Comparing Quasar Varying Timescales to Black Hole S Radius

In summary, the question discusses the comparison between the maximum size of an emitting region of a varying quasar and the Schwarzschild radius of a 109 MSun black hole. The calculation of the Schwarzschild radius is straightforward, but the concept of varying quasars and their emission regions may require further understanding. Assuming the maximum size of the emitting region is 4 light months, it would be approximately 1000 times larger than the Schwarzschild radius. However, the actual emission may come from a larger accretion disk, further complicating the comparison.
  • #1
CaptainEvil
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Homework Statement



If a quasar varies on a time scale of four months, how does the maximum size of the emitting region compare with the Schwarzschild radius for a 109 MSun black hole?

Homework Equations





The Attempt at a Solution



Calculating the S radius of the black hole is trivial, but I think I missed the lecture on varying quasars. I don't know of any equations for 'emitting regions' let alone how to use its rotation period to do so. Can anyone start me off on the right track?

fwiw I calculated the S radius by the eqn 3km(M/Msun) = 3 x1012 m
 
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  • #2
if the source varies on a time scale of 4months what's the maximum size it can have?

hint - you are probably supposed to picture it's extent in a line of sight to you and assume the actual brightness change is instantaneous an comes from the full extent of the source.
 
  • #3
mgb_phys said:
if the source varies on a time scale of 4months what's the maximum size it can have?

hint - you are probably supposed to picture it's extent in a line of sight to you and assume the actual brightness change is instantaneous an comes from the full extent of the source.


I see, so are we assuming that it can only extend to a maximum size of 4 light months?
4 light months corresponds to roughly 3.1 e15 meters, which is about 1000 times the size of the S radius of the black hole.

Does this sound right?
 
  • #4
That's how I read it.
In reality the emission is going to come from a large acreation disk around the hole so it's easy to imagine that as 1000x the Rs
 

FAQ: Comparing Quasar Varying Timescales to Black Hole S Radius

1. What is a quasar?

A quasar is an extremely luminous and distant active galactic nucleus, powered by a supermassive black hole. It is the most energetic and powerful type of active galactic nucleus.

2. How can we measure the varying timescales of a quasar?

The varying timescales of a quasar can be measured by observing the changes in its brightness over time. This can be done through monitoring the light curves of the quasar using telescopes and other astronomical instruments.

3. What is the relationship between a quasar's varying timescales and a black hole's radius?

There is a direct relationship between a quasar's varying timescales and a black hole's radius. As the black hole's radius increases, the timescales for the quasar's brightness variations also increase. This is because the larger the black hole's radius, the longer it takes for matter to fall into it, resulting in longer timescales for changes in brightness.

4. Are there any other factors that can affect the varying timescales of a quasar?

Yes, there are other factors that can affect the varying timescales of a quasar. These include the mass of the black hole, the angle at which we observe the quasar, and the orientation of the quasar's accretion disk.

5. How does comparing quasar varying timescales to black hole's radius help us understand these objects?

Comparing quasar varying timescales to black hole's radius helps us understand these objects by providing insight into the physical processes happening in and around the black hole. The timescales can also give us information about the size and behavior of the black hole, which can help us better understand the role of black holes in shaping the universe.

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