Stars Definition and 890 Threads

Wikipedia says that the core temperature of our Sun is 15.7×10^6 Kelvins. I don't know what that means in terms of protons' velocities inside the core, but I bet they move pretty fast. Could they move that fast that they have a noticeable increase in mass due to their relativistic speed...

Hi, Does anybody know a place where i can find a list of electron densities of stars?

I always wondered why we see light from stars. If the light travels outward in all directions from a star then you could imagine the light as a growing sphere and the portion we see is a small area on the surface of this sphere. Well if a star is a million light years away this would mean the...

"Electroweak stars: how nature may capitalize on the standard model's ultimate fuel," De-Chang Dai, Arthur Lue, Glenn Starkman, Dejan Stojkovic, http://arxiv.org/abs/0912.0520 Pretty far out, and I'm not sure I believe it. One thing that surprises me is that they claim the standard model has...

Homework Statement Two equal spherically symmetrical stars, A and B, each of mass M and radius r have their centers 6r apart. Make a sketch showing the lines on which the gravitational potential takes the values: 1. \frac{-10GM}{11r} 2. \frac{-2GM}{3r} 3. \frac{-GM}{3r} Accurate plotting...

Please help me with this question. Thanks

Ho :), I would like to know how exactly stars and galaxies are spread out throughout the universe. Are stars only found within galaxies? How many stars are without any planets? Whats the average number of planets in a star with planets? Whats the maximum/minimum number...

Some black holes may actually be "Quark Stars" http://www.usatoday.com/tech/science/space/2009-12-07-quarkstar07_ST_N.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+UsatodaycomScienceAndSpace-TopStories+%28Tech+-+Science+and+Space+-+Top+Stories%29": excerpts below: So how...

Neutrinos can pass through solid objects like the Earth easily, and a light-year of lead would only stop half of them from passing through. What about something very dense like a white drawf or neutron star? How readily can neutrinos penetrate that? What % flux reduction would be achievable...

Are the stars fixed according to RA and Dec? If not is there equations using Julian Date for their movement?

Homework Statement The Sun rotates about the center of the Milky Way Galaxy at a distance of about 3.00x10^4 light years from the center (1ly= 9.50x10^5 m). If it takes about 200 million years to make one rotation, estimate the mass of our galaxy. Assume the mass distribution of our galaxy...

Homework Statement Figure 1 showed the light curve for an exlipsing binary system. This system consists of 2 stars. Star is is the larrger of the stars, and has a surface temp of T1=5000 K. Star 2 has a surface temp of T2=10000K. The ratio of their radii is R1/R2=4. Fnormal is the flux...

Why do the stars blink, but the planets do not? I need good explanation, please!

Is it possible for a star and a black hole to rotate each other in a relatively stable way without the BH feeding on the star and if yes could that star have planets rotating around it?

Hello everyone. I have a problem listed below. I am very lost due to the fact that my teacher literally just gave us this problem to do and expects us to hand it in soon without even teaching/talking about this topic in class. I did some research over the Internet on IMF, but still am pretty...

Sorry if this is a newby question, but it was something I was tinkering with a bit last night "As an object increases its speed relative to you, its relative mass increases. Therefore, if a neutron star passes by you at a certain speed, it should turn into a black hole." The schwartzchild...

Hi, I'm sure this has been tried but I was just wondering if it's possible to use the distribution of stars and planets in the sky and see how much that deviates from true randomness. With that calculation in mind, I would then think it's possible to determine the gravitational force present...

“There are several ways in which a planet can disturb the internal motions of matter in its host star, thereby rearrange the distribution of the various chemical elements and possibly cause the destruction of lithium. It is now up to the theoreticians to figure out which one is the most likely...

Homework Statement The solar-like star HD209458 with a mass of 1.14 solar masses exhibits radial velocity variations with a period of 3.52 days and an amplitude of 84m/s. What is the mass of its companion and what type of object is it? Homework Equations M/m = r/R = v/V [M,R,V = star, m,r,v...

Homework Statement The Gravitational binding energy of an object consisting of loose material, held together by gravity alone, is the amount of energy required to pull all of the material apart, to infinity. the gravitational binding energy Ug is roughly given by GM^2/R. how fast do you have...

So far as I understand, most stars found in the galaxy are single or double stars. However, they are born in nebulae by the hundreds. What happens to spread them out such? I would think that gravity would keep them together in the way that they were formed, by the hundreds. Or am I...

Homework Statement Certain neutron stars (extremely dense stars) are believed to be rotating at about 6 rev/s. If such a star has a radius of 15 km, what must be its minimum mass so that material on its surface remains in place during the rapid rotation? G=6.67*10-11m3 kg-1 s-2 Homework...

Hey. Is there a sort of percentage known of how much mass in the universe is in molecular clouds compared to stars. I need this for a work I am doing. Thanks

They don't look that way in the sky, but are there stars that look that way up close?

Homework Statement The sun rotates around the center of the Milky Way Galaxy at a distance of about 30,000 light-years from the center (1 light year=9.5x10^15 meters). If it takes about 200 million years to make one rotation, estimate the mass of our Galaxy. Assume that the mass distribution...

Homework Statement The sun rotates around the center of the Milky Way Galaxy at a distance of about 30,000 light-years from the center (1 light year=9.5x10^15 meters). If it takes about 200 million years to make one rotation, estimate the mass of our Galaxy. Assume that the mass distribution...

I have a series of questions here all around me attempting to get a better image of what has happened around here over the last 14 billion years. You don’t have to answer them individually. One good explanation might answer them all. Q1: About how many novas, supernovas and such have the...

Homework Statement The Spectral lines in a double-lined spectroscopic binary exhibit sinusodal motion with ampliutudes of 15 and 35 km/s in a period of 80hrs. assuming that we view the system close to edge on, calculate the individual masses in solar masses. What would you look for...

Homework Statement A binary star is resolved on the sky, the orbit is circular, it has a period of 30 years and the semi-minor and semi-major axes are observed to be 0.5 and 4 arcseconds respectively. If the distance to the system is 10pc, what are the masses of the stars? give an answer in...

Homework Statement One of the thermonuclear or fusion reactions that takes place inside a star such as our Sun is the production of helium-3 (3He, with two protons and one neutron) and a gamma ray (high-energy photon, denoted by the lowercase Greek letter gamma, ) in a collision between a...

Homework Statement (a) About half of the visible "stars" are actually binary star systems, two stars that orbit each other with no other objects nearby. Consider the motion of the center of mass of a binary star system. For a particular binary star system, telescopic observations repeated...

Gravity acceleration value depend on planet and stars mass. On the earth, the well known average value is 9.81 ms-2. On the sun, I read 1200 ms-2; is it true ? does exist a curve giving values depending on mass ?

What is the chance of planets forming from gas clouds without a star? has anyone calculated this? are they more likely to form than stars? could there be billions of rogue planets floating arround our galaxy?

Homework Statement A binary star system has a period of 90 days. It consists of two equally massed stars each with a mass of twice that of the sun, that rotate like a dumbbell about the center of mass at the midpoint between them. How far apart are these stars? Homework Equations F =...

Stars eventually die because they use up their fuel right? If all of this fuel was to be used up, would there be no suns?

I'm wondering how realistic it is for a 50 solar mass star to have a core temperature of 3.14*(10^7) K. This isn't much greater than the core temperature of the sun, which is 1.5*(10^7) K. Have I made some huge miscalculation, or does this seem feasible? Thanks.

when you log into google Earth it seems to go generally above where i am. when i press the sky button on it does it show the sky-space directly above me? I'm very new to this as you might tell. very clear skies tonight though so i thought i'd try to get my bearings on a few stars. any tips also? tx

Is it correct that the age of a star, such as the sun, is calculated by measuring the amount of helium made from fusion? If so, how do we know if that the star didn't form from a cloud that already had helium in it?

Somebody once told me that when you look into the night sky to view stars, you are actually looking at something that happened a long, long time ago (millions?, billions?, trillions of years ago?). I understand this has something to do with the speed of light and the distance of the stars...

How do we determinate the mass of stars (or planet) in other solar systems?

My friend lives in south Carolina , and he said even on a clear night he can't the stars does anyone have some insight ? And he said the air quality is good .

All the stars are Dead !??! My physics teacher says all the stars we see today are ones that are either dead or near death. All this is due to light. When a star is first created we don't see it take around 200 light years for the light of the star to reach us. Is that amazing or what...

This may be a totally silly question, it's nagging at me and I figure you guys can give me peace. We observe that the Universe is expanding, and draw the conclusion that matter started of in a dense state..., .. so why is it, that when we look back in time, to the furthest observable part...

Hi, in a lecture I was told that the cooling of neutron stars cannot happen via the 'direct' Urca process (beta decay and inverse beta decay), because the created particles cannot go into occupied states (Pauli exclusion). The 'modified' Urca process was introduced, with an additional neutron...

Hello physicists, I'm trying to understand thermal equilibrium, I used to know that a body is in thermal equilibrium if it has a uniform spatial temperature distribution. This definition couldn't hold up after I knew that stars emit black body radiation, i.e. stars are in thermal...

I was wondering about the light emitted by one of these neutron stars. To my limited knowledge, neutron stars are among the discrete objects in the observable universe with the strongest gravitational and EM fields [black holes beat the living crap out of neutron stars, but that's besides the...

The universe is around 13.5 to 14 billion years old. That means that if everything started from one singularity which was the big bang, and nothing can travel faster than the speed of light, the size of the universe must be at most 14 billion light years in size. But even that is an extremely...

Hi all, I have this question: Stars in a cluster have gravity influence on each other, so why they do not clump together? Bigger scale : stars in a galaxy.

What are the best books (upper undergraduate / beginning graduate) for stellar structure, stellar evolution, compact stars, etc. ?

my teacher told me that if i look at the stars too long i become deaf since the stars emit special elctromagnetic waves which make my ears not work properly. but i don't get why. because stars don't make any sound...