Startling Facts Of Universe

1. The current theory of the origin of the universe is the Big Bang, which holds that the universe began as an explosion that filled all space.
2. When we look at quasars which are 10-15 billion light years away, we are looking 10-15 billion years into the past. Pretty amazing, right?
3. Many astronomers believe that quasars are the most distant objects yet detected in the universe. Quasars give off enormous amounts of energy - they can be a trillion times brighter than the Sun!.Quasars might be the ancestors of all galaxies, the violent beginnings of us all.
4. Universe consists of 4 percent “normal” atoms (the stuff we are made of), 23percent dark matter, and 73 percent dark energy.
5. Expansion of the universe is accelerating.
6. Large amount of evidence suggests that the center of our Galaxy harbors a 
   massive black hole.Galactic centre appears to be the location of a black hole of several million solar masses.At the centre of every galaxy contains a massive black hole.
7. Each galaxy contains several hundred billion stars, typically about 100 times as many 
   stars as there are people on our planet.
8. If the 
   Earth were compressed to the 
   size of a marble—yet retained its 
   current mass—a velocity greater 
   than the speed of light would be 
   required to escape its marblesized 
   surface. Such an object 
   would be, effectively, a black 
   hole.
9. All supernova explosion does not lead to black hole.
   We recognize two types of supernovae. Type I supernovae contain little hydrogen, whereas Type II are rich in that element. Only Type II supernovae are associated with the core collapse of high-mass stars and forms black hole. Type I supernovae are associated with our friends the white dwarfs and Neutron stars.
10. A giant is a star with a radius between 10 and 100 times that of the Sun.A supergiant is a star with a radius more than 100 times that of the Sun. Stars of up to 1,000 solar radii are known.A dwarf star has a radius similar to or smaller than the Sun.
11. To produce energy, hydrogen atoms in the Sun’s core plow into one another and thereby create helium atoms. In the process, a little mass is converted into energy. That little bit of energy for each collision equates to enormous amounts of energy when we count all of the collisions that occur in the core of the Sun. With this energy source, the Sun is expected to last not 1,000 years or even 100 million years, but about 8 to 10 billion years, typical for a star with the Sun’s mass.
12. The Sun doesn’t keep its energy to itself. Rather this energy flows away in the form 
    of electromagnetic radiation and particles. The particles (mostly electrons and protons) 
    don’t move nearly as fast as the radiation, which escapes the surface of the Sun 
    at the speed of light, but they move fast nevertheless—at more than 300 miles per 
    second (500 km/s). This swiftly moving particle stream we call the solar wind. the 
    gases are sufficiently hot to escape the tremendous gravitational pull of the Sun. 
    The 
    surface of Earth is protected from this wind by its magnetosphere, the magnetic field, 
    a kind of “cocoon,” generated by the rotation of charged material in Earth’s molten 
    core. Similar fields are created around many other planets, which also have molten 
    core material. The magnetosphere either deflects or captures charged particles from the solar wind.
13. Most asteroids are rather small; it is estimated that there are 1 million with diameters greater than 1 km. Some, perhaps 250, have diameters of at least 100 km, while about 30 have diameters of more than 200 km. All of these planets and asteroids are the debris from the formation of the Sun that coalesced slowly through the mutual attraction of gravity.
14. Rings around planets are indeed made up of particles, primarily of water ice.
15. Ganymede is the largest moon in the solar system (bigger than the planet Mercury) orbiting Jupiter.
16. There are 62 moons (at least) 
    for Jupiter, 60 for Saturn, 27 for Uranus, and 13 for Neptune.
17. The Moon is in a synchronous orbit around Earth; that is, it rotates once on its axis every 27.3 days, which is the same time it takes to complete one orbit around Earth. Thus synchronized, we see only one side of the Moon.
    
18. Clearly visible on images produced by Martian probes are runoff and outflow channels, which are believed to be dry riverbeds, evidence that water once flowed as a liquid on Mars.
19. The Martian surface contains large amounts of iron oxide, red and rusting that’s why it’s a red planets.
20. The rotation period of venus is negative because the rotation of Venus is retrograde; that is, the planet rotates on its axis in the opposite direction from the other planets.The rotation period of Uranus is negative because it is retrograde; like Venus, it rotates on its axis in the 
    opposite direction from the other planets.If at 59 days, Mercury rotates on its axis slowly, Venus is even more sluggish,
    consuming 243 Earth days to accomplish a single spin. all the planets (terrestrial and jovian) spin counterclockwise—except for 
    Venus, which spins clockwise.
21. The gravitational field of a passing star from time to time deflects a comet out of its orbit within 
    the Oort Cloud, sending it on a path to the inner solar system.
    After a short-period or long-period comet is kicked out of its Kuiper Belt or Oort 
    Cloud home, it assumes its eccentric orbit indefinitely. It can’t go home again.It may then collides with the planets.
22. Mercury and venus have 0 moons,earth has 1,mars has 2,Jupiter 62,Saturn 60,Uranus 27 and Neptune has 13 moons.
23. Jupiter,the largest planet in the solar system, is over 300 times the mass of Earth, but the Sun is more than a thousand times more massive than Jupiter and about 300,000 times more massive than Earth.
24. Astronomical unit (A.U.), which is the average distance between Earth and 
    the Sun—that is, 149,603,500 kilometers or 92,754,170 miles.
25. Pluto, long counted as the ninth planet, was 
    recently downgraded from a full-fledged planet to a mere “dwarf planet.”
26. Right now, the fastest rockets are capable of achieving 13.333 km/s or 30,000 miles per hour (48,000 km/h), 
    or 262,980,000 miles per year (423,134,820 km/y). 
    Maybe—someday—technology will enable us at least 
    to approach the speed of light.
27. Light travels at extraordinary speeds (about 984,000,000 feet—300,000,000 meters—every second), but the 
    light that we now see from many objects in the sky left those sources thousands, millions, 
    or even billions of years ago. Remember 
    the Andromeda galaxy? We can see it, but the photons of light we just received from 
    the galaxy are 2 million years old. Now that’s a long commute!.
28. we are not alone in this universe….there may be another planet,revolving a star in the universe,which may contain lives.
29. To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole. Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it. At the same time, all processes on this object slow down, for a fixed outside observer, causing emitted light to appear redder and dimmer, an effect known as gravitational redshift. Eventually, at a point just before it reaches the event horizon, the falling object becomes so dim that it can no longer be seen.
    On the other hand, an observer falling into a black hole does not notice any of these effects as he crosses the event horizon. According to his own clock, he crosses the event horizon after a finite time without noting any singular behaviour. In particular, he is unable to determine exactly when he crosses it, as it is impossible to determine the location of the event horizon from local observations.
30. Centre of the Universe is every where.

Dark Energy and Dark Matter

The distances to the galaxies that they are in show that the universe appears to have been expanding more slowly in the past than now. So not only is everything rushing away from everything else, but, these days, it’s also rushing away more quickly. In other words, the expansion of the universe is accelerating. And what is causing it to accelerate? Well, it might be the “vacuum energy” that Einstein thought he needed to support the universe from collapsing on itself.

Interestingly, this force increases with distance—as opposed to gravity, which weakens with distance. Scientists have dubbed this new energy required to power an accelerating expansion “dark energy,” implying that, as with “dark matter,” we know it is there, but we don’t know what it is. The expansion of the universe appears to be accelerating, powered by an as yet unexplained “dark energy.” The universe consists of 4 percent “normal” atoms (the stuff we are made of), 23 percent dark matter, and 73 percent dark energy.

Beyond galaxy,So what is all this other stuff we cannot see directly? Whatever its makeup, it apparently emits no radiation of any kind—no visible light, no x-rays, no gamma radiation. But it cannot hide completely. We “see” it because it has mass and its mass affects the

way in which the stars and gas of the Milky Way orbit. Astronomers call the region containing this mass the “dark halo,” and the Milky

Way is not alone in possessing such a region. Many, if not all, galaxies have the same signature in the rotation of their stars and gas. Presumably, the dark halo contains—what else?—dark matter, a catchall term that we use to describe a variety of candidate

objects. The truth is, we’re not sure what dark matter is, but we do know it’s there because we clearly can see its gravitational effects.it is difficult-to-detect low-mass stars (brown dwarfs or faint red

dwarfs) might be responsible for the mass in this region. And neutrinos do have nonzero mass, so their presence might contribute to dark matter.Because dark matter accounts for a great deal of the mass of a galaxy—up to 10 times more than the mass of visible matter—the shocking conclusion must be that 90 percent

of the universe is dark matter, utterly invisible in the most profound sense of the word. Dark matter neither produces nor reflects any electromagnetic radiation of any sort at any wavelength. The majority of the mass (90 percent) of most galaxies and clusters (99 percent) is made of dark matter, material we cannot observe but only see by its gravitational effect. Although several lines of evidence exist that confirm dark matter is very real, we are still unsure of what it might be.

Galaxies

Each galaxy contains several hundred billion stars, typically about 100 times as many stars as there are people on our planet. Galaxies (of which the Milky Way is one) are enormous collections of stars, gas, and dust. The different parts of the Milky Way are not static but are in constant motion. The disk rotates about the Galactic center, and at large radii, the rate of rotation does not trail off but remains fairly constant.

Galaxies may be Spiral,elliptical and irregular.

A large amount of evidence suggests that the center of our Galaxy harbors a massive black hole.Galactic centre appears to be the location of a black hole of several million solar masses and is the same source that has been imaged with the new orbiting Chandra X-ray Observatory. The x-ray emissions from the Galactic center show the presence of hot gas and a jet, both of which are often associated with the presence of a black hole.The stars are orbiting a supermassive black hole: a monster in our closet.

Within 1 million parsecs (3 million light-years) of the Milky Way lie about 20 galaxies, the most prominent of which is Andromeda (M31). This galactic grouping, called the Local Group, is bound together by gravitational forces. The generic name for our Local Group is a galaxy cluster. Some clusters contain fewer than the 20 or so galaxies of the Local Group, and some contain many more. The Virgo Cluster, an example of a rich cluster, is about 15 million parsecs from the Milky Way and contains thousands of galaxies, all bound by their mutual gravitational attraction. From the velocities and positions of galaxies in clusters, one thing is very clear. We

cannot directly observe at least 90 (perhaps as much as 99) percent of the mass that must be there. Galaxy clusters, like the outer reaches of spiral galaxies, contain mostly dark matter.

Galaxy clusters themselves are grouped together into what we call superclusters. Many galaxies are grouped in galactic clusters, which, in turn, are grouped into superclusters that are found together on the edges of huge voids.

Asteroids

Asteroids are small Solar System bodies that are not comets.

Asteroids are One of thousands of small, rocky members of the solar system that orbit the Sun. The largest asteroids are sometimes called minor planets. The majority of known Asteroids are in the asteroid belt between Mars and Jupiter.Most asteroids are rather small; it is estimated that there are 1 million with diameters greater than 1 km. Some, perhaps 250, have diameters of at least 100 km, while about 30 have diameters of more than 200 km. All of these planets and asteroids are the debris from the formation of the Sun that coalesced slowly through the mutual attraction of gravity.The solar system contains a great many comets and billions of smaller, rock-size meteoroids.Asteroids are composed of stony as well as metallic—mostly iron—materials and are basically tiny planets without atmospheres.It is believed that a few asteroids of more than a half-mile diameter might collide with Earth in the course of a million years. Such impacts would be cataclysmic, each the equivalent of the detonation of several hydrogen bombs. Not only would a great crater, some 8 miles across, be formed, but an Earth-enveloping dust cloud would also darken the skies. Some think the great extinction of the dinosaurs 65 million years ago was due to such an impact. Were the impact to occur in the ocean, tidal waves and massive flooding would result. Earth impacts of smaller objects are not uncommon, but on June 30, 1908, a large object—apparently the icy nucleus of a small comet—fell in the sparsely inhabited Tunguska region of Siberia. The falling object outshone the Sun, and its explosive impact was felt more than 600 miles away. A very wide area of forest was obliterated—quite literally flattened.

Meteors,meteoroid and meteorites

A meteoroid is a sand- to boulder-sized particle of debris in the Solar System.Actually meteorides are the debris left by comets.

Each time a comet passes close to the Sun, a bit of its mass is boiled away—about 1⁄1,000 of its mass with each pass. After some 100 passages, a comet typically fragments and continues to orbit as a

collection of debris or coalesces with the Sun. As Earth passes

through the orbital paths of such debris, we experience meteor showers. Whenever a comet makes its nearest approach to the Sun, some pieces break off from its nucleus. The larger fragments take up orbits near the parent comet, but some fall behind, so that the comet’s path is eventually filled with these tiny micrometeoroids.

Periodically, Earth’s orbit intersects with a cluster of such

micrometeoroids, resulting in a meteor shower as the fragments burn up in our upper atmosphere. Meteors are often called shooting stars, although they have nothing at all to do with stars. A meteor is a streak of light in the sky resulting from the intense heating of a narrow channel in Earth’s upper atmosphere. The heat generated by friction with air molecules as the meteoroid hurtles through Earth’s atmosphere ionizes—strips electrons away from atoms along—a pathway behind this piece of space debris. The ionized path in Earth’s atmosphere glows for a brief time, producing the meteor. The meteor streaks across a part of the sky, whereas a comet does not streak rapidly and may, in fact, be visible for many months because of its great distance from Earth. A meteor is an event occurring in Earth’s upper atmosphere, whereas a comet is typically many A.U. distant from Earth. Meteor is the term for the sight of the streak of light caused by a meteoroid—which is the term for the actual rocky object that enters the atmosphere. Most meteoroids are completely burned up in our atmosphere, but a few do get through to strike Earth. Any fragments that reaches the earth surface without burning up in atmosphere and then recovered are called meteorites. Millions of meteors occur in the Earth's atmosphere every day.

Comets

A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma (a thin, fuzzy, temporary atmosphere) and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles.Comets are distinguished from asteroids by the presence of a coma or a tail.

The word comet derives from the Greek word kome, meaning “hair.” The name describes the blurry, diaphanous appearance of a comet’s long tail. most comets (called long-period comets) travel even beyond Pluto and might take millions of years to complete a single orbit. So-called “short-period” comets don’t venture beyond Pluto and, therefore, have much shorter orbital periods.

As a comet approaches the Sun, the dust on its surface becomes hotter, and the ice below the crusty surface of the nucleus sublimates—that is, immediately changes to a gas without first becoming liquid. The gas leaves the comet, carrying with it some

of the dust. The gas molecules absorb solar radiation, then reradiate it at another wavelength while the dust acts to scatter the sunlight. This process creates a coma, a spherical envelope of gas and dust (perhaps 60,000 miles across) surrounding the nucleus and a long tail consisting of gases and more dust particles. Both the ion and dust tails point away from the Sun, regardless of the direction of the comet’s travel. This is because a comet tail is “blown” like a wind sock by the solar wind, a constant stream of matter and radiation that escapes from the Sun.

The solar system has two cometary reservoirs. The nearer reservoir is called the Kuiper Belt,the short-period comets, those with orbital periods less than 200 years. gravitational influence sends one into an eccentric orbit that takes it outside of the belt. Long-period comets,originate in the Oort Cloud a vast area surrounding the solar

system.The gravitational field of a passing star from time to time deflects a comet out of its orbit within the Oort Cloud, sending it on a path to the inner solar system.

After a short-period or long-period comet is kicked out of its Kuiper Belt or Oort Cloud home, it assumes its eccentric orbit indefinitely. It can’t go home again. Each time a comet passes close to the Sun, a bit of its mass is boiled away—about 1⁄1,000 of its mass with each pass. After some 100 passages, a comet typically fragments and

continues to orbit as a collection of debris or coalesces with the Sun. As Earth passes through the orbital paths of such debris, we experience meteor showers. Whenever a comet makes its nearest approach to the Sun, some pieces break off from its nucleus. The larger fragments take up orbits near the parent comet, but some fall behind, so that the comet’s path is eventually filled with these tiny micrometeoroids. Periodically, Earth’s orbit intersects with a

cluster of such micrometeoroids, resulting in a meteor shower as the fragments burn up in our upper atmosphere.
Most comets actually have two tails. The dust tail is usually broader and more diffuse than the ion tail, which is more linear. The ion tail is made up of ionized atoms—that is, atoms that are electrically charged. Both the dust tail and the ion tail point away from the Sun, but the dust tail is usually seen to have a curved shape that trails the
direction of motion of the comet.

Quasars

Quasars are extremely distant objects in our known universe. They are the furthest objects away from our galaxy that can be seen. Quasars are extremely bright masses of energy and light. The name quasar is actually short for quasi-stellar radio source or quasi-stellar object. Quasars are the brightest objects in our universe, although to see one through a telescope they do not look that bright at all. This is because quasars are so far away. They emit radio waves, x-rays and light waves. Quasars appear as faint red stars to us here on Earth.

A quasar is believed to be a supermassive black hole surrounded by an accretion disk. An accretion disk is a flat, disk-like structure of gas that rapidly spirals around a larger object, like a black hole, a new star, a white dwarf, etc. A quasar gradually attracts this gas and sometimes other stars or or even small galaxies with their superstrong gravity. These objects get sucked into the black hole. When a galaxy, star or gas is absorbed into a quasar in such a way, the result is a massive collision of matter that causes a gigantic explosive output of radiation energy and light. This great burst of energy results in a flare, which is a distinct characteristic of quasars.

The light, radiation and radio waves from these galaxies and stars being absorbed into a black hole travel billions of light years through space. When we look at quasars which are 10-15 billion light years away, we are looking 10-15 billion years into the past. Pretty amazing, right?

Many astronomers believe that quasars are the most distant objects yet detected in the universe. Quasars give off enormous amounts of energy - they can be a trillion times brighter than the Sun! Quasars are believed to produce their energy from massive black holes in the center of the galaxies in which the quasars are located. Because quasars are so bright, they drown out the light from all the other stars in the same galaxy.

Despite their brightness, due to their great distance from Earth, no quasars can be seen with an unaided eye. Energy from quasars takes billions of years to reach the Earth's atmosphere. For this reason, the study of quasars can provide astronomers with information about the early stages of the universe.

If a supermassive black hole is the source of a quasar’s power, then about 10 Sunlike

stars per year falling into the black hole could produce its enormous luminosity. Quasars might be the ancestors of all galaxies, the violent beginnings of us all.

A quasi-stellar radio source ("quasar") is a very energetic and distant active galactic nucleus. Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that were point-like, similar to stars, rather than extended sources similar to galaxies.Quasars show a very high redshift, which is an effect of the expansion of the universe between the quasar and the Earth.

Types Of Stars (Red Dwarf,Red Gaint,White Dwarf,Neutron Star,Yellow Star,Blue Star etc)

Red Dwarf Stars : 

Red dwarfs are very low mass stars. Consequently they have relatively low temperatures in their cores and energy is generated at a slow rate through fusion.Hence these stars emit little light, sometimes as little as ¹⁄_10,000 that of the Sun. Even the largest red dwarfs have only about 10% of the sun's luminosity.

Red Dwarf stars are smaller than our sun. And since they are smaller, they also have less mass. Because of their small size, these stars burn their fuel very slowly, which allows them to live a very long time. This also causes these stars to not shine as brightly as others.  Some red dwarf stars will live trillions of years before they run out of fuel.

Red dwarf stars only burn a little bit of fuel at a time, they are not very hot compared to other stars.  Think of a fire.  The coolest part of the fire is at the top of the flame where it glows red, the hotter part in the middle glows yellow, and the hottest part near the fuel glows blue.  Stars work the same way.  Their temperature determines what color they are.  Thus, we can determine how hot a star is just by its color.Very few stars that you see in the sky are red dwarfs. This is because they are so small and make very little light,that they are masked by brighter stars.They look red because they are less luminous.

Yellow Stars :

Like the Sun, these medium-sized stars are yellow because they have a medium temperature.Their higher temperature causes them to burn their fuel faster. This means they will not live as long, only about 10 billion years or so.  Near the end of their lives these medium-sized stars swell up, becoming very large. When this happens to the Sun, it will grow large enough to engulf even the Earth. Eventually they shrink again, leaving behind most of their gas. This gas forms a beautiful cloud around the star called a Planetary Nebula.

The sun is only about 5 billion years old. It still has another 5 billion years or so before it will expand and turn into a planetary nebula.

The Sun is so hot that when it dies, it will take a long time to cool off.  The Sun will die in about 5 billion years, but it will still glow for many billions of years after that. As it cools, it will be what is called a White Dwarf Star. Eventually, after billions, maybe even trillions of years, it will stop glowing. At that point it will be what we call a Black Dwarf Star. Because the process for a star to become a black dwarf takes such a long time, it is believed there are still no black dwarf stars in the universe.

White Dwarfs : 

A white dwarf is what stars like the Sun become after they have exhausted their nuclear fuel. Near the end of its nuclear burning stage, this type of star expels most of its outer material, creating a Planetary nebula. Only the hot core of the star remains. This core becomes a very hot white dwarf, with a temperature exceeding 100,000 Kelvin. Unless it is accreting matter from a nearby star, the white dwarf cools down over the next billion years or so. Many nearby, young white dwarfs have been detected as sources of soft, or lower-energy, X-rays.A white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored thermal energy.

White dwarfs are thought to be the final evolutionary state of all stars whose mass is not high enough to become a Neutron star.White dwarfs form as the outer layers of a low-mass Red Giant Star puff out to make a planetary nebula. Since the lower mass stars make the white dwarfs, this type of remnant is the most common endpoint for stellar evolution. If the remaining mass of the core is less than 1.4 solar masses, the pressure from the degenerate electrons (called electron degeneracy pressure) is enough to prevent further collapse to form neutron star.

Red Giants :

When the star exhausts the hydrogen fuel in its core, nuclear reactions in the core stop, so the core begins to contract due to its gravity. This heats a shell just outside the core, where hydrogen remains, initiating fusion of hydrogen to helium in the shell. The higher temperatures lead to increasing reaction rates, producing enough energy to increase the star's luminosity by a factor of 1,000–10,000. The outer layers of the star then expand greatly, beginning the red giant phase of the star's life.

Due to the expansion of the outer layers of the star, the energy produced in the core of the star is spread over a much larger surface area, resulting in a lower surface temperature and a shift in the star's visible light output towards the red – hence red giant, even though the color usually is orange.

Blue Giant Stars : 

Blue stars are large and compact, this causes them to burn their fuel quickly which in turn makes their temperature very hot.  These stars often run out of fuel in only 10,000 - 100,000 years. 

A blue giant is extremely bright.  Like a lighthouse, they shine across a great distance.  Even though blue giant stars are rare, they make up many of the stars we see at night because they shine so brightly.

Blue giant stars die in a spectacular way.  They grow larger just like the sun-sized stars, but then instead of shrinking and forming a planetary nebula, they explode in what is called a Supernova. Supernova explosions can be brighter than an entire galaxy, and can be seen from very far away.

Giant and Super Giant Stars : 

As a sun-sized star gets old, it starts to run out of its hydrogen fuel.  When the process of burning hydrogen in the star's core begins to slow down, the core gets more compact and dense. This means all the stuff in the middle of the star gets really close together.  As the center gets smaller and smaller it starts to heat up again. When it gets hot enough it will start to burn a new fuel called helium.

Once ignited, helium burns much hotter than hydrogen. The additional heat pushes the outer layer of the star out much further than it used to be, making the star much larger. Imagine a hot air balloon. As the air inside the balloon gets hotter, it stretches the balloon out further and further. As the giant star gets hotter, its outside stretches out further and further. When our own sun begins to stretch into a giant star, it will engulf Mercury, Venus, Earth and Mars.

The only difference between Giant Stars and Super Giant Stars is their size. Super Giant Stars are much bigger.  If the Sun were replaced by a super giant star, it would extend from the center of our Solar System almost all the way out to Uranus.

Neutron Star :

 If the core mass is between 1.4 and 3.2 solar masses, the compression from the star's gravity will be so great the protons fuse with the electrons to form neutrons. The core becomes a super-dense ball of neutrons. Only the rare, massive stars will form these remnants in a supernova explosion. Neutrons can be packed much closer together than electrons so even though a neutron star is more massive than a white dwarf, it is only about the size of a city. The neutrons are degenerate and their pressure (called neutron degeneracy pressure) prevents further collapse.If the core remnant has a mass greater than 3 solar masses, then not even the super-compressed degenerate neutrons can hold the core up against its own gravity. Gravity finally wins and compresses everything to a mathematical point at the center. The point mass is a Black Hole. Only the most massive, very rare stars (greater than 10 solar masses) will form a black hole when they die.

In general, compact stars of less than 1.44 solar masses – the Chandrasekhar limit – are white dwarfs, and above 2 to 3 solar masses (the Tolman–Oppenheimer–Volkoff limit), a quark star might be created; however, this is uncertain.Gravitational collapse will usually occur on any compact star between 10 and 25 solar masses and produce a black hole. Some neutron stars rotate very rapidly and emit beams of electromagnetic radiation as pulsars.