Questions tagged [interstellar-matter]

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3answers
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Are 40 Kelvin interstellar gas clouds evidence of virtual positron and real electron annihilation

Given that Hawking radiation includes separation of a virtual electron-positron pair, then why cannot it be the case that in the vicinity of a real electron it annihilates with the virtual positron? ...
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1answer
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Opacity of ionized/non-ionized gases

In which state is matter more opaque to radiation? I'm talking about gaseous vs plasma. I know that opacity is a function of frequency in general, but I thought that, since a non-ionized gas has more ...
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1answer
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The interstellar medium reflects extremely low-frequency radio waves. Could we use this fact to build a more efficient photon rocket?

According to the equations of MHD, electromagnetic waves cannot propagate in a plasma if they are below the plasma frequency. (For more information, see this question about astronomical-wavelength ...
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1answer
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Describing the Sun's interior

Can the interior of the Sun be described as an ideal gas? From my knowledge, to describe a body of gas as an ideal gas, the separation between the particles must be much greater than the size of the ...
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2answers
145 views

Is there any form of matter in space?

As per I know that vacuum have capability to attract gas to fill itself. It has been proved through experiments. In space there is a huge vacuum and a vacuum of this quantity can create huge pull, but ...
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1answer
296 views

What is the quantum structure of the interstellar matter?

Consider an interstellar medium of one hydrogen atom/cm$^3$ with $500$ photons/cm$^3$ coming from CMB. This density of particles is very weak according to quantum decoherence. So, according to ...
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1answer
45 views

Is there any known or near future way to shield a spacecraft traveling at 0.1c from micrometeorites and dust ? Or even for 0.01c ?

Question is in title, the following are mere thoughts/ideas to make it happen. I was thinking at 5-10 layers of kevlar or other polycarbonates reinforced with carbon nanotubes and water added in ...
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1answer
42 views

Astrochemistry: reaction rates in clouds

Given the reactions: $ H + H \rightarrow H_2$ $ H_2 + \gamma \rightarrow H + H$ Reaction rate 1 is given by: $$\frac{d[H_2]}{dt} = c . n_H . [H]$$ and the Reaction 2 rate is given by: $$\frac{d[...
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1answer
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What's that? It seems, they were meteoroids but i am not sure, please help! [closed]

I guess that thing must be meteoroid! Strange thing about them was they appear and disappear then appear again! I think that was meteoroid but why were some of them disappearing and reappearing? P.S. ...
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1answer
185 views

Density distribution of the interstellar medium

Can anyone point me in the direction of some resources - or know themselves - regarding the density distribution of the ISM? So far googling has turned up very little. I realise there will be nuances ...
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Why Hydrogen is not solid in the outer space?

Why Hydrogen doesn't get solidified in the outer space?
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2answers
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Why can't space become fuel for spaceships? [closed]

I read somewhere that space is constitued mostly of hydrogen. So why can't space and its constituants (not only hydrogen) serve as fuel for future spaceships? The dreamer I am simply imagine a ...
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1answer
212 views

Mach no. should be constant for existence of similarity solution

I am reading some research papers on Taylor-Sedov type self-similar solution to the blast wave problems... It is written that for the existence of similarity solutions Mach number should be constant.....
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0answers
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Dust mass-loss rate from a massive star given a set of parameters?

I've been looking for examples at how mass-loss rates are determined. I'm studying a circumstellar dust shell ejected from a Wolf-Rayet star. I have some parameters like, expansion velocity of the ...
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1answer
382 views

Why is $\text{CO}$ a good tracer for $\text{H}_2$? How are those molecules correlated?

One often hears that $\text{CO}$ is a good tracer for $\text{H}_2 .$ How are they correlated? How can you deduce from the (measurable) $\text{CO}$ the amount of the (unmeasurable) $\text{H}_2$ in the ...
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1answer
58 views

What would happen to a planet at the heliosphere's termination shock?

Assuming that a planet with an atmosphere already existed which orbits at the radius of the termination shock of a star, what would happen to it over time? As a follow-up, would it be possible for a ...
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1answer
974 views

Why is hydrogen, nitrogen, carbon and oxygen the most common constituents of interstellar molecules?

Could someone elaborate more on the use of the word "constituent"? Is the question basically asking why these four elements are the most prevalent in interstellar molecules? If so, why are they the ...
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1answer
208 views

How long does a black hole last after it becomes white hole?

According to Stephen Hawking's theory of black holes, once a sufficient mass has been lost through evaporation, the escape velocity $3 \times 10^8$ meters per second so light is able to escape from ...
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7answers
27k views

What is the speed of sound in space?

Given that space is not a perfect vacuum, what is the speed of sound therein? Google was not very helpful in this regard, as the only answer I found was $300\,{\rm km}\,{\rm s}^{-1}$, from Astronomy ...
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0answers
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Interstellar electron velocity distributions

I've found an estimation for interstellar electron density which ranges from $3.0 \times 10^4$ electrons per cubic meter (pcm), to $5.0 \times 10^4$ electrons pcm close to the galactic plane. However,...
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0answers
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What is the interstellar density of mm sized “dust” particles? [duplicate]

If you assume an interstellar spacecraft of 100 m in diameter traveling to the nearest star - that ship would plow through 3 x 10^20 m^3 of interstellar space. At 0.5 c the energy release of such a ...
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1answer
466 views

Does tritium hydride exhibit measurable spontaneous fusion via proton tunneling?

In a fascinating 30 June 2013 article in Nature Chemistry, researchers from the University of Leeds found that when molecules of hydroxyl (OH, a fairly stable radical) and methanol (CH$_3$OH) are cold ...
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5answers
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Interstellar dust/matter distribution

It is known that one of the main problems of interstellar flight is a presence of matter between stars in form of very fine dust and huge asteroids. Which can slowly (or fast) destroy any ship. What ...
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2answers
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One Particle in a Vacuum

I recently watch a lecture by Neil Tyson where he said the closest thing we have to a vacuum is interstellar space. I believe he said there will be one atom per 1 cubic meter or something close to ...
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1answer
92 views

Voyager 1 cosmic ray strips

In the last months Voyager 1 has experienced a dramatic drop in the cosmic ray radiation, which was been exceptionally uniform for the last 10 years, except for the past july 28 and august 14 events, ...
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2answers
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What star processes throw strange matter into space?

My understanding is that strange matter is stable in low pressures or vacuum, but correct me if this is wrong I'm wondering how likely is to find strange matter in empty space. What physical ...
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2answers
351 views

Why should space be empty? [duplicate]

Possible Duplicate: How vacuous is intergalactic space? The emptiness of space is explained in many articles... But, space does contain some matter due to these possible reasons: During the ...
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2answers
369 views

relativistic spaceship, CMB radiation and thermodynamics

Scenario: a spaceship is travelling at a high fraction of $c$. The interstellar gas and CMB radiation has blueshifted significantly and we are facing a possible melting of the front radiation shield! ...
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2answers
288 views

On the Existence of Interstellar Meteoroids

A meteoroid in orbit around the Sun has a heliocentric velocity in the vicinity of Earth of about 42.1 km/s. So if a meteoroid has a heliocentric velocity exceeding that, it will have an open (...
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3answers
133 views

What's in my box?

Let's say that I have a box which is 100% empty. I fly into the vacuum of space, open the box and close it after a certain time. Then I go back to earth and my question is.. What's in my box? (...
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1answer
126 views

What is the best evidence/theory about the first generation of stars

In particular, during what range of years after the Big Bang did the stars form? What is the expected range of masses of these stars and what is the expected lifetime before they supernova? I assume ...
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1answer
4k views

How vacuous is intergalactic space?

You often hear intergalactic space is an example for a very good vacuum. But how vacuos is space between galaxy clusters and inside a huge void structure? Are there papers quoting a measurement/...
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2answers
149 views

What are some molecules stable in outer space that are unstable under terrestrial conditions?

What are some molecules stable in outer space that are unstable under terrestrial conditions? So there are many molecules that violently react on Earth because they're too charged, have unfilled ...