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Harel Boren | all galleries >> Galaxies > The Twin Quasar Q0957+561 and NGC 3079
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The Twin Quasar Q0957+561 and NGC 3079
Jan. 12, 2013 Harel Boren

The Twin Quasar Q0957+561 and NGC 3079

Negev Desert, Israel

Dedicated to my lovely friend for life and lady, dearest Gali - my whirling flower of fire, and beauty and depth

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The Twin Quasar (Twin QSO or Double Quasar or Old Faithful), also known as SBS 0957+561, or TXS 0957+561 (also Q0957+561 or QSO 0957+561 A/B), was the first identified gravitationally lensed object.

The light recorded here started its journey before our solar system existed.

NGC 3079 is the small spiral galaxy in this image, in the winter constellation Ursa Major. It's distance of 50 million light years away is a mere stroll, as compared to the unimpressive two little objects it is pointing at (outlined) and which lay 10 arcmin. away, and shown in this image inside the red boxes (the right hand box is a zoom in image of the quasar).

These two images are in fact an image of one quasar - the most luminous kind of object in the universe. Quasars are the incredibly powerful cores of galaxies that are energized by super massive black holes gobbling up stars and other material.

QSO 0957+561 A (SBS 0957+561 A) and QSO 0957+561 B (SBS 0957+561 B) are the two components of a double-imaged quasar, meaning that an intervening mass concentration between Earth and the quasar bends light so that two images of the quasar appear in the sky. This is known as gravitational lensing, and is a consequence of Einsteinian warped space-time. The quasar lies at redshift z = 1.41 (8.7 billion ly), while the lensing galaxy lies at redshift z = 0.355 (3.7 billion ly). The lensing galaxy with apparent dimension of 0.420.22 arcminutes lies almost in line with the left image of the quasar, lying 1 arcsecond off. The astronomical data services SIMBAD and NASA/IPAC Extragalactic Database (NED) list several other names for this system.

The Twin Quasar's two images are separated by 6 arcseconds. Both images have an apparent magnitude of 17, with the right component having 16.7 and the left component having 16.5. There is a 417 3 day time lag between the two images.

The lensing galaxy, YGKOW G1 (sometimes called G1 or Q0957+561 G1), is a giant elliptical (type cD) lying within a cluster of galaxies that also contribute to the lensing.

The quasars QSO 0957+561A/B were discovered in early 1979 by an Anglo-American team around Dennis Walsh, Robert Carswell and Ray Weyman, with the aid of the 2.1 m Telescope at Kitt Peak National Observatory in Arizona/USA. The team noticed that the two quasars were unusually close to each other, and that their redshift and visible light spectrum were surprisingly similar. They published their suggestion of "the possibility that they are two images of the same object formed by a gravitational lens".

The Twin Quasar was one of the first directly observable effects of gravitational lensing, which was first described in 1936 by Albert Einstein in his General Theory of Relativity.

Critics however identified a difference in appearance between the two quasars in radio frequency images. In mid 1979 a team led by David Roberts at the VLA (Very Large Array) near Socorro, New Mexico/USA discovered a relativistic jet emerging from quasar A with no corresponding equivalent in quasar B. Furthermore, the distance between the two images, 6 arcseconds, was too great to have been produced by the gravitational effect of the galaxy G1, a galaxy identified near quasar B.

Young et al. discovered that galaxy G1 is part of a galaxy cluster which increases the gravitational deflection and can explain the observed distance between the images. Finally, a team led by Marc V. Gorenstein observed essentially identical relativistic jets on very small scales from both the left and the right images of the quasar, in 1983 using VLBI (Very Long Baseline Interferometry). The difference between the large-scale radio images is attributed to the special geometry needed for gravitational lensing, which is satisfied by the quasar but not by all of the extended jet emission seen by the VLA near the right image.

Slight spectral differences between the two images of the quasar can be explained by different densities of the intergalactic medium in the light paths, resulting in differing extinction.[8]

30 years of observation made it clear that light forming the right image of the quasar reaches earth about 14 months earlier than the corresponding light forming the left image, resulting in a difference of path length of 1.1 ly.

This image is:
1600x900 pixels
Focal Length 599.7 mm Roundness 0.070 FWHM 2.966
Location RA 10h 01m 02s, Dec +55 52' 59" // Pos Angle +181 53'

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