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What inspired you to pursue a career in science?
My father was a farmer, and the physical labor and economic risks involved in that occupation seemed really high. (I'm sure I'm not alone in that opinion.)
I did not know any scientists when I was growing up, but when I watched movies (science fiction in particular) it seemed liked the scientists had the most fun, or at the very least, were the most likely characters to know what was really going on. I think I was attracted to the idea that scientists are the smart people (regardless of the reality:) )
So I can say, real people like Einstein, fictional characters like Mr. Spock, these were my heros when I was a kid, and when I started to take courses like physics and geometry, I really hoped that I would be good at them. I turned out to be good at math and science, and so when I went to college, I thought maybe I'd be a physics major if I could survive the courses. I asked my advisor what a physicist did, and he gave me some of the best advice ever: "Work for one, and find out." So I did, I worked for astrophysicists, and just kept doing it! (I continued in astrophysics in grad school.)
It didn't always seem to be the most prudent choice, since a PhD in astrophysics doesn't guarantee a research career in astrophysics. (I was surrounded by sensible people going into engineering of many flavors.) But it worked out for me, and I've been very happy I took the chance!
Is there anything you're really hoping to see with the Chandra telescope? What would be the most exciting thing for you to observe happening in the gas clouds you're studying?
Einstein said: The most incomprehensible thing about the world is that it is comprehensible.
What I love to see are patterns and trends! I'm most discouraged by random scatter plots: plots of one property vs. another property, that show no relationship, no trend, no pattern. It's always exciting to make a plot of something new, and reveal a pattern or trend which has never been seen before! It means that there is something there to explain, or maybe something that was predicted (but not yet seen). I like to work with theorists (like my husband Dr. Mark Voit), both to test their explanations and to present them with new challenges.
I also like to see detailed data of great beauty: when the images are of high enough quality to show where the clouds have bubbles or filaments or shock fronts, I'm very happy. With higher detail, we can answer questions like how much energy is being injected into the cloud from phenomena surrounding black holes and accelerated gas clouds from star explosions. These data allow us to test very specific physical predictions about how the gas should behave under extreme conditions, and allow us to use those same models to infer things about the environment of the gas clouds: about how much dark matter is present, for example.
In some sense, the most exciting thing might be counter-intuitive to most folks: the most exciting situation would be one where very little is happening except for the gas resting in a deep gravity well. Astronomers view many situations where there seems like there is a zillion things going on: explosions, galaxy mergers, gas sloshing around. In astronomy, we don't get to go out into the universe and tell it to "Settle DOWN! I want to study what happens when only one thing is going on at a time!" Other scientists can usually control their experiments, and set up what they call a comparison or control trial, and vary just one condition at a time. Astronomers must usually deal with a lot of messy experiments done by Nature, and sort out the patterns after many observations.
That said, I am always thrilled to view a major black hole outburst in the center of a cluster: those represent some of the biggest explosions in the nearby universe, and I'm thrilled that we can use these data to bear witness to these amazing events.
I read about this void they found in space that apparently is supposed to make us rethink the big bang theory. Do you know about this void? Has your telescope studied it? What's the deal?
A word of caution: the big bang theory is fairly simple. It posits that the universe started as hot and dense, and has expanded to be what we see today. The discovery and further studies of the cosmic microwave background confirmed this early hot and dense state of the universe, and the recession of galaxies away from us confirms the expansion part. So there is not much left to go wrong with that theory.
Sometimes media like to make a statement like "rethink the Big Bang theory" to get reader attention, but really, what that phrase usually translates to is something more like "reconsider the ways that galaxies collect into filaments, clusters, and voids", which is NOT a rethink of the Big Bang, but is more a reconsideration of what happened to matter afterwards. There is a standard picture of structure formation (meaning how voids and clusters form) that predicts how dark matter and ordinary matter collect together through gravitational interactions. The broad brush ideas of that picture seem fairly secure (like gravity is the main force in the universe, and the contribution to gravity from dark matter is large), but there are some features of that model that occasionally come under test, like how much dark matter is out there, how does dark matter behave, how do structures "light up" (we can only see structures like voids by the absence of stars and galaxies). We don't have the last word on all these questions, so they are still active topics of astronomical research.
So hold on to your Big Bang stock! Announcements of its demise are premature (to paraphrase Mark Twain.)
How long will the telescope last up in space? Are their plans to launch more "Great Observatories"?
Chandra is in a very high orbit around the Earth, so it doesn't need extra boosts (like the Hubble Space Telescope does.)
The Chandra scientists tell me that the main thing that limits the lifetime of Chandra is its ability to point using a fuel called hydrazine. Because its initial boost to its orbit did not use as much fuel as the engineers planned, the extra fuel is available for the much smaller control thrusters. So if the hardware survives particle damage and random electronic problems, the telescope may be around for a much longer time than we could have hoped for when it was launched in 1999: it could go to 2018 and beyond.
The next telescope in that category of large missions available for the full astronomical community is the James Webb Space Telescope. It is a successor to Hubble Space Telescope, in that it will be an optical and infrared telescope (but no ultraviolet capabilities), and will be a much larger telescope. Its main goal is to detect the very first stars born in our Universe. It will also be able to tell us amazing things about planets outside our own solar system. Its planned date of launch is 2013. My friends at NASA tell me that it is being built, and everything is looking very good.
What happens after James Webb is still being discussed. The astronomical community discusses their priorities and plans in a big project called the "Decadal Survey". NASA and other science funding agencies, like the National Science Foundation, pay close attention to these studies, done once every 10 years. They represent our chance, as scientists, to give our opinion about what the most important astronomical projects should be, given what opportunities may exist. The 2010 decadal survey process is just starting up.
What are black holes? What causes them?
If Superman could squish the Earth into the size of a child's marble, it would be a black hole.
A black hole is any object that is so densely packed that its gravitational attraction is too powerful for light to escape it.
The Sun would be a black hole if it compressed to a radius of about 3 kilometers (little less than 2 miles). You would be correct to imagine that it's really really difficult to make a black hole out of anything.
So black holes are created in fairly extreme conditions. The explosive death of a very massive star is called a supernova. These supernova are caused by the implosion of the nuclear structure of the iron nuclei that accumulate in the cores of these stars. The center of very massive stars gets more and more loaded up with iron (a by-product of advanced nuclear fusion that can only happen in these stars). Iron is the element where energy is used to either fuse or split (fission) it, so that reaction doesn't happen. Once there is too much iron for the core to hold it up, the core collapses, the outer layers fall in then bounce out, and under the most extreme circumstances, a black hole is left behind.
Black holes can also merger and become ... bigger black holes. So the giant ("supermassive") black holes - millions to billions times more massive than our Sun - that we find in the center of galaxies are not from a single star. (The biggest stars are only about 100 solar masses or a bit larger.) Those supermassive black holes are the product of the merger of lots of black holes and the accretion of matter.
Although their gravity is very powerful, it's important to remember that they don't suck (as in suck in the whole Galaxy!) It would be very difficult for us to shoot something into a black hole, even if it were relatively nearby! Even if they are massive, they are excruciatingly tiny compared to the distances between the stars. Even if matter is caught by the gravity of a black hole, the tendency is for it to orbit the black hole, not to fall in. In order for black holes to grow by accreting matter, it has to develop an accretion disk of orbiting matter that is dense enough for collisions between gas particles to be common. These collisions allow the gas particles to transfer some of their orbital angular momentum to other particles, and the particles that lose the most, settle closer and closer to the terrible black hole. (Even this process is pretty slow.)
We can "see" these black holes in binary star systems by their gravitational influence on their companion star. We can also detect black holes from the high temperatures of their accretion disks, which make these disks visible in X-ray light (so Chandra can see them).
There's lot more work to be done though -- we no way know the full black hole story.
Is there a place to go to see "live" images from your telescope?
The quick answer is "no" - the telescopes I use do not provide "live" views of the universe. One reason for that is that the raw images from the telescopes are usually not clean enough and clear enough to view without adding many of them together. Some telescope images require background subtraction (so the galaxies show up better); and many of the things I study are very very faint. So very long exposures are created out of many images, pointed in the same direction. Any one of those images are not very interesting, but all summed up, they are beautiful!
But there are websites that can give live views of the sky from a telescope. We use one such "fish-eye" telescope in Chile to track the sky conditions during the night. Those images only update when it is dark in Chile and when the fish-eye telescope is working. (Click on "observing" then click on "Site Monitors" low down on the left-hand side of the page.)
You can also get data and images from the NASA Great Observatories from these websites:
Hubble Space Telescope
Chandra X-ray Telescope
Spitzer Space Telescope
All of these pages have links to Education and Public Outreach, which are loaded with beautiful images recently obtained from their favorite telescope!
Does the universe ever end? If so, what's beyond it, and how can it be not in the universe if you know what I mean?
Here's a case where the definition of the terms really does matter:
Universe: the sum total of all matter, energy, and spacetime. So by definition, the Universe is everything, and nothing is outside of it. So you're right: nothing can be beyond the universe, because by definition everything is in it.
I know that's not hugely satisfying an answer, so allow me to go on. The "observable Universe" does have a size: the observable Universe is the universe that we are, in principle, able to observe. The universe is about 14 billion years old, so the observable universe extends about 14 billion light-years away from us in every direction. Light travels 1 light-year in one year, so anything farther than that has not had time for its light to reach us. So the boundary of the observable Universe is more like a boundary in time, in that sense. "Beyond" the observable universe is before the universe began, and we don't have a framework to say what was "then". (I put "then" in quotes because it's hard to talk about events before time, or even a direction in time, had been established.)
But the concept of the "observable universe" is a useful one, and we use it a lot in cosmology. Our observable universe could be a tiny piece of a much larger Universe, but the observable universe offers us all the clues we can hope to accumulate about our situation.
Why do stars twinkle?
Phew! Finally an easy question. You guys are making me work!!
The Earth is surrounded by a thin, but important! layer of gas we call our atmosphere. The atmosphere is turbulent: like a swimming pool with little waves bouncing here and there, our atmosphere is not perfectly calm.
If you were able to lay down at the bottom of a swimming pool (yes, you have to let a lot of air out of your lungs to do that!) and look up through the water at someone watching you, you'd see their image shift around, as the water bent the light rays reflected from that person to your eyes.
A similar thing happens to the light rays from a star, which is so far away that it would appears as a nearly perfect pin-point of light to our eyes or even a telescope. The light-rays get shifted around very slightly as they pass through the atmosphere, and that causes us to see them "twinkle". The pin-point of light is dancing around in the sky, over an angle of 1-2 arcseconds (1 arcsecond = 1/60 arcminute = 1/3600 degree).
The planets don't twinkle -- at least not as much as stars -- because they are close enough to look like small disks in the sky, not perfect pin-points. So they still twinkle, but their images don't seem to move as much, according to our eyes.
If you were an astronaut on the space shuttle, and you looked at the stars through the window of your helmet, unobscured by gas from the shuttle or anything like that: you'd see the stars shine back you you, unwavering. I think that would be really cool to see.
Would you be able to use the x ray telescope to tell if a distant planet had an Earth-like atmosphere?
That would be a very cool thing to do!
But unfortunately, an X-ray telescope is not the tool for that job. Our own Sun is a very poor source of X-rays, and the Earth, from an X-ray viewpoint, is a better absorber of X-rays than it is a reflector.
The Earth's atmosphere interacts with X-rays in a very thin high layer called the exosphere. Mars has an exosphere too. The Chandra X-ray telescope has been used to look at Mars, and it was very faint. By analogy with Mars, searching for similar emission from planets over 100,000 times farther away would be impossible.
What one wants to do is to use the planet's star as a background source of light. What you see in the telescope is the star, as viewed through the atmosphere of the planet (for very short times during the planet's orbit.) During those special times, if you spread the light out into a spectrum, you not only see the light from the star, but also
the pattern of absorption lines of elements in the gas. These absorption lines have been imprinted on the starlight as it passes through the atmosphere of a planet. It does require a special situation, where the planet is orbiting through an imaginary line strung directly between us and its star. That experiment has already been done by infrared (long-wavelength light) on board the Spitzer Space Telescope and the Hubble Space Telescope, and while they could tell the planet had an atmosphere, it was the atmosphere of a gas giant, with methane and water.
A telescope of the future will be able to try the same experiment, but with a larger set of stars and planets -- if you are able to observe fainter things, there are usually more potential targets for you to work on!
How many shooting stars are there everyday? And what makes u think the reason is for them being lucky?
"Shooting stars" or, more technically, meteors are what we see when dust-sized to pea-sized pieces of space rock enter our atmosphere and burn up as they fall to the Earth.
Some thousands of TONS of space dust and rock fall through the Earth's atmosphere every year. The vast majority of it burns up before it hits the ground.
I'm not sure why people call them "lucky" but I suppose it's because seeing one is relatively rare on a typical night. When the Earth passes through a comet's trail, like the trail of Swift-Tuttle we call the Perseids, one can see perhaps a dozen or more in an hour. But it's more typical to see a few per hour during the night, after your eyes have adapted (dilated) to see better in the dark.
What is a black hole ?
A black hole is any object whose gravity is so strong that light cannot escape it.
So anything in principle could become a black hole if somehow some way, it became very very tiny compared to its mass.
For example, if somehow, the Sun was squished into an sphere with the radius of a small Texas ranch (2 miles), it would be a black hole. (However, the Sun is not going to do that.)
Black holes can form when a star much more massive than the Sun dies in a supernova explosion. The (iron) cores of the oldest of these stars are unable to support their great weight, and when that core collapses, the rebound from the collapse forms the supernova explosion outward, and a black hole is left behind, the survivor of the core collapse.
The biggest black holes in the universe are thought to form from the mergers of black holes of star-sized masses. These black holes can also acquire hefty amounts of mass from accretion disks. An "accretion disk" is made up of gas and dust orbiting the black hole. Collisions and other types of interactions cause the particles of dust and gas to lose energy and angular momentum, and slowly get pulled into the black hole. (Note: if these interactions did not happen, the gas and dust would happily orbit the black hole forever!)
These supermassive black holes grow over time, and we see them (actually their very hot accretion disks, not the black hole itself) with the Chandra X-ray telescope in other galaxies.
When will our sun burn out ?
About 5 billion years from now.
The hydrogen in the Sun's core is sufficient to power the Sun for about 10 billion years, and we're about 5 billion years through that fuel supply right now. When the Sun's core runs out of hydrogen, it will turn into a red giant, with a size almost the same as the Earth's orbit. It then goes through some very short phases of life as a more compact helium core-burning star, then swells back up to a red giant again. Since the Sun isn't massive enough to allow carbon fusion reactions to occur, this last phase ends with the Sun's atmosphere pulsing off into space, leaving behind a white dwarf.
A white dwarf is about the size of the Earth, and starts out extremely hot. But from this point onward, the Sun as a white dwarf will just gradually get cooler and dimmer with time.
What dangers does the Earth face from solar flares?
The Earth itself is pretty well protected from the high energy particles in a solar flare. The Earth has a magnetic field which re-directs charged particles along the field lines (sometimes causing a light show we call the Northern Lights in the northern hemisphere.) Our atmosphere also provides some protection, as dust particles collide with particles in the atmosphere, the largest particles can burn up, and the atomic particles (like protons) share their energy as they interact with the atoms of our atmosphere.
However, our satellites aren't so well protected, so a big solar flare can disrupt communications and other satellite functions.
We're in a solar minimum right now, hence the low level of light shows from aurora displays. It should pick up in a few years again.
When I was young my parents used to take me camping and we would watch the stars. I noticed that the stars were always moving. Is this due to the earth's rotation?
You are correct!
You'd have to watch for a while to notice the stars move during the night, but that's the real beauty of camping: you have the time to notice the sky and how it changes! Good for you and your parents. Pass that gift along to the next generation! It seems as if fewer kids are getting the chance to really notice the night sky.
One way to get kids into some night sky viewing is to purchase a green laser and use it to point at stars. The green laser light interacts with the dust in the atmosphere and acts like a giant pointer -- it's perfect for singling out stars and planets for kids.
Where do astroids come from
The same place the Sun and the planets came from: a giant interstellar gas and dust cloud. Most of that cloud eventually wound up in (or as) the Sun, but some of the leftover gas and dust formed planets, asteroids, and comets, in a big disk (like an accretion disk that I mentioned above -- same physics!)
Not all of that disk made planets. Asteroids and, farther out where ice could form, the comets are leftovers from planet formation. Most of the asteroids in the solar system orbit the Sun between Mars and Jupiter.
You might ask why the asteroids are just in that location, and not closer in or farther out. One explanation is that gravitational interactions with Jupiter and other gas giants did a pretty good job of clearing out any leftovers in other places in the solar system, except between Mars and Jupiter, and farther out beyond Neptune, where the comets (and Pluto) survived.
I hope this answered your first question, but also I hope this lets you know that we don't know everything about the asteroids (and other space stuff): there's a lot of explanations that we have that still need a lot of testing!
(And a lot more that we don't even have explanations for yet!)
Hi! Ihave a few questions.They are if there will be any future or even a possibility of other galaxies to support life like ours?
One typical galaxy hosts about 100 billion star systems. There are about 100 billion galaxies in the observable universe, so there are about 10 billion trillion star systems in our observable universe (10^22, or 1 with 22 zeros after it.) Give or take a factor of 2 - 4 either way.
So ... I don't think I'm taking a big risk by saying there are plenty of systems out there that are capable of supporting life like ours.
Space...it's a really big place.
How old is the universe? And how long will it last?
According to our latest and greatest data and models about the history of the expansion of the universe, the Universe is about 13.7 billion years old, and is not only still expanding, the expansion is getting faster and faster.
We don't know what is causing that acceleration. We call it dark energy, but that's about as far as we've gotten. Until we know what "dark energy" is and how it behaves (it could change over time, for example) we don't really know how long the universe will last.
However, if the expansion continues forever, the universe in that sense lasts forever. Even if dark energy stopped accelerating the universe instantly everywhere right "now" (for some random reason) there is not enough matter in the universe to reverse the expansion, not even when we count the dark matter.
So odds are (if you're a gambling type) the universe lasts forever. But that's just a guess until we learn more about dark energy and how it behaves over long periods of time.
How do we know how old stars are, and how long they live if we are not around for the beginning and end? zoe
I'm sorry to be so late with this reply - I guess I thought there weren't anymore questions.
Anyway, that is one awesome question. Astronomers needed help from physicists to figure out the answer: the key came from answering the question: why does the Sun shine? Around the turn of the last century, astronomers could estimate the lifetime of the Sun if it got all its energy from gravitational contraction. It seemed like a long time - about 25 million years or so - but that time was way shorter than the age of the oldest rocks geologists knew about at the time. The resolution of that controversy was that the Sun gets its energy from nuclear fusion, the fusion of hydrogen nuclei to make helium. Nuclear fusion was completely unknown to scientists in 1900. But by the 1930s, astronomers knew the Sun was a vast ball of hydrogen and helium, and in the center of that ball, the hydrogen was hot enough to fuse, and make helium.
Once scientists knew the process by which stars generated their energy, they could make models of hydrogen and helium gas balls with different amounts of gas to predict what stars of different masses would look like. And they reproduced a feature on a luminosity-temperature plot of stars that astronomers call the "main sequence". These models improved, as the scientists' understanding of quantum physics increased, and these models predicted what would happen to stars after the hydrogen in the core ran out. These models could be compared to data (particularly observations of stars in clusters, because these stars were all born together, with the same chemical mix and birthday). Astronomer observers and theorists would go back and forth, taking data and comparing them to models, until they had a pretty good understanding of what stars did.
They can test their models by comparing what it predicts with observations of a star cluster which is, say 100 million years old (like the Pleiades) and another cluster which is 7 billion years old or so (like NGC 188). It's like taking a picture of a kindergarten class and then a class of college seniors. You don't have to watch a kindergartner grow to adulthood to get a pretty good idea of how humans age. In a hospital, humans are born and humans die, and even spending a week in a hospital might give you a pretty good idea of how both those events go. Similarly, if we're watching stars die in one cluster, and stars being born in another, we don't have to watch individual stars through their whole life.
Stars are a lot simpler than people too, their stories aren't nearly so complicated.
What school skils do you need to know to become an astonomer?
Same apology as above - I thought the question time ended sooner than it really did!!
Here's what you need:
Physics & math, as much as you can get into your college schedule. Most astronomers major in physics, or if they do major in astronomy, they take a LOT of physics classes anyway.
Know how to write. That sounds kind of counter-intuitive - probably nobody tells you, but if you can't write about what you did, and if you can't write a compelling argument for why you want to do something (like an experiment or an observation), you won't be able to write your own proposals. If you want to lead your own experiments, you have to learn how to write well. Physics majors who can't (or don't like to) write generally work for those who can.
Most astronomers write their own programs, and know enough about computers to analyze and use programs written by other astronomers. It's probably not too surprising to appreciate that the software world mainly writes programs for business and maybe medical uses, but not science. So we are often in a situation where we need to use a computer, but there's no software that can do the task we need it to do. So most if not all of us can write simple programs, and some of us can write amazingly complex (but testable) programs. So...not only learn how to use a computer, but learn how to make it dance. :)
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