Astronomy and Cosmology

Swansont - why is the temperature of the Sun's surface in the order of thousands of degrees Kelvin, whilst the outer 'layer' and the centre are in the order of millions of degrees Kelvin. I hate to divert a hot thread but it does puzzle the heck out of me?

I've read that the fastest possible speed for a fusion-powered spacecraft that carries its fuel with it, is about 1/3rd light speed. I'd like to know- what is the fastest possible speed for a spaceship that uses antimatter as fuel?

Why has there been so much activity with the sun as of lately, I live in Pennsylvania and I saw the Northern Lights earlier this year in February following one of these Coronal Mass Ejections On April 9th a fireball the size of Jupiter shot out of the sun, I have heard these are some of the most extreme mass ejections in recorded sun history?

My understanding was the circular patterns found by analyzing the anisotropies of the CMB provided observational evidence of inflation. Two questions: 1) are these circular patterns the same patterns that Penrose etal. uses to support his conformal cyclic cosmology theory? 2) Are the anisotropies derived from software analysis (i.e. Fourier analysis) or are they derived from slight rotations in the telescope?

Some publications say its the sheer mass pulling in on itself, others say its due to the orbit and spin? And also can the Milky Way be compared to a hurricane? What is in the eye? We are one of many solar systems and other debris flying around at what speed? Do we know that?

NASA now has a satellite orbiting Mercury and snapping photos. http://blog.seattlepi.com/aerospace/2011/03/29/heres-mercury/ http://www.latimes.com/news/science/la-sci-messenger-20110330,0,7061787.story The second article is from the LA Times. It states that NASA's photos capture "areas near the planet's southern pole that have never been seen before — areas that could host water in the form of ice." How is this even possible? The surface temperature of Mercury would instantly evaporate any form of water, without even taking into account the amount of pressure that close to the sun.

First of all, are there astronomers/astrophysicists who study the asteroid belt and specifically the gravitational effects among asteroids? Second, if gravity meters were placed on one or more asteroids, what would they reveal? Would they primarily reflect complex tidal effects caused by gravitational interactions, the gravity of the specific asteroid on which they were placed, or a combination? Would there be some stabilizing "net gravity" of the belt as a whole that would influence all gravitational interactions between the individual asteroids?

Like planets.

I really like this forum on the first look, at least one science forum that does not look rudimentary. To my question, excuse my lack of knowledge, I just was watching a documentary about Astronomy and there was Stephen Hawking explaining his own theories and the newest findings about the universe and how life originated. While all this is happening, I'm wondering how does a man who is paralyzed even do his researches in a way that he's brining innovative theories to the table? Obviously he doesn't have the same possibilities like others, for example working all day in the labor using telescopes. The only explanation I have is that he's simply reading A LOT, be …

Consider if you could compare the same cloud of dust, e.g. a nebula, at different volumes. All the particles are the same distance from each other at any given volume, thus the gravitational attraction for any particle in the direction of any other particle is always the same proportion to its attraction to the other particles surrounding it. So the question is how the volume of the cloud affects developments occurring within it. Do various concentrations form into gravity-wells in the same way they would at other volumes? Would the evolution process occur the same but faster because of the higher density and thus higher gravitational gradations? Would other forces i…

wouldn't we have to see stars from everywhere during night? Shouldn't the space be so full of light that there is no darkness? Isn't that what they mean by no end to space? Infinite numbers of stars as well? OR do they mean space has no end but there are limited number of stars?

The energy density of magnetic fields is [math]U \approx \frac{B^2}{\mu_0} = \epsilon_0 \, c^2 \, B^2[/math]. For an inter-galactic magnetic field strength of ~10-12 T, this produces a mass-density equivalent of 10-35 km/m3. This does not appear to be a principal component of the critical density.

If we agree that universe has a beginning and if we know that the entropy increases over time (a broken window won't fix itself), I reckon that entropy had to be zero or a constant some point in past. Then if universe is to begin shrinking, that means it's returning to the primal state of higher order and least entropy - the entropy'd start to decrease- in that case the usual thermodynamic direction of time will reverse - the window pieces will jump together and the window will be whole again. The psychological direction of time would also reverse: we wouldn't remember past but future - but that also raises paradoxes like "Could we die before we're born?" etc. These…

Hi Everyone, this is my first post so hopefully the topic title got your attention. I've been thinking about this for some time and I'm getting confused. Hubble's arguement is that the further away an object is the faster it is moving. I understand that type 1a supernovae are used to determine this because thay are standard candles. So it goes if you know how bright something is you can calculate its distance and then by measuring its red shift you can calculate its speed. The results are that the further away something is the faster it is moving so if its twice as far away its moving twice as fast. This would suggest that as an object it moves away it gets faster, it…

The Universe is expanding. Is it possible that we can see the same red-shift everywhere? Do we have any problem? Or, are we at the center of the Universe?

Is it possible for a black hole to lose power? If the answer is no, shouldn't it be virtually impossible for anything other than a single large black hole to exist? And in result would the big bang theory not be an event but rather a cycle? Thanks!

The article explains how you can log in to Zooniverse and assist in the hunt for exoplanets by sifting through the data from Kepler. Good luck! http://www.universetoday.com/81734/become-an-exoplanet-hunter-with-newest-zooniverse-citizen-science-project/ http://www.zooniverse.org/home

Does gravity as strong as that of the sun or other star cause sub-atomic particles to separate and stratify the way solid, liquid, and gas do on Earth? Does gravity reach such a level of strength that it overcomes the force of electrostatic attraction, essentially ionizing all the atoms? If so, it would seem like the sun and other stars would have an atmosphere of negative charge as their outermost layer. Yet, I've never heard of the sun being surrounded by an "atmosphere" of static electricity. Why?

Is the fusion in the sun the same fusion as the general deuterium-tritium fusion? How to make neutron at that fusion reaction? Are there any catalytic fusion system at the core of the Sun?

I have been reading a little about simulating gravity in space and thought that maybe gravity is evidence that the universe is in some sort of motion that allows centrifugal force to "hold" us onto the planet. Does anyone think that some sort of complex centrifugal motion is at work that allows us to stay put on this planet? The idea here is that an opposing centrifugal force is responsible for gravity on this planet. The Earth, of course, is spinning so perhaps the opposing force is provided by spinning as well. Evidence for this spin could be supported by extremely minor fluctuations in the weight of an object and that the force is travelling "around" this planet very r…

Gas Rich Galaxies Confirm Prediction of Modified Gravity Theory Surprising comming from an astronomy professor! What do you think about that. Personnaly I prefer MOND, but I don't know if it explain the lensing by close galaxies of distant galaxies.

Hello everybody. During the Chinese Song Dynasty (960-1279 AD), the polymath scientist Shen Kuo (1031-1095 AD) could be viewed as China's greatest astronomer in terms of sheer amount of discovery and innovation. Although there are and were notable Chinese astronomers in modern times, none of them are pioneers in their field like Shen was in his. As his wikipedia article states: http://en.wikipedia.org/wiki/Shen_Kuo Shen also discovered the concept of True North relative to a navigator's position while using a compass, as opposed to magnetic declination towards the magnetic north pole. But Shen Kuo was more than just an astronomer. As his wiki articl…

Hi all, I looked around, but maybe I missed it if this topic exists somewhere on these boards. I'm not so much interested in debating the dynamics of the bang or the assertion that it was "not an explosion of matter out into empty space" (but rather an "expansion of space itself"... which doesn't really address what "space itself" is besides empty volume...) I'm interested in how science deals with the "something out of nothing" problem. Such an assertion seems to me no different than the bogus religious belief that it all came out of "God's Magic Hat" if I may speak tongue in cheek as an amateur scientist with NO religious beliefs. I like an oscillating (bang/c…

what is background radiation and is it everywhere?

"A paper published on Friday in the Journal of Cosmology claims that NASA discovered microscopic evidence of fossilized structures that may be remains of extraterrestrial bacteria or what is being termed “alien bacteria. "The report was written by Dr. Richard B. Hoover, an astrobiologist for NASA. The report provides details of fossilized remains found in meteorites that appear to be remains of ancient alien bacteria. The findings would lead credibility to claims that life did not originate on Earth, but has existed in some form in the universe for millions of years." http://www.ecanadanow.com/space/2011/03/07/paper-alleges-nasa-scientist-found-alien-fossil-eviden…