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Questions tagged [radiation]

Questions regarding the emission of high energy particles or waves through a vacuum or a partice medium.

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Radiative Flux, Irradiance and Luminosity confusion

First of all I know there is a similar question here, but I feel is wasn't answered at all. My question is that I have seen many texts which says that Radiative Flux is equal to the Irradiance of a ...
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1answer
53 views

Radiation from Neutron Star impact?

As I understand it, objects falling into an old/inactive/dead/non-pulsar neutron star would be ripped apart, form an accretion disc and eventually emit a burst of radiation as they fall onto the ...
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1answer
76 views

How harmful is Saturn's magnetic field for human life?

AFAIK, Jupiter has the strongest magnetic field in the solar system, and it's so powerful that I've been told humans only could survive the radiation generated by it in its mooon Callisto, with proper ...
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2answers
91 views

How to Distinguish between Temperature and Doppler effect using Black-body radiation?

I understand that the radiation of a body can be described using the curve for black-body radiation. In the sense that a hotter body will be blue shifted and a cooler body will be red shifted. The ...
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2answers
126 views

Is Titan Better or Mars? [closed]

Isn't Titan better to colonize than Mars? It has a thick atmosphere which is made up of nitrogen like our planet's. It doesn't have a magnetic field, but it does get a type of protection from Saturn. ...
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1answer
62 views

Deep space radiation distribution

What frequency distribution law applies to a random point in deep space that is assumed to be far away from any particular source of radiation. Can it be expressed by some form of Plancks/Bose-...
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2answers
63 views

How much radiation would something need to output to sufficiently affect the CMB? [closed]

Let’s say that I had some device capable of outputting insane amounts of radiation, across the entire EM spectrum. If I wanted to affect the CMB to the point that, were Earth-based scientists to know ...
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1answer
116 views

How dark would the sun become if we traversed a Bok globule?

Bart Bok gave his name to dust clouds of 2-50 solar masses, which by their darkness may be 100 times more frequent than telescopes can detect. If the solar system traversed a Bok Globule, how dark ...
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3answers
140 views

Why can't a quasistar exist now?

From my research, I found out that quasistars theoretically existed because of a black hole core whose radiation pressure counteracted gravity within the star. However, a few websites stated that ...
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3answers
102 views

Account for radiation energy in the statement “total energy of universe is zero”

I've read in Hawking's book The Theory of Everything that total energy of the Universe is zero. He explained this by saying that if there are two bodies separated by a distance and having some mass, ...
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1answer
58 views

Scattered Intensity of Light vs Angles of Incidence and Emission

So I just derived an expression for the scattered intensity of light from an atmosphere with ideal isotopic scattering: $I/F=\frac{cos(i)}{4(cos(e)+cos(i))}$, where $I$ is intensity, $F$ is flux, $i$ ...
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2answers
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Strange behaviour of black holes [duplicate]

We know black holes emit streams of radiation ,also recently discovered that they emit visible light when they eat any nearby matter . "We find that activity in the vicinity of a black hole ...
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1answer
492 views

Can radiation affect gravity?

I was wondering if the sun's radiation affects the gravity when it passes through space? Like can radiation strengthen or weaken the force of gravity?
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1answer
115 views

A question about calculating the radius of a comet

A Comet is orbiting around the sun with period of $T= 5.5$ years. The comet has radius $R$. After 5.5 years (A period) we understand that its radius has decreased about $20cm$. How can we calculate ...
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0answers
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What is the radiant intensity of the celestial sphere?

Specifically, excluding the Sun and the Moon. How much energy, as light and other frequencies reaches a point in space on the average, if you add up all the sources like distant stars, the Milky Way, ...
2
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1answer
376 views

What does Eddington Limit (Eddington Luminosity) Show?

We know Eddington Limit (Eddington Luminosity) is calculated with this formula: $$L_{Ed} \approx 3 * 10^4 * L_{sun} * \frac{M}{M_{sun}}$$ Example: For a black hole with $10^4 M_{sun}$, we get $$L_{...
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2answers
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Question about radiation pressure

A spaceship with mass $m = 25\:kg$ is moving toward a red giant with $M = M_{sun}$ and $L = 1000\:L_{sun}$ (L: Luminosity). It is moving on a line (so this is not an orbital question). When it gets ...
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0answers
255 views

Radiometer Equation for Flux Density

In Duncan and Lorimer's Handbook of Pulsar Astronomy, the equation for the flux density using a radio telescope is given as (for a top-hat function): $$S=\frac{\beta\,\mathrm{SNR}\, T_{sys}}{G\sqrt{...
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2answers
129 views

What Types of Radiation Emanate in the Future and are Perceived in the Present?

Years ago I came upon a scientific text which mentioned different types of radiation and how they are perceived. One such form of radiation was described (from our perspective and understanding of ...
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2answers
206 views

Compton scattering of high energy radiation

I was reading up on compton radiation, and a question came up which I could not quite answer. Compton scattering is known to be less efficient at high energies, due to the fact that the Klein-Nishina ...
3
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0answers
114 views

What is the spectral power output of a typical galaxy?

I'm looking for a function which gives the typical isotropic spectral power of light emitted by an entire galaxy on the whole electromagnetic spectrum (in watts per frequency unit), as a function of ...
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1answer
101 views

Why aren't stars like Eternally Collapsing Objects?

We know that stellar radiation pressure balances the gravitational compressive forced of a star. Are there other factors which resist such a collapse? Also, if radiation pressure balances ...
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1answer
142 views

Do other planets with a magnetic field also have two Van Allen belts?

On Jupiter and Saturn, aurora is seen around the planet's poles, so that implies that there must be a kind of magnetic field around those planets. Perhaps even the moon Europa could have a magnetic ...
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1answer
109 views

What would happen if an astronaut orbiting Earth was exposed to radiation? [closed]

I know that astronauts are constantly being protected from radiation from the sun and the cosmos. They are normally very safe from the harmful effects of radiation but what if their protection wasn't ...
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2answers
232 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?
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1answer
297 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 ...
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1answer
321 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 $3.9*10^...
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1answer
105 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 ...
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2answers
305 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 ...
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5answers
2k 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 ...
4
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1answer
81 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 ...
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1answer
116 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 ...
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1answer
47 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 ...
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1answer
52 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 ...
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2answers
369 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?
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1answer
5k 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 ...
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1answer
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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 ...
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1answer
80 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 ...
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1answer
153 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 ...
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1answer
619 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 ...
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3answers
355 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)?
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3answers
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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, re-...
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2answers
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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 ...
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3answers
414 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; ...
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2answers
690 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 ...
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2answers
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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, ...