The discovery of quasars
had to await advances in both radio astronomy
astronomy. It had long been known that galaxies
outside our own emitted radio waves, investigation of one of these sources, 3C48 by Jodrell Bank radio telescope, showed the source to be somewhere in an area of the sky 1 arc
second in size.
Advancement of the radio telescope at Caltech
were able to refine the location of the souce to within 5 seconds of arc
. This resolution
was fine enough to allow the Palomar optical telescope lock the source down to a single object, a sharp point of light, apparently a star
. Measurement of the stars spectrum
gave a result unlike anything
ever seen before, in astronomy or physics
, the exact nature of the object remained a mystery.
In February 1963 a Dutch astronomer
, Maarten Schimdt was investigating a similar object, 3C273 in the catalogue. It occured to him the strange spectrum could be explained if the object had a red shift
of 16%, or in other words receeding from the earth at 16% of the speed of light.
If this were the case then the spectrum of 3C48 showed it must be moving at 37% of the speed of light. This really ruled out the object being a star in, or near, our galaxy (and you can't observe individual stars in other galaxies, they're too far away). Further detailed work on the spectrum really proved it to be extremely unlikely the 'star' was hurled out at such speed from our galaxy.
What are they....?
The only explanation that made any sense was that these sources must be very far away, and their speed was due to the the expansion of space
itself. (See the big bang
). Calculations gave figures of 2 billion
light years distance for 3C273 and 4.5 billion light years for 3C48. Now 3C273 was so bright it had be observed since 1895, with only (relatively) primitive telescopes, this distance meant it had to be giving out 100 times more energy
that even the most luminous
galaxy. Nobody had any real idea what such an energy source could be.
One more observation
only made the problem worse; that 3C273's brightness
had changed over periods at little as a month. Nothing can go faster than light, so whatever it was causing the change limited the size of the object to one light month. Our galaxy is about 100,000 light years in size, meaning this 'quasi-stellar' or quasar
was emitting 100 times more energy from a region 10 18
times as small.
How do can they emit so much energy....?
The energy source driving this had to be massive to pack enough energy into such a small area, it had to be a super-massive black hole
Detailed observations of the structure of material surrounding the light emitting core, made in the early 1980's convinced everybody that this must be the case. There are usually two large lobes
of gas opposite each other outside the quasars, fed by perfectly straight jets up to a million light years in length leading from the core. This system had to be steady as a gyroscope
over the lifetime of the jets; a million years. The only thing this stable, and able to pack so much power into such a small area has
to be a gigantic, spinning black hole
Also see the Blandford Znajek process
for information on how a black hole could drive these jets.
Primary source:- Black Holes and Timewarps
by Kip S. Thorne.