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Gravitationally lensed quasar


FraserClarke
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Prompted by a question in the AstroLounge about whether you can image gravitational lenses with amateur equipment, I tried to get an image of the "Twin Quasar" (QSO0957+561). Turned out quite nicely actually :D

The apparent double star in the middle of the image is actually two images of the same quasar, lensed by an intervening galaxy (not really visible here). The quasar itself is at z=1.4 -- more than half way across the visible universe. Each image is ~17th magnitude, and separated by 6-arcseconds -- I think this is the easiest of the lensed quasars to image.

5x300s in V band with a 16-inch LX200. Binned up the pixels 2x2 to 1.6"/pixel, but that undersamples the image quality a bit, so I should try with 1x1 at some point. Haven't bothered flat fielding the data yet. I might try to make a colour image of this at some point.

post-18754-133877551602_thumb.jpg

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Good shot, and 17th mag.. that's quite bright.

I wonder if anyone at SGL has a spectrometer... at 17th Mag it ought to be possible to actually prove it's the same object AND that it has a substantial redshift...

The Hydrogen B line will have shifted to... tap tap into excel.. oh!

1170nm.. hmm maybe it should be called Infrared-Shift.

could be a challenge matching up the lines, but proof of it being the same object would be fairly trivial.

Thanks for bringing this up.

Derek

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Thanks for the comments all -- not exactly the prettiest picture on the forum, but I'm glad it's proved interesting nonetheless :D

Spectroscopy would be tough for this, but maybe feasible in low-res. As you point out though, the bright lines are 'inconvenient' at this redshift (lyman-alpha isn't into the visible yet either). Maybe get some C-IV lines.

There is another way to prove they are one-and-the same. There is a time delay of 417 days between one component and the other -- so if you're willing to monitor this every few days for a year or two, you could see exactly the same light curve repeat itself a year and 2 months later...

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There is another way to prove they are one-and-the same. There is a time delay of 417 days between one component and the other -- so if you're willing to monitor this every few days for a year or two, you could see exactly the same light curve repeat itself a year and 2 months later...

so it varies?.. anyone know why?.. jet of plasma being the origional source perhaps?

Thanks again TeaDwarf for bringing this up.

Derek

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so it varies?.. anyone know why?.. jet of plasma being the origional source perhaps?

Thanks again TeaDwarf for bringing this up.

Derek

Longer lightpath? If the quasar were perfectly aligned behind the lensing source then you would get an Einsein ring, I imagine, so one of the lightpaths must be longer than the other?

Olly

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so it varies?.. anyone know why?.. jet of plasma being the origional source perhaps?

All quasars vary. Very loosely, the light we're seeing comes from the accretion disc around the black hole - which is not a very stable environment; clumpy matter in the disc, magnetic fields, x-ray flares etc etc. So you see variability on periods of a few days (in the visible) because the accretion disc changes on that timescale.

The pathlength difference explains the delay in variability between the two images. I think from this you can work out Hubble's constant and hence get the age of the Universe? (as you have an angular size and a pathlength difference, it should be a solved geometry giving you a physical distance?? maybe you need the redshift to the lensing galaxy rather than the quasar though...)

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Hi,

I'm old enough to remember this being discussed in the early 1970's as a visible effect of the general theory of relativity. I think it was only recorded professionally in the late 1970's, so it's amazing to see what can be achieved.

Many thanks for posting.

Peter

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maybe not pretty but truly fascinating! I thought this sort of stuff was in the realms of the Hubble or peruvian/hawaiian leviathans only - great to see that it's within reach of amateur rigs (albeit rather impressive ones!)

d

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