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NES Video Chat With Astronomer Sten Oldenwald
December 14, 2010
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For years, science fiction writers as well as astronomers have thought about the existence of black holes. Then, recently, evidence began to support the existence of black holes. And now, we know they are out there - and in greater numbers than was once thought. Astronomers even have captured photographic evidence of black holes.


Odenwald is an award-winning astronomer at NASA's Goddard Space Flight Center in Greenbelt, Md., and author of a number of books. Odenwald was born in Karlskoga, Sweden. As a child, he was afraid of the dark. But when he was 10 years old, his father showed him the stars in the constellation Orion. Ever since then, Odenwald has been interested in astronomy. In grades 8-12, he read many books - some fact, some fiction. But it was science fiction that drove his curiosity about astronomy.
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After graduating high school, he attended college at the University of California, Berkeley, where he concentrated on physics and mathematics. While at UC Berkeley he took an introductory astronomy course and, after that, decided to pursue a career in astronomy. In 1981, he received his doctorate in astronomy from Harvard University.

Involve your students in Black Hole Math by using the NES module, Black Hole Math, on the NES Virtual Campus or by going to http://www.nasa.gov/pdf/377674main_Black_Hole_Math.pdf for specific problems about black holes.

For general mathematics problems, check into Space Math @ NASA.

Do you want even more information about black holes? You're in luck. On Jan. 26, NES will be posting NASA Now: Black Holes on the Virtual Campus.

If you're a K-12 educator in the U.S. or a U.S. territory and haven't registered yet for the NASA Explorer Schools project, take a few minutes and complete the NES registration form to become part of NASA's exciting K-12 gateway to the future.

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Chat Transcript

Hello and welcome to this month's NES career chat. This month we're excited to have astronomer and black hole expert Dr. Sten Odenwald with us. Sten will answer your questions about careers in astronomy and space science as well as any questions you have about those mysterious black holes. Submit your questions by entering them in the ASK window below. Questions asked during the live event will be answered on-air as time allows.

Sten_Odenwald(P) Hello and welcome to today's chat. Let's begin!

ccs4thgrade (Q) how long have you been studying the stars?
Sten_Odenwald(A) Since I was ten years old and it's been a continuous love affair ever since.

ccs5(Q) Have you ever discovered anything new?
Sten_Odenwald(A) Oh yes. As an astronomer it's difficult to not discover new things. By the time you get to my age you discover many things, so I have a long list. Some include stars, and strange clouds in the Milky Way, a variety of things.

ccs5(Q) what made you want to become an astronomer?
Sten_Odenwald(A) I was very interested in science since I was 4 years old. My dad introduced me to constellations when I was10 years old. That got me interested in astronomy.

ccs5(Q) Is it true that when you go through a Black Hole time is reversed?
Sten_Odenwald(A) No, when you fall into a Black Hole, time is still moving the same as it was outside, just at a different rate.

ccs4thgrade(Q) how far away are the stars?
Sten_Odenwald(A) Well, the nearest is four light years away - a light year is the distance light travels in one year. Typical stars are between 100 and 1,000 light years away. The faint band of the Milky Way is even further away, but stars are different distances from Earth.

ccs5(Q) what is a Black Hole?
Sten_Odenwald(A) A Black Hole is an object that is so compact that even light cannot escape it.

ccs5(Q) Where does a black hole lead to?
Sten_Odenwald(A) That's a very good question. Some theories suggest that they might lead to different universes. Other's suggest they might lead to different places or time in our own universe. We don't really know for sure.

ccs5(Q) How long have you been studying Black Holes?
Sten_Odenwald(A) I first became aware of Black Holes in the late 60's when I was in college. That puts it since around 1971.

ccs4thgrade(Q) how do Black Holes form?
Sten_Odenwald(A) It's actually kind of complicated because there are different types of Black Holes and they form from different kinds of processes. Star sized Black Holes come from stars that have gone supernova. We also know of Black Holes that are millions and billions of times the size of our sun which are usually found in the center of galaxies. We're not exactly sure where those come from.

ccs5(Q) How big is a Black Hole?
Sten_Odenwald(A) Well, size depends on how much mass the Black Hole contains. So if you have a mass the size equal to our sun, that Black Hole would be only 6km in diameter. If it has the mass of Earth, that Black Hole is the size of a ping pong ball.

ccs5(Q) Is it fun being an astronomer?
Sten_Odenwald(A) It's a lot of fun, what other job can you have to study stars and space?

ccs4thgrade(Q) what is your favorite part of your job?
Sten_Odenwald(A) Keeping up with new discoveries. That inspires me to think very creatively. It's very stimulating, the coming together of new things and I really enjoy that part of the job.

ccs5(Q) How long did it take for you to become an astronomer?
Sten_Odenwald(A) After graduating from high school, I went through four years of college learning physics and math. Then I went through six years of graduate school to get my doctorate degree. About ten years in all.

ccs5(Q) What instruments do you use to look for evidence of a Black Hole?
Sten_Odenwald(A) There are a variety of things we can use. One of the earliest ways was to look at stars that seem to be moving as though there were something else orbiting the star, but you couldn't see what it was. That's a sort of visual clue. Looking for invisible things is not as easy as it sounds. One nice thing about Black Holes is that they absorb things from their environment, so we can look at that material as it goes into the Black Hole and it often gives off radio waves, x-ray light and things like that. X-ray and radio telescopes are very common tools that we use.

ccs4thgrade(Q) what do Black Holes lead to?
Sten_Odenwald(A) We don't know. All we have is math to guide us. Some have lead us to other universes, and some have lead us to distant places and time within our own universe. Both are not accessible.

ccs5(Q) If a Black Hole is big enough would it effect Earth?
Sten_Odenwald(A) For a Black Hole to affect us it would have to be close to our sun. Most Black Holes are not close to our sun.

ccs4thgrade(Q) where is the best place to stargaze in the US?
Sten_Odenwald(A) Well it's always been the case that the best places are far away from city lights, so go out into the country and get as far away from the city as possible. In the eastern seaboard that is often difficult to do. In the western and midwest states it's quite easy to do because it's rural and not as densely populated.

ccs5(Q) What size do you believe Black Holes are?
Sten_Odenwald(A) That is a very difficult question. The ones that we think are common in our universe today are the mass of our sun or a little more. Black Holes that are larger than that require the merging of star clusters and that is a very slow process. Black Holes require a lot of energy to form and those that are much less than the size of our sun have a very difficult time forming.

ccs5(Q) Where do you live?
Sten_Odenwald(A) I live in Bethesda, Maryland.

ccs4thgrade(Q) what does a star look like close up?
Sten_Odenwald(A) It looks very much like our sun. It has a very luminous outer layer. Depending on how hot the star is, it's going to have a different color but most stars look very similar to our sun.

ccs5(Q) How does a Black Hole form?
Sten_Odenwald(A) It's actually kind of complicated because there are different types of Black Holes and they form from different kinds of processes. Star sized Black Holes come from stars that have gone supernova. We also know of Black Holes that are millions and billions of times the size of our sun which are usually found in the center of galaxies. We're not exactly sure where those come from.

ccs4thgrade(Q) have you ever seen a comet?
Sten_Odenwald(A) I have seen several comets. I saw comet Bennett in 1971 back when I was in high school. I saw comet West back in 1976 and Haley's comet in 1986. Those were three of my favorites.

ccs5(Q) Where has evidence shown that a Black Hole exists?
Sten_Odenwald(A) We have evidence from the observations we make using x-ray spectrum.

ccs4thgrade(Q) how big are Black Holes?
Sten_Odenwald(A) Well, size depends on how much mass the Black Hole contains. So if you have a mass the size equal to our sun, that Black Hole would be only 6km in diameter. If it has the mass of Earth, that Black Hole is the size of a ping pong ball.

ccs4thgrade(Q) how did you become so smart?
Sten_Odenwald(A) Haha. I'm not very smart, I guess I just keep my facts more organized than most people. I don't know, it's like anything, how do you improve at running a marathon or get better at tennis? It's just something you get better at with practice over time. I just got better at thinking.

ccs5(Q) Are there different types of Black Holes?
Sten_Odenwald(A) Yes. There are two major types of Black Holes. They are different in properties. One rotates and the other doesn't. The ones that do not rotate are very simple in site. The ones that do no rotate are complicated in site.

Jordan(Q) How many Black Holes are there?
Sten_Odenwald(A) There are probably thousands of Black Holes within our Milky Way galaxy from stars that went supernovae and produced them. We think just about every galaxy has a huge Black Hole in it's center.

ccs4thgrade(Q) why do stars twinkle?
Sten_Odenwald(A) Light from stars passes through our atmosphere, the atmosphere moves the star light around a little bit and that is what we see as twinkling.

Jordan(Q) Why is a Black Hole black?
Sten_Odenwald(A) Because although light and particles can fall into a Black Hole, they can't get back out. Therefore they do not reflect light and appear to be black.

Mmarcy(Q) How many Black Holes have we found?
Sten_Odenwald(A) We can't confirm a number just like we can't confirm how many planets there are in the Milky Way either. The catalog just gets bigger and bigger all the time, but right now there is on the order of a few hundred that are known in the Milky Way. But there are probably many thousands.

Mmarcy(Q) Would a Black Hole pull other objects into it?
Sten_Odenwald(A) Yes because Black Holes have gravity and anything that got too close would fall into it, if the orbits were appropriate. It's not like a vacuum cleaner, it only affects it's environment through it's gravity.

Mmarcy(Q) How are Black Holes named?
Sten_Odenwald(A) There's no real consistent way. They are often named according to the part of the spectrum where they're discovered. There are a number that were identified as x-ray sources, so those have the same names as x-ray sources in catalogs. Others are identified as radio sources, so that's another set of catalogs. It's by a catalog number, and there are many different types of catalogs where these things appear.

Judy_B(Q) I have heard of a term called a frozen star - what is a frozen star?
Sten_Odenwald(A) That was an old description that was given to Black Holes that sort of reflected Newton's theory of relativity that goes into describing how these things form. It turns out as an object is collapsing to form a Black Hole, there is a tremendous distortion in time that goes on. If you were far away as that star was collapsing, it would collapse slower and slower until it would stop whereas if you were closer you would see it collapsing at a constant rate. Calling it a frozen star describes how things are moving whereas calling it a Black Hole is describing what it is that you are actually seeing.

Judy_B(Q) When was the first Black Hole discovered?
Sten_Odenwald(A) The first one was discovered in 1970 it is called Cygnus X-1. It was found in the constellation Cygnus.

Mmarcy(Q) What would happen if a person fell into a Black Hole?
Sten_Odenwald(A) If a person fell into a Black Hole the mass of our sun, he would be torn to shreds before reaching the Black Hole because of the intense gravity. If a person fell into one several million times the mass of our sun, he could fall without any effects but would die when reaching the center.

Mmarcy(Q) Will our sun ever become a Black Hole?
Sten_Odenwald(A) The sun is not massive enough to become a supernova and the only way to form Black Holes, that we know about, is for stars to go supernovae. Therefore, the sun will never become a Black Hole. Instead it will end life as a white dwarf.

Mmarcy(Q) What part would mathematics play in studying Black Holes?
Sten_Odenwald(A) Well, the only way we know about Black Holes is by studying the geometry of space. And so math comes into that because it is the language we use to describe the relationships in space and time for that matter. So that's how it applies. In fact, the only thing we know about Black Holes is from the detailed mathematical study of these things. So it plays a critical role in the understanding of Black Holes.

Judy_B(Q) I read that scientist have simulated, for the first time merger of two Black Holes of different sizes. what does that tell us?
Sten_Odenwald(A) They used a supercomputer to solve very complicated mathematic equations that described the merger of Black Holes. What they were trying to understand is how these things produce gravity waves and what happens to them after the merger.

Mmarcy(Q) What did you study in school to become an astronomer?
Sten_Odenwald(A) Informally I was an amateur astronomer, and then when I went to college I took mathematics and physics and then special courses in astronomy.

Sten_Odenwald(P) Thank you everyone. Have a great day.

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Sten Odenwald
Sten Odenwald
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NASA
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Artist rendition of a black hole
Artist rendition of a black hole.
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NASA
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Artist rendition of a black hole accretion disk
Artist rendition of a black hole accretion disk.
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NASA
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