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12
votes
2answers
252 views

What is radiation pressure and how does it prevent a star from forming?

This is a follow up to: Is there a theoretical maximum size limit for a star? The answer there talks about the radiation pressure preventing a star from forming. What reaction is causing this ...
10
votes
1answer
239 views

Is it safer to be near a star or a black hole?

If a star or black hole neared the solar system, which would do the least damage? For the sake of a good comparison, lets assume the candidate star is an "average" 5 solar mass star, and the black ...
8
votes
2answers
580 views

Where does the radiation in space come from and can we observe it?

I have recently been reading that space travel is strongly influenced by "space radiation" and how it poses a threat to human space exploration. Does this radiation originate from stars like our Sun, ...
6
votes
2answers
167 views

Why do black holes choke?

I read that a black hole can sometime "choke" on a star: "...the disrupted stellar matter was generating so much radiation that it pushed back on the infall. The black hole was choking on the ...
6
votes
3answers
185 views

Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?

we know that stars fuse hydrogen into helium starting at 3 MK; 13 MK in the Sun's core; carbon fusion starts at above 500 million K, and silicon fusion starts at over 2700 million K for comparison; ...
6
votes
2answers
76 views

What happens to the energy from a GRB?

A gamma ray burst produces somewhere around 1044 J of energy, according to Wikipedia. Only a small portion of that energy will be absorbed by other objects. The rest of that energy will go on to ...
4
votes
1answer
56 views

Are there naturally radiation shielded areas on Mars? (shadowed by terrain formations)

Mars' thin atmosphere and lack of magnetosphere exposes its surface to lots of Solar UV radiation and cosmic radiation. But Mars also has some dramatic altitude gradients in for example Valles ...
3
votes
1answer
46 views

Why Free-Free emission is regarded as Thermal emission?

I read that thermal emission/radiation are the ones whose spectra is similar to that of a Black body radiation. Also thermal radiation depends solely on the temperature of the object. How can we ...
3
votes
1answer
139 views

Conceptual Doubt regarding the calculation of the Solar Constant

The Solar constant is the intensity of the solar radiation in the upper atmosphere. It's value is about $1400$ $Wm^{-2}$. Now we begin by stating that the Power radiated by the sun is about ...
3
votes
3answers
218 views

Does the Sun have hard radiation?

Does the Sun spread hard radiation waves around the Solar System? If so, why are we safe here (or are we even safe)?
3
votes
5answers
211 views

Why does gravity increase in star formation?

When a star ignites ( ie. fusion starts ), the star maintains its form by balancing gravity's inward pressure, and radiation's outward pressure. I get that the fusion of hydrogen atoms releases ...
3
votes
1answer
66 views

How much of the ambient radiation on Mars is arriving line of sight from the Sun?

I read a lot about the amount of radiation bodies like the Moon and Mars receive, but it's hard to find information about where the radiation is coming from. It seems to me that it's cosmic radiation ...
2
votes
1answer
49 views

In what manner is the spectrum of a black body really a continuum?

Usually they say the spectrum of a black body is a continuum and emits radiation at every frequency. Is it really a continuum like a line or are there (small) intervals? For example, can a body emit ...
2
votes
1answer
85 views

What is the ratio of cosmic microwave background radiation to normal radiation?

I would like to know the ratio of cosmic microwave background radiation to normal radiation in the universe. I am considering cosmic microwave background radiation to include the microwave, and any ...
2
votes
3answers
799 views

The formation of absorption lines in solar spectrum

It is said that absorption lines originate from regions higher in the photosphere where the gas is cooler. The gas should be absorbing photons, then re-emitting them... absorb, re-emit, absorb, ...
1
vote
1answer
58 views

Why there are three equations governing blackbody emission?

I learnt that the spectrum of a black body can be explained using Planck distribution Rayleigh -Jeans equation and Weins displacement law Can anyone tell me why there are three different equations ...
1
vote
2answers
142 views

What is space temperature around Earth?

What is the equilibrium temperature that a black body will reach at the Earth's distance from Sun?
1
vote
1answer
36 views

Amount of EM radiation (and particles) Earth “receives” from other planets in our solar system?

Can it be (or has it been already?) measured how much and what kind of EM radiation (apart from visible light)/particles Earth "receives" from a specific planet in our solar system? Can other planets ...
1
vote
1answer
673 views

what planet is the most radioactive?

So as I understand it the source of most geothermal energy on Earth is due to radioactive decay. Jupiter is the most massive planet but if the bulk of it's mass comes from gaseous elements instead of ...
1
vote
1answer
34 views

If we pumped an large EMP into High Earth orbit and it detinated would it act as a shield against solar radiation?

Could this pulse potentially shield spacecraft from harmful solar radiation. I was assuming an EMP would have little effect as a radiation shield because the pulse would not be rapid enough to ...
0
votes
1answer
72 views

How much heat is generated from waxing and waning of reflected radiation from the Sun?

According to this article, the greatest cause of global warming would be from the waxing and waning of reflected radiation from the Sun. (Placing carbon emissions at 10-20%) So really, how much heat ...
0
votes
0answers
89 views

In a finite universe, what happens when light reaches the boundary?

If a universe is finite and is not expanding at a speed equal to or greater than c, what happens when light or another form of electromagnetic radiation traveling reaches the boundary?
0
votes
0answers
23 views

What all application can be possible using the SiPM (silicon photomultiplier) and radiation detection in space? [duplicate]

I am searching about the radiations in the space, during my search I come across the SiPM by using that we can detect the radiations as per my understanding;But I am not getting that what type of ...