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Quickie Questions - Astronomy - Black Holes

Date Answered Questioner (age, location) Question Answer
May 11, 2010Dorna (Scotland)how does blackhole act with the light?According to Einstein's General Relativity Theory, light is also affected by gravity. Black holes are very massive objects with extremely intense gravitational field. There is something call "event horizon" around black holes. It is the point where the gravitational attraction becomes so strong that the velocity at which an object would have to move to escape the gravitational field equals the speed of light. Since the speed of light is, according to the relativity theory, the maximum possible speed, nothing, not even light, could escape the black hole once it is inside the event horizon.
May 3, 2010Albie (Indian)suppose a Blackhole appeared just 1cm from Earth,will Earth be safe or will Earth be sucked into the Blackhole?Black holes are formed as the result of the collapse of a very massive star at its death. They canīt "appear" from nowhere. But letīs assume that they do, then the huge gravitational field of the black hole would surely atract the Earth towards the black hole.
May 3, 2010Narayanan (India)Black hole absorbs everything into it.Mass cannot be destroyed.So where do it go?Why don't we think of a star evolving from a black hole?Black Holes may form as the result of the collapse of a very massive star at its death. All the matter of the star's core is crushed to an infinitely small point, a singularity. Now, although it is true that mass can't be destroyed, it can be transform into energy (that's the meaning of the famous equation E = mc2). Black holes may be an important source of gravitational waves, and may also be important for helping other stars to form. For example the gravity of black holes (like other large stellar objects) may promote nebulae to form stars.
March 10, 2010chervon (malaysia)where does a black hole leads to?Nowhere. All of the mass of the star from which the black hole was formed is still there, maybe even mass from more than one star!
February 5, 2010Van (California)How fast is a black hole?In 2002 it was discovered that the stellar-mass black hole called GRO J1655-40, is moving across space at a rate of 250,000 miles per hour, four times faster than the average velocity of the stars in that galactic neighborhood! More information here.
February 3, 2010Narayanan (India)What is the absolute fate of a Black Hole ?I don't think there is anything considered "absolute" regarding black holes. One of the hypothesized fate of a black hole depends on the temperature of its surroundings. If the universe is cold enough it will evaporate incredibly slowly. If the background is warmer it will grow slowly until the temperature drops low enough for the hole to start to evaporate.
January 7, 2010L.Prashanth (Karnataka/India)If not even light can escape a black hole,it means that they are invisible. Then how do we know that there are black holes ??Black holes can be observed through its interaction with other matter, for example, by tracking the movement of a group of stars that orbit a region in space. This animation is a simulation of gravitational lensing caused by a black hole.
January 7, 2010L.Prashanth (India)Does the SINGULARITY of a black hole have any mass and is the universe infinitely vast ??According to the theory, at the center of a black hole lies the singularity, where matter is crushed to infinite density. More information in our web pag Black Holes.
January 5, 2010Hassan (USA)if a black hole speeds up time in a way that if i went near it and didn't get sucked in ( impossible feat by the way) time would speed up but to me it would feel as though little time passed what would happen to atomic clock ( since it supposedly adjusts to different time speeds because of the speed atoms move differs in space and clock adjusts to it) would it move very fast near a black hole or would it move at regular speed ?Albert Einstein's theory of General Relativity states that as you approach a black hole your time slows down. The closer you get to the black hole the more you appear to be in slow motion as seen by Earth. If you were to change your mind right before crossing the event horizon and return to Earth you would find it in the very distant future.More information on our web page Black Holes.
October 27, 2009Narayanan (India)Sir , from this site itself I heard the news of two black Holes orbiting themselves . How does Scientists got information about this ?Yes, you are right, it was recently published in the article a href="http://news.bbc.co.uk/2/hi/science/nature/7924414.stm">Dancing black hole twins spotted. From this article I quote, "As matter falls into black holes, it emits light of a characteristic colour that in turn gives information about the direction in which the black hole is moving. In a binary system, two beams should be emitted, each a slightly different colour. The black holes emit two beams, each a slightly different colour Todd Boroson and Tod Lauer of the US National Optical Astronomy Observatory analysed some 17,500 spectra from the Sloan Digital Sky Survey, and have now found just such a pair of emissions coming from a distant quasar."
October 19, 2009Alec (Arizona)How do black holes work?Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black. Which makes it pretty hard to observe directly. Black Holes may form as the result of the collapse of a very massive star at its death. Just as neutron stars form during a supernova explosion of a very massive star so do black holes. But in the black hole case the initial star was so massive that nothing could stop its gravitational collapse. All the matter of the star's core is crushed to an infinitely small point, a singularity. More information can be found at our web page Black Holes.
October 13, 2009Phil (ct,usa)Scientists say that matter in a black hole gets crushed out of existence. If that is true then how can a black hole grow? Matter must remain in existence to have an affect in our universe, and thereby adding to the mass of the black hole causing it to grow. An explicit relationship between the size of a black hole and the energy it has absorbed has been recently published. See this article for a discussion on this topic.
October 8, 2009Narayanan (India)Will all neutron stars become black holes?Extracted from our web page Black Holes: Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black. Which makes it pretty hard to observe directly. Black Holes may form as the result of the collapse of a very massive star at its death. Just as neutron stars form during a supernova explosion of a very massive star so do black holes. But in the black hole case the initial star was so massive that nothing could stop its gravitational collapse. All the matter of the star's core is crushed to an infinitely small point, a singularity.
September 30, 2009Narayanan (India)Sir, is there any possibility for a black hole to become a star again?Or is black hole the last stage of the evolutional process of star?Sir please give me an answer.I am really waiting for this reply.Black Holes may form as the result of the collapse of a very massive star at its death, so massive that nothing could stop its gravitational collapse. All the matter of the star's core is crushed to an infinitely small point, a singularity.
August 21, 2009APARAJITH (India)gravity slows down time,so IF we reach the event horizon,the time will stop,then if we pass near a black hole and return to the earth then the time which passes on earth will be more than the time which passes on the spaceship.then if we keep passing the blackhole for a year,can we return to earth and find that 20 or so years have passed?Theoretically, once you have passed the event horizon, it is not possible to escape the black hole. Under this premise, your question doesn't have an answer.
July 23, 2009 what the odds of are planet getting caught in a black hole and us surviving.From our web page Black Holes: What would it be like to enter a black hole? Not pleasant. First, as you approach the black hole the difference in the gravitaional pull on your head compared to your feet (known as tidal forces) would rip you apart.
July 20, 2009Liam (Georgia, North America)Do supermassive black holes orbit anything? If not, how do they travel?Yes, they could orbit a twin, as it as recently published in the article Dancing black hole twins spotted.
July 20, 2009Owen (alberta)Can a black hole be destroyedI am not sure if there is an answer to your question. Black Holes are theoretical objects with such high gravitational pull that not even light can escape. They are supposed to exist in the center of galaxies. Our web site Black Holes provides more information.
July 17, 2009Owen (Canada)Can a black hole be destroyedI am not sure if there is an nswer to your question. Black Holes are theoretical objects with such high gravitational pull that not even light can escape. They are supposed to exist in the center of galaxies. Our web site Black Holes provides more information.
June 2, 2009Aparajith (India)There is a planet near a blackhole.what will happen to the position of the black hole?Nothing. Black holes are so massive that they will swallow the planet without changing their own state.
March 25, 2009anthony (ma)pondering on this for a while. is pull a speed? if so than black holes would be pulling faster then the speed of light which would mean black holes are the fastest? is this true? i feel like it could be. id rather you let me know on your thought. thanks in return. i get this idea from the knowledge that light cant escape black holes. light is sucked in black holes. thanks.Pull is a force, and in this case is due to gravity. The huge gravitational field around a black hole exerts an immense attractional force over all masses, including light. Visit our web page Black Holes for more information.
March 11, 2009Bilal (Canada)what would happen "if" a human were to go inside a black hole?? what would he see??From our web page Black Holes: What would it be like to enter a black hole? Not pleasant. First, as you approach the black hole the difference in the gravitaional pull on your head compared to your feet (known as tidal forces) would rip you apart. But suppose you survived that. Once you cross the event horizon there is no turning back. Then the only thing to do is avoid the black hole itself at all costs. If you run into that singularity it will crush your body right out of existence. If people from Earth were watching your journey into a black hole they would never see you cross the event horizon. Albert Einstein's theory of General Relativity says that as you approach a black hole your time slows down. The closer you get to the black hole the more you appear to be in slow motion as seen by Earth. Eventually you appear to be frozen in time as you cross the event horizon. You would notice nothing different whatsoever. If you were to change your mind right before crossing the event horizon and return to Earth you would find it in the very distant future. You've become a time traveler!
November 4, 2008Emily (texas)What happens after wew get into a black hole, how do we know there is a black hole in side of every sprial and elpitical galaxy if we cant go near one because we would get sucked in?Extracted from our web page Black Holes: Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black. Which makes it pretty hard to observe directly. Black Holes may form as the result of the collapse of a very massive star at its death. What would it be like to enter a black hole? Not pleasant. First, as you approach the black hole the difference in the gravitaional pull on your head compared to your feet (known as tidal forces) would rip you apart. But suppose you survived that. Once you cross the event horizon there is no turning back. Then the only thing to do is avoid the black hole itself at all costs. If you run into that singularity it will crush your body right out of existence.
September 18, 2008fara (malaysia)is it true black hole doesn't have an ending?my father said black hole doesn't have an ending,howcome?everything do have an ending.I am not sure what your father meant by that. Black holes are an enormous amount of mass confined in a very small volume, so they have a well define limit all around.
September 16, 2008priyanka (india)why can't light escape blackhole only within a particular radius?This limit is known as event horizon. This is the boundary within which the black hole's escape velocity (minimum velocity to escape a gravitational field) is greater than the speed of light. In other words, within this radius a radiation will have to moves faster than light to escape, but because the speed of light in a vacuum is the speed limit, nothing can escape from inside the event horizon of a black hole!.
September 3, 2008John (United States)What is a dark hole, what causes it, and how many years from now until there is another one?Extracted from our web page Black Holes: Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black. Which makes it pretty hard to observe directly. Black Holes may form as the result of the collapse of a very massive star at its death. Just as neutron stars form during a supernova explosion of a very massive star so do black holes. But in the black hole case the initial star was so massive that nothing could stop its gravitational collapse. All the matter of the star's core is crushed to an infinitely small point, a singularity.
August 19, 2008Tom (Kansas USA)Does time exist in a super massive black hole or is it completely stopped?Anything about black holes is purely theoretical. Keeping this in mind, this link will answer your question.
August 15, 2008roli (india)how do you locate a black holeBlack holes are supposed to exist in the center of galaxies, but be aware that they are theoretical objects! See more in our web page Black Holes.
August 15, 2008Mary (Tanzania)what are black holes and what are they made out of???Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black. Which makes it pretty hard to observe directly. Black Holes may form as the result of the collapse of a very massive star at its death. More information can be found in our web page Black Holes.
April 7, 2008joshua (north carolina)scientists theory about the black hole is that if you go in it, is there a 5th demention? if there is, how does a 5th demention go like? i need your answers. peace!"A black hole is a very massive object with such an enormous gravity that almost nothing can escape from its atraction (except what is known as Hawkings radiation). There are other theories that mention new dimensions, but are not related to black holes.
February 4, 2008Nicco (Indiana, U.S.A)What happens if 2 black holes get extremely close to
eachother and/or collide.
They will merge in an extremely big and dense object, releasing in the process huge amount of energy.
December 17, 2007Conrad (Australia)Is this true that when you go into a black hole and cannot escape with the speed of light, when your inside it do appear in a diffrent universe or time or is this what wormholes do?No, once you are in the vicinity of the black holes, strong forces will act over you, and several interesting things will happen. This site offers detailed answers to the comon questions about black holes.
December 10, 2007shania (TX)on average about how long do black holes last????I don't think there is a unique theoretical answer to this question, but what seems to be generally accepted by physicists is that if an event occurs close enough to a black hole where antimatter is thrown in but the matter escapes from the black hole (this is known as Hawking Radiation), and this happens enough, the black hole will begin to "evaporate".
August 21, 2007Mark (New Zealand Christchurch)What causes black holes to have such a gravitational pull?The gravitational force is a function of the product of the interacing masses and the inverse of he square of the distance between them. Black holes masses are enormous, for example, the giant elliptical galaxy M87 is believed to contain a supermassive black hole of several billion solar masses at its center. The observations indicate that approximately 3 billion solar masses are concentrated in a region at the galactic core that is only about the size of the Solar System.
July 25, 2007veena (india)can we go in black hole?The short answer is yes, but we can't get out of there!
July 25, 2007Veena (india)where did a nearest black hole was?We have a very massive black hole at the center of our own galaxy, the Milky Way.
July 23, 2007vik (america)what is black hole .Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black (which makes it pretty hard to observe directly). Black Holes may form as the result of the collapse of a very massive star at its death. More detailed information at our web page Black Hole.
July 21, 2007piyu (india)what is black hole?Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black. Which makes it pretty hard to observe directly. Black Holes may form as the result of the collapse of a very massive star at its death. More information in our web page Black Holes.
July 21, 2007Elric (Iowa)Can black holes escape echoter, or rip echothers mass apart?Although there is no observational evidence of the collision of two black holes, the theory predicts what will happen to them. This article from the National Science Foundation discusses the latest finding. This impressive video shows how it is predicted that the black holes will behave.
July 18, 2007Elric (Iowa)How big is a supermassive black hole?The mass of a supermassive black hole is of the order of a billion solar masses at their center.
July 11, 2007Kim Hale (Minnesota)Why are black holes said to be black?Because due to their incredible gravitational field, almost nothing, including light, can escape from them, and so no radiation can be detected friom them.
July 9, 2007DEEPSHIKA (INDIA)why do black holes have so much of gravitational force?Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. And all that mass will end concentrated in a very small (for cosmic standards) region.
May 30, 2007Aheli ( India)What is a black holl? Do they really exists? please try to explaim me in full details.Black holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black (which makes it pretty hard to observe directly). Black holes may form as the result of the collapse of a very massive star at its death. More detailed information at our web page Black Holes.
March 2, 2007Veena (india)What is a black hole?Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black (which makes it pretty hard to observe directly). Black Holes may form as the result of the collapse of a very massive star at its death. More detailed information at our web page Black Hole.
March 1, 2007karthick (india)what is black hole?what is the range of its gravity?what is the age of the star which can turn into a black hole?Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black (which makes it pretty hard to observe directly). Black Holes may form as the result of the collapse of a very massive star at its death. More detailed information at our web page Black Holes.
May 19, 1999Linda and Ellen (Alaska, USA)According to Quantum Electrodynamics, the electromagnetic force is transmitted by photons, yet black holes are said to have the characteristic of a magnetic field. How can this be when photons are transmitting the field and they travel slower than the escape velocity of a black hole?Magnetic field lines are generated by movement of electric field lines. An electric field forms when electric charge falls into a black hole. In this case, the "swallowing" of photons produces an electric charge within the hole, creating an electric field around it. When the black hole rotates, this electric field rotates as well. This creates a magnetic field.
May 13, 1999Carly(British Columbian, Canada)Why do scientists suspect a black hole just on the outer edges of the Solar System and what are the chances of it really being there?There really couldn't be a black hole at the edge of the solar system because a black hole would devour the solar system!
September 2, 1998Lalita (Maharashtra, India)Can a black hole be destroyed , is it true that a black hole gets larger and larger ????Black holes can gain mass that falls into them from their surroundings and grow. They also can evaporate if there is nothing entering them. However, for star-sized black holes, this evaporation can take more than 10^100 years.
August 5, 1998Steve (England)If there are black holes, are there such a thing as white holes?A white hole is the purely theoretical counterpart to a black hole from which light and matter are expelled. Such an object has never been detected, and our current understanding of the physics involved argues that even if they had existed at one tim e, they would necessarily have been destroyed by now.
May 27, 1998Kaelyn (Oklahoma, USA) What is the name of the largest known star? Do black holes have names?The most massive star known is R136a1, a star 155 times as massive as our Sun. It is one of many extremely massive stars in a very young "super cluster", R136, in the 30 Doradus region of the Large Magellanic C loud.

Black holes don't have names like the bright stars in our sky, such as Betelgeuse. We cannot detect black holes directly, but we can sometimes detect x-ray emission from the material surrounding them. This related x-ray source may be named. Cygnus X-1, for example, is the 1st x-ray source detected in Cygnus, and is probably a disk of gas and dust spiraling into a black hole.

April 30, 1998Travis ( Minnesota, U.S.A.) Is it true that the gravity of a black hole is so strong that it can even pull molecules apart?Yes. Only elementary particles ever could come out of a black hole. Even things as small as molecules are destroyed.
April 30, 1998Rahul (New Jersey, U.S.A.) Could the universe have formed by a white Hole? Suppose another physical universe such as our own underwent a big crunch. Could not have all the matter in the big crunch create a black hole powerful enough to entirely devour all the matter in that uni verse and eject it into a new universe in the form of a white hole. Thus this theory partly accepts the big bang theory, that states that the universe started from a single point from which space and time started, except this big bang was created by an enormous and powerful black hole. Can this be possible?This question is a very difficult one... the answer is that no one knows the answer. For a (complicated) discussion on this topic, you might try this page. The thing about white holes is that based on our current knowledge of the universe, they are not possible. (They violate the second law of thermodynamics.) However, as the article says, there is no guarantee that the rest of the universe is like what we know now. Thus, we can't totally rule out the possibility of the universe having come from a white hole.
April 14, 1998Howard (Australia) If black holes have the same attractive force as the star from which it formed, why then is it black. I.e. why can't light escape as it could from the preceding star?The extraordinary effects of gravity for a small black hole are only felt up to a few hundred miles away. Farther than this, the gravity felt is that corresponding to the original mass of the star. However, as the light which enters that radius is u nable to escape and becomes part of the black hole, the black hole grows and its gravity is felt at a greater distance.
April 8, 1998Howard (Australia) Why is the attraction of a black hole so much greater than the star from which it formed, shouldn't they have the same gravitational attraction?They actually do have exactly the same gravitational force. Gravity is proportional to mass, so if the mass is exactly the same, they will have the same gravitational attraction. For example, if our Sun were to suddenly become a black hole, the plan ets would experience no change in orbit, because the gravitational pull of the Sun would remain constant.
April 7, 1998Maggie (Norway) Is it possible for us humans to make any use of black matter?So far, the existance of dark matter is only a theory. We would have to prove its existence before making any use of it!
April 3, 1998Michael (Denmark) How come the theory about dark matter is that common, when nobody has ever proved the excistance of it?The reason it is a theory is that it hasn't been proved yet. Since we are unable to see dark matter, we can only see its effects on other objects, such as gravitational pull. Based on calculations involving things like gravity, it seems very likely that dark matter does exist.
March 19, 1998Giulio (Milan, Italy) What makes people think that in the center of our galaxy thers'a black hole?Current data indicates that there is a very dense 'point mass' at the center of our galaxy, containing mass up to 1 million times the mass of our sun. This indicates that there is probably a black hole located there.
March 17, 1998Camille and Ken (Massachusetts, USA) We were just wondering, if there were a black hole in our solar system, that went in and out of the solar system (we'll call it Thesus) every 26 million years, wouldn't it disrupt the cycles of the asteroids, comets and planets, causing many of those asteroids to crash on the planets? That could be why the dinosaurs became extinct, right? Do you think that is a debatable theory?A black hole would certainly disrupt the asteroids and comets, but you underestimate the strength of a black hole. Such a thing would destroy the solar system, not just divert the orbits of asteroids.
March 13, 1998Thomaz ( Brazil) Is that proved the black holes exists?How can they (astronomers)prove that?As their name implies, black holes are black! Not even light can escape from the strong gravity of a black hole. Does that mean astronomers have no hope of ever detecting one?
Fortunately, while direct detection of light from a black hole is not possible, astronomers can indirectly detect them via their gravitational effect on other objects. For example, some black holes are sucking in the material around them, formin g what is known as an accretion disk. As the material in the disk is packed together, spiraling in towards the black hole, it gets heated up and emits high energy photons such as x-rays, which can be detected by astronomers. Black holes in bina ry systems can be "weighed" by measuring the orbital parameters of the system.
Evidence of supermassive black holes in the centers of galaxies has been provided by the Hubble Space Telescope. HST observed stars very near to the centers of galaxies. By measuring the velocities of these stars, it was possible to tell how much mass w as contained in the center of the galaxy. These measurements showed that as much as 100 million times the mass of the Sun may be contained in an area only a few parsecs across. Matter of this density almost certainly implies the existence of a supermass ive black hole.

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