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Hubble vs. Webb - How Far Back Will They See?
Roland Piquepaille writes "According to Forbes, reporting in "Peering Back At The Universe's Past," space telescopes are really acting as time machines. They can watch objects which are so far from us that light has taken billions of years before reaching their mirrors. The Hubble telescope is able to look at events that took place 13.3 billion light-years ago. But the James E. Webb space telescope, currently under construction, and scheduled to be launched in 2011, will be able to see even further and catch phenomena which happened 13.5 billion light-years ago. The astronomers think the Webb telescope might even be able to see up to 13.7 billion light-years ago, when our universe was just 200 or 300 million years old. We are used to see fantastic images from Hubble, without paying too much attention to the characteristics of the telescope itself. So here is a thorough comparison between the two space telescopes."
As I'm sure everyone will be quick to point out, lightyears isn't a measure of time, rather of distance.
It is more accurate to say that the hubble could see images 13.3 billion years ago, and the Webb telescope may be able to see images 13.7 billion years ago.
Somebody place a mirror on the other end!
Then we can look into the history of our own Earth!
"We can confirm that Debian does *not* ship the version with the trojan horse. Our version predates it." [CA-2002-28]
13.5 billion light years ago? Maybe I am being stupid, but I always thought that a light year was a measurement of distance?
if they could only see a few days back and tell me where I left my mobile phone.
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I think the imagery provided by Hubble to date has been phenominal and expect that imagery from Webb will just as good or better. Looking back that far in the past though is just that ... the past. When we look back and see light that is 13.3, 13.5, or 13.7, or whatever billions of years old, it is exciting and adds more to the knowledge base. However, when I see galaxies that old I can't help wonder if they're still there (probably not) and what has taken their place. What's there now ...
13.7 / 13.3 = 1,030075188 => 0.03 % performance increase with the new, latest, more expensive system.
Nahh, I'll maybe void my warranty, but I'll just increase the fsb of my old Hubble...
Anyone has tips on deep space overclocking ?
It takes 40+ muscles to frown, but only four to extend your arm and bitchslap the motherfucker
is the fact that while Hubble can view things in the optical, James Webb will be looking at things in the infra-red. The two Wiki links (from the article) provide much more information.
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/. is screwing up the text, but the links should still work.
http://en.wikipedia.org/wiki/James_Webb_Space_Tel
http://en.wikipedia.org/wiki/Hubble_Space_Telesco
Grr...
It's rather more complicated than you think. The light reaching the telescopes is x billion years old, meaning that the objects that emitted the photons have long since moved elsewhere and are no longer there where the telescope sees them. So, when looking out into the universe, you are seeing mirages of the past. The more distant the object, the older its light. So yes, telescopes are time machines in that regard because such is the nature of spacetime - if you look over any given distance you are in effect looking into the past.
----- One learns to itch where one can scratch.
well, if hubble could actually see as far as (light speed * age of the universe) light years than we could gain new knowledge about the big bang theory and the creation of the universe.
as it is, knowing what the universe looked like at age 300Million is quite nice by itself and simply saying that it "ain't nuttin' new" is quite ignorant!
as the light has traveled millions of light years, we ARE actually seeing something that existed millions of years before our time and thus you could call it some kind of "looking into the past"!
Dear Sir,
Some of us prefer the universe the way it is, more mature and filled out. I think its disgusting that these perverts want to spend so much money to ogle at the universe when it was a young hottie.
No doubt they are also hoping to get a glimpse of some of the banging the universe got up to in the exuberance of youth.
Shame on you all I say.
Yours etc.
Outraged
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I worked on the Webb telescope project for a short period of time (back when it was Next Generation Space Telescope) and, believe me, they had a hard enough time scrounging up the money to create what they have now. Making the mirror "a little bigger" or increasing the size of the infrared array would require much more effort than you might think.
http://www.astronomycafe.net/qadir/acosmbb.html
Just for the record, the Big Bang theory is becoming as accepted in cosmology as the theory of evolution is in Biology.
There will eventually be a limit to how far back we can look in time. The Big Bang itself will just appear to be an incredible brilliance everywhere.
That same brilliance has cooled to the point that nowadays, it's only detectable as an almost-universal background microwave radiation.
The detection of that radiation is considered one of the strongest "proofs" of the Big Bang theory, by the way.
There is an optical limit or boundary which cannot be seen past - the surface of last scattering - preventing you from actually seeing right to the beginning.
Batman: "Slake your thirst. You'll have worse than a parched sensation when we're through with you!"
isn't the speed of light not actually a constant but changing with the expansion of the universe
Short answer no, longer answer we don't know. Pretty much all of modern physics is built off the idea that the speed of light is a constant. If you start changing the speed of light then all sorts of thing "break" like conservation of energy. So if you can change the speed of light, you could create matter out of nothing. Neat trick if you could pull it off. That said changing the speed of light does solve some nasty problems surrounding the big bang.
There's also the question that if the speed of light was changing if we'd even have any way of noticing because everything would be skewed along with it. Fun stuff.
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It will be located at Lagrangian point L2 which as you say is a million miles from Earth. The logic being that gravity is equalised there so it wont move and its deep enough in space to reduce heat interference on the IR camera. Part of the project goal is to reduce operational costs as Hubble incurs 230-250 Million US a year to run so there are no service missions envisaged, it will be a standalone effort.
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13.7 / 13.3 = 1,030075188 => 0.03 % performance increase with the new, latest, more expensive system.
As another poster has pointed out, it's actually a 3% improvement.
The point is, that's only 200 or 300 million years from the very beginning of the universe, and it gets exponentially more difficult the further back you want to see.
Rather than 13.7 vs. 13.3 billion years back from now, think 200/300 million years from the start versus 600/700 years from the start. That's a pretty good improvement.
There are 2 main methods:
the 1st one is called parallax (or triangulation) and consists on measuring the position of the star from different points of the earth's orbit (i.e., at different times of the year). The differences in the angular position are then used to calculate the distance of the object.
For objects (stars) that are too far away to give a measureable parallax (more than 400 light years), an indirect technique is used. It is known that different kinds of stars have different emission spectra (colors), and every kind of star has a characteristic brightness. This has been proven by observation of close stars. This way one can analzye the spectrum of a given star and guess how bright it should be. Since the light emission of a star is a spherical wave, the theoretical attenuation of its intensity can be used to calculate the distance. This does not mean that single photons lose energy on their way: they don't. A photon's energy is related with light's frequency (color), while the apparent brightness of the star is related to the number of photons that get here. Since thay propagate as the surface of a sphere, the further you are the fewer photons you get per unit area.
... information wants to be forwarded
And if it doesn't work, we're all just going to sit down and have a good long cry together.
(I understand the logic, but I really like contingency plans...)
You are missing the fact that NASA spends a lot of money making housecalls on Hubble, which have greatly extended its lifetime. This will not be possible with Webb because it is much further out.
Running Webb at L2 will save money. It's difficult and expensive to run a large space telescope in low Earth orbit (LEO). Observations have to be planned carefully since the Earth gets in the way for most of the sky every 90 or minutes. The satellite also has to have batteries to power the systems when the satellite/telescope is eclipsed by the Earth. Batteries are heavy, have to be recharged and they fail. Hubble's are failing. Large satellites in LEO slowly see a degeneration of their orbits because of drag from the very highest parts of the Early atmosphere. This requires them to be reboosted very so often. Any future service mission to HST needs to also reboost it.
Finally, satellites in LEO - least ones in orbits like the one HST is in - have to travel through a radition belt every orbit that can cause electronics to fail and bits to flip. This sometimes causes the telescope to go into safe mode and ruins observations. While in safe mode, operations crews are standing around and more observations have to be either cancelled or rescheduled.
Many of these problems are avoided at L2 or similar locations. Webb's life will be limited by the amount of sensor coolant on board, but space telescopes like the International Ultraviolet Explorer have operated for 20 plus years. IUE used a small crew, was easy to operate and produced more then 3,000 papers at a very low cost - a great return in value for tax payer.
No, sorry. There is a limit to how far we'll ever to able to see, and it's called our "light cone".
John Barrow's book "Impossibility" has a nice description of this (and other limits).
The orbit is about 1.5 million km distance from the earth, at something called the L2 Lagrangian. The Webb wiki page has a link to the Lagrangian page, but for the lazy people, it's here. The orbit was chosen to keep the position of the sun constant relative to the telescope, so that the big 'parasol' can be used to shield the infra-red sensor.
As for Hubble, it's been able to give some awesome images, but it has its limits. I was hoping that the JW (henceforth called J-Dubya?!) would be able to start spotting planets around other stars, but it's not designed for that. I'd like to know if it's theorically possible to keep both in orbit and use them in parallel somehow, in the same way that ground-based radio telescopes have been linked together in arrays. Probably not worth the hassle?
The 'infra-red only' sensor troubles me. Since the telescope's aim is to study the Big Bang, the light/photons it'll be receiving will have travelled for a long time/distance and I guess be red-shifted way down to the IR band. This is all very well, but it means that the telescope shouldn't be considered as a replacement for Hubble, which carries out a wider range of observations.
As an aside, I believe that there is a limit to how far back we can look. At some point, probably less than 1 million years (a guess, can anyone help?), the universe was just too dense for photons to travel around unhindered as they seem to these days. Who said it was better back in the old days eh?
Now two questions. First why beryllium? I know that it's lightweight so easier to lift into orbit. Any other reasons? And secondly what happens if a micro-meteor hits this shield? Do we get a permanent bright spot on all subsequent images, like a broken pixel on an LCD display?
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I'm going to butcher the explanation, but modern cosmology posits that there is no center to the universe in the way you mean.
It's important to remember that at the moment of the big bang, there wasn't a universe outside of it. That is to say that when the big bang occured, it didn't expland into some already exisiting space, rather it was the space that was expanding. As such, all objects are moving away from all other objects.
http://www.astro.ucla.edu/~wright/nocenter.html
has a decent drawing to illustrate how this leads to no "real" center.
The other explanation that has always helped me picture it is to imagine the universe as an un-inflated balloon. In this model, we've reduced the universe to a two-dimensional, unbounded, infinite space in order to help us visualize this principle. Before inflating the balloon, mark several points with permanent marker, Now, when you inflate the balloon, you can see that each point grows more distant (over the surface of the balloon) from every other point you've marked and that the farther one mark is from another, the faster it moves away from it. From the point of view of a given mark, everything else is moving away from it, which would give the impression that it's at the "center" of the balloon's surface. At the same time, however, that impression would appear to be true for every other mark.
This is a tough one to comprehend but heres a shot. It doesnt matter where you look. Its everywhere, and here is why:
When you look away from the earth, you are looking back in time. This is due to the fact that photons travel at the speed of light. So if you look at the moon, you see the moon a half a second ago. Mars is several minutes ago. Alpha Centari is about a year ago. So the futhrer out you see, the further back in time.
Now think of the universe as expanding. If you look out a to a distance where the light is half as old as the universe, you see the universe as it was at that time. But the universe was much smaller then so the galaxy you look at seems bigger than it should given how they look today. So the expansion of the universe and the traveling of photons acts as a lense making things look bigger as you look back further (theres less universe to fill the sky so objects look bigger).
OK so then you look all the way back. The big bang then fills the sky. It is everywhere. And we see it. Its what is refered to as the 3 degree Kelvin background radiation. And in the radio, no matter where you look, you see it.
Now this is not actually the big bang itself. The universe was too dense for anything to be seen. So what we see is what is referred to as the universe at the time of last scattering, when the light from the big bang was finally able to escape as the universe had expanded enough that it was not so dence to capture all the light. So when you hear about people studying the fluctuations in the background radiation, they are actually studying this period of the universes expansion.
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Astronomers have a whole range of different ways to measure distances, each of which works in a different regime. They form a "cosmological distance ladder" - you attempt to calibrate each new method during its overlap region with the previous method.
Parallax is the method for the very shortest distances (nearby stars).
For intermediate distances (distant stars in our own galaxy, relatively nearby galaxies), most of the methods come down to finding some sort of "standard candle" - something that you know the intrinsic brightness of, so you can use its apparent brightness and the inverse square law to calculate its distance. Astronomers tend to use particular types of variable stars (stars with a well-defined cycle of brightness changes) for this purpose. For galaxies, you can sometimes use averaged properties of all the stars to estimate the distance.
For cosmological distances (very distant galaxies) the most common trick is to use redshift. Because of the universe's expansion, an object twice as far away is receding from us twice as fast, and so its light is Doppler-shifted twice as much. Ideally, you look for known features of the object's spectrum and see what wavelength they have ended up at. This is what people are talking about when they measure the distance to Hubble's latest find.
There is also a complementary method that uses standard candles at cosmological distances. In this case, you use Type Ia supernovae, a particular type of exploding star that looks pretty much the same every time. They're bright enough to be seen very far away, and again you can get the distance using the inverse square law (modified by general relativity). It's the difference between this method and the redshift method that provides the strongest evidence for dark energy - it shows us that the universe is expanding faster than we expect, and that this expansion is accelerating.
Also, you're perception of the past is wrong. If I'm a light-year away from something and see something happening, I can say that in my reference frame, that happened a year ago. Someone travelling at speeds approaching c might disagree, but that's another story.
And a light-year is a measure of distance. If you specify "the time it takes for light to travel a light-year" than you have a measure of time, but that was not what the original story poster wrote (although you could assume it since the telescopes are recieving light).