how are stars created and why are they in the sky?
131331
Stars are big fiery balls of gas. Essentially the gases cluster together and become stars through gravity and fusion. It's a rather complicated process; check the link below for a more detailed explanation.\n\nStars appear to be in our sky because they are in space. Most stars appear to be small points of light, although many of these stars are smaller than our sun. The sun simply appears larger because it is much nearer to the Earth.
5974
The main reason is dust in space that absorbs the light.  For instance, we are in a great big spiral galaxy.  Generally, if you look at a spiral galaxy, you see an immense, bright core.  So why don't we see such a core?  It's because of the dust.  The core, if visible, should be right around the constellation of Sagitarius.  But since there's so much dust in the plane of the galaxy, we can't see it in the invisible spectrum.  Astronomers have managed to infer the direction of the center of the galaxy by looking for a type of light (21 cm radiation) that is regualrly produced by astronomical phenomena, and which has an ability to pass more easily through the clouds of dust in space.  By gauging the direction of most of this radiation, they can infer that the bulk of the galaxy is in the direction of Sagitarius.\n\nAnd really, there is "light" coming from all directions, but most of it isn't in the visible range.  Cosmologists have found what is refered to as the 3K (three "degrees" Kelvin--a very cold temperature) radiation background that exists in direction.  This is seen not as the product of stars, but as a remnant of the big bang.\n\nBut most importantly, there are not really "infinite" stars.  The universe, though boundless, is not truly infinite.  There are some mathematical oddities that you find when you try to deal with the infinite and the boundless.  For instance, there are an infinite number of poritive integers, and there are an infinite number of irrational numbers between 0 and 1.  As odd as it seems, there are actually more irrational numbers between 0 and 1 (what my math professor called the "uncountably infinite") than there are positive integers (so-called "countably infinite").  Due to the relativity of simultneity shown by Einstein, one cannot exactlt quantify the total number of stars in the universe at a given point in time, because an observer moving at a different speed and looking at that moment in time would disagree as to which stars had already exploded or not, and which stars had already formed or not.  So while you can really make a definitive statement as to the number of stars, the number is not really infinite in the general sense of the word, as neither is the universe truly infinite.
568822
black holes happen when stars colapse.  Stars are massive fusion engines.  Their mass alone should make them colapse on themselves due to gravity but the nuclear fusion reactions going on in them where hydrogen atoms are being smashed together and forming helium atoms create huge constant explosive energy forcing the gasses in a star outward.  Eventualy the hydrogen gets used up.  The fuel for the star is gone and the star has nothing to keep it's mass from collapsing on itself.  All the star's gas molecules attract each other toward the center through the force of gravity and finaly all that mass which had taken up the space of thousands of planets is contained in the space of, ooohhhh I don't know a bowling ball.\n\nThat small ball of used up star has a huge density.  Density is mass divided by volume.  For example,  A nerf ball and a small marble may both weigh the same, but the nerf ball has a larger volume so the density is smaller and therefore the nerf ball is softer and if it has a density less than 1g/cc it will float while the marble will sink.\n\nSee when the the mass is in the numerator and the volume is in the denomenator is the volume.  As the volume (denomenator) gets bigger while the mass (in the numerator) stays the same the whole number gets bigger. \n\nThis is what happens in a black hole as it collapses.  It has the same number of gas molecules as it collapses but they get closer together and the volume gets smaller.  Let's say the mass of the star is 1 and watch what happens to the density as you divide it by a smaller and smaller number.\n\n1/10 = .1\n\n1/1 = 1\n \n1/.01 = 10\n\n1/.001 = 100\n\n1/.000 1 = 1000\n\n1/.000 01 = 10 000\n\nSee as the mass stays the same and the volume decreases the density gets bigger.  It quickly approaches infinity.  Math doesn't handle infinity well and we can't predict what happens at this point.  We call a point of infinite density a singularity.  \n\nThis singularity in a black hole has a huge density and huge gravity so nothing can get out, not even light, hence the name BLACK HOLE.  \n\nSo how do we know they're there?  We can see the efects of the black hole on other stars and Stephen Hawkins predicted that the black holes would actualy emit radiation which was detected proving him right and proving black holes.
495658
1. Its mass, its age, its energy state\n\n2. The earth's atmosphere makes stars appear to twinkle owing to their vast distances from us. They appear as points of light and so the light rays are bent differently by small ongoing variations in the earths atmosphere and so cause minor movements and fluctuations. However planets are disks rather than points (even though our eyes do not perceive their size). They are large enough to not appear to move like stars do as the position variations caused by bending of light by the atmosphere are 'within' the size of the planetary disk. Also the visible planets are very very bright compared to most visible stars so variations in light intensity are not so obvious.\n\n3. This is a difficult one. For example:\n\nIs it hydrogen, the primordial element of the universe??\nIs it energy as energy is what makes it all happen??\nIs it gravity as gravity causes clouds of hydrogen to condense into stars??\nIs it fusion as without fusion of hydrogen and then other elements nothing works??\n\nNo I cannot answer it. I put this one in the "too hard" basket.
513007
reflection of light\n\nDuring daylight the sky has the appearance of a deep blue surface, but this is the result of the air scattering sunlight. [1] There is no "blue object" above the earth in any normal sense, so it is hard to say what object the sky is. The sky is thus sometimes defined as the denser gaseous zone of a planet's atmosphere. At night the sky has the appearance of a black surface or region scattered with stars. But if we then say that the sky is the entire visible universe, it would not be the same thing we see during the day.
227171
STARS AND NEBULAE.\n\nMost of the things you can see in the night sky are stars: a few thousand are visible to the unaided eye. A star is a hot ball of mostly hydrogen gas; the Sun is an example of a typical, ordinary star. Gravity keeps the gas from evaporating into space, and pressure due to the star's high temperature and density keeps the ball from shrinking. In the core of the star, the temperature and densities are high enough to sustain nuclear fusion reactions, and the energy produced by these reactions works its way to the surface and radiates into space as heat and light. When the fuel for the fusion reactions is depleted, the structure of the star changes. The process of building up heavier elements from lighter ones by nuclear reactions, and adjusting the internal structure to balance gravity and pressure, is called stellar evolution. \nLooking at a star through a telescope can tell us many of its important properties. The color of a star tells us its temperature, and the temperature depends on some combination of the star's mass and evolutionary phase. Usually, observations also allow us to find the luminosity of the star, or the rate at which it radiates energy as heat and light. \nAll stars visible to the unaided eye are in our galaxy, the Milky Way. The Milky Way is system of roughly 100 billion stars, along with a great deal of interstellar material. The galaxy is shaped like a flattened disk embedded in a round, faint halo. Gravity keeps the stars from drifting away, and the motions of the stars keep the system from falling in on itself. The Milky Way has no distinct edge - the distribution of stars tapers off gradually with increasing distance from the center. The SDSS detects stars more than a million times fainter than can be seen with the unaided eye, far enough to see the outer structure of the Milky Way. \nStar Colors and Luminosities: The H-R Diagram\nAstronomers often make plots of the luminosities of stars compared to their colors. The first such charts were made in the early twentieth century, when astronomers took spectra of thousands of stars, then placed the spectra into a sequence based on the appearance of several different features. The classes of stars were given different letters as names; in order of decreasing temperature, they are OBAFGKMLT. The hottest stars are class O, while the coolest are class T. Two astronomers, Ejnar Hertzsprung and Henry Norris Russell, independently started to wonder what would happen if they compared stars' luminosities to their spectral classifications (or, alternatively, to their temperatures). They knew that some stars were hotter and more luminous than the sun, and that others were cooler and less luminous. Hertzsprung and Russell found that 90% of the stars fell into a narrow band they termed the "main sequence." Today, we call this type of plot a Hertzsprung-Russell (or H-R) diagram. \nAstronomers further divide each letter into ten categories from 0 to 9, with 0 being the hottest star in that spectral class and 9 being the coolest. So, a B1 star is hotter than a B2 star, and a B9 star is hotter than an A0 star. Our own sun is at the "hot" end of the G range with a surface temperature of 5,770° K; therefore, it's called a G2 star. \nSpectral classes give us a convenient way to refer to most types of stars - from O0, the hottest at over 25,000° K, down to T9, the coolest failed stars at 1,000° K. Each spectral type of star is associated with a specific color: all G-type stars like the sun are yellow, all M-type stars appear red, and all B-type stars are bluish. Thus, this system of letters and numbers tells us where a star is on the horizontal (color or temperature) axis of the H-R diagram. \nTwo alternative systems tell us approximately where on the vertical (luminosity) axis a star can be found. One system uses absolute magnitude, a measure of luminosity derived from the apparent magnitude, or brightness of the star
127269
Yes, new stars and new planets can form from the remnants of dead stars.  We can see this process happening, although it is extremely slow, a process that take millions of years.\n\nEven our sun is thought to be a 3rd generation star.  When our sun dies, it will expand to become a Red Giant star, eventually cooling/contracting into a white dwarf, as this happens, a lot of stellar meterial will be released and will float off into space to make new stars in the future.
64348
Most of the stars we see with the naked eye are within our galaxy.  If you lived in the southern hemisphere, you could see the Mangellanic clouds, which are two small satellite galaxies of the Milky Way.  You would not be able to see induvidual stars, but you would see the glow of millions of stars within them.\nIn the northern hemishere, if you are in a very dark place, you can see the Andromeda Galaxy, which is 2.5 million light years away but you can see the glow of the billions of stars that make up that galaxy.\nBut all the induvidual stars we see in the night sky with the naked eye, they are within our Milky Way galaxy.\n\nAnd for stars between galaxies...yes there are.  There are a few stars that get cast off and tossed into intergalactic space.  There is one right now that has been flung out of our galaxy at a bit over a million miles an hour when it had a close encounter with the black hole in the core of our galaxy.  There are millions, perhaps billions, of stars in the galactic halo around the Milky Way...they are just difficult to see, even in a big telescope, as they are mosly dim red dwarfs.  The space between galaxies is not empty...things are just spread out a bit more.
22935
The sky is blue because the nitrogen in the air scatters the blue light out of sunlight. \n\nOur sun is a yellow star, so it has slightly yellow light, but it is still pretty close to white light.\n\nSunlight on earth is slightly yellower than it is in space because some of the blue light in sunlight gets scattered out by the presence of nitrogen in the air, making the sky appear blue. So \n\n(White light) - (Some Blue light) = (Yellow light)\n\nAs the sun sets, the sunlight travels through more air, and the nitrogen scatters out more blue light and the sun appears first orange, and then finally red.\n\nAs the sun starts to set:\n\n(White light) - (More Blue light) = (Orange light)\n\nand finally as the sun has almost set:\n\n(White light) - (Lots of Blue light) = (Red light) \n\nEdit   Delete
618256
They start out as an enormous gas cloud. Gravity causes the parcicles in the cloud to spin around the point of center mass, and the velocity of the spin subsequently flattens it into a disk. That's how galaxies, and on a much smaller scale, planetary systems form.
81359
Gravity is only half of the picture.\n\nThe stars gravity does tend to pull the stars material towards the center of the star.\n\nHowever, there is also an expansive force - the force of the nuclear fusion reaction that is taking place inside the start.  This reaction creates light, heat, x-rays, cosmic rays and so on.. but it also pushes against the infalling star material, trying to push it back out.\n\nThe balance between gravity and fusion energy is why the star stays (about) the same size.\n\nSometimes gravity wins, and the star compresses all the way town to a neutron star or even a black hole.\n\nSometimes the nuclear reaction wins and the star explodes in a nova or supernova.\n\nMost stars are stable for a VERY long time (billions of years).
66917
Our sun is a star.  All stars could be called suns.  As for the size of space....  some theorize that space is expanding, some say that space is contracting, so I think there is no real answer to your question.  Personally, I think this goes beyond science and into meta-physics.
242064
To Answer the First part:\n\nThe life of a star is a continual struggle between the two forces of GRAVITY and NUCLEAR ENERGY. \nThe star’s self gravity or weight tries to compress the star into a smaller sphere of gas. But when a gas is compressed it gets hot, and in the core of a star the gas gets so hot (10 million Kelvins or more) that nuclear reactions occur. In a star like the Sun the nuclear reactions release more energy each second than one billion hydrogen bombs. As this energy works its way out of the star it balances the star’s self-gravity. For most of a star’s life an equilibrium is maintained between self gravity and energy.\n\nPSS Part 2\n\nNot sure what they want here. Since the "young star" is formed from the older star dust, it would have a higher proportion of heavier elements (like Iron and Silicon), since those elements would have been created in the older stars. A new protostar would never have been exposed to these heavier elements, so it would be still Hydrogen and Helium.
674551
The sky is beautiful, but clouds are just water vapors. How does a tree grow? Photosynthesis. Knowing how something occurs does make it less beautiful does it?
635365
sky is nothing but made up of gases . as gases rise uo they all collect above
68401
Shooting stars form first in the mesosphere, which is about 50-80 km above sea level.\n\nIf we look for a maximum, we assume you are at sea with no obstructions on the horizon, the meteor begins glowing at 80km, and is infinitely bright, and appears for a split second right at the horizon, then it could be as far away as about 1,400 km (around 900 miles).  Changing the height from 80 to 50 km lowers that distance to 1,100 km or 700 miles.\n\nHowever, that just frames an unlikely maximum distance for a shooting star of incredible brightness.  I'd wager it's likely that most shooting stars are far too dim to be seen from such a distance, and any necessary inclination above the horizon necessarily lowers that distance a bit.  (I can't calculate much on that, however, because I don't have a calculator handy that can do the trig functions).
466096
There is no fire on the sun.  Our star is converting hydrogen into helium (which is nuclear fusion and thus creates heat) because it is so massive that the atoms its made from are being compressed by its own gravity.\n\nEventually, it will run out of fuel and stop "burning" all together, becoming a white dwarf, then a black one.\n\nLarger stars will explode and disperse their materials (the things you and I are made of) across the universe.  The largest will become black holes and try to fix the mess created by the others.