The Herschel Telescope Close To Blast Off

pha7boy writes "The Herschel space observatory, the European Space Agency's answer to the Hubble Telescope, is about to be sent into orbit. With a mirror 1.5 times the size of the Hubble mirror, the Herschel will look at the universe in the infrared and sub-millimeter range. This 'will permit Herschel to see past the dust that scatters Hubble's visible wavelengths, and to gaze at really cold places and objects in the Universe — from the birthing clouds of new stars to the icy comets that live far out in the Solar System.'"

Comments

Cant wait

[dilvish_the_damned]

till they first post the images from this baby.

Re:Cant wait

[Piata]

I think Hubble has been one of the most interesting and successful space based missions ever. A lot of the most mind blowing images I've ever seen of space have come from that telescope. Hopefully this telescope will continue the trend.

Re:Cant wait

[von_rick]

A lot of progress has taken place in the the field of optics, electronics, cryogenics, material science and communications. Given the additional 1m on the reflector, it'd be safe to assume a far better performance than Hubble.

Re:Cant wait

[Chris Burke]

Given the additional 1m on the reflector, it'd be safe to assume a far better performance than Hubble.

Yep. Meters matter. A lot. The summary says the mirror is 1.5 times as big (3.5m/2.4m), but really area and thus quantity of incident light is what matters so it's more like 210% as big as Hubble (3.5^2)/(2.4^2). This is a big space telescope. All else being the same, I'd expect this to show a good deal more distant/faint objects.

It says it's infrared, so this may be more comparable to Spitzer than Hubble. Spitzer is only 0.85m. This beast is 17 times the light bucket Spitzer is.

Re:Cant wait

[Anonymous Coward]

As to resolution, every size listed should be expressed in wavelengths however. And Hubble observes at smaller wavelengths...

Re:Cant wait

[mcgrew]

gaze at really cold places and objects in the Universe

I would think a stethoscope would be a better instrument for examining my ex-wife's heart!

Re:Cant wait

[MBGMorden]

Due note too, that the James Webb Space Telescope (the US's next telescope slated to launch in 2013, assuming funding doesn't dry up) is slated to have a 6.5m mirror, which should produce some REALLY nice results.

Re:Cant wait

[Clandestine_Blaze]

Well, that depends. How far away is she? :)

Re:Cant wait

[Chris Burke]

I thought focal length was the biggest factor in resolution? But then again all I know about telescopes comes from hobbyist visible light scopes.

Herschle has half the focal length of Hubble. Kinda surprising, but then again maybe Hubble is designed to have a wider field of view.

Re:Cant wait

[mustafap]

OR how deep ;o)

Re:Cant wait

[Chris Burke]

Looks similar in design to the huge-primary-made-of-adjustable-smaller-mirror-hexes Hobby-Everly ground-based scope which is 9.5m.

Color me exited. =D

Re:Cant wait

[Pictish Prince]

Especially since they probably didn't screw up the mirror this time.

Re:Cant wait

[Anonymous Coward]

In addition to that, the JWST will feature a micro-shutter array, composed of over 62,000 individual shutters in the area of a postage stamp. The idea is that each shutter can be independently opened and closed so visible light from near, bright objects can be blocked out making it easier to view objects that are further away.

I had the opportunity to tour the clean room at Goddard Space Flight Center where the array is being fabricated. The techniques used seemed to mirror the techniques used to manufacture modern microprocessors. It was very interesting to be guided through the process, there are definitely some incredibly smart people at Goddard.

Here is some more information and pictures of the array.

Re:Cant wait

[Anonymous Coward]

They stole that idea from me, the lazy bastards...they should come up with their own ideas and stop posing as rocket scientists, oh wait, you said shutters...never mind.

Re:Cant wait

[SargentDU]

Ok, you're outta here! (Chris Burke said "Color me exited." Did he mean excited? Not what he said. :P)

Re:Cant wait

[nsayer]

That, and presumably it's not ground like Mr. Magoo's glasses (unlike Hubble was).

Re:Cant wait

[NCG_Mike]

I'm hoping they finally get some photos if those canals on mars.

Re:Cant wait

[navyjeff]

Stone generally requires different instruments, such as saws, picks and drills.

Re:Cant wait

[Chris Burke]

Of course that's what I meant. I don't make typos.

The tricky part is... what is the color of not being here?!

Re:Cant wait

[rts008]

Unicorn Pink?

Hey, this is a trick question, right?

Re:Cant wait

[Iron Condor]

I thought focal length was the biggest factor in resolution?

Diffraction limit is set by lambda/diameter -- the longer the wavelength to larger the mirror required to get the same limit.

But then again all I know about telescopes comes from hobbyist visible light scopes.

On the ground you're almost always resolution limited by the atmospheric seeing, as long as your aperture is over ~10cm or so. Anything larger form there is going to help with collecting more light (i.e. detecting fainter objects with shorter exposures) but not with resolution any more.

Re:Cant wait

[davester666]

I just hoped they triple-checked the math used for the design of the lens system...

Re:Cant wait

[Nyeerrmm]

In a certain respect, it is related to the focal length, if you consider the eyepiece or sensor fixed. If you have a fixed pixel size on your CCD, then changing the focal length will change the angular size of each pixel, and thus change the resolution, although I think this kind of result is usually called magnification. Similarly, when using an eyepiece, the magnification is related to the ratio of the focal lengths, so a longer focal length will change the magnification

When the CCD pixels get small enough though, that size is no longer the limit on the resolution. Instead (neglecting atmospheric effects) you run into the fact that photon impacts are defined by probability densities that behave like waves, and you get a certain 'spreading' around the nominal impact location. The diameter of this spreading (the Airy disk) means that two sources that are too close together cannot be distinguished from each other, and this is called the diffraction limit. (There are other equally valid explanations for this effect, particularly coming from a wave perspective, this is just the one that I started typing.)

Now, in order to reduce this you want to bring in more photons from further seperated distances, meaning you want a larger aperture in order to improve the diffraction limited resolution. Generally the limiting angular resolution is given by theta_r = 1.4 lambda/D. Of course, if you have too strong of aberrations in the optical system, have to deal with atmospheric 'seeing' effects, the system is not diffraction limited, and the point spread function spreads out more.

Of course, its dangerous to compare the capabilities of telescopes at different wavelengths (Hubble is visible, Herschel is infrared to millimeter wave), because the total amount of light available changes, the angular resolution changes, and the engineering requirements change. Really, Hubble is about the maximum size optical space telescope you can make with current launch vehicles without moving to a completely new kind of telescope (active feedback with wavefront sensing like JWST). Herschel is able to be bigger easily because it requires significantly lower precision, due to the larger wavelengths.

Re:Cant wait

[Xandu]

True, but JWST and Herschel are looking at vastly different wavelengths of light (mostly visible and near-IR as compared to submillimeter) so they really compliment each other. JWST is a replacement for Hubble in the truest sense of the word. The article is misleading in it's claim that Herschel is a replacement for Hubble.

Re:Cant wait

[Xandu]

If you'd like a preview, check out the results from BLAST (more results and even prettier pictures coming out very soon). Although it only has a 1.8 meter mirror, it has the same version of detectors that the SPIRE instrument on Herschel uses. To be cheaper and faster, BLAST flys on a high-altitude balloon platform. Slashdot has covered it in the past. And there's a documentary about BLAST as well (also covered by slashdot).

Disclaimer: I work on the BLAST project.

Re:Cant wait

[ZarathustraDK]

I would think a stethoscope would be a better instrument for examining my ex-wife's heart!

Or you could jizz in its general direction and watch the accretion-disk form around the singularity.

hubble mistakes?

[ArcadeX]

are we putting money on if they learned from the hubble mistakes?

Re:hubble mistakes?

[Anonymous Coward]

Personally, I'm curious whether lunar orbit was considered to avoid the earth orbit trash.

Re:hubble mistakes?

[phosphorylate this]

How rude you yanks are, us europeans don't have to learn from YOUR mistakes.

We are perfectly capable of making our own mistakes while repeating your technological ideas 10-years later and at twice the cost.

Re:hubble mistakes?

[Anonymous Coward]

Actually you're almost 20 years behind. Hubble went up in 1990.

Re:hubble mistakes?

[MBGMorden]

Actually you're almost 20 years behind. Hubble went up in 1990.

But it was essentially broken until 1993.

Re:hubble mistakes?

[GigG]

The problem is if you repeat our mistakes in this case you don't have a shuttle to go up and fix them.

Re:hubble mistakes?

[sidyan]

As described in here, the point of putting the observatory in a Lissajous orbit around the Earth-Sun L2 Lagrange point is to have the three nearest and largest sources of infrared light pollution (the earth, the moon, and the sun) sufficiently far away and in the same hemisphere relative to the observatory, allowing for a clear viewing angle anywhere in the other hemisphere.

Re:hubble mistakes?

[Anonymous Coward]

So? It will not only be a bigger telescope, it will be an even bigger mistake. We beat you twice!

Re:hubble mistakes?

[nicolas.kassis]

Didn't know there was a competition for the biggest failure. I guarantee that the US has enough crap mars missions that failed to outdo all the Euro mistakes.

Re:hubble mistakes?

[Anonymous Coward]

Not really. Despite the botched mirror, it was still taking pictures of far higher quality than any other telescope.

not about imaging

[Anonymous Coward]

This instrument is capable of great science, but spatial resolving power is not it's strong suit. Since it is measuring at wavelenghts much greater than hubble (100-1000x), the 3.5 meter mirror doesn't give you anything like hubble.

It will be intresting for sure

[SGDarkKnight]

As for all the new discoverys i'm sure these new telescopes will find, i'm curious if they will do the same thing with these as they did with the hubble, by pointing it at a "black" region of space and leaving it there for a while gathering exposures, only to discover that the region wasn't "black" at all, it was completely filled with all sorts of different galaxies, and this was only a small point in space they were looking.

Here is the link for the Hubble info in case you're intrested.

http://hubblesite.org/newscenter/archive/releases/1996/01/text/

Re:It will be intresting for sure

[ceoyoyo]

I'm sure they'll do many deep fields.

Astronomers were well aware that the region of sky used for the Hubble deep field was full of distant objects. It was chosen because the lack of bright, close objects makes it simpler to do really long exposures of the distant, dim ones.

One of the stated goals of the Herschel is to look back to the beginnings of the universe. The best way to do that is by choosing a dark area of the sky and exposing as long as you can.

Re:It will be intresting for sure

[physburn]

Being infrared means it will much better good chance to find exo-planet and asteroid belts. Wonder which of the Herschel or Kepler missions will find more planets.

Extra Solar Planets Feed, Astronomy Feed

Re:It will be intresting for sure

[Anonymous Coward]

In fact, there is no case for very long exposures like the Hubble Deep Field or the Chandra Deep Fields (X-rays) with infrared telescopes, because the maximum depth reachable is not limited by sensitivity (exposure time) but by confusion (resolving power).
The confusion limit is reached when you can not detect any more sources because the field is so crowded that they start overlapping with each other. This limit is usually reached in infrared telescopes long before the detection limit (a few minutes), because the wavelength of the light in this spectral range is so big that the resolving power is very poor.
Note that resolving power is proportional to the diameter of the main mirror and inversely proportional to the observing wavelength, so a ~4.5m telescope like Herschel operating at 100 microns has aproximately half resolving power of an amateur 6cm telescope operating in visible light.
This also implies that the "ESA response to Hubble" statement is absurd and misleading

Re:It will be intresting for sure

[ceoyoyo]

Kepler. Kepler is designed to find lots and lots of planets.

Herschel is general purpose, so it will spend a lot of it's time looking outside the galaxy. But it should be very useful for looking in more detail at the planets Kepler finds.

Re:It will be intresting for sure

[James Youngman]

This is somewhat ironic considering that William Herschel discovered a planet (Uranus) while Kepler did not.

Re:It will be intresting for sure

[IWannaBeAnAC]

Astronomers were well aware that the region of sky used for the Hubble deep field was full of distant objects.

Wow, what a bunch of historical revisionism. How, exactly, were astronomers supposed to be 'well aware' that that pointing Hubble at a patch of sky where all previous surveys had shown nothing at all, would produce such interesting results?

What actually happened was that the director of the observatory has some 'discretionary' observing time on the telescope, that he/she is completely free to do what they want with, without the usual procedure of submitting an application for approval (a process that is quite competitive). Most likely, a normal application to observe in the deep field would have been rejected, on the grounds that there is insufficient justification and it could easily have ended up as a waste of time. Imagine submitting an application saying "we propose to point this multi-billion dollar instrument at a region of sky that is completely black and as far as we know, contains nothing" ? But Robert Williams, the then-director, decided to devote a large proportion of his discretionary time in 1995 to deep field imaging. The rest is history. And pretty pictures.

Re:It will be intresting for sure

[nicolas.kassis]

Nice one. if I had mod points you would get them.

Re:It will be intresting for sure

[ceoyoyo]

Bravo. The post full of true but irrelevant detail, the tone of righteous indignation... excellent troll.

Just in case you were serious, have a read through the wikipedia entry for the Hubble deep field, and the original paper (PDF link).

Pay particular attention to the "Field Selection" section of the paper. Note that both the Wikipedia article and the introduction to the paper talk about how the project was designed to image a "typical" field, with the intention of studying (among other things) galaxy morphology in the very early universe. Also, the introduction to the paper outlines several other preceding medium and deep field studies that provided the motivation for the Hubble deep field project (goes to how the astronomers knew they were likely to find galaxies - previous studies did NOT show nothing at all).

Now, moving on to the field selection part of the paper, note how the target field was chosen because of the absence of nearby sources, and upper limits on the strength of the sources present (not NO sources present, but rather no STRONG, CLOSE sources present).

The kicker of course, is this quote: "Eisenhardt (1995) kindly provided KPNO 4m R-band CCD images (2x300 second exposures) as further verification that the fields were typical in terms of source counts..." (emphasis mine). A truly empty portion of the sky, with no observable signal sources would be VERY atypical.

Taking a quick tour through the source table in the paper, I noticed a source at around magnitude 17. The tables later in the paper suggested that there are sources present up to magnitude 15. That's pretty faint, but magnitude 15 is reachable by moderate amateur telescopes and the naked eye. Considerably better can be done with amateur CCD equipment and long exposures.

One of the fundamental assumptions of cosmology is that, on the large scale, the universe is pretty much the same no matter what direction you look. A totally blank area back as far as Hubble can see would be very unusual.

Again, I'm sorry to ruin your beautiful troll with actual references, but it was so well done someone might believe you!

PS: the "a normal application... would have been rejected" claim doesn't seem to be nearly as iron-clad as your tone implied.

Re:It will be intresting for sure

[RichiH]

ceoyoyo did the fact-based demolition of your arguments, let me do the logical one.

Assuming they knew nothing about the field of sky and it was just black to everyone, they would either have found stuff or not.

Found stuff: Well, neat. Let's look at it.

Found nothing: Whoah! Edge of the universe? _Huge_ interstellar/galactic structure? Black hole? In any case: amazing.

So they would have known they would find out neat stuff, anyway. And that is _without_ everything ceoyoyo told you in http://science.slashdot.org/comments.pl?sid=1121617&cid=26793955

Re:It will be intresting for sure

[IWannaBeAnAC]

I don't get it: my main point was to refute the comment "Astronomers were well aware that the region of sky used for the Hubble deep field was full of distant objects.". You, at least, seem to agree with me that that statement is a bunk, since you allow for the possibility that they see 'nothing' but claim that would sill be interesting (well, maybe, but I doubt it would have been nearly as interesting as what they did see). What, exactly, are you trying to argue?

Re:It will be intresting for sure

[RichiH]

My point is that they _were_ aware (or next to 100% certain) that there would be distant objects as the current theory says that we can not see the edge of the known universe in any direction. Everything else (barring technical defects, etc) would be an even greater discovery.

And that is without the facts (no, I did not verify them myself) ceoyoyo gave us.

Re:It will be intresting for sure

[strikethree]

I do not think he was trolling. I did some fact checking just now and it does indeed seem that the research was done on the Directors discretionary time. From http://hubblesite.org/newscenter/archive/releases/1996/01/text/

  "The landmark research was carried out under Williams' direction, and using a significant fraction of his own director's discretionary time on the Space Telescope. He decided to conduct the Hubble Deep Field program to use Space Telescope's exquisite resolution and high sensitivity to push back the very limits of time and space."

Furthermore, I can see how you might interpret the above posters comments about "nothing being there" as trolling as well, however, I think you saw it only due to your seemingly aggressive nature. When I read his words, I saw the words "nothing known to be interesting" since everyone knows that the universe is supposedly homogenous on a large scale.

*shrug* I do not think it is wise to assume so quickly that people are trolling.

Re:It will be intresting for sure

[ceoyoyo]

Did you read back to the beginning of the thread? A poster wondered if the Herschel would be used to do a deep field, like Hubble, and seemed to be under the impression that the presence of galaxies in the Hubble deep field was a surprising discovery. I mentioned that it was not, then the poster you're referring to began his post with:

Wow, what a bunch of historical revisionism. How, exactly, were astronomers supposed to be 'well aware' that that pointing Hubble at a patch of sky where all previous surveys had shown nothing at all, would produce such interesting results?"

My post didn't contain any mention of HOW the deep field came to be or who organized it, simply the statement that astronomers were aware there were structures in that region before the deep field was imaged. So which of our posts was aggressive?

I doubt IWannaBeAnAC was purposely trolling either, but his post IS a very nicely put together troll. After all, you fell for the completely irrelevant, but, as you say, accurate, information about the director's discretionary observing time.

You're absolutely correct, if IWannaBeAnAC had replied to my post politely, I would have replied in kind. However, when he starts his factually incorrect post with "Wow, what a bunch of historical revisionism," one of the nicest things I can assume is that he's trolling.

Infrared?

[oneiros27]

If it's in infrared, then it's NOT a Hubble replacement, it's a Spitzer replacement.

Re:Infrared?

[brilinux]

If it's in infrared, then it's NOT a Hubble replacement, it's a Spitzer replacement.

Isn't that David Paterson?

Re:Infrared?

[Logical Zebra]

Right. The Hubble looks at visible wavelengths; this new Herschel does not.

Isn't the Hubble beyond its original estimates for service life? I don't think it will really be around for too many more years, and there aren't plans for another visible spectrum space telescope.

Re:Infrared?

[ceoyoyo]

It depends what you're comparing. Hubble looks a bit into the near IR too. Spitzer is mostly mid-IR, and Herschel is designed to look at very long wave IR and the higher frequency microwave region. Herschel and Spitzer overlap in wavelength a little bit, but not really that much.

In terms of application, Spitzer is not in the same sensitivity class as Hubble or Herschel, so for really deep field imaging the comparison between Hubble and Herschel is fairly apt.

Re:Infrared?

[karllark]

Actually, it is very complementary to Spitzer. Spitzer observes at wavelengths from 3.6-160 microns, Herschel observes at wavelengths 55-672 microns. The do overlap, but have different strengths.

Re:Infrared?

[Xandu]

And it's not really a Spitzer replacement, as it's looking at mostly longer wavelengths than Spitzer. It complements both. Virtually all different wavelengths are worth looking at as they all tells us unique things.

Herschel, mostly with the SPIRE instrument, will be looking at the earliest star forming galaxies. A nearly identical instrument to SPIRE was flown on a high-altitude balloon, BLAST, which got Slashdot coverage as well.

Disclaimer: I work on the BLAST project.

Manager quote

[Anonymous Coward]

"The mirror is an enormous piece of hardware," enthused Thomas Passvogel, Esa's programme manager on the Herschel space observatory.

Sounds like all managers.

Infrared == looks far away

[mangu]

A telescope with a bigger mirror can concentrate more light, therefore it sees fainter, more distant, objects. And the further away things are in the universe, the more red-shifted their light is. It really makes sense a space telescope being designed for infrared light, rather than visible.

Re:Infrared == looks far away

[Anonymous Coward]

That depends. EMR that is on shorter wavelengths than light, for distant objects, get red-shited into the optical spectrum. If you want to see a really, truly distant X-Ray or Gamma emitter, the visible spectrum makes a lot of sense.

Re:Infrared == looks far away

[wastedlife]

I thought red-shift was caused by the direction and speed the object is traveling in relation to us, not its distance.

Re:Infrared == looks far away

[mangu]

I thought red-shift was caused by the direction and speed the object is traveling in relation to us, not its distance.

That's correct, but the more distant objects are moving away faster than the nearest ones.

Re:Infrared == looks far away

[Dreadneck]

Yes, but observations have confirmed that the more distant the object the faster it is receding from us.

Re:Infrared == looks far away

[DeltaStorm]

I thought red-shift was caused by the direction and speed the object is traveling in relation to us, not its distance.

It's both actually. Due to the expansion of the universe, objects that are further away from us are moving away from us faster than closer objects. Hubble's Law

Re:Infrared == looks far away

[wastedlife]

Thanks for the info. One thing that confuses me about that is assuming everything is moving away from the origin of the universe, wouldn't all galaxies always move away from each other. I recall reading that in some many billions of years, another galaxy will collide with ours. Wouldn't these 2 outcomes be mutually exclusive? Genuinely curious about this.

Re:Infrared == looks far away

[niklask]

Thanks for the info. One thing that confuses me about that is assuming everything is moving away from the origin of the universe, wouldn't all galaxies always move away from each other.

On large scales yes that is correct...

I recall reading that in some many billions of years, another galaxy will collide with ours. Wouldn't these 2 outcomes be mutually exclusive? Genuinely curious about this.

...but not on local scales, where the gravitational effects are larger. The Mily Way is gravitationally bound in the Local Group (see Wikipedia).

Re:Infrared == looks far away

[Anonymous Coward]

You're right. There are a lot of observed contradictions in the "redshift=doppler effect" explanation. The recent explanations conclude that we have no idea what is causing the red shift.

Re:Infrared == looks far away

[Anonymous Coward]

Gravity acts on irregularities in the expanding matter to form clumps which continue to move outward from the center. Otherwise, nothing larger than hydrogen atoms would exist.

Re:Infrared == looks far away

[Anonymous Coward]

First of all, everything is not "moving away from the origin". Everything is moving away from everywhere else--there is no center. The cliche analogy is quarters taped to an inflating balloon--every quarter sees all of the others recede.

But the reason we can hit the Andromeda galaxy is that we're relatively close--we're in the same local cluster of galaxies, which you can think of a unit of structure bigger than galaxies. These are actually staying together--gravity opposes the spatial expansion, so (for example) the solar system stays together, the galaxy stays together, and the cluster stays at least somewhat together. It's not galaxies receding from galaxies, it's clusters receding from clusters.

Incidentally, in some models of our universe, the expansion speeds up and eventually rips everything apart, but that's unconfirmed.

Re:Infrared == looks far away

[Shrike82]

Hold the phone. You're saying that the eventual destruction of the galaxy hasn't been confirmed?

Get the scientists on this right away, I have plans for New Years Eve and want to know if I should cancel them.

Re:Infrared == looks far away

[Xandu]

However, if you do the math, you'll see that even the earliest possible galaxies (redshift = z = 10 (or less)) don't get visible light redshifted into the submillimeter (where Herschel looks). This is because the earliest galaxies are very dusty, and this dust obscures most of the visible light coming from the stars. However, to obscure the light, the dust is absorbing the energy, heating the dust up (to about 35K give or take) and this dust re-radiates at like 10-100 microns or so, which is redshifted into the submillimeter (200-600 microns) that Herschel looks at.

I work on a precursor to the SPIRE instrument (a major instrument on Herschel, called BLAST which flew on a high-altitude balloon (you need to get about the atmosphere to look in the submillimeter and balloons are way cheaper than sattelites).

Krustovsky?

[Facetious]

Now why did that pop into my head?

Re:Krustovsky?

[bradgoodman]

MOD UP

Not offtopic - was the first thing that I thought of too!!

Anyone who mods down is just prejudiced against Jewish clowns.

Oblig.

[escay]

and to gaze at really cold places

you mean, like Uranus?

sorry, couldn't resist.

Re:Oblig.

[Dreadneck]

Or the wife's hoo-hoo?

Re:european telescope?

[Anonymous Coward]

And which revisionist history would you be basing that comment on?

Read a history book, dill-hole.

Here's hoping

[Onyma]

someone ground the reflector to the correct shape!

I too can't wait for the first images... it is a great time to be alive if you love learning more about the world / universe around us.

Why not visible light?

[tjstork]

I don't understand why all of the newer space telescopes seem to forsake visible light.

Re:Why not visible light?

[StaticEngine]

Redshift, probably.

When you're looking at things really really far away, the frequencies shift towards the red end of the spectrum due to the doppler effect of the Hubble Expansion. If we only looked in the visible spectrum, we wouldn't see anything, because the light had already shifted out of the proper range. Thus, but looking towards the infrared and longer wavelengths, we can actually detect things that originally light emitted in the visible spectrum but are reaching us in a heavily stretched state.

Re:Why not visible light?

[Adambomb]

I wasn't exactly sure myself until this comment and this wiki entry. If we focused them on visible spectrums, we'd not notice the most distant emissions. Since attempting to detect obejects that are extremely distant is the apparently the whole bit with the Herschel telescope it starts to make sense.

Re:Why not visible light?

[Anonymous Coward]

Because the radiation emitted by stars isn't just visible light. There's all sorts of EM waves being transmitted. By gathering a range of EM waves, instead of just visible light, we can gather information, which is critical when you think of the tiny numbers of photons we receive from these distant stars.

Re:Why not visible light?

[burris]

I'm only an amateur astronomer but... With adaptive optics we can get better visible light images with ground based telescopes like Keck than with any orbiting telecope that could be launched any time soon. However, infrared is blocked by the atmosphere so an observatory without an atmosphere is required.

Re:Why not visible light?

[Rich0]

Yup. I don't know that I'd even call myself an amatuer astronomer but I remember being fascinated by a Nova episode about IRAS ages ago.

This is a very poorly explored region of the spectrum, hence the interest. I think the issue with sending up another Hubble is that it just isn't as much bang for buck.

Don't get me wrong - it seems silly not to have ONE visual spectrum space telescope, but looking into different wavelengths is far more likely to turn up revolutionary results and advance the field.

Here's an analogy. We discover a planet on a distant star. Which is more likely to turn up new results - a detailed observation of that distant planet, or a careful high-resolution analysis of craters on the Earth's moon? Sure, the latter might be good science, and turn up results, but it just isn't going to be as likely to change how we think about everything.

Re:Why not visible light?

[Alinabi]

Because visible light is scattered by dust a lot more that IR. So if you want to look inside a protoplanetary disc, visible light is not of much use.

Re:Why not visible light?

[mjaga]

It's because it makes sense to use space telescopes to look at radiation that can't be observed with ground based telescopes, because the Earth's atmosphere absorbs all of it. Herschel with its three instruments (HIFI, PACS and SPIRE) operates in the submm and far infrared, a part of the spectrum inaccessible from ground, and will spend a lot of observing time e.g. to look at interstellar water, a molecule believed to play an important role for the cooling of star forming clouds.

Re:Why not visible light?

[Hordeking]

I'm only an amateur astronomer but... With adaptive optics we can get better visible light images with ground based telescopes like Keck than with any orbiting telecope that could be launched any time soon. However, infrared is blocked by the atmosphere so an observatory without an atmosphere is required.

Then imagine what we could do if we put an AO telescope array in space!

Re:Why not visible light?

[ceoyoyo]

Get really expensive, not much better images?

Adaptive optics help cancel out the distortions produced by the atmosphere. That's not particularly useful on a space telescope.

Once you've got adaptive optics to take away most of the biggest advantages for space telescopes, the ease of building giant mirrors on the ground takes over and you get much better performance for your budget.

Re:Why not visible light?

[ceh2624]

Fascinating except the objects that far away aren't going anywhere near the speed of light and therefore should not red shift beyond visible, even at that distance.

Re:Why not visible light?

[Hordeking]

Get really expensive, not much better images?

Adaptive optics help cancel out the distortions produced by the atmosphere. That's not particularly useful on a space telescope.

Once you've got adaptive optics to take away most of the biggest advantages for space telescopes, the ease of building giant mirrors on the ground takes over and you get much better performance for your budget.

Depends on what your goal is. However, you are correct in this matter.

Yes, AO is generally a specific application of a telescopic array designed to thwart distortions caused by an atmosphere. I should have been a bit more clear on this. In this case, I was mixing up AO with a composite mirror/detector telescope.

However, imagine an array much larger than we could build on the ground. For instance, multiple telescopes in orbit around the moon, earth, and the sun? You could use that for all sorts of interesting research (is there an application for multiple parallaxes?), but you could get a hell of a lot of resolution with an array the size of 2AU diameter (for instance, multiple telescopes in an earthlike orbit.)

Re:Why not visible light?

[Anonymous Coward]

If only the Hubble Space Telescope took into account this "Hubble Expansion" of which you speak...

Re:Why not visible light?

[cowscows]

A lot of these objects are really far away, and over the billions of years since the light was emitted, the actual space that its had to travel has grown as the universe expands. All of that adds up and the light is significantly red-shifted.

Re:Why not visible light?

[dgatwood]

That still doesn't answer the question about why they didn't include the visible spectrum. The way I see it, if you're building this giant space telescope with multiple sensors anyway, why not throw in a visible light camera for good measure? Sure, it may not be the main focus of the mission, but when Hubble's electronics finally bite the dust (and at this rate, that may be before too long), there's going to be a real lack of these breathtaking images of space for many years. All of that could be avoided by simply having something to take over that load when the time comes. And remember, while the infrared instruments may give you data that scientists want, public funding comes only in response to pretty pictures....

The same argument applies to the U.S. telescope scheduled to replace Hubble in 2013 for the same reason. It's all infrared as well.

Re:Why not visible light?

[Bemopolis]

ASTRONOMY FAIL.

Re:Why not visible light?

[Anonymous Coward]

Fascinating except the objects that far away aren't going anywhere near the speed of light and therefore should not red shift beyond visible, even at that distance.

High red shifts have been observed. Most people agree on one with z=7 and some have suggested objects have z=10. These shifts are high enough to shift visible light into the infrared.

Re:Why not visible light?

[ceoyoyo]

I thought you might be referring to interferometry in your original post, when you mentioned an array.

You CAN build very high resolution interferometers in space. There are some problems though. As far as I know you couldn't build a bigger visible or infrared interferometer than we can already build on the ground. The individual elements of those have to be linked by fibre optics because we don't have a good way of recording phase information for optical frequencies.

Space interferometers definitely work at radio frequencies, but they do different things than telescopes like Hubble. An interferometer has very high resolution (and very small field of view) but doesn't have matching light gathering ability. If you want to try to image extrasolar planets or count sunspots on other stars, an interferometer is the way to go. If you want to look at the early universe or do sky surveys, they are not.

Re:Why not visible light?

[Phil06]

Redshift happens

Re:Why not visible light?

[tomz16]

Because an optical design for IR will not work well in the visible. It's not as simple as slapping an Si detector somewhere in the field and snapping images. The optical prescription of the telescope has to be tailored to the operating wavelength.

Re:Why not visible light?

[RichiH]

> Can your shell do this? ls |where {$_.Length -gt 2000}|format-table Name, Length

I am sure mine can do a lot which yours can not, but I am always willing to try out new stuff.

zsh here. You?

Re:Why not visible light?

[Xandu]

True. But the oldest galaxies (what Herschel is mainly designed to look at) don't emit in the visible, even in their own (rest) frame. That's because the earliest galaxies are very dusty, and all this dust is opaque to the visible light. The stars are still there, glowing away, but their light is absorbed by this dust. This absorption heats the dust, warming it to 35K (give or take), which, as all things with non-zero temperature do, emits radiation like a blackbody. This light is then redshifted such that it's blackbody spectrum peaks in the submillimeter, which is what Herschel looks at.

Disclaimer: I work on BLAST, a balloon-borne experiment (cheaper than a satellite) which has detectors nearly identical to the ones of the SPIRE (main) instrument on Herschel.

Re:Why not visible light?

[Hordeking]

I thought you might be referring to interferometry in your original post, when you mentioned an array.

You CAN build very high resolution interferometers in space. There are some problems though. As far as I know you couldn't build a bigger visible or infrared interferometer than we can already build on the ground. The individual elements of those have to be linked by fibre optics because we don't have a good way of recording phase information for optical frequencies.

Space interferometers definitely work at radio frequencies, but they do different things than telescopes like Hubble. An interferometer has very high resolution (and very small field of view) but doesn't have matching light gathering ability. If you want to try to image extrasolar planets or count sunspots on other stars, an interferometer is the way to go. If you want to look at the early universe or do sky surveys, they are not.

As I recall, the communications issue is the reason we're still having trouble with getting interferometry working for visible-light wavelengths and shorter.

Re:Why not visible light?

[Hordeking]

I thought you might be referring to interferometry in your original post, when you mentioned an array.

You CAN build very high resolution interferometers in space. There are some problems though. As far as I know you couldn't build a bigger visible or infrared interferometer than we can already build on the ground. The individual elements of those have to be linked by fibre optics because we don't have a good way of recording phase information for optical frequencies.

Space interferometers definitely work at radio frequencies, but they do different things than telescopes like Hubble. An interferometer has very high resolution (and very small field of view) but doesn't have matching light gathering ability. If you want to try to image extrasolar planets or count sunspots on other stars, an interferometer is the way to go. If you want to look at the early universe or do sky surveys, they are not.

As I recall, the communications issue is the reason we're still having trouble with getting interferometry working here on Earth for visible-light wavelengths and shorter.

Re:Why not visible light?

[ceoyoyo]

You're right. There are big optical interferometers like Keck, but the telescopes can't be too far away, and they have to be physically linked.

Re:Why not visible light?

[dgatwood]

I assume you're referring to chromatic aberration? Bear in mind that the James Webb satellite I mentioned already detects the red and possibly orange portions of the visible spectrum. If you're not getting too much chromatic aberration there, then even in the worst case, I'd expect the amount you'd get in the visible spectrum to be minor enough to be correctable in software. It should be easily correctable with an additional lens, with a modified sensor design, or with some combination of those two plus software post-processing.

Even with something designed for the far infrared, though, I would think you could still correct for the aberration with an additional lens on the front of the camera. Less ideal than using a full set of lenses specifically optimized for focusing visible light? Sure. I still think it would be better than nothing.

Besides, AFAIK, the Herschel telescope is fundamentally a reflecting telescope, not a refracting telescope. There's no chromatic aberration from a mirror, and I suspect that any lenses involved are likely to be per-instrument, not shared among the various detectors. Thus, dropping in a visible light detector should be pretty much a non-issue. Am I missing something fundamental here?

Re:Why not visible light?

[tomz16]

Kudos for knowing about chromatic aberration.

I was being quick in my reply and not very exact. Sorry for the confusion. You are correct that the chromatic aberrations do not matter until you get into the refractive components of the individual science instruments.

Assuming that the reflectivity of the surfaces is still good at visible wavelengths, the part of the prescription that changes are the surface figure requirements and tolerancing (spacing, alignment, etc.)

The operating range of the of the Herschel is 60-670 microns.

In order to get to diffraction limited in the visible with the same telescope, you would have to do a few orders of magnitude better in surface quality and alignment. Think of it this way, a wave at 600nm (visible) is 100 times smaller than a wave at 60 microns (Herschel IR). So you have to be about that much more exact in everything you do! So you CAN stick a Si detector on the Herschel, but you will get crap for an image.

The JWST design wavelength is at 2 microns (close to visible), and it is required to be diffraction limited at that wavelength. There was originally a requirement to have the JWST diffraction limited all the way down into the high visible, but it has been lifted to save costs AFAIK. It'll still be pretty damn good at visible, but no guarantee that it will be diffraction limited anymore.... So, expect some beautiful visible shots from the JWST!

Re:Why not visible light?

[Urkki]

Early galaxies dusty? How? I mean, where did the dust come from? Isn't dust heavier elements, formed in stars, so in early universe and early galaxies, there would have been much less dust than in current galaxies?

Misleading story summary is misleading

[Anonymous Coward]

This is not a "competitor" to Hubble, it's not the same type of telescope as Hubble. It's in the same family of observatories as Spitzer/SIRTF:
http://www.spitzer.caltech.edu/spitzer/index.shtml

Re:european telescope?

[Dishevel]

Silly AC. It is European, not French only.

GL, HF

[jack2000]

20 bucks sez the mission goes smooth, without a hitch.

Blastof, Russia

[slashdotmsiriv]

Am I the only one who read it as:
"the Herschel telescope close to the Russian city of Blastof" ?

Re:Blastof, Russia

[Anonymous Coward]

Am I the only one who read it as: "the Herschel telescope close to the Russian city of Blastof" ?

Yes.

Re:Blastof, Russia

[Fluffeh]

Yes. Yes you are.

Re:european telescope?

[Hordeking]

And which revisionist history would you be basing that comment on? Read a history book, dill-hole.

He's probably referring to the French involvement in launch vehicle, Ariane 5

To Be Announced...

[Hordeking]

Not to be outdone by Europe, the US plan to launch the next generation follow-up to the Hubble Telescope!

Re:To Be Announced...

[MBGMorden]

Not to be outdone by Europe, the US plan to launch the next generation follow-up to the Hubble Telescope!

That would be the James Webb Space Telescope, and it's been in the works for quite a while.

Re:To Be Announced...

[Sperbels]

It would be nice if they did. Something has to keep politicians interested in funding science.

Re:european telescope?

[Anonymous Coward]

"Hope it doesn't surrender when Hubble passes it by :)"

Nope. The German bits will strike across the short distance between them, roll a two-pronged tank advance around the Hubble, and incorporate it into their glorious thousand-year astronomical plan....

Comment removed

[account_deleted]

Comment removed based on user account deletion

Launch is still months away

[Anonymous Coward]

Scheduled apparently for April 16

Launch Date: April 16

[onco_p53]

April 16 Ariane 5 Herschel & Planck
Launch time: approx. 1230 GMT (8:30 a.m. EDT)
Launch site: ELA-3, Kourou, French Guiana

Arianespace Flight 188 will use an Ariane 5 rocket with an ECA upper stage to launch the European Space Agency's Herschel and Planck observatories. The Herschel infrared telescope will study the evolution of stars and galaxies and the Planck spacecraft will observe the cosmic background radiation left over from the Big Bang. [Jan. 14]

http://www.spaceflightnow.com/tracking/index.html

Main Task...

[Anonymous Coward]

How well does it find oil?

James Webb == Hubble Replacement

[oneiros27]

There aren't any plans?

The article linked to showed the size comparison for the James Webb Space Telescope, and its spectral range vs. Hubble (further into IR, but also further into the visible spectrum)

Re:James Webb == Hubble Replacement

[CraigParticle]

The article linked to showed the size comparison for the James Webb Space Telescope, and its spectral range vs. Hubble (further into IR, but also further into the visible spectrum)

No no -- not further into the visible than Hubble. The Hubble spectral range from that figure was for the NICMOS (infrared) camera only. It ignored all other Hubble instruments from far-ultraviolet through visible light!

By and large, the original assertion was correct -- Hubble's emphasis was on UV, visible and near-infrared wavelengths. Most of the "pretty pictures" came from the visible light cameras. James Webb will be a large telescope optimized for near/mid infrared observations, with some capability at the red end of the visible spectrum. Herschel is optimized for far-infrared and submillimeter wavelengths.

All three observatories are hugely significant and will give us very different views of the Universe.

Re:european telescope?

[Anonymous Coward]

Nope. The German bits will strike across the short distance between them, roll a two-pronged tank advance around the Hubble, and incorporate it into their glorious thousand-year astronomical plan....

NUTS!

About time

[Stonefred]

Watching tv is getting boring ...

Re:Cant wait (not just America)

[divisionbyzero]

According to wikipedia: "JWST is a NASA-led international collaboration between NASA, the European Space Agency and the Canadian Space Agency. "

Mirror

[Nom du Keyboard]

So are they getting the mirror right this time before launch?

Isn't this similar to Spitzer Space Telescope?

[Neanderthal Ninny]

This is same idea, but a much larger mirror, as the Spitzer Space Telescope:
http://www.spitzer.caltech.edu/about/index.shtml

The ESA, NASA and JPL have collaborated on this project since this appears to scaled up version of Spitzer Space Telescope with 6 years of advanced technology and lesson learned from Spitzer Space Telescope.

Good luck ESA with sending Herschel and Planck in space.

Re:Isn't this similar to Spitzer Space Telescope?

[MightyDrunken]

Good luck ESA with sending Herschel and Planck in space.

Seconded. Not only will Herschel's findings be very interesting, but Planck is also one to watch.

Planck's mission is to look at the cosmic microwave background in even more detail then WMAP. By mapping the lumpiness of the CMB and its polarisation many potential theories regarding the early Universe can be discounted or strengthened. Even the shape of the (visible) Universe may be deduced. You could view Planck as a telescope which can look at the furthest distance/time that is thought possible.

Re:Isn't this similar to Spitzer Space Telescope?

[Xandu]

Not fully. Spitzer is mostly a shorter wavelength (best at 1-25 microns) observatory than Herschel (best at 200-600 microns). You can understand vastly different things with that difference in wavelengths.

Poor old Planck

[Zoxed]

What: no mention of poor old Planck, Herschels tandem partner ?
Or is the measuring of background less "sexy" than looking at galaxies forming ? :-)

This just in! Slashdot editors are Math Retards!

[Mr. Firewall]

With a mirror 1.5 times the size of the Hubble mirror....

No, it's 2.3 times the size.

It's 1.5 times the diameter of the Hubble mirror. That equals 2.3 times the size.

Some days, you just gotta wonder about the /. editors' intelligence....