0
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0answers
23 views

Calculate the gravitational binding energy of a white dwarf with mass 10^57 * (mass of proton)? [on hold]

And what can we infer if the gravitational binding energy is higher/lower than the energy liberated by fusing C_12 and O_16 to Ni_56?
0
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1answer
56 views

Inward Pressure of Gravity

We are looking at White Dwarfs in Quantum and specifically how they are stabilized between gravitation pressure inwards balanced by the Fermi pressure due to electrons. To start the problem off ...
0
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1answer
56 views

What is the intrinsic colour of the star? [closed]

Hey I have this question and I am wrestling with it all day and I am completely lost. The V magnitude of a star is 15.1, B-V =1.6, and absolute magnitude Mv= 1.3 The extinction in the direction of ...
4
votes
3answers
170 views

Calculating the solar power hitting Earth

I'm trying to calculate the amount of power from the sun hitting the earth, but I am getting a number which is off by a factor of ~4. I calculate the "area" of the earth, as seen from the sun, and ...
2
votes
1answer
112 views

Strömgren Sphere of Sun

I have a homework problem: The Sun emits $ \sim5 x 10^{23}$ photons per second with $hν > 13.6$ $eV$. If the density of hydrogen atoms in interplanetary space is $n =$ $109 m^{-3}$, what ...
0
votes
1answer
47 views

Power radiated by a star, black body model

let's say I want to model a star of radius $R$ at a distance $r$ from the Earth. I need to show that the apparent luminosity for frequency $\nu$ is equal to $$\ell(\nu)=\frac{2\pi h}{c^2}\left( ...
1
vote
0answers
69 views

Solar sail area going to Proxima Centari [closed]

I have a physics question that I need some help with: "Proxima Centauri is a star in the Alpha Centauri solar system, it’s the nearest star to our sun (4.24light−years) ...
2
votes
1answer
80 views

Why does $H_2$ form on such a long time scale?

If we were trying to figure out the time scale for a gas-phase reaction between two hydrogen atoms in a molecular cloud (which has density $~10^4/$cm$^3$), apparently the reaction would happen on a ...
0
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0answers
95 views

Mass loss rate of planetary nebulae

The “interacting wind” model of planetary nebulae is based on the idea that the white dwarf phase of stellar evolution is preceded by a red giant phase. A fast wind from the hot white dwarf overtakes ...
3
votes
1answer
1k views

Escape velocity of a rocket standing on Ganymede (Moon of Jupiter)

I want to calculate the escape velocity of a rocket, standing on the surface of Ganymede (moon of Jupiter) and trying to leave Ganymede. My thinking was, the kinetic energy $E_{\text{KIN}}$ must be ...
4
votes
2answers
110 views

Balmer lines and their positions

I have two stars, both of which have Balmer lines at the same wavelength positions. The depths of the Balmer lines on each star are different, and the stars are different as well. Why does this ...
3
votes
1answer
461 views

Hydrostatic equilibrium of a star - simplification math error

I am trying to do this question and getting stuck at interpreting what the question is asking for. $$dP/dR = -g(R)\rho(R) = -[GM(<R)/R^2]\rho(R).$$ Thus when we descend a distance $\Delta R$ ...