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1
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1answer
35 views

Regarding luminosity monitor of particle collider

I am sorry if my question is completely wrong or foolish I would feel glad to be corrected On the wiki page for Bhabha Scattering, it is mentioned that it is used as luminosity monitor in many ...
0
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1answer
19 views

How does intensity differ from apparent luminosity in the context of photometry?

Context: photometry in astronomy. Background: The total luminosity $L$ of a star is the energy that radiates in all spatial directions in all wavelengths and is given by the following formula, where ...
5
votes
1answer
60 views

Question on luminosity of a radiant source and its dependence on temperature, and involvement of Doppler Effect

A few days ago, I happened to go through the chapters on Radiation, and Photometry, studying them at quite an elementary level. I studied Wien's displacement law, and the dependence of luminous flux ...
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2answers
85 views

Quick question on astronomical units

I'm trying to solve for $\frac{M*}{M_0}$ and $p''$ using these two equations: Here is the lecturer's working, I worked it out several times and I got a different answer! Surely when you use ...
0
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0answers
20 views

Angular and luminosity distance in general?

Consider a non-Friedmannian Universe in which we know the trajectories of photons, ie in which we know null geodesics $\left(\eta, x^{1}, x^{2}, x^{3}, a, z\right)$ where : $\eta$ is the conformal ...
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2answers
74 views

how to model the exponential growth of luminosity when you flick a light on

My original thought was: $$ L = L_0 \left( 1 - e^{-t/\tau} \right) $$ where $L$ = luminosity and $L_0$ = initial luminosity. But when I tested this I found that the time constant $\tau$ was higher ...
4
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3answers
282 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 ...
5
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2answers
103 views

How many watts of light do instruments in modern telescopes need?

I just calculated that if the European extremely large telescope(978 m^2 area) would be pointed at the Andromeda galaxy once it is built, it will only get mere 1.2*10^-6 Watts of power from Andromeda. ...
3
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2answers
605 views

Is light brightness subjective or can it be quantified?

What is the relationship between brightness perception and physical properties of light, such as light intensity?
1
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1answer
2k views

Find temperature of surface (Blackbody Radiation) [closed]

An astronomer is trying to estimate the surface temperature of a star with a radius of $5 \times 10^8\ m$ by modeling it as an ideal blackbody. The astronomer has measured the intensity of ...
2
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5answers
2k views

Eye sensitivity & Danger signal

Why are danger signal in red, when the eye is most sensitive to yellow-green? You can check luminosity function for more details...
3
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2answers
2k views

What is the luminosity per square meter hitting the Earth's surface from the Sun?

So I know that the Sun's luminosity is $3.839 \cdot 10^{26}$. What I want is the luminosity per square meter at the Earth's surface. So this is what I have got so far: I know the distance to the ...
1
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2answers
191 views

What is the Schechter luminosity function's domain of support?

I'm trying to fit a Schechter luminosity function to some data points, but it's not clear from this definition what the domain of support of the PDF should be. I'm familiar with the standard Pareto ...
1
vote
0answers
474 views

What is the relationship between Luminosity, Intensity, and Flux?

I am always confused by the terminology: In high energy particle scattering, and in particular, in the context of collider physics, what is the relationship between luminosity, intensity and flux? ...
23
votes
2answers
702 views

Why does laser light not affect glowing materials?

I have this childrens rubber ball which glows in the dark after it's exposed to light. I "charge" it with a flash light then play with my dogs at night. I thought to try a very intense green laser, ...
3
votes
0answers
305 views

How to integrate over rapidity for Parton Luminosities in LHC?

I want to make a comparison of parton luminosities between Tevatron and LHC. According to Factorization theorem the cross section in hadron colliders, as long as the partonic cross section has $\hat ...
3
votes
1answer
50 views

How do you transform between theoretical Hertzsprung-Russell Diagrams and Colour-Magnitude Diagrams?

When discussing stars, theorists tend to use effective temperature $T_\text{eff}$ and luminosity $L$ (on logarithmic scales). Observers, on the other hand, usually talk about observed colours and ...
1
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3answers
3k views

Why is moonlight less colourful than yellow light?

Just what the title states; and this isn't an original question ... On full-moon, moonlight is almost as bright as mid-dawn ; yet there is hardly any colour visible. This is not the case with ...
9
votes
2answers
29 views

How will the luminosity of the current very near supernova Ia “PTF 11kly” develop in the next weeks and why?

Currently there is a unique chance for amateur astronomers to observe a very near type Ia supernova, named PTF 11kly. As standard candles are very important to measure distances in the universe, can ...
4
votes
1answer
56 views

Vision vs. limiting magnitude

Does anyone know how the acuity of your vision translates to a difference in limiting magnitude? e.g., the kind of answer I'm looking for would be "For each factor of 2 improvement in your vision ...
4
votes
4answers
128 views

What objects/states of objects with absolute magnitude do we know of?

For measuring distances the knowledge of absolute magnitude or luminosity is often crucial, especially for very big distances. Unfortunately we can't measure the diameter of far distant objects and ...
2
votes
2answers
361 views

Are there formulae for calculating stellar luminosity and effective temperature as a function of age?

Is there a manageable formula or set of formulas or simple algorithms that approximate stellar luminosity and effective temperature (or radius) as a function of stellar age? I'm aware that accurate ...
1
vote
1answer
247 views

Mass of a galaxy via Luminosity [closed]

Is there a way of calculating the mass of a galaxy, or even a nebula from the luminosity? EDIT I'm deleting this, and moving the question to Astronomy Stack Exchange - thanks david
6
votes
3answers
547 views

Binary stars' apparent magnitude

If you plot the apparent magnitude of a binary system (so you are unable to see 2 distinct stars) against time, it gives a repeating 'M' effect. (from http://accessscience.com/) Assuming one star ...
1
vote
2answers
455 views

Particle Accelerator Energy and Luminosity

Both beam energy and luminosity are important for succesful particle accelerator experiments. The LHC's nominal design is for 7 TeV beams and 1E34 cm^-2 sec^-1 luminosity, while the SSC's nominal ...