dark absorption lines] 'punch-through' and are readily recorded in lo-res spectra :)

Thanks for the plug Ken :p

Edited by nytecam
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