a. 1. Brightness is proportional to distance (its inversely proportional). 2. It's inversely proportional to the square of the distance.2. Compare brightness to the Sun (in terms of its brightness), and use inverse square law.
Re: Astronomy C
Posted: September 15th, 2020, 6:39 am
by RiverWalker88
astronomybuff wrote: ↑September 15th, 2020, 5:04 ama. 1. Brightness is proportional to distance (its inversely proportional). 2. It's inversely proportional to the square of the distance.2. Compare brightness to the Sun (in terms of its brightness), and use inverse square law.
Yep, all correct (I actually made a mistake in the question, Newton originally assumed that brightness was inversely proportional, but didn't account for luminosity. Just for historical accuracy, I figured I'd point out my mistake).
Your turn!
Re: Astronomy C
Posted: September 18th, 2020, 4:40 am
by astronomybuff
A supermassive blackhole within a quasar consumes 2 solar masses a year with a mass-to-energy conversion efficiency of 12%.
a. What is its energy output per seconds, in Joules?
b. What is the lower bound to its mass, in solar masses?
c. How do you know the answer to b?
d. If it has an apparent magnitude of 11.3, how far is it from Earth?
Re: Astronomy C
Posted: September 19th, 2020, 6:15 pm
by RiverWalker88
astronomybuff wrote: ↑September 18th, 2020, 4:40 am
A supermassive blackhole within a quasar consumes 2 solar masses a year with a mass-to-energy conversion efficiency of 12%.
a. What is its energy output per seconds, in Joules?
b. What is the lower bound to its mass, in solar masses?
c. How do you know the answer to b?
d. If it has an apparent magnitude of 11.3, how far is it from Earth?
a. 2 solar masses * .12 = 0.24 solar masses. 0.24 solar masses = ~1.51*10^22 kg. 1.51*10^22 kg*c^2 = 1.36J
b. I converted the luminosity calculated in part a to solar luminosities and plugged that into (L/Lsun)=3.2*10^4(M/Msun) (an approximate equation for Eddington luminosity) and got... 1.113*10^8 solar masses. That doesn't quite seem right...
c. The Eddington Luminosity is the maximum luminosity a body can radiate at, so it can be used to determine a limit for mass, as well.
d. Black holes really can't be seen (they emit no light), but theoretically, we can still make these calculations work. Using the luminosity of the black hole, I calculated the absolute magnitude to be -26.549. Using the Distance modulus, I get 3.714*10^6 parsecs.
Re: Astronomy C
Posted: September 22nd, 2020, 4:10 pm
by RiverWalker88
Oops... I forgot about posting a question (sorry).
Just a basic one, I can't properly think right now.
A MACHO passes in front of a star.
What is a MACHO?
What is the effect on the brightness of this star of the MACHO passing in front of it?
The star appears brighter.
The star appears dimmer.
The star appears unchanged.
The star actually blinks out of existence.
What is the effect that caused the change in brightness known as?
astronomybuff wrote: ↑September 18th, 2020, 4:40 am
A supermassive blackhole within a quasar consumes 2 solar masses a year with a mass-to-energy conversion efficiency of 12%.
a. What is its energy output per seconds, in Joules?
b. What is the lower bound to its mass, in solar masses?
c. How do you know the answer to b?
d. If it has an apparent magnitude of 11.3, how far is it from Earth?
a. 2 solar masses * .12 = 0.24 solar masses. 0.24 solar masses = ~1.51*10^22 kg. 1.51*10^22 kg*c^2 = 1.36J
b. I converted the luminosity calculated in part a to solar luminosities and plugged that into (L/Lsun)=3.2*10^4(M/Msun) (an approximate equation for Eddington luminosity) and got... 1.113*10^8 solar masses. That doesn't quite seem right...
c. The Eddington Luminosity is the maximum luminosity a body can radiate at, so it can be used to determine a limit for mass, as well.
d. Black holes really can't be seen (they emit no light), but theoretically, we can still make these calculations work. Using the luminosity of the black hole, I calculated the absolute magnitude to be -26.549. Using the Distance modulus, I get 3.714*10^6 parsecs.
Uh for A where is your 10 to some power? Or am I just blind . B and C are spot on! For D, I believe it should be 10^8 instead of 10^6
Re: Astronomy C
Posted: September 23rd, 2020, 4:45 am
by astronomybuff
RiverWalker88 wrote: ↑September 22nd, 2020, 4:10 pm
Oops... I forgot about posting a question (sorry).
Just a basic one, I can't properly think right now.
A MACHO passes in front of a star.
What is a MACHO?
What is the effect on the brightness of this star of the MACHO passing in front of it?
The star appears brighter.
The star appears dimmer.
The star appears unchanged.
The star actually blinks out of existence.
What is the effect that caused the change in brightness known as?
No, no it's my fault for not replying quickly!
An object that has an almost 0 luminosity. So they appear nearly invisible, and as they pass in front of a massive body, they bend it's light rays. 2. Make it brighter. 3. Gravitational lensing.
astronomybuff wrote: ↑September 18th, 2020, 4:40 am
A supermassive blackhole within a quasar consumes 2 solar masses a year with a mass-to-energy conversion efficiency of 12%.
a. What is its energy output per seconds, in Joules?
b. What is the lower bound to its mass, in solar masses?
c. How do you know the answer to b?
d. If it has an apparent magnitude of 11.3, how far is it from Earth?
a. 2 solar masses * .12 = 0.24 solar masses. 0.24 solar masses = ~1.51*10^22 kg. 1.51*10^22 kg*c^2 = 1.36J
b. I converted the luminosity calculated in part a to solar luminosities and plugged that into (L/Lsun)=3.2*10^4(M/Msun) (an approximate equation for Eddington luminosity) and got... 1.113*10^8 solar masses. That doesn't quite seem right...
c. The Eddington Luminosity is the maximum luminosity a body can radiate at, so it can be used to determine a limit for mass, as well.
d. Black holes really can't be seen (they emit no light), but theoretically, we can still make these calculations work. Using the luminosity of the black hole, I calculated the absolute magnitude to be -26.549. Using the Distance modulus, I get 3.714*10^6 parsecs.
Uh for A where is your 10 to some power? Or am I just blind . B and C are spot on! For D, I believe it should be 10^8 instead of 10^6
Ahh... I dropped those orders of magnitude very badly. I can't find my work on them, so I'm not sure what they were supposed to be.
RiverWalker88 wrote: ↑September 22nd, 2020, 4:10 pm
Oops... I forgot about posting a question (sorry).
Just a basic one, I can't properly think right now.
A MACHO passes in front of a star.
What is a MACHO?
What is the effect on the brightness of this star of the MACHO passing in front of it?
The star appears brighter.
The star appears dimmer.
The star appears unchanged.
The star actually blinks out of existence.
What is the effect
that caused the change in brightness known as?
No, no it's my fault for not replying quickly!
An object that has an almost 0 luminosity. So they appear nearly invisible, and as they pass in front of a massive body, they bend it's light rays. 2. Make it brighter. 3. Gravitational lensing.
a. Yep (I was looking for MAssive Compact Halo Object, but your definition is better)
b. Yep
c. Yep
a. 2 solar masses * .12 = 0.24 solar masses. 0.24 solar masses = ~1.51*10^22 kg. 1.51*10^22 kg*c^2 = 1.36J
b. I converted the luminosity calculated in part a to solar luminosities and plugged that into (L/Lsun)=3.2*10^4(M/Msun) (an approximate equation for Eddington luminosity) and got... 1.113*10^8 solar masses. That doesn't quite seem right...
c. The Eddington Luminosity is the maximum luminosity a body can radiate at, so it can be used to determine a limit for mass, as well.
d. Black holes really can't be seen (they emit no light), but theoretically, we can still make these calculations work. Using the luminosity of the black hole, I calculated the absolute magnitude to be -26.549. Using the Distance modulus, I get 3.714*10^6 parsecs.
Uh for A where is your 10 to some power? Or am I just blind . B and C are spot on! For D, I believe it should be 10^8 instead of 10^6
Ahh... I dropped those orders of magnitude very badly. I can't find my work on them, so I'm not sure what they were supposed to be.
RiverWalker88 wrote: ↑September 22nd, 2020, 4:10 pm
Oops... I forgot about posting a question (sorry).
Just a basic one, I can't properly think right now.
A MACHO passes in front of a star.
What is a MACHO?
What is the effect on the brightness of this star of the MACHO passing in front of it?
The star appears brighter.
The star appears dimmer.
The star appears unchanged.
The star actually blinks out of existence.
What is the effect
that caused the change in brightness known as?
No, no it's my fault for not replying quickly!
An object that has an almost 0 luminosity. So they appear nearly invisible, and as they pass in front of a massive body, they bend it's light rays. 2. Make it brighter. 3. Gravitational lensing.
a. Yep (I was looking for MAssive Compact Halo Object, but your definition is better)
b. Yep
c. Yep
That's fine, your 1.36 was correct, so you probably had the correct power as well.
a) An elliptical galaxy has been observed to have an Ha line of 715.68 nm, while it's "true" wavelength of Ha lines is 656.28 nm. How far away is the galaxy, in parsecs?
b) How long is the major axis of the galaxy, in parsecs?
Show/explain your work.
Re: Astronomy C
Posted: September 23rd, 2020, 12:41 pm
by nobodynobody
a) An elliptical galaxy has been observed to have an Ha line of 715.68 nm, while it's "true" wavelength of Ha lines is 656.28 nm. How far away is the galaxy, in parsecs?
b) How long is the major axis of the galaxy, in parsecs?
Show/explain your work.
A) Using the 2 wavelengths, the redshift is calculated to be 0.090510. Since that is a small redshift, I'll approximate the recessional velocity to be about 2.7153 * 10^4 km/s. Assuming Hubble's constant to be 72, the distance is 377 mpc, or 3.77 * 10^8 parsecs.
B) I'm not sure if you can calculate the major axis of the galaxy using the information from the problem?
. B and C are spot on! For D, I believe it should be 10^8 instead of 10^6