|Galaxy NGC 3079 and "Twin Quasar" Q0957+561
Spiral galaxy NGC 3079 resides 56 million light years away. It is a Seyfert type II galaxy containing an active galactic nucleus, powered by a supermassive
black hole. But the more exciting part of the photo is Twin Quasar Q0957+561, which is identified by an arrow. What appears as a small double star is
actually a single primitive galaxy 9 billion light years away. A quasar is a "quasi-stellar radio source", which arises from a primitive galaxy glowing extremely
bright from matter falling into a supermassive black hole. The distance of the quasar is calculated by its extreme red shift. This quasar would be invisible to my
camera, were it not for an intervening giant elliptical galaxy at a distance of 4 billion light years, too dim to be seen by my camera, but documented by the
Hubble Space Telescope. This intervening galaxy has enough mass to distort space-time, acting as a gravitational lens to condense the light from the more
distant quasar into two points of light.
This image combined 100 minutes luminance with 28 minutes of red, 36 minutes green and 28 minutes of blue exposures, all unbinned. A QSI583wsg camera
was used through a 12" Astro-physics Ricardi Honders Astrograph at f/3.8.
Music: Who - I Can See for Miles and Miles
Why is this Quasar Blue? Because of its extreme redshift, one might expect the quasar to appear
blue. But as explained by David H. Roberts , Professor of Astrophysics at Brandeis University:
The spectrum of a quasar contains emission lines of common elements such as H,
C, and N, and a non-thermal continuum due to the accretion disk around the black
hole. This is not the same at all as the spectrum of an ordinary galaxy, which
is simply that of the hot surfaces of its stars. As a result the colors of
quasars are very blue compared to galaxies, and the redshift doesn't change
this. In the early days of quasar astronomy quasars were discovered by looking
for "blue stellar objects."
Reference: Nature 279, 381-384 (31 May 1979) "0957 + 561 A, B: twin quasistellar objects or gravitational lens? "