Luminosity of black hole accretion disc November 30    2

The luminosity of a black hole accretion disc gaining mass at a rate $dM\over dt$ can be estimated as${1\over 12}{dM\over dt}c^2$That is a substantial proportion of the rest mass of the in-falling matter. The linked document explains that the factor

Calculating the age of the universe November 30    2

Is the calculated age of the universe that of the visible universe or the entire universe? I dont know how the age is calculated but if it is believed that all we see visibly IS the entire universe then that means it is finite. If it is not finite th

What was the orbit of the meteor that impacted the Moon on 2013 September 11 November 30    1

What was the orbit of the meteor that impacted the Moon on 2013 September 11
On 2013 September 11th, a meteor impacted the Moon leaving a 34-meter crater. So far the only info I've found was from youtube ( and this site: ht ...

Why doesn't the sun pull the moon away from earth November 30    3

If the suns gravitational pull is strong enough to hold much larger masses in place (all the planets) and at much greater distances (all planets further away from the sun then earth) why does it not pull the moon away from earth?Why doesn't the sun p

Does the Sun's light travel fast enough to have a straight path to Earth November 30    1

Does the Sun's light travel fast enough to have a straight path to Earth
Hopefully this question isn't too silly.When we travel through space, we use a curved path following an orbit to reach our destinations. As far as I'm aware, we could take a more straight li ...

What would Earthlike planets bigger than Earth with November 30    1

Large is bigger than Earth. Assuming that such planets exist (though I guess if such planets don't exist that would explain much of the Fermi paradox).Maybe some amount of iron is needed though, to make a magnetic field.I guess you could also have a

Can we see Earth by looking into space November 30    1

It is known that spacetime is curved,so I am wandering to know if its possible to look into space and we see earth (light from earth long long ago). Did I understood spacetime correctly and if its possible then can some one after million years can se

Why do objects all orbit in the same direction November 30    2

In a solar system or a planet that has many moons, why do their orbiting objects all orbit in the same direction?Is it possible for two orbiting masses to orbit in the opposite direction of each other?This video provides a visual answer: https://yout

Does 2 merging black holes necessarily make a quasar November 30    1

2 black holes are about to merge to become a larger black hole. Does this mean it'll become a quasar?From what I know, quasars are supermassive black holes or a collective amount of them. So, if it merges and becomes a supermassive black hole, does t

How can we derive photometric redshift November 30

Is there any good tool than can derive photometric redshift or good reference paper?We need to assess photometric redshift based on GALEX(Fnu and Nuv), Sloan(ugriz) and 2mass(jhk) magnitudes.Could the photometric shift precision be better than 0.1 if

Why is the Boomerang Nebula colder than the CMB November 30    1

An earlier answer on temperature mentioned that the temp of the CMB is 2.4K and the temp of the Boomerang nebula as 1K. How did the nebula cool faster than the CMB?The Boomerang Nebula (or Bow Tie Nebula) is a cloud of gas being expelled from a dying

Why does hydrogen ionization happen in HII regions November 30    1

Why does hydrogen ionization happen in HII regions
Why does hydrogen ionization happen in HII regions? Why is the hydrogen there ionized? Stars are responsible.HII regions$^\dagger$ can refer to several things, but usually I guess one thinks ...

Two body transient solution November 30    2

In the two body problem, if each body is given an initial condition as a momentum vector, what is the transient part of the solution as it settles into the steady state orbit?Your question is very unclear. As long as the orbit is bound (i.e. the tota

Hubble law, cosmological redshift and distance November 30    1

I have got confused with some cosmology formulas which calculate distance.The most famous formula is indeed the Hubble law which says (nowadays) velocity is proportional to Hubble's parameter at current time. On the other hand we can find the velocit

Detecting motion November 30    2

In the television show " Ascension " they are supposed to be 50 years into a 100 year journey to another Star System but get this, they never left Earth . They are here on Earth in a huge biosphere . My question is if this is possible that peopl

Road map for a faster spaceship closed November 30    1

New Horizons, speediest yet, is currently running at about 15 km/sec relative to the sun. What is the roadmap for future ? How is it possible to reach much faster speeds ?Here's a Wikipedia page discussing various theoretical methods of propulsion. I

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