Quasars

In a previous post I mentioned quasars as part of binary systems, but what are they exactly?

Quasars are among the most energetic objects in the universe. They are supermassive black holes that are actively consuming matter and energy in an accretion disk. An accretion disk is a plane of matter that is superheated as it accelerates into the gravitational well of the black hole. This disk gives off incredible radiation as the matter is turned into energy by its gravitational plummet. In nuclear fission, a massive atom splits into smaller atoms, and about 0.1% of the mass is converted into energy. In nuclear fusion – a far superior process – almost 0.7% of the matter is converted into energy. Accretion boasts a 10% matter to energy conversion rate. This is 100 times more powerful than fission, and 14 times greater than fusion per unit of input mass. This absurd energy output is why quasars are among the most energetic objects in the sky with luminosities greater than 100 times the luminosity of the entire Milky Way.

In case this isn't cool enough already, an accretion disk can generate two relativistic jets of matter and energy that are dispelled along the axis of rotation. Black holes (and quasars by extension) usually emit a mixture of electrons, positrons, and radiation. The matter in these jets moves at relativistic speeds (95%–99% of the speed of light) and thus extremely high energies. The major proposals for the formation of these jets are Blandford-Znajek processes in which magnetic fields around the accretion disk oppose the black hole’s spin, and the Penrose mechanism. In the Penrose mechanism, a rotating black hole creates an area of rotating spacetime in which the black hole’s angular momentum can be spent to eject particles at relativistic velocities along the rotational axis. When the jet is viewed directly, (the jet is directed at or near the observer) the resulting phenomenon is a blazar. The relativistic effects of the jet amplify the observed luminosity of blazars directed toward the observer, and diminish the luminosity of those directed away from the observer.


One may ask why quasars are near impossible to find int he sky for an unassisted observer considering their immense energy output. This is because they are so far away that they experience massive redshifts shifting their radiation signals into radio waves. Their very name suggests this: QUAsi -StellAr Radio source = QUASAR.


Sine Quasars are so far away, they are useful for tracking the movements of "fixed" stars in the celestial sphere because the quasars are even more "fixed" than the foreground stars providing a freelance point for measuring interstellar movement.

As Lawrence M. Krauss says in his book The Physics of Star Trek, "you would not want to encounter one of these objects up close.  The encounter would be fatal."