Active Galactic Nuclei and Quasars!
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- Опубліковано 12 лип 2024
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Some galaxies have cores that outshine the entire rest of the galaxy. What are these amazing phenomena, and how do they manifest? This is part of my complete intro Astronomy class that I taught at Willam Paterson University and CUNY Hunter.
Active galactic nucleus: en.wikipedia.org/wiki/Active_...
Quasar: en.wikipedia.org/wiki/Quasar
Messier 87: en.wikipedia.org/wiki/Messier_87
Gamma Rays in Active Galactic Nuclei: svs.gsfc.nasa.gov/20135
Bremsstrahlung X-Rays: hyperphysics.phy-astr.gsu.edu/...
Synchrotron Radiation: hyperphysics.phy-astr.gsu.edu/...
Synchrotron Radiation: en.wikipedia.org/wiki/Synchro...
0:00 Introduction
0:41 Discovery of Active Galaxies
4:04 Observations of Active Galaxies
7:28 Observations of Seyfert Galaxies
8:20 Normal Galactic Nuclei
12:55 Radio Galaxies
18:15 Radio Galaxy Lobes of Cygnus A
21:57 Active Radio Galaxy "Hercules A"
23:15 Synchrotron Emission of Radio Light
27:33 Radio Emission from M87
33:32 AGN are extra-luminous over all wavelengths
34:27 Centaurus A in Ultraviolet (GalEx Mission)
35:23 Centaurus A in X-Rays (Chandra Mission)
35:58 X-Rays from Inverse Compton Scattering
37:14 Active Galaxy Spectrum Schematic
37:53 Active Galactic Nuclei Spectra Explained
38:27 Active Galaxy Spectrum for NGC 1086
39:51 Active Galactic Nuclei Time Variations NGC 3783
41:36 Quasi-Stellar Radio Sources
42:33 Odd Spectra of Quasars Understood.
45:25 Quasars have strange spectra
48:01 Cosmic Beacons
49:11 HST Spies Galaxy-Quasar Connection in 1994
50:03 Quasars and Radio Lobes
50:26 Luminosity Ranges of Galaxies and Quasars
51:35 Galaxy Activity Compared - Наука та технологія
Please see the updated version here: ua-cam.com/video/FEcVCph9bjA/v-deo.html
Fascinating. Amazing series Dr. Kendall.
Excellent series Dr. Kendall. Thank you.
thanks for this excellent video
Great!
Thanks!
So is the ejection of the gases from the centers of galaxies the source of dark matter, once the activity turns off? They have dome of the same blobbiness. Also on the quasars, how can the red shift do to Hubble motion be differentiated from the source being in a strong gravity field, that could also cause red shift? Then how do we know we are not looking directly down emission column of an active source and then assuming that the source is spherical, way over estimating it's effective luminance? Thanks for these lectures.
These are good videos Jason. If i had found them sooner it would have saved a lot of time learning what i have so far.
Well thanks! Please share them around!
How are quasars, blazars and other agn different from Hawking radiation? Can you give me some explanation, I try to understand?
Hawking radiation is expected to come from just above the event horizon. Just above means atomic scales. Pair production that occurs there may have one particle fall into the black hole and the other depart. This takes mass away from the hole.
AGNs are not to be primarily powered by this process. They are a combination of strong magnetic fields redirecting in falling matter into the fields’ outbound jets. They don’t get as close as the source of HR.
Another way to think about it in very loose terms is the following.
AGN: from far away, throw something at the black hole. Before it gets too close, all sorts of stuff going on there fires it away.
HR: dig some dirt right around a pit. Divide the shovelfuls in half. Throw half in the pit and throw the other half far away.
Really nice lecture. So what is the actual visible light colour of the jet that comes off the AGN? From what I understand it is blue, but it looks red when it is obscured by gas/dust. And then once it expands and interacts with the intergalactic medium it becomes reddish like the gas from supernovae - is this correct?
They would mostly be white. the nature of the broadband spectrum of an active galactic nucleus, simply usually means that it’s bright at all wavelengths.
@@JasonKendallAstronomer thank you for the response. I've come across a study where they talk about red and blue quasars, where does the blue come from in this case? Thank you
How do we conclude the size of it from the time of the variability of its brightness
If the brightness varies coherently, then the “surface area” that we see must all be doing the same thing at the same time. The best first thought is to use the speed of light to show how this varies coherently. If time is no more variable than on the order of, say, 5 seconds, then it’s about 900,000 miles in size.
Yeah , but are they bright?
Is this stuff being ejected from the super massive black holes at the center?
More specifically, the black hole’s accretion disk is highly magnetized and rotates rapidly. This creates a jet-like conduit that lifts some material off the disk before it reaches the event horizon. It then gets shot out in these helical jets.
Easier to understand: how to get to nearly the speed of light? Throw yourself directly at a black hole and miss.
@@JasonKendallAstronomer so you explain how bright quasars are but what are they? Are they neutron stars or black holes?
The engine that powers them is in this video: The Realm of the Galaxies:
ua-cam.com/video/muJV2FyUJaA/v-deo.html
Do we orbit around the center of the galaxy 26,000 light years away? or do we orbit around where the center of the galaxy WAS 26,000 years ago?
Good question! Since galaxies (spirals in particular) are semi-circular and not distorted in the direction of motion, then what’s up? Your question begs the idea that all the mass of the Milky Way is centered on the exact center. It’s not. The mass is distributed throughout the disk, holding it into its shape.
@@JasonKendallAstronomer If you have a few moments, I have some serious questions, that I can't get answered elsewhere... like Is there evidence of expansion other than redshift? and can we use redshift as both distance, and velocity away from us at the same time? what if light just loses energy from existing for billions of years traveling through an imperfect vacuum?!? like how a sunset is more red because the suns light travels through the atmosphere for longer.
@@JasonKendallAstronomer If gravity is a deflection in spacetime, doe what is displaced have to be accounted for elsewhere, like between the galaxies, and does this account for dark matter?.... like the old cannon ball on a sheet, if the sheet is rubber and impermiable it must deflect upward to account for the displacement equally and oppositely, near the edges... Thank you. -Bri
Yes, there is. The Distribution of 1a supernova data, the WMAP and Planck measurements of the CMB, the Sloan galactic sky survey (catalog of the galaxies), the decline time for the brightness of supernovae, nucleosynthesis from the early universe giving the H/He ratio, the fact that stuff looks different farther away than nearer. But most directly is that the past temperature of the Cosmic Microwave Background Radiation (CMBR) has been directly measured and found to be substantially higher than it is today. Its reduction in temperature over time is direct evidence of expansion.
"Tired light" hypothesis have been extensively researched and investigated, and it has been shown to not be happening.
Coil
Why are magnetic fields important in radio galaxies and is a strong field more important than a weak B-field?
Hope the test went well!
Thanks
Welcome