1. ### I Lab frame and accelerator frame

In the file I present below,it shows a way to calculate luminosity in boost frame when crossing angle exists.I can't understand why luminosity calculation is done in boost frame instead of lab frame where calculations are much easier.I also have difficulty understanding lab frame,accelerator...
2. ### B Intensity of Spherical Shell of Stars

Given that L is the luminosity of a single star and there are n stars evenly distributed throughout this thin spherical shell of radius r with thickness dr, what is the total intensity from this shell of stars? My calculations were as follows: Intensity is the power per unit area per steradian...
3. ### I Resources to find Data/Models for Nonradial Pulsations of Va

Hello! I'm currently working on a project in which I need to make an animated visualization demonstrating the physical changes and luminosity changes of a star with non radial stellar pulsations. This visualization has to be based on real or theoretical data or a real or theoretical model but I...
4. ### I What does L star mean in the Schechter function?

I'm trying to understand the Schechter function, I read on Wikipedia that the L star term in the function is the 'characteristic galaxy luminosity where the power-law form of the function cuts off'. What does this mean exactly?
5. ### Accretion and Quasars

Homework Statement Quasars arise when supermassive black holes swallow nearby gas, or even entire stars. Their masses are typically 10&7 solar masses, and their luminosities are typically around 10&39 W. Hide the children! Roughly how many stars must one of these monsters eat per year, in order...
6. ### B Apparent magnitude / absolute magnitude / luminosity

Hello, When we talk about the luminosity, apparent magnitude or absolute magnitude of a star, are we talking about all wavelengths of EM radiation or just a certain range? I've read that luminosity is basically the power output of all types of radiation, but the apparent magnitude scale is...
7. ### I Average Luminousity measured by a moving body

Lets suppose a radiating body moving relative to a frame. At a certain time because of relativistic beaming one observer in that frame would observe a different luminousity of the body. But observes placed at a different angle in that frame relative to the body would also observe different...
8. ### I How does the luminosity equation work?

I've read that L = 4 x Pi x b x d2 Where L = Luminosity (W) d = distance (m) b = brightness (W m-2) But in a real life applied situation, how does it work, how does one measure the distance and its brightness? And what does the 4Pi do?
9. ### I Changing luminosity in days?

The video: When Astrophysicists detected Quasars, they thought that they could not be more than a few light-days across as they were changing their brightness in just a few days. If we assume that they are light-years long, then the change in brightness from the other side would be observed...
10. ### Apparent Flux and number of stars

The stars in our Galaxy have luminosities ranging from $L_{\text{min}}$ to $L_{\text{max}}$. Suppose that the number of stars per unit volume with luminosities in the range of $L$, $L+dL$ is $n(L)dL$. The total number of stars per unit volume if clearly $$n = \int_{L_{min}}^{L_{max}} n(L)dL.$$...

The video:
12. ### A satellite, the sun and the satellites heat protector

Homework Statement A spacecraft is protected from the Sun’s radiation by a planar baffle whose size is much greater than that of the spacecraft itself. The baffle is aligned perpendicular to the direction of the Sun. Show that the equilibrium temperature of the baffle is...
13. ### Using Eddington Luminosity to calculate mass

Homework Statement The nuclear reactions in a star’s core are very sensitive to pressure and temperature, so high mass stars have much higher luminosities. The luminosities of massive stars have been observed to obey the following scaling relationship with mass (M): Lstar = (34.2)*M^2.4...
14. ### How to calculate delivered luminosity?

I found CMS total delivered luminosity from Cern Statistics web site (22.98 inverse fb). But i want to calculate myself and using values from website's supertable page. (https://acc-stats.web.cern.ch/acc-stats/#lhc/overview-panel) But my result is 8.16E+42 Where is my mistake?
15. ### How to convert Ohms to luminosity?

So, I recently joined a stargazing club, and for our summer activity, we're supposed to use a telescope, a photoresistor, and a multimeter to measure the luminosity of the moon. I know that luminosity can be calculated with the equation, L = σ AT 4, and that brightness can be measured with the...
16. ### Stefan-Boltzmann law, luminosity, brightness and magnitude?

From what I understand, in the equation P=\sigma AT^4, P is the power output of the star which is the energy radiated per second in EM radiation of all frequencies, and I think luminosity is also defined as the energy radiated per second in EM radiation of all frequencies. Therefore luminosity...
17. ### Binary Stars and Apparent Magnitudes

Homework Statement A binary star system at a distance of 85pc consists of two stars of equal luminosity that are so close together that they are observed in a telescope as a single image. If the apparent magnitude of the two stars combined is 10.7 what would be the apparent magnitude of just...
18. ### Luminosity Equation Question

Hello, I've been trying to solve for the luminosity of Gliese 581 using its brightness. I've been using the equation below: F = (L/(4*pi*r^2)) I have the flux as the absolute brightness of Gliese 581, which is 11.6. The distance, r, to the star is 1.89210568 × 10^17 meters. However, when I...
19. ### Luminosity of Sun

I'm trying to work out the luminosity of the sun. 1630 Watts/m2 apparent magnitude reduces with distance squared so 1/(1.496*1011)2 = 4.468*10-23m2 has the same brightness 1630 Watts from earth Surface area of the sun divided by 4.468*10-23m2 = # of 1630 Watt sections *1630 = 2.21*1044...