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NASA Chat: Giant Black Holes in the Early Universe
June 15, 2011

Artist concept of matter swirling around a black hole Artist concept of matter swirling around a black hole. (NASA/Dana Berry/SkyWorks Digital)
A growing black hole, called a quasar, can be seen at the center of a faraway galaxy in this artist concept. Artist concept of a growing black hole, or quasar, seen at the center of a faraway galaxy. (NASA/JPL-Caltech)

More Information
› Field Guide to Black Holes→
› Images of Black Holes from Chandra→
› For Kids: Black Hole Rescue!→
› Chat Transcript

Portrayed in movies and on television most often as gateways to another dimension or cosmic vacuum cleaners sucking up everything in sight, the misconceptions surrounding black holes are many and varied. In reality, black holes form when, at the end of their life cycle, heavy stars collapse into a supernova. These relatively puny black holes may provide a "seed" for the development of the giant black holes - called supermassive - found at the center of galaxies, which grow by absorbing gas, stars and other black holes.

On Wednesday, June 15, NASA announced a new discovery about giant black holes in the early universe. This discovery was made using the Chandra X-ray Observatory. Chandra gives astronomers a powerful tool to investigate the universe, especially those hot spots where black holes, exploding stars and colliding galaxies are most likely to live. Since the Earth's atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes, requiring a space-based telescope to make these observations. Chandra launched in 1999 aboard the Space Shuttle Columbia during the STS-93 mission.

Astrophysicists Ezequiel Treister and Kevin Schawinski were online at 3:00 p.m. EDT on June 15 to answer your questions about the new announcement and about black holes in general.

About the Experts

Ezequiel Treister is an astrophysicist for the Institute for Astronomy at the University of Hawaii at Manoa. He has a doctorate in astronomy from the Universidad de Chile, two masters degrees in astronomy from Yale University and a bachelors in physics, also from Universidad de Chile. His interests include active galactic nuclei - the compact regions at the centers of galaxies with higher than normal luminosity over the electromagnetic spectrum. He studies these nuclei in relation to the cosmic X-ray and Infrared backgrounds of the universe.

Kevin Schawinski is currently an astrophysicist at Yale University in New Haven, Conn. He has a doctorate in astrophysics from the University of Oxford and a bachelors in physics and mathematics from Cornell University. His interests include how galaxies formed and how they co-evolved with the supermassive black holes that lurk at their centers.


Chat Transcript



Jason (moderator): Hi all. We're beginning to get set up for today's chat which begins at 3 p.m. EDT today in about 20 minutes. In the meantime, please begin to think about your questions and type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box.

Jason (moderator): We'll be getting started here in about 10 minutes. Do you have a question you want to ask when we start? To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box.

Jason (moderator): Welcome to the "Black Holes" Chatroom. We're chatting with Astrophysicists Ezequiel Treister and Kevin Schawinski about the newest Chandra X-ray Observatory findings on massive black holes in the early universe and about black holes in general. This is a moderated chat. To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

Jason (moderator): We're also joined by Astrophysicist Priya Natarajan as well.

Jason (moderator): We're working on answering the first few questions. To ask your own, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

dean: hey, i have a few questions today :), my first one: Light canot escape from black holes, we can conclude that the speed of light has changed by that, so in theory , when travelling through a black hole, we can go faster than the speed of light. ( Don't mention the typos , my english isn't that good)

priyanatarajan: Great question! actually even light and in fact no matter at all can escape a black once it has crossed the point of no return called the event horizon. It is not that the speed of light changes. The `slowing down' refers to what we imagine the fate of light once it enters the event horizon. For example, if I get sucked into a black hole once I cross the event horizon you will not be able to hear me scream and I will pulled out and stretched out like spaghetti!

natasha_qurban: how we can detect blackholes?

Kevin: There are two basic ways we can tell whether there's a black hole. Black holes are of course dark by definition - not even light escapes them!

patci: Several studies have estimated the size and mass of the Andromeda Galaxy. When The Milky Way and Andromeda collide, what situation is likely to occur between the two centers?

Ezequiel: That's a great question. What we think that will happen is that once Andromeda and the Milky Way start colliding, the gas that is floating around in both galaxies will start falling to the center and eventually falling onto the resulting black hole. So, while the andromeda's BH is ~10 million solar masses and the milky way's 4, the resulting BH after the merger sequence can be 100 million solar masses or larger.

Nathan: When a black hole is described as being so many solar masses, is this referring to the mass of the singularity?

priyanatarajan: Solar masses is a unit of measure of the mass content of the black hole.

NaVaM10: Speak spanish or no?

Ezequiel: Yo hablo español... alguna pregunta? Saludos!

natasha_qurban: what is black hole?

Kevin: The first way we detect black holes by their gravitational influence. For example, at the center of the Milky Way, we see an empty spot where all the stars are circiling around as if they were orbiting a really dense mass. That's where the black hole is. The second way is by observing the matter falling into the black hole. As matter falls in, it settles in a disk around the black hole which can get very hot. Some of the energy liberated from falling in is turned into light, which we can then see, for example in X-rays.

cloudGeek: They say the theory of relativity breaks down at the point of singularity, but I've always thought that there really is no such thing as a point of singularity, because if you were in the center of a black hole the dense matter on all sides of you would be pulling you and the forces would cancel out... so there really is no spot where r (radius) equals zero... what are your thoughts?

Ezequiel: Mathematically, there are singularities at the centers of black holes, however, they are all inside the "event horizons", which means that physically nothing can get there... This is an idea in astronomy: There are no "naked" singularities... Not everything that is mathematically allowed happens physically

natasha_qurban: is there any blackhole in our solar system

priyanatarajan: There is no evidence for the presence of a black in our solar system. However there is a super massive one in the center of Milky Way (our galaxy) and likely several tiny ones which are dead stars in the solar neighborhood....

Systemmessage: Is there a way for black holes to deteriorate?

Kevin: In principle, yes! There is a process called "Hawking radiation" by which black holes can SLOWLY lose mass. This process is really, really slow - the black hole at the center of a galaxy would take many many times the age of the universe to lose even a little mass...

keith2000: When will NASA launch the james webb space telescope to study black holes and the universe,if they have a set date?And where could I find images of the black holes Chandra found?

Ezequiel: Hopefully around 2018 or so... I think there's no set date at this point. You can find great Chandra images at cxc.harvard.edu

kim: Black holes, a lunar eclipse, reaching interstellar space. What a busy day for humans in the universe!

priyanatarajan: Yep - an exciting day! indeed....

Jason (moderator): We're working to answer your great questions. Keep them coming! To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

Flower: Black holes from the past can be shown now? hows that possible?

Kevin: Even though light is really fast, the Universe is HUGE. So light emitted by a black hole very far away will take a long time to reach us. Thus, by looking deeper into the universe we can look into the past.

natasha_qurban: where they exist inthe universe?

priyanatarajan: Do you mean black holes? there is one at the center of our galaxy and in fact it appears that there is one at the center of every galaxy in the Universe!

wafllufc: Is it possible for one Black Hole to swollow another Black hole. Stupid question i know but thought i would ask anyway.

Kevin: Yes! Black holes can definitely merge. They will form a more massive black hole and (at least theoretically) radiate away a lot of energy as gravitational waves. Scientists are trying to detect these waves.

Miss_Maybe: all the pics of black holes are real? or could it be some fake pics?

Ezequiel: Some of the pictures that we presented were graphics made by artists, but some of them are real images. If you remember, the first animation that I presented, with the zoom into the deep fields, is all real data... Very cool, right?

MissAshley: If there is a black hole in the center of our galaxy then will our galaxy eventually be sucked into itself? Or is the space around a black hole just empty because it's sucked up as things as far as it can? I'm not sure if that second question made sense..

Kevin: Yes there is a black hole at the center of the Milky Way. At the moment it's quiet but we'd love to see it start feeding again. It won't suck us in as even though it's really massive (four million times the mass of the sun) it's gravitational reach does not go very far beyond the very center of our Galaxy. So no need to be worried ; )

Grievous: Ezequiel: ¿porque algunos cientificos creen que los ahugeros negros puede llevarnos a otros lugares en el espacio tiempo???

Ezequiel: La verdad es que no sabemos que pasa adentro de un agujero negro, y es bastante dificil saberlo porque las reglas de la fisica se cumplen solo hasta el "horizonte de eventos". Lo interesante es que de acuerdo a la relatividad, si tu caes en un agujero negro, te toma un tiempo infinito en caer, con lo cual realmente nunca estas dentro de un agujero negro. Por supuesto, desde nuestro punto de vista es diferente, y te vemos caer en el, pero no sabemos que pasa una vez que pasaste el horizonte de eventos

dean: question 2) If the nearest star would explode and this would lead to a black hole, what effects would it have on planet earth and the rest of our solar system?

priyanatarajan: By the time the nearest one explodes we will not be around, given our life spans!

Jason (moderator): Do you have a question you've been waiting to ask? Go for it! To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

MooCow: so when galaxy canabalism occurs and the massive blackholes join, does the more dominant one become even bigger, is there a limit to the size the black hole?

Kevin: We think that when two galaxies merge, their two black holes will fall towards the center of the new, bigger galaxy and merge there. How exactly they merge is not really understood yet and theorists are working on getting them close enough in....

Janus: Were black holes in greater quantity early in the universe's life, or is the quantity larger now?

Ezequiel: Excellent question! we know that most (or all) of the galaxies have black holes, and probably had black holes since very early Universe (that's what we reported today). Then the question is when do black holes do most of the growth, and then the answer is far away, about 1/3 to 1/2 of the age of the Universe ago.

MissAshley: Is the reason the one at the center of our galaxy isn't "feeding" anymore because it's graviational reach only goes so far?

Kevin: Yes, basically. There's no food in its immediate neighbourhood...

patci: Is there a point where a black hole can become too large for itself?

priyanatarajan: Yes, indeed, we currently believe that black holes eventually stunt their own growth. They cap how large they can get. This we think happens as once the black hole gets too large the X-rays emitted by the gas that in flowing in will be so energetic that they will expel all the remaining gas and essentially starve the hole.

Jason (moderator): To learn more about supermassive blackholes, check out Chandra's field guide to supermassive black holes: http://chandra.harvard.edu/xray_sources/blackholes_sm.html

me: shouldnt blackholes, after sucking in so much mass and energy, get unstable and explode or something of that sort?

Ezequiel: Black holes are extremely stable... even if they keep "eating" they will be stable over the age of the Universe.

Mr.Nice: how can light be emitted from a black hole if it sucks everything including light?

Kevin: The light doesn't come from inside the black hole (that's impossible) but from the material falling into it while it's still outside the event horizon.

Jason (moderator): Earlier today, a new discovery about black holes was announced. http://www.nasa.gov/mission_pages/chandra/news/H-11-183.html

Miss_Maybe: Yea definitley so cool! but as kevin said that there is a black hole in our galaxy! so our solar system cant bel in a black hole?

Ezequiel: There is a black hole in our galaxy... it has a mass of 4 million solar masses, but it is in the center of the milky way, about 20 thousands light years from us... so we are safe!

Flower: How Can A Black Hole Apear ?Isnt The Solar System Full Of Wonders?

priyanatarajan: Black holes are detected by their gravitational influence in their vicinty.

Lysol: You mentioned that the center of the Milky Way is a black hole.... Have any other black holes been discovered in our galaxy? If yes, how far are they from our solar system?

Kevin: Yes! The Milky Way is full of black holes that were formed in the deaths of stars. Some of them are on their own so we cannot really see them, but others formed in a binary star system and we see them feed on their companion star. I think the closest know such black hole binary star system is a few hundred light years away... wouldn't worry about it ; )

Systemmessage: Do black holes rotate? If so do you know if any of the ones you looked at do?

Kevin: They can rotate and astrophhysicists are trying hard to measure their spin. It's very challenging though even for the closest black holes to us.

NaVaM10: Ezequiel: Existe alguna otra teoria de lo que suceda cuando caes en un agujero negro?

Ezequiel: hay muchas teorias, pero como decia antes, no "importan" mucho en el sentido fisico, porque es algo que nunca podemos probar, y desde tu punto de vista si estas cayendo en un agujero negro, te toma un tiempo infinito en llegar.

Jason (moderator): We're working to answer your great questions. Keep them coming! To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

Betelgeuse: So, why do all of these black holes exist? Were there lots of deaths of stars in the centers of these galaxies?

Kevin: That's one hypothesis. One way to make these baby black holes is from the death of one of the first generation of stars which were much more massive than today's stars. The other is when a disk of gas in a young galaxy collapses straight to a black hole.

mkjohnst: Is it possible for one black hole to orbit another black hole? I suppose this is related to the question about how black holes merge

priyanatarajan: Great question! yes black holes do orbit around each other, they get captured and eventually merge. This happens fairly routinely in the Universe when galaxies merge since most galaxies harbor a central black hole. And in their dying gasps black holes emit gravitational radiation

Janus: Can galaxies form without black holes?

Ezequiel: great question! there are some galaxies without black holes... but in general, and particularly in the near Universe all massive galaxies have black holes... At large distances, in the early Universe, not all galaxies need to have a black hole

eolijah: Jason, do you think that black holes like apple pie?

Kevin: Who doesn't like apple pie?

Jason (moderator): Do you have a question you've been waiting to ask? Go for it! To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

mkjohnst: We know that there are basically two types of galaxies: eliptical and spiral, and that there is evidence most of these have black holes at their center, correct? Are the black holes at the center of eliptical galaxies different from the black holes at the center of spiral galaxies?

Kevin: We definitely think that both spirals and ellipticals have black holes at their centers and that the way they co-evolve may be very different. We found this with the help of the citizen scientists taking part in the Galaxy Zoo project...

natasha_qurban: is it possible to orient a black hole ?

Kevin: Yes. Black holes can rotate so that would define a spin axis.

Jason (moderator): Learn more about Galaxy Zoo at: http://www.galaxyzoo.org/

Something: What are the most exciting black hole-related research projects going on today? And how long did it take your to get time on the Chandra Obsv.?

Ezequiel: Well, I'm obviously biased, but I really really want to know how did the first black holes formed. I'm working on that and hope to get the answer soon... It takes a very long time to get time with the Chandra observatory. There are call for proposals only once every year and then only about 1 in 5 gets approved. So, you have to have a very good idea and be a bit lucky to get Chandra time. Same with Hubble and all the large telescopes... There is so much to do in astronomy!

steve: You mentioned that there's a black hole at the center of the Milky Way. Exactly at the center? Do most galaxies form around black holes, or are centered on them?

priyanatarajan: Yes, there is a black hole at the center of the Milky Way and pretty much every galaxy in the Universe. Since black holes are massive they do sink into the center although they do jiggle around a bit and dont stay still! It does appear that the formation of the black hole and the stars in a galaxy are intimately related, however, not easy to determine what came first!

hunnylover2: If this is a stupid question, don't post it. I was wondering if we know what is on the other side of the hole?

Kevin: There isn't really another "side". At its center the black hole is just a point where all the mass is concentrated as far as we can tell.

Jason (moderator): For a good primer on the basics of black holes, check out: http://science.nasa.gov/astrophysics/focus-areas/black-holes/

Grievous: Antes del BigBang, existía un agujero negro que luego explotó?

Ezequiel: Mi opinion es que no tiene sentido hablar de "antes" del Big Bang, porque el tiempo en si se invento con el Big Bang. Sin embargo, si te fijas, el Big Bang es una singularidad de la que salio todo, asi que puedes pensar en el big bang como un "agujero blanco"

Jason (moderator): We're working to answer your great questions. Keep them coming! To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

Janus: Is there any evidence of multiple galaxies orbiting around one massive black hole?

Kevin: No.... (supermassive) black holes live at the centers of galaxies. This is because galaxies are MUCH more massive, so the black holes just fall to their centers.

sagex90: At the end of the universe, Say when everything is supposed to rip appart, wouldn't that mean that black holes would lose most of their gravitational pull and thus emit more matter into the universe causing more matter to have more gravitational attraction over a larger area making it so that instead of accelerating out, it would stop somewhere and slowly start falling in on itself again?

priyanatarajan: Actually the ultimate fate of our Universe (which is expanding and accelerating) is that will be a cold, lonely place. Existing black holes will not get ripped part, they simply wont be able to grow as they will not be able to capture huge amounts of gas...

Janus: I don't mean in the center of one galaxy, rather the way a planet rotates around a star

Kevin: Sure... no there is no such case. Such a black hole would have to be even more massive than a galaxy but as far as we know there is no such black hole.

Thomaspoke: Close to what hunnylover2's answer was, does that mean that a black hole isn't like a tunnel, it is more of a puncture?

Ezequiel: That's a good way to see it... matter "bends" the space time around it. You can image that at the center of the black hole it makes a hole in the space time that we call singularity. What happens at the singularity? Who knows!

Chateau: Are we able to measure or calculate black holes' effects on dark matter?

priyanatarajan: Once matter crosses the event horizon of a black hole, its immaterial (note pun here!) whether it was ordinary atoms or exotic dark matter! We do not

keith2000: Is it possible to send a sattelite into a black hole and still have it be able to send and recieve signals?

Kevin: No, once a probe passes the event horizon of the black hole, it's gone and can never communicate with us again.

priyanatarajan: continuing from earlier.....

Jason (moderator): Since black holes inspire everyones imagination and raise lots of questions in relation to things like 2012, read our frequently asked questions and learn more about 2012: http://www.nasa.gov/topics/earth/features/2012.html

natasha_qurban: what is supernova ? is it a type of black hole.(i know that its a stupid question but its my curiosity. i am the student of 9th grade and wants to be an astronaut.)

Kevin: A supernova is the fiery death of a massive star (much more massive than our sun). Black holes can be born in such a supernova.

DavPal: Is it possible to exist 'White Holes' from where matter (and light) would be expelled?

Ezequiel: You can think of the Big Bang at the ultimate White hole... By definition, a white hole cannot be created, so the only why to have it is if the Universe "comes" with one...

priyanatarajan: continuing from earlier....we cannot tell the difference once the matter is accreted what is was composed of. So yes indeed a small portion of the mass of the black holes that we detect in the centers of galaxies could be dark matter!

wafllufc: Is there anything at all that can escape from a Black hole?

Ezequiel: No... Once you pass the event horizon, nothing can come back...

Jason (moderator): Do you have a question you've been waiting to ask? Go for it! To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

Flower: Is There Any Chance Of A Black Hole Apearing Near Our Solar System Or Is There One Near Already?

Kevin: There are probably lots of black holes formed in supernovae as stars in the Milky Way die wandering the Galaxy, but the odds of such a black hole coming anywhere near our solar system is TINY.

arvind: hi all the scientists

Kevin: Hey!

RihannaNavy: CAN ENERGY MOVE OR ACT & REACT IN A SPEED MORE THAN LIGHT SPEED?

priyanatarajan: Nothing can exceed the speed of light!

Bekamancer: Is there a large difference between galaxies that have a black hole at the center, and those that do not?

Ezequiel: at least in the "local" Universe, we found that all massive galaxies also have massive black holes, while very small galaxies do not have central black holes at all.

Chateau: Do you have a favorite black hole?

priyanatarajan: Yes, its the one in the center of the galaxy M87. Its one of the most massive nearby black holes and produces an impressive jet that is visible nicely in radio waves.

natasha_qurban: what happen when some object will exceed the speed of light

Kevin: The theory of relativity tells us that unfortunately nothing can move faster than the speed of light...

Thomaspoke: For how long do you think the black holes have been growing?

Ezequiel: which ones? We know that after a galaxy merger, black holes can grow very rapidly for 10-100 million years, and that's how these black holes get most of their mass

Jason (moderator): Do you have a question you've been waiting to ask? Go for it! To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

Flower: Is There Any Thing Thats Gotten Close To The Black Hole.

Kevin: Sure. When we see black holes with telescopes, what we actually see is the matter falling into the black hole.

MooCow: is there something that a black hole can't digest?

priyanatarajan: Nope - it can chew up anything and everything.

Something: Can you explain in slightly more detail what your research involves, and where your studies will go from her?

Kevin: Well we'd love to peer further into the first billion years with the help of more Hubble and Chandra observations. Our hope is to push just a little further to really figure out what the first black hole seeds were.

Jason (moderator): Check out Chandra's field guide to supermassive black holes for more information about these large black holes: http://chandra.harvard.edu/xray_sources/blackholes_sm.html

me: if gamma rays have higher energy than visible light then shouldnt those have a higher speed and maybe able to escape the gavitational pull of blackholes?

priyanatarajan: The speed of light (at all wavelengths ) is fixed. However the energy and frequency of waves are inversely proportional. So more energetic waves simply have shorter wavelengths.

dean: If the sun explodes into a supernova , and a black hole appeares in the centre of the solar system, all planets will be sucked into it ?

Ezequiel: well, first, when the black hole goes supernova it will not create a black hole... it is just not massive enough. But... Let's assume that for some reason the sun turns into a black hole with the same mass... Turns out that the orbits of the planets will not be changed, will remain exactly the same... Of course, for life on Earth it will be the end...

ayz: do black holes last forever? or do they have finte lifetimes like the stars which created them?

Kevin: In theory black holes can evaporate via Hawking radiation but this process is very VERY slow. The age of the universe wouldn't be ebough to make even a dent in a supermassive black hole

Jason (moderator): Every wanted to see a black hole? Check out some of these images from the Chandra X-ray Observatory: http://chandra.harvard.edu/photo/category/blackholes.html

vdls612: What happened to all those giant early black holes? They were destroyed/transformed? Are they still here?

Kevin: They keep growing and merging and end up as the monsters at the centers of massive galaxies in the nearby Universe.

Janus: This is unrelated: Many scientists say that the universe is infinite. However, they also say that it has a "shape." How can something infinite have a shape?

Ezequiel: It is infinite in the sense that it has no boundary, but it can have a shape... Actually, it is the space itself that has a shape... We now know that it is basically flat.

William: can a black hole swallow another black hole?

Ezequiel: sure! And we think that it happens, when two galaxies merge.

Bernard: Do you hope to find the origin of the black hole, by looking at the first 'seeds' ?

priyanatarajan: Yes indeed. To figure out how the first black holes formed in the early Universe we need to see as far back into the Universe as we can. Deeper views of the Universe with more data from say the Chandra satellite will help us track down the first ever black holes to form

Jason (moderator): Want to learn more about the Chandra X-ray Observatory? See the latest news, learn about the spacecraft and find lots of other related information at http://www.nasa.gov/chandra

Jason (moderator): We're working to answer your great questions. Keep them coming! To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

MooCow: do black holes power quasars?

Kevin: Yes, quasars are massive black holes feeding on gas.

amanning: What do the jets that extrude from the center of a black hole consist of,... possibly photonic energy?

priyanatarajan: The jets we see often consist of energetic particles electrons, positrons as well as photons.

juan: HEY

Kevin: Hey!

gandelf: What would happen if antimatter fell into a normal matter blackhole?

Kevin: I think the same as to regular matter... black holes will eat everything!

--: The following question is just a matter that has confused me for a while: A neutron star is masssive as are black holes but black holes are far more dense and massive. However, it is not possible for a black hole to be a point in space-time right? That would not make any sense to me. Do black holes have an actual physical radius? Is there a relation between the mass and the area of the even horizon?

Ezequiel: That's a good question... and I can see why you are confused. The amount of matter is not important, but the density is. You can turn into a black hole, but in that case your size will be about a few atoms... The size of the event horizon, which we know as the "size" of a black hole is directly proportional to the mass of the black hole. For example, for an object of the mass of the Sun, it will need to have a size of 3 kilometers.

spacegen: Is space-time warped by black holes? And are the baby black holes CHANDRA sees actually now much older because of the distance light has to travel for us to see them?

Kevin: Yes space-time gets warped by black holes. And the baby black holes seen by Chandra are really really old! To see them we are looking so far into the universe that the light we see from them now left when the universe was less than a billion years old.

tobyc: What is the estimated diameter of the outer event horizon of the black hole at the centre of the Milky Way?

Kevin: It's roughly the size of our solar system.

patricia: What is need to make to the enter in the NASA?

Ezequiel: What do you want to do? There are several things that you can do at NASA, so it depends on your interest... Are you interested in becoming an astronomer?

ayz: If nothing can escape a black holes gravitational attraction...can you explain th "extruding jets" please.

Kevin: The jets don't come from inside the black hole but from just outside the event horizon.

me: is our technology advanced enough to detect the gravity waves emited by the blackholes?

Kevin: Not yet, but scientists are working hard on it!

veeranna: how will the James Webb telescope help in solving unsolved mysteries about black holes? Is it better than hubble telescope?

Kevin: Webb will be able to study those first galaxies and their baby black holes i fabulous detail. It's similar to Hubble but not exactly the same.

Jason (moderator): Have a question you've been wanting to ask? We'll be answering questions for a little bit longer, so don't hesitate to ask your question. To ask your own, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

mkjohnst: I've been reading about how scientists like you can use gravitational lensing to weigh clusters of galaxies, and that the lensing effects indicate a lot more matter than is visible, apparently evidence for dark matter. But how do you distinguish between dark matter and black holes in exercises like this?

priyanatarajan: The distribution of dark matter that is inferred from gravitational lensing studies suggests that it is distributed quite smoothly throughout a galaxy - from the inner regions all the way to the outskirts or the halo. While black holes might constitute one form of dark matter, they cannot account for all the dark matter in the Universe (90% of all the matter in the Universe is dark) or even what is inferred in individual galaxies.

Mr.Nice: how big is a black hole itself?and how big is the event horizon...generaly speaking

Ezequiel: It depends on the mass of the black hole. For example, for the mass of the sun, the event horizon is 3 kilometers. And then, the size of the event horizon is proportional to the mass of the black hole.

Janus: My goal: Major in astrophysics; work at NASA :D

Kevin: Awesome, good luck!

Flower: What Is The Most Dangrouse Black Hole Or Threating [is That Possible for it to be Danger TO Eg;Milkey Way]?

Kevin: There aren't any black holes that we know that are anywhere near being dangerous.

Jason (moderator): For a good primer on the basics of black holes, check out: http://science.nasa.gov/astrophysics/focus-areas/black-holes/

MooCow: what are the chances of the Voyager 1 and 2 being eaten by an undiscovered black hole?

Kevin: Very very VERY low...

Jason (moderator): Do you have a question you've been waiting to ask? Go for it! To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

Systemmessage: You said you look forward to maybe getting some more time for observations with Chandra. Do you want to focus on the same areas that you did in this publication or move on to new ones as continue your research?

Ezequiel: That's a good question... Ideally we want to concentrate with Chandra on fields that were already observed by Hubble and other telescopes, so that we can supplement the X-ray data. Depending on how much area we can cover, there are some ideal fields. For example, for this study the Chandra Deep Field South was perfect, but if we want to cover a larger area, a larger Hubble field, like the COSMOS survey, in which I'm also involved, would work better.

blackholeuser: Which is hte biggest blackhole know of?

Kevin: We know of some quasars with massed of about 10 billion times the mass of the sun.

sagex90: intersting. Regarding the fate of our universe and how black holes wont rip apart, is that because they are infinitely dense? What I'm saying is that, if hawking radiation is able to be released (by only emitting one state of their quantum superposition) then as the universe ages, would black holes just decay like that over billions of years and inevitably just become cold matter like the rest of the universe?

priyanatarajan: The timescale for decay by evaporation is too long....so they will simply be sitting around as the Universe becomes a colder and colder and lonelier place!

--: are you guys gonna do another one of these in the future on another subject?

Jason: Yes. We try to do lots of chats from time to time. Keep checking http://www.nasa.gov/chat for the latest list of chats, both upcoming and previously held. We'll also post them to the NASA Facebook page and the @NASA twitter account. Thanks for your interest!

blackholeuser: Has anyone ever seen a black hole how do you know if black holes really exsict ?

Kevin: There are a number of ways. For example in the case of the black hole at the center of the Milky Way, we can work out the mass of whatever is there becuase we see stars orbiting a particular spot. And this object is so massive and compact that even if it was not a black hole, it would immediately collapse into one.

Chateau: How large is the smallest black hole you've seen?

priyanatarajan: The smallest black hole that we infer exists is something that likely weighs roughly as much as our Sun....10^33 grams.

Chateau: How large is the smallest black hole you've seen?* (I should say, "measured" instead of seen) ;)

Kevin: The lightest black holes are black holes formed in supernovae and I think the lightest of them can be just a few times the mass of the sun.

RihannaNavy: How many black holes are there in universe?

Ezequiel: that's a hard number to estimate... Probably millions of millions... At least as many as galaxies. In the Universe there are both supermassive black holes, like the ones we study, and stellar mass black holes, about 10 times the mass of the sun or so... A typical galaxy can have hundreds of black holes.

William: i'm a fan of michio kaku

priyanatarajan: So am I....!

blackholeuser: Can blackholes suck up magnets

Kevin: Black holes can eat ANYTHING.

Jason (moderator): We've got about ten minutes left in todays chat. Ask your questions now in order to get them answered before we end our chat today. To submit your own question, please type it in the box at the bottom of the window and click the 'Ask' button on the right side of the box. Thanks for your patience as we answer your questions.

Aisha: is there a danger where a black whole could be too close to the Earth? ( thank you for answering :D )

Kevin: It's theoretically possible but really really really really unlikely.

Janus: If it can suck up light, of course it can suck up magnets...

priyanatarajan: Yep - even monster magnets!

blackholeuser: What is the coolest fact about a Blackhole?

Kevin: They shape the galaxies they live in!

Janus: When black holes deteriorate, what happens to everything they sucked in? Also, what takes its place?

Ezequiel: black holes do not deteriorate... They keep growing and growing, and they are very stable...

vdls612: Un-related question I'm planning to be a physicist, I'm currently waiting for the admission results at the university , but I have always wondered, how hard is for anyone to success and develop in their carrears?, What's the most difficult part on it?

Kevin: The most important part is to love research and be enthusiastic. Plus, physics is a great subject to study regardless of what you want to do in life.

Miss_Maybe: you siad black holes can eat anything did she ever eat a space shuttle?

Kevin: No : )

Wolf: why are you not talking about white holes

Kevin: White holes are speculative and there's no reason to think they exist.

Miss_Maybe: is it really hard for you to study black holes? or practicing made it easier?

priyanatarajan: Anyone who is excited about science and works hard can study black holes!

blackholeuser: What can be beyond blackholes?

Kevin: There is nothing "beyond" black holes. Once you reach the center, that's it.

Voice09: is there a possibility of something in the universe that is more vicious than a blackhole? like something that could beat up a black hole in a street fight

Ezequiel: Nope! A black hole is the ultimate fighter and will eat anything...

veeranna: do we have telescopes which can capture gamma spectrum. we now that hubble catches visible part of spectrum, chandra catches x-ray and so on..?

Kevin: Yes, the Fermi gamma ray space telescope is observing the Gamma ray sky: http://fermi.gsfc.nasa.gov/

Patricia_Brazilian: hello

Kevin: Hello to you too!

me: does blackholes move from place to place or is it just stuck in a fixed place like the center of our universe?

Ezequiel: they move... they still follow the same gravitational laws as you or me.

ahuman: Black holes are not black. why we call them black holes?

Kevin: It was originally a whimsical name for a pehnomenon that was poorly understood.

Flower: What Exactly Is Chandra And How Does It Work With Nasa And This Amazing Subject ? [Sorry I'm Not Fully Aware Of Chandra]

Jason: Chandra is an x-ray telescope. Chandra gives astronomers a powerful tool to investigate the universe, especially those hot spots where black holes, exploding stars and colliding galaxies are most likely to live. Since the Earth's atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes, requiring a space-based telescope to make these observations. Chandra launched in 1999 aboard the Space Shuttle Columbia during the STS-93 mission. Learn all sorts of interesting things about Chandra by visiting http://www.nasa.gov/chandra

Jason (moderator): We've got time for just a few more questions....

Aisha: im only 14 so excuse my knowledge but i have another question: what would happen if two black holes would collide and merge into each other? (thank you for answering another of my questions)

Kevin: If two black holes get close enouhg they will merge into a bigger black hole.

eolijah: On that "biggest black hole" note, one of you mentioned earlier that you think there is a mass at which black holes will cap out and reach a sort of equilibrium, where it cannot grow any more.. are there any estimations as to what that soft/hard cap could be?

priyanatarajan: Sure - we can estimate this for every epoch in the Universe. So at the present time no black hole can grow beyond about 2 - 6 X 10^10 times the mass of the sun...note that this cap is different at various times in the Universe....

Jason (moderator): Learn about all of NASA's great observatories at http://www.nasa.gov/audience/forstudents/postsecondary/features/F_NASA_G...

Miss_Maybe: can we see a black hole using a telescope? or ofcourse not?

Kevin: We can see the matter falling into black holes and sometimes also the jets launched at the poles of black holes. Of course once something is inside the event horizon, we cannot see it.

GRRower: Does every galaxy have a supermassive black hole? Which came first - black hole or galaxy formation?

Ezequiel: most nice and big galaxies have supermassive black holes in their center. We know that black hole growth and galaxy formation and evolution are directly connected. Which one came first? We don't know, and it is something that we would like to answer soon

tulasitj: what is in the center of a blackhole? how can you just go in something and never come out?

Kevin: At the center of a black hole is a singularity, which is a point in space where all the mass of the black hole is concentrated.

vdls612: is it possible to arrange through gravity interactions something like a black hole "solar system", I mean like a huge black hole with smaller black holes orbiting around him?

Kevin: Yes but it's likely that the two black holes would eventually merge.

rositacr: a black hole stops growing ?

Kevin: when it runs out of food!

Bernard: Is there a lot of Philosophy involved in the study in Physics? I mean, do seperate scientists, or groups of scientists, have diffrent but plausible ideas ?

priyanatarajan: Yes, there are a lot of philosophical issues at stake in Physics. For example one of the profound questions that philosophers and scientists grapple with is `Why is there anything in the Universe?' Philosophers and cosmologists typically ask different questions but they do have a common thread often.

Sondra: Are there jobs at NASA for those who are not physicists? Astronomy was my first love, but I just graduated with a degree in political science and currently lack the funds to go back...

Jason: Learn more about working for NASA by visiting http://www.nasa.gov/about/career/index.html

Janus: So all mass that enters a black hole just ends up being compressed at singularity point?

Kevin: yes, as far as we know from relativity

Jason (moderator): It's time for our last questions for this chat...

beih: Guys keep up the good work -you and your research make the world a more understandable place! I envy ur job! It must be amazing - I wish I had the brains :D I'll stick with galaxy zoo tho!

Kevin: Anybody can get involved in research, whether as a citizen scientist (zooniverse.org) or by becoming a professional.

Alien: what is the biggest black hole in space

Ezequiel: The biggest black holes that we know live in the center of the big elliptical galaxies in the centers of galaxy clusters... There can be about 10^10 solar masses... that's 10 billion times the mass of the sun.

Wolf: How about the fact you can not prove anything about black holes ( the inside) since no one has ever seen them.

priyanatarajan: We do observe their gravitational effects fairly directly. For instance if you

spacegen: Why don't galaxies get pulled into their black holes?

Ezequiel: There are many forces at play. Galaxies are in a dynamical equilibrium, which explains why they don't collapse to their center. Also, a black hole is a small fraction of the total mass in a galaxy.

Miss_Maybe: were all of you interesting in space scinece since you were kids? or it naturaly suddenly appeared?

Kevin: I always liked science...

priyanatarajan: continuing.... from the motions of the stars around the center of our galaxy (their closed elliptical orbits) we know that there is a large compact object in the center..

blackholeuser: Can black holes be used to explain the missing mas in the universe

Ezequiel: As far as we know there are not enough of them.

Jason (moderator): This ends our chat today. We're glad you can join us today. Thanks to Ezequiel, Kevin, and Priya for the great answers to everyone's questions. We appreciate your taking time out of your day to sit down with us. Our chat is over! Thanks for participating. A transcript will be available within the next few business day.

 

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