Astronomy and Cosmology

The atomic bomb demonstrates the conversion of mass-into-energy. Are there known (cosmological) phenomena which are instances of energy-into-matter ?

While it seems that some scientists/astronomers/pundits now have a fair idea about the average distribution of dust grains in outer space (one per million cubic metres, according to one source, ref. link below), I can find no such confident claims when it comes to the distribution of micrometeoroids in the interstellar medium - i.e. objects around 300 - 500 micrometers diameter (or wide). The silence here - if silence it is - intrigues me almost as much as my desire to know the answer. Maybe the answer lies in the future. Who knows? I don't, that's for sure http://science.jrank.org/pages/3656/Interstellar-Matter.html

Hello! I see subject hypervelocity stars is not very common here. Just a few threads about it, years ago. So if you're not familiar with them please read first http://www.space.com/24432-hypervelocity-stars-ejected-from-milky-way.html http://www.space.com/8801-superfast-star-shot-milky.html Quote from article: "None of these hypervelocity stars come from the center, which implies there is an unexpected new class of hypervelocity star — one with a different ejection mechanism." I would like to share my hypothesis how this could happen (at least for some of them): Hypervelocity star (or two not joined together yet, but accelerated normal stars), ejected from center of …

fig. 1 -- HR Diagram one-zone approximation for star-core pressures Assuming spherical-symmetry, and hydro-static equilibrium, w.h.t. [math]\frac{dP}{dr} = -g® \rho®[/math]. Then, discretizing that differential equation, and taking solely a single 'step', from star surface to star core (one-zone approximation), w.h.t. [math]-\frac{P_c}{R} \approx - \frac{G M}{R^2} \frac{3 M}{4 \pi R^3}[/math], or (ideal gas law) [math]\frac{\rho_c T_c}{\bar{m}} \approx \frac{3 G}{4 \pi k_B} \frac{M^2}{R^4}[/math]. PP [math]\left( 1/2 - 2 M_{\odot} \right)[/math] Observationally (from fig.1), the luminosities, of 'intermediate mass' stars ([math]1/2 - 2 M_{\odot}…

Slightly bizarre idea... 67P/Churyumov–Gerasimenko looks like two bodies that assembled loosely. I suggest instead (not even a claim, rather an idea to chew on) that it can have been one sigle, more regular body that has lost more material at what looks now like a neck. This apple core model could for instance have occured as the object's axes had a different orientation. What is now the neck was then the equator and was more or less ecliptic. It received hence more sunheat and sublimated more quickly. After the object got its shape, it tumbled to rotate around the biggest moment of inertia, or flat if you prefer. That's the behaviour of all objects that aren't pe…

Please see the following presentation at pg 15 http://www.ifa.hawaii.edu/~barnes/ast110/MilkyWay.pdf There is an image of the galactic rotation random vectors in the nearby Solar Neighborhood. It is stated: "Most stars near the Sun have random velocities of a few tens of km/sec. These stars orbit the galactic center at ~230 km/sec." Let' assume that few tens of km/sec is about 25 to 50. Hence, each star in the Solar Neighborhood, has a random velocity of about 10% to 20% with related to the orbit velocity. In this image, we see that those random velocity vectors are pointing all directions. Up, down, left and right. Therefore, if those stars will maintain their mo…

As we are all aware neutrinos have been emitted from the big bang (approx 13.7 billion years ago). Does aging impact these neutrinos? Will they decay or lose momentum ? Will there be any artifacts from the big bang after another 13 billion years ?

There are 1 to 11 Dimention is to be explored can explain this?! How is the view in these Dimentions??

http://www.vancouversun.com/technology/truth+there+Stephen+Hawking+Russian+billionaire+launch+100M/11228828/story.html There seems to be a big difference in hunting UFOs and searching for signals from far distance planets. I wish them luck. When I was a kid I saw a v shaped formation of moving lights with the Milky Way as a background. This was in Southland (NZ) where there are no city lights so the view of the Milky Way was just spectacular. It was a long time ago now (possibly in the 1960s) but I see on YT that there were other sightings of a similar v shaped lights in the 1950s. I would have to think if that was a real sighting these UFO and possibly ET…

So something can come out of nothing... No space, no time. no matter and out of nothing a false vacuum can fluctuate into existence and turn into a cosmos. Now, doesn't that mean that the concept of vacuum must exists for it to occur? In other words, doesn't that mean that something always exists, I mean if nothing existed, there is nothing, no possibility of a vacuum, no fluctuation, nada... Or am I totally off?

The article in physics.org http://phys.org/news/2015-04-gravitational-constant-vary.html indicates that even G varies and this can be because the length of our day can also vary which can also vary the atomic decay rates. But if our planets rotation varies 0.1% then our time varies as well. So is the speed of light constant or is it related to magnetic spin time of our solar sun?

How much would it take to solve the missing antimatter problem? Is there enough? Is it testable ever?

Bonjour Je voudrais savoir si les relations ci-dessous sont connus? THawking le rayon de CMB t1 / THawking le rayon de CMB T0 = (M = masse totale de l'énergie sombre inclus) unrhu accélération THawking avec le rayon de la CMB t1 / unrhu accélération THawking avec le rayon de la CMB = t0 pour la simplicité: M * t1 (t0 rayon CMB) ^ 2 * G / (M * T0 (t1 rayon CMB) ^ 2 * G ) (1) = Omega lambda t0 * rayon de la CMB t1 / (t1 * Omega lambda * rayon de la CMB t0) (2) égalités (1) et (2) sont simplifier ainsi: Omega lambda t0 * (rayon t1 CMB) ^ 3 * M T0 / (Omega lambda t1 * (CMB rayon T0) ^ 3 * M t1) = 1 qu'elle simplifie Omega lambd…

If the universe's star formation is to last around 100 trillion years and we are currently only about 14 billion years into that epoch, would it be correct to say that our (humanity's) particular slice of time is a "six-sigma" event when placed in the context of possible or potential slices of time? Not to be misunderstood though, I realize picking out any one moment from practically any range of time could said to be abnormally unlikely. What I'm referring to is the chunk of time that one would expect us to exist within, given the timeline and all of the stars existing on it. So, in the current model of the universe, would one not expect the graph of stars existing a…

When protons and electrons fuse they produce neutrons. This happens when neutron stars form. Further compression results in the creation of black holes. What happens to these neutrons ? Do they still exist in the black holes or are they converted into pure energy ?

Lightning as we know it on terra-ferma uses the conduit from a water bearing cloud to the Earth. On another planet where clouds are composed of Methane (as an illustration), :- a) Does lightning occur ? b) Does it have analogous properties ?

Below is an Harvard paper, in it it's mentioning H2O & OH Mega-Masers and also Star-Formation. Could the EXPERTS explain what they are meaning in this paper, is Water and Hydroxide actually present, are they meaning these two Mega-Masers are a component in Star-Formation, if there are more Water Masers to One Hydroxide Maser would this lead to the creation of a larger star etc? Link to paper; http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1993ApJ...402L..69M&db_key=AST&page_ind=1&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES

We know that space has an above zero temperature so an empty volume of space must contain some massless energy that could be magnetic. As free space has magnetic permeability then E=1/2*L*I^2 per metre cube.

I do not know much of Astronomy but this felt a interesting question to me posed by my cousin. My cousin wanted me to think on it but I enjoy and prefer discussions more than just doing it alone. As far as I know, when we walk or run on earth, we apply force against gravity. I read Newton`s third law of action and reaction in my School and college and that also applies here but I want to keep it simple. Also, jet rising up from the earth also work against gravity. All of these requires force against gravity but is this possible to reduce or even finish this gravity. I am not talking about doing this to the whole earth but some thing like a person wearing a specific clothe…

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Just a fun game to play; Rules: State a word related to astronomy/astrophysics/cosmology. The next person states a word that starts with the letter the previous word ends on. Then state an interesting fact about that word. I'll start Pluto - Named after the Roman god of the underworld.

In this article they suggest the surface of Pluto may be geologically active, which would erase craters. No mention it could be because of its' location in a very rarified region of the Kuiper Belt. It seems reasonable to me that the inner solar system would be much more battered by meteors, but the outer solar system objects are so far apart that Kuiper Belt dwarf planets would be very small targets and not have the cratering as the inner solar system. Pluto's orbit is eccentric and orbits out of the plane of the solar sytem. Does the entire Kuiper Belt also have this inclination? http://www.businessinsider.com/pluto-surface-photos-no-craters-geologically…

Hey man.Lets say i have a super space vehicle and can get near black hole but not get suck in,close enough for time dilation,lets say 1 day is like 5 years,and with me is super telescope and can see the people of the earth..so the thing is will i see them moving very fast bcause time dilation apply to me but not to them...and if i were to look at the super telescope and zoom on people while moving away from the black hole what it would be like then?

Hello I noticed during a summer holiday in Tenerife that it got dark rather earlier than it would do in England. I thought that being nearer the equator, it would stay lighter till later in the day. Please explain in simple terms or an animation recommendation might help me. Regards to all Alan

".......Actual resolution is limited by atmospheric turbulence, well known for its degradation of astronomical seeing. The good news for spy satellites is that turbulence close to the object and far from the camera isn't as disruptive as turbulence close to the telescope. That's a good thing, because adaptive optics don't work as well for large-area images as they do for small astronomical objects..... " I found that as I read article about reading newspaper from space via surveillance satellites. So is that true about atmospherical seeing from above.Is it less and can someone tell exactly how much less would it decrease for instance if we are trying do monitoring from sp…