What does the word quasar stand for?

Quasi-stellar object (or quasi-stellar radio source) — they looked like stars but were not Quantum Stellar Acceleration Region Quick Astronomical Stellar Radiation source The name is not an acronym — it was chosen arbitrarily

Why were astronomers surprised when they first measured the distances to quasars?

The redshifts showed quasars were actually inside the Milky Way but moving extremely fast The redshifts showed quasars were billions of light-years away, meaning they must be unimaginably luminous to appear so bright from that distance The redshifts showed quasars were not receding at all, contradicting Hubble's Law The redshifts showed quasars were made of antimatter instead of normal matter

What powers a quasar?

A giant nuclear fusion reaction involving trillions of stars compressed together A supermassive black hole of 10 million to 10 billion solar masses actively consuming surrounding material The annihilation of dark matter and dark energy at the galaxy's center Magnetic reconnection events involving the galaxy's entire magnetic field

How does the luminosity of the most powerful quasars compare to the Milky Way?

The most luminous quasars produce about the same energy as the Milky Way The most luminous quasars are slightly brighter than the Sun but dimmer than the Milky Way The most luminous quasars outshine the entire Milky Way by a factor of 100 or more Quasars and galaxies cannot be compared because they emit different types of radiation

Why are quasars mostly seen at large distances (lookback times of many billions of years)?

Quasars are faster than light and have escaped beyond the observable universe Quasars were far more common in the early universe when supermassive black holes had abundant gas to consume; today that fuel has mostly been used up Quasars only formed near the edge of the universe during the Big Bang and have always been far away Nearby quasars are invisible because they have moved behind other galaxies

What famous quasar is bright enough to cast shadows if it were only 33 light-years away?

3C 273, the brightest quasar in the sky with an absolute magnitude of -26.7 Cygnus A, the nearest radio galaxy Markarian 421, the nearest blazar NGC 1277, the galaxy with the largest central black hole relative to its size

When in cosmic history were quasars most common?

In the first second after the Big Bang About 10 billion years ago (when the universe was 3-4 billion years old), at a redshift around z=2 About 4.5 billion years ago, when the Sun and Earth were forming Today — the quasar population is at its all-time peak

What is the connection between quasars and the galaxies that host them?

Quasars are independent objects unconnected to galaxies, found in the vast spaces between galaxy clusters Quasars are formed when two galaxies collide and their central black holes merge Quasars are extremely active phases in the lives of ordinary galaxies, powered by the galaxy's central supermassive black hole consuming gas Quasars are the bright cores of globular clusters located in distant galaxies

How are quasar distances determined?

By measuring their parallax shift as Earth orbits the Sun By identifying Cepheid variable stars in the host galaxy By measuring the redshift of known spectral lines in their light, then applying Hubble's Law to convert recession velocity to distance By comparing their apparent size to the known physical size of quasars

What does the discovery of quasars teach us about the universe's past?

The universe has always looked the same — quasars existed in equal numbers at all times The universe looked very different in the past — it was more violent and energetic, with many more active supermassive black holes consuming gas The early universe had far fewer galaxies and thus fewer quasars Quasars prove the universe is not expanding, because they are distributed equally in all directions