Calculating luminosity given accretion power

In summary, the conversation discusses the question of converting accretion power given in solar masses per year to solar masses per second in order to solve for luminosity in joules per second. The solution involves converting the units to SI units and using the conversion factors between solar masses and kilograms, and years and seconds. The efficiency will be a dimensionless number, allowing for a simple multiplication to obtain the answer in joules per second.
  • #1
natxio
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0

Homework Statement



I have a question regarding calculating luminosity given accretion power. I have accretion power given to me as Δm/Δt= 1.5 solar masses/yr, in order to solve for luminosity are we supposed to convert the accretion power into solar masses/seconds or is it just some kind of variable where it doesn't matter. [I have to find the luminosity in Joules/sec]

Homework Equations



Luminosity= η x (Δm/Δt) x c^2


The Attempt at a Solution



My answer would be that I do have to convert because one joule= kg x m^2/ s^2 and if I have to find the Joules/sec I cannot leave the years unconverted.

(sorry if it was a dumb question, I think I answered it myself just working through explaining it to you guys)
 
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  • #2
Yes, to get an answer in SI units you have to convert the accretion rate into kg/s through the conversions between solar masses to kilograms, and years to seconds. Then, you can use c in m/s and the efficiency will be a dimensionless number, so you can just multiply through and your answer will be in J/s, as you observed.
 

1. How do you calculate luminosity given accretion power?

To calculate luminosity given accretion power, you can use the equation L = ηM∙c^2, where L is luminosity, η is the efficiency factor, M is the mass accretion rate, and c is the speed of light. This equation relates the amount of energy released from accretion to the luminosity of the object.

2. What is the efficiency factor (η) in the luminosity equation?

The efficiency factor (η) is a measure of how efficiently the accretion process converts mass into energy. It takes into account factors such as the strength of the magnetic field and the geometry of the accretion disk. The value of η can range from 0 to 1, with 1 being a perfectly efficient process.

3. How is the mass accretion rate (M) determined?

The mass accretion rate (M) is typically determined by observing the rate at which material is accreting onto the object, such as through the measurement of X-ray or radio emissions. It can also be estimated using theoretical models that take into account the physical properties of the accretion disk and the object being accreted onto.

4. What units are used for luminosity and accretion power?

Luminosity and accretion power are typically measured in units of watts (W) or ergs per second (erg/s). In some cases, units of solar luminosities (L☉) or solar accretion powers (L☉/s) may also be used.

5. How does calculating luminosity given accretion power help in understanding astrophysical objects?

Calculating luminosity given accretion power is an important tool for understanding the physical processes at work in astrophysical objects, such as black holes and active galactic nuclei. It allows scientists to estimate the amount of energy being released from the accretion process, which can provide insights into the properties and behavior of these objects. It also helps in studying the evolution and growth of these objects over time.

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