Object of the Week, February 23, 2014 – Double Quasar - QSO 0957+561

Double Quasar
QSO 0957+561

RA: 10 01 21.1
Dec: +55 53 52

Mags: 17.3, 17.4
Separation: 6.2”

Distance: Just under 14 billion light years


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Labelled DSS image

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SDSS image


Basically, lensed quasars are a result of a background quasar that happens to be directly behind a massive galaxy with sufficient gravity to bend the quasar light around it and make it appear as multiple points. The most famous example is the Einstein’s Cross located in Pegasus. To introduce this class of objects as a potential observing list, the Double Quasar in Ursa Major is probably the easiest, so start with this one.

The double quasar is physically located just under 14 billion light years away, but the lensing galaxy, YGKOW G1, lies about 4 billion light years distant. This system was the first object of this class to be observed. Take a look at the Hubble photo below.
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Since I’ve observed this object more than a dozen times, sometimes resolving and others not. It depends on aperture, seeing and sufficient magnification. I used at least 450x+ in all of my observations. Some of my more memorable observations are as follows:

With my 22” reflector (June 2003), several of us saw both as distinct blue points of light that pops in and out, about 75% in. Very well resolved. The same group of us saw it as two white steady points of light in Gregg’s 25” reflector. It was pointed out to me that the figure and smoothness of my mirror must be fantastic since we could perceive color. I’m not quite sure though. Any optics gurus out there could comment? Both the 22” and 25” are figured by John Hall (Pegasus Optics) during the height of his career about 15 years ago.

With Steve Kennedy’s personal 28” f/3.66 at Shingletown Star Party, I swung his scope down pretty low, about 20 degrees above the horizon. It was rock solid, two bright points of light at over 500x.

With Jimi’s 48” reflector, Faith, Jimi and I saw this object. It was BLAZING! Faith was the only one that night saw the lensing galaxy, YGKOW G1! I didn’t see it. Jimi saw it on an earlier night.

For those who wants a short, but very challenging list of lensed quasars, take a look at my Galaxy Trios guide on my website. I’ve included 8 of them at the end of the book. It’s free!

So…
"GIVE IT A GO AND LET US KNOW"

I have observed the double quasar a few times with my 22", but I was never as successful as Alvin. I never succeeded in cleanly splitting them. Any attempts remained always ambiguous. 6" separation sounds like a lot, but it's not when the two spots can be seen with confidence with averted vision only :-(

An interesting fact about the double quasar is that the light pathes of the two images differ in length by 417 light days, which has been confirmed by monitoring the variability of the quasar.

Wow Alvin,

while others bending their eyes for the separation, the "Texas gang" looks for the lensing galaxy...that is great cinema!

My experience with this guy with different apertures, limiting magnitudes and seeing:
16", 515x, fst 6m5+, Seeing III
easy visible with averted vision; no separation, not elongated, only stellar

20", ~500x, fst 6m0+, Seeing III
easy visible with averted vision; a little bit elongated but not separated

20", 575x, fst 6m5+, Seeing II
easy with averted vision; with 400x N-E elongated; with 575x both stellar point popping in and out of view repeatedly for seconds; despite my expectations the seeing is NOT the limiting factor but the limiting star magnitude (transparency) in combination with the aperture (when I saw both spots simultaneously, both were separated with a lot of space between the points, the difficulty is to see both faint stellar spots - under excellent transparency for sure possible to separate say with 16"-18")

27", 586x, fst 7m+, Seeing I
under nearly perfect conditions (seeing, NELM) both components easy direct vision objects with a large space between them (large enough to plan a freeway between both spots ;))

My most satisfying view of the Double Quasar with my 28 inch was from Likely Place in Northern California in 2012:

"Even in this so-so seeing the DQ (Double Quasar) was pretty easy - easy averted vision 100% of the time and a clean split about a third of the time, also with easy averted vision. Too bad I didn't think of the DQ two nights ago when the seeing was so much steadier. 695x, 21.78 SQM."

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The very best view I've had was through the 90 inch Bok telescope on Kitt Peak in 2010:

"Easy to see both (lensed) images in a clean split with direct vision at both 668x and 1210x, but no trace of the lensing galaxy. Even so, seeing both images of this very old light is rather spine tingling. 21.51 SQM."

Two other observers that night did see the lensed galaxy in the 90 inch, but I think seeing has a lot to do with it. It was an extremely windy night and the seeing settled down only when the wind did, which wasn't very often as I recall. I didn't note any color to the DQ in either my 28 inch or the Bok 90 inch, but I wasn't looking for it either. The view was exactly like my 28 inch sketch above only much brighter, but I'd sure like another shot at seeing the lensing galaxy though.

As a side note, I always use NGC 3079 as my starting point to see the DQ, and have always found the view of it and it's attendant galaxies to be a wonderful sight.

I remember the night several years ago that Gary Myers and I first saw the galaxy that was lensing the double Quasar The view is still etched in my mind. It was a excellent night with good seeing! At 813 X the Quasar lens was split wide and one of the components looked ice blue to my eye and the other had a gold hue to it. It also had a faint small halo around it I was surprised by this. I had seen this object many times over the years with my old 25" but had never seen that faint halo before. Gary who had a 30" scope had never seen it also. We observed it for a while and I did a quick rough sketch of the field for reference and we went on to another object. It was the next day when I found on line deep images of the double quasar that I realized what we had seen. I was shocked to see that the faint halo that we had observed was the galaxy that was lensing the quasar.

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