30 Nov 2000ASTR103, GMU, Dr. Correll1 Ch 16--Quasars and AGNs.

30 Nov 2000 ASTR103, GMU, Dr. Correll 1

Ch 16--Quasars and AGNsCh 16--Quasars and AGNs


What do you think?What do you think?

• What do quasars look like?• What powers a quasar?


Quasars DiscoveredQuasars Discovered

• 1936--Amateur astronomer, Grote Reber, builds the first radio telescope in his backyard. He find several strong radio sources– Sagittarius A--from the galactic nucleus– Cassiopeia A--supernova remnant in our galaxy– Cygnus A--unusual

• first optical measurements were in 1951, showing a strange galaxy in the direction of the radio source

• red-shift indicated a distance of 690 million light years!

• The strong radio signal, at such a great distance, indicates a luminosity about 107 times that of a normal galaxy!


QuasarsQuasars

optical

radio


Quasar Red ShiftsQuasar Red Shifts


Quasars, AGNs, etcQuasars, AGNs, etc

• Quasars--quasi stellar objects, the oldest (most distant) and most energetic galaxies

• Active Galactic Nuclei--not as far away and not as powerful as Quasars– exhibit rapid variability--indicating small energy

sources (solar system size!)– diverse spectra--some dominated by absorption, some

by emission, some featureless--classified by names such as peculiar galaxies, seyfert galaxies, BL Lac objects

– optical/xray emission near nucleus and extended radio lobes


Seyfert Galaxy ExampleSeyfert Galaxy Example

• Ground based visible, HST visible, and x-ray reveal very localized central nucleus


M87--Elliptical Galaxy ExampleM87--Elliptical Galaxy Example

• 50 Million light years from Earth; 3 billion solar mass nucleus (supermassive black hole?)


Supermassive Central EnginesSupermassive Central Engines


Radio Maps of the Milky WayRadio Maps of the Milky Way

• HST Images consistent with Supermassive black hole central engine--billion solar masses within hundreds of ly nucleus


Gamma Ray BurstersGamma Ray Bursters

• Gamma ray detectors on satellites have discovered that many gamma ray burst sources occur.

• Recent observations confirm they are very energetic and very distant--suspected that they are energized by black hole engines, possibly capturing other black holes or neutron stars


Gamma Ray BurstersGamma Ray Bursters

• 21-cm radiation– penetrates through the

interstellar dust to reveal spiral structure


Quasars, AGNs, etc--SummaryQuasars, AGNs, etc--Summary


What do you think?What do you think?

• What do quasars look like?– They look like stars, but they radiate many times more

energy than any star

• What powers a quasar?– A quasar is believed to be powered by a supermassive

black hole at the center of the galaxy

30 Nov 2000ASTR103, GMU, Dr. Correll1 Ch 16--Quasars and AGNs.

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Transcript of 30 Nov 2000ASTR103, GMU, Dr. Correll1 Ch 16--Quasars and AGNs.