light, ultraviolet, X-ray and even gamma rays .Emission lines of hydrogen, helium,
carbon, magnesium, iron and oxygen in the visible and ultraviolet spectra of quasars
are the brightest lines .Now a quasar cannot continue to feed matter at high rates for
10 billion years. Hence after it finishes accreting the surrounding gas and dust, it
becomes an ordinary galactic nucleus. But quasars may be re-ignited from normal
galaxies when they merge and the supermassive black hole is infused with a fresh
source of matter. In fact, it has been suggested that a quasar could be formed as the
Andromeda galaxy collides with our own Milky Way galaxy in approximately 3-5
billion years.
->The first quasars (3C 48 and 3C 273) were discovered in the early 1960s by Allan
Sandage with the aid of small telescopes and the Lowell telescope as an
interferometer.
->The term quasar was coined by Chinese born US astrophysicist Hong-Yee Chiu in
May 1964 in the Physics Today magazine.
->Quasars also exhibit gravitational lens effect predicted by Einstein’s General
Theory of relativity.
->Quasars are useful reference points in establishing a measurement grid on the sky
because of their high brightness and small apparent size.
->Two or three quasars may be closely related in time and space and gravitationally
bound to one another. They are known as ‘Quasar pair’ and ‘Quasar triplet’
respectively.
->A single quasar can produce its multiple images by bending the emitted radiation
with its strong gravitational field.
Although astronomers have explored quasars to a great extent, these luminous bodies
still continue to remain some of the most mysterious and puzzling objects in the
universe. More research and better theories are still required to explain some of the
strange natural phenomena linked to quasars.