Unveiling Quasars: The Power of Supermassive Black Holes

#ActiveGalaxies #Quasars #SupermassiveBlackHoles #AstronomyLecture #GalacticEvolution #Astrophysics #HubbleSpaceTelescope #ExtragalacticAstronomy #CosmicEngines #galaxyformation

What you’re about to watch is an in-depth exploration into the formation and evolution of active galaxies and quasars. Welcome to another exciting chapter in our journey through the cosmos. Tonight, I’ll lead you into the heart of these incredibly luminous objects and uncover the central engines that power them.

In our previous lectures, we delved into the nature of galaxies, quasars, and active galaxies. This time, I’ll show you how these fascinating entities form and evolve. One of the key questions we’ll tackle is: What powers an active galactic nucleus (AGN)?

Active galactic nuclei have some pretty amazing properties. They’re extremely luminous, emitting enormous amounts of non-stellar energy. Their energy output is highly variable, which tells us that the source is incredibly compact. You’ll also see that they display jets and other signs of explosive activity, often featuring broad emission lines that suggest rapid rotation.

To explain this incredible luminosity and variability, we turn to supermassive black holes. These black holes are typically 1 million to 1 billion times the mass of the sun, with diameters that can even exceed the orbit of Saturn.

Material falling into these black holes forms an accretion disk that becomes incredibly hot, emitting light across a wide range of wavelengths, from radio waves to gamma rays. The inner parts of this disk heat up to emit X-rays just before the matter crosses the event horizon.

I’ll show you some amazing observational evidence to back this up. For instance, images from the Hubble Space Telescope of objects like NGC 4261, an elliptical galaxy with a supermassive black hole at its core, display jets that stretch tens of thousands of light years. Another fascinating example is M87 in the Virgo cluster, home to one of the largest known supermassive black holes, with rapid gas motions around it.

As we explore these phenomena, you’ll see how jets of material are launched from the vicinity of the black hole, constrained by powerful magnetic fields. Depending on our viewing angle, these AGNs may manifest as quasars when viewed head-on or as radio galaxies when viewed from the side.

I’ll also delve into the energy processes involving synchrotron radiation and inverse Compton scattering. This will help you understand how these objects emit such a broad spectrum of light. Observations of jets in objects like Centaurus A reveal the immense power of supermassive black holes, even in nearby galaxies.

You’ll learn how the variability of these AGNs, whether in X-rays or visible light, underscores their dynamic nature. This rapid energy emission results from material falling into these black holes and producing these variations.

Turning to quasars, the most luminous and distant AGNs, I’ll explain how they represent an early stage of galaxy development. Quasars peaked around 10 billion years ago and provide key insights into the youthful universe. Surveys like the 2DF Quasar Survey chart their distribution and show that quasars were significantly more common in the distant past.

The evolutionary path of galaxies involves multiple mergers and interactions, resulting in the formation of larger galaxies and their associated supermassive black holes. This journey from small, irregular shapes to grand spirals and ellipticals reflects a dynamic cosmic history.

I'll will help you understand how supermassive black holes power active galactic nuclei and how these phenomena fit into the broader picture of galactic evolution. Join me as we uncover the secrets behind these cosmic powerhouses.

0:00 Introduction
0:57 What powers AGNs?
1:32 The Black Hole Paradigm
5:37 Models of Active Galactic Nuclei
6:16 Core of Galaxy NGC 4261 Hubble Space Telescope
8:27 The Central Engine of an Active Galaxy
10:42 Gas Disk in Nucleus of Active Galaxy M87
19:02 X-Rays from Braking Radiation
23:39 How do supermassive black holes form?
24:47 How are supermassive black holes fueled?
25:18 Black holes in Colliding Galaxies Arp 299
26:49 Do most galaxies have supermassive black holes?
27:37 Black Holes in Galaxies
34:08 Black Holes and Galaxy Evolution

[dstudiomike]

Thx Jason. You're still the GOAT astronomy prof.

[jason]

Would a dead pulsar mimic a stellar mass blackhole?

[sonarbangla]

The strong gravitational attraction of the BH ensures nothing gets out, not even light. So, what is the mechanism of the various things that are given out, like Hawking radiation, jets and god knows what else?

[deltalima]

The fewer artsts pictures the better. Those were terrible, they didnt even have the recent update from kip thornes movie project.