Accreting black holes in galaxies

Jun 28, 2012
A Hubble image of the Seyfert galaxy NGC 7742. A new paper argues that the existence of two types of Seyfert galaxies may be the result of their different physical mechanisms, and not simply differences in viewing angles. Credit: NASA/Hubble Space Telescope

(Phys.org) -- Seyfert galaxies are like normal galaxies, our own Milky Way included, except in one critical respect: their nuclei are fantastically bright. In some instances they are as luminous as 100 billion Suns, though even the weakest Seyfert nuclei are as luminous as a million Suns. Scientists believe that these huge energies are being generated by a massive black hole in the nucleus, not an ensemble of stars. Matter, as it falls in towards the vicinity of the black hole, heats up and glows intensely. Astronomers think our Milky Way also has a massive black hole at its center, but (for reasons that are not yet entirely understood) our galactic center is not particularly bright.

There seem to be two types of Seyfert galaxies: those whose bright nuclei also emit light from highly excited atoms moving at high velocities (providing evidence for ) and those without these atomic lines. The most widely accepted explanation for these two types is the so-called "unification model": The galaxies are intrinsically the same, but in the former the disk-like galaxy is seen face on and its nucleus is visible, while in the latter the galaxy is seen edge-on and the nucleus and its atomic emission is obscured by dust.

In the decades since it was first proposed, the unification model has gradually encountered increasing criticism from astronomers who argue that there may also be something physical going on to create the different kinds of Seyferts. CfA astronomers Andrea Marinucci, Fabrizio Nicastro, and Andy Goulding, with two colleagues, have analyzed data on a set of thirty-nine Seyferts using what they consider more reliable measures of the nuclear activity in the atomic lines. They provide evidence in the latest issue of the that the rate also differs in the two types. If confirmed, this conclusion would mean that there are physical differences between objects in the Seyfert family, and that viewing angle is not the only story.

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antialias_physorg
4.2 / 5 (5) Jun 28, 2012
but (for reasons that are not yet entirely understood) our galactic center is not particularly bright

Wasn't there something about radiation pressure driving gas away from black holes until they practically starve (i.e. stop producing radiation from in-falling matter) - which then again leads to a time where matter can fall in for lack of that radiation pressure until the it again increases so much as to halt that process? Maybe the center of our galaxy is just in one if those 'starving' phases?
TkClick
Jun 28, 2012
This comment has been removed by a moderator.
Tuxford
1 / 5 (2) Jun 28, 2012
So at least 40 percent of active galaxies have massive outflows of gas?

http://phys.org/n...les.html

Yes, there is more going on than observing angle..... Likely the rapid outflows are unlikely to suddenly turn around and feed the core star again?

Eliminate the standard explanation of accretion, and one must acknowledge the obvious: that the matter originates from within the core star. New idea for some? See my links in the comments here:

http://phys.org/n...lei.html

Shinichi D_
4 / 5 (3) Jun 28, 2012
Hey Tux. You've got balls of steel, writing this stupid nonsense a week before Nustar's first light. Idiot. At least know when to shut up.
jsdarkdestruction
not rated yet Jun 29, 2012
since tuxford has felt the need to promote laviolette's theory in every astronomy article possible i feel i should show just what it is we are dealing with when it comes time to consider laviolettes cosmological theories.
here are some works from tuxfords idol laviolette, it illustrates how based in reality his worldview really is.this is a book he wrote.
First time proof of the existence of interstellar radio signals of intelligent origin being sent to us.
Evidence that pulsars are part of a vast network of ETI communication beacons.
This exhaustive study presents first time proof that astronomers have been receiving radio signals of intelligent origin. As early as 1967 and continuing to the present, radio astronomers have been carefully studying and cataloging unusual interstellar beacons called pulsars thinking them to be stars of natural origin.Dr. LaViolette, who has been researching pulsars for 27 years, shows that, up to now, the nature of these radio sources has been grossly
jsdarkdestruction
not rated yet Jun 29, 2012
misunderstood. He has discovered that a number of very unique pulsars are nonrandomly distributed in the sky and mark key Galactic locatations that have particular significance from an ETI communication standpoint. He also presents evidence of unusual geometric alignments among pulsars and intriguing pulse period relationships. Equally compelling is the message they are sending-a warning about a past Galactic core explosion disaster that should help us avert a future global tragedy.

Contains extensive analysis of pulsar data, revealing new ideas about the origins and functions of pulsars

Provides proof of an extraterrestrial communication network

Includes information about the formation of crop circles and force-field-beaming technology
jsdarkdestruction
not rated yet Jun 29, 2012
see, this is what i mean about science fiction fantasy based worldview that laviolette employs in his cosmological theories. and all the others fields of science he's claimed to make breakthroughs in because of it while having no training in the fields he claims to have proven wrong.
AtlasT
1 / 5 (2) Jun 29, 2012
The steady state universe model requires the mechanism for fast evaporation of black holes (I mean a way faster, than the Hawking mechanism allows). One such a mechanism based on axions has been proposed recently here.

I do presume, even neutrino jets may be involved in evaporation of black holes. It would correspond the common experience, inside of old galaxies the black holes are quite quiet and insignificant, no matter how massive such a galaxies are. The dwarf galaxies are often considered as a remnants of way older and larger galaxies - well, an these galaxies often lack the black holes completely. Whereas in standard black hole models, the old galaxy should have most massive black holes in their center.
Tuxford
1 / 5 (2) Jun 29, 2012
Hey dark,

I don't read your posts. Why do you read mine??? How is it you know so much about LaViolette's work if you are not an NSA agent? (I guess the gov't hires low level types with bad spelling skills.) No one else here can quote so much from his various books. Why are you so concerned with slamming his non-mainstream theories???

Many should note that in the 1990's LaViolette published theories on how the B-2 flies. (Anyone who has seen the B-2 fly may understand this point.) He has been on the NSA black list ever since. Serious minds should consider this fact before dismissing his work.
jsdarkdestruction
5 / 5 (1) Jun 29, 2012
i read about his theories to see if they had any value. dont you read the works we advise and familarize yourself with them? thats what someone who truly wants to understand the world around them does. i do so i did. its not my fault laviolette is crazy as hell and his theories fall apart so easily. wtf is nsa? that accusation is baseless. i just want to make sure people know ALL about laviolete and not your cherry picking parts you like.