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This is a common misconception and completely untrue. It is impossible for ground based telescopes (ANY ground based telescope) to take images that Hubble can.

OK let's assume for a moment that you're correct, can you give us some more detailed information to make your case? As far as I recall the deep-field photos were sustained week-long exposures, something which of course would be impossible on a terristrial scope.

But most scans don't require week long exposures, especially since the terrestrial scopes have over 60X the light-gathering capacity of Hubble's primary mirror. As far as I recall there are at least 2 major projects using optical and infra-red interferometry between 3 or 4 8-meter mirror arrays. 4X10meters plus the resolving power of interferometry(distance of say 200meters between mirrors) results in pound-for-pound a much more versitile viewing instrument than Hubble. Don't get me wrong Hubble was a great scope, but interferometry and adaptive optics are the future of optical astronomy.

If you end up responding, please explain clearly why I'm wrong because I would like to know.

I don't quite understand yet how they encode the accuracy. Bit depth? Well, in astronomy there have been for quite some time now two competing efforts to have a scheme of efficiently searching the sky. different outset, two angular coordinates with funny non-cartesian properties. They also come up with a single bit pattern to designate an area on the globe: HTM (hierarchical triangular mesh) and HEALPix. actually the HTM group at Hopkins has close ties to the MS Research group in the Bay area, under guidance of Jim Gray. It's fascinating stuff, as this makes searching large databases a lot more efficient. Something that is useful for the Virtual Observatory efforts.

I don't think because a star's light dims, we can assume we've found a new planet.

Well, think again :)

The argument is not "the star's light dimmed, so there must be a planet!". The "lightcurve" (brightness as a function of time) must have particular properties that make the hypothesis of an eclipse event by a small body the most likely explanation: the lightcurve is flat except for a small interval during which it dips by a few percent, remains at that level for a short time, and then rises back up to its original level. This flat-dip feature is periodic, and achromatic (it doesn't affect the star's color).

There is no internal physical process in stars that can produce such a lightcurve. Some stars can vary in brightness by pulsating, but the lightcurve in this case is sinusoidal, and it oscillates in color as well as brightness (because the surface temperature changes as the star "breathes").

We understand stars well enough that we know which ones oscillate, and which ones should have a rock-steady lightcurve. When you see a square-shaped, periodic, achromatic dip in the lightcurve of a star that has no business varying its luminosity, the most (only?!) reasonable hypothesis is that "something" is orbiting the star and eclipsing it. The fraction of light blocked during ingress gives you a limit on the size of the eclipsing body (relative to the known size of the star), which will tell you if the eclipsing body is a planet (small) or brown dwarf (big).

it appears there isn't even anything on the drawing board which would be able to achieve this feat

This unique telescope will have twin 8.4-meter (27.6 foot) mirrors that sit on a single mount

Considering the ESO's VLT I dont understand why this is such a big deal.
The VLTI has four 8.2 meter telescopes supplemented with a further three 1 meter telescopes. All with adaptive optics, can be used as an interferometer etc.
http://www.eso.org/projects/vlt/VLT http://www.eso.org/projects/vlti/VLTI
Now if only the Irish government would sign up to the ESO

This unique telescope will have twin 8.4-meter (27.6 foot) mirrors that sit on a single mount

Considering the ESO's VLT I dont understand why this is such a big deal.
The VLTI has four 8.2 meter telescopes supplemented with a further three 1 meter telescopes. All with adaptive optics, can be used as an interferometer etc.
http://www.eso.org/projects/vlt/VLT http://www.eso.org/projects/vlti/VLTI
Now if only the Irish government would sign up to the ESO

Sorry to say it, but it's already done.

While the second part of this statement has some truth, the first part of this statement is completely false. Adaptive Optics on ground-based optical telescopes are just barely starting to get in the same ballpark as HST, when it comes to resolution. You have diffraction-limited imaging on HST, which gives you a resolution of 0.05 arcseconds (see here). I have NEVER heard of anyone getting better than 0.3 arcseconds from the ground (and rarely even anything approaching that). Moreover, optical interferometry has NOT been shown to work reliably in any sort of consistant way. I think they've managed to get two of the telescopes of the VLT to work as an interferromerter in a very clunky way, but nothing NEAR what would be necessary for regular users.

That said, you're right to say that ground-based telescopes have some advantages: easier repaired, bigger mirrors (although this becomes less true with JWST), cheaper.

But, as the parent notes, space-based telescopes also are able to observe at wavelengths normally blocked by the atmosphere.

Normally, the achievable image sharpness of a ground-based telescope is limited by the effect of atmospheric turbulence. However, with the Adaptive Optics (AO) technique, this drawback can be overcome and the telescope produces images that are at the theoretical limit, i.e., as sharp as if it were in space.

The clever reader by now has already figured out that HST was a costly publicity stunt, providing limited scientific return that's "invaluable", but could be obtained in cheaper ways. I object to the space program's spending spree. I support that the space program should be stopped in favour of actual science being done. I wonder, how far could've gone if the space program's funds were applied more responsibly? Perhaps we could have intelligent robots already, doing our jobs so that we could better enjoy life. What do you rather have? Pretty pictures of faraway galaxies or a better life down here on Earth?

It seems, from this image, linked from the ESO press release, that we've more than maybe seen the first planet out of our solar system with our own eyes.

It looks like we've also confirmed that brown dwarfs are glowing, white stopsigns. Let's just hope that no one needs to build a space lane straight through our solar system with great-big bulldozer things.

[/lame attempt at humor]

~UP

The preprint of the paper lists the parent brown dwarf as 2MASS J12073346-3932539 , which is indeed at the above coordinates. The candidate planet (much in the same way Ralph Nader is the candidate president, but there's my bias showing) will be 0.46 arcseconds south and 0.63 arcseconds east.

In case I didn't discourage any amateur astronomers thus far, here's some more: That's a separation of 0.77 arcseconds, when the seeing at most sites is of order 1 arcsecond. The companion is 100 times brighter than the parent brown dwarf in the K band. The parent brown dwarf has a K of about 12, and for an M8 spectral type, that's a V-magnitude of about 19 or 20. For those of you scoring at home, the parent brown dwarf is one million times fainter than anything you can see with the human eye.

The companion is an even redder object, so the colors will be much, much worse at V (there's a reason we try to detect these in the infrared). With a state-of-the-art AO system (look what we did with the same system earlier this year imaging the surface of Titan) on an 8 meter telescope with excellent infrared detectors, the companion lies one magnitude above the detection limit on their sensitivity/separation curves.

Sorry to depress people looking forward to pointing your telescope at this system tonight, but if it makes you feel better, it's probably not a planet.

I just checked that RA, by the way. It's behind the sun right now. You'll have to wait until January to observe it. Or to point your telescope there and not observe it, as the case may be.

The preprint of the paper lists the parent brown dwarf as 2MASS J12073346-3932539 , which is indeed at the above coordinates. The candidate planet (much in the same way Ralph Nader is the candidate president, but there's my bias showing) will be 0.46 arcseconds south and 0.63 arcseconds east.

In case I didn't discourage any amateur astronomers thus far, here's some more: That's a separation of 0.77 arcseconds, when the seeing at most sites is of order 1 arcsecond. The companion is 100 times brighter than the parent brown dwarf in the K band. The parent brown dwarf has a K of about 12, and for an M8 spectral type, that's a V-magnitude of about 19 or 20. For those of you scoring at home, the parent brown dwarf is one million times fainter than anything you can see with the human eye.

The companion is an even redder object, so the colors will be much, much worse at V (there's a reason we try to detect these in the infrared). With a state-of-the-art AO system (look what we did with the same system earlier this year imaging the surface of Titan) on an 8 meter telescope with excellent infrared detectors, the companion lies one magnitude above the detection limit on their sensitivity/separation curves.

Sorry to depress people looking forward to pointing your telescope at this system tonight, but if it makes you feel better, it's probably not a planet.

I just checked that RA, by the way. It's behind the sun right now. You'll have to wait until January to observe it. Or to point your telescope there and not observe it, as the case may be.

If you read the ESO press release you'll see that in addition to imaging it they've also taken spectra of it. The H-band spectrum they shows is similar to other sub-stellar objects, and it also shows fairly strong water absorption bands. This means that it's has to be fairly light. Evolutionary models have been run that predict that this object is about 5 times the mass of Jupiter.

Don't worry, most astronomers don't base their predictions on one image of something, they always follow it up with either multi-wavelength studies or spectral analysis, or both.

Here's a link to the ESO press release.

In Roman times, one theory was that comets were (or contained) the souls of dead people, rising to heaven. Not just any old dead person, of course, but important people, such as Roman emperors, on their way to become gods. Or, perhaps a comet might carry a soul *from* heaven to earth: consider the star of Bethlehem, now believed to be a comet, in one prominent religion.

Another theory, related to that same religion, is that a comet is what an angel looks like from a distance.

In Greek times, comets were thought to be a phenomenon of gases in the atmosphere, much like meteors (the word "meteor" derives from "high in the air").

The word "comet" derives from "coma", meaning hair: a hairy star. (The modern English usage for "coma" came about because the continuing growth of hair was observed to be one of the few obvious changes in a person in a coma.) Early observers might not have known what the hair came from, but it (a comet's tail) was clearly hair of some form.

http://www.skyscript.co.uk/comets.html
http://www.eso.org/outreach/info-events/hale-bopp/ comet-history-1.html

Although it is Uranus-sized, it is close to the star, and so it may not be similar.

ESO press release: http://www.eso.org/outreach/press-rel/pr-2004/pr-2 2-04.html

Is it possible to see any of USA or USSR equipment left there from Earth? (Using powerful telescopes, of course.)

I suspect that the Hubble telescope or the VLT in Chile might be able to see something at a landing site, probably long shadows just after sunrise or before sunset at the site, but I can't imagine either scope being put to such "frivolous" use, even if you paid for the viewing time, considering how much demand for legitimate astronomical use these things have.

Too bad this is only a false-color image and has no relation to the colors visible to the human eye.

There are pictures corresponding to approximately what the human eye would see - kind of boring, and similar to the pictures taken by Voyager 2. The improvement in Cassini's false-colour pictures is due to the use an infra-red camera and some carefully tuned filters, letting the spacecraft peer straight through Titan's distinctly murky atmosphere. This is the breakthrough - it's finally possible to figure out what's under that atmosphere, and at high resolution too!

The preliminary maps of Titan from Cassini's imagery are already beating the best images taken from Earth - including the astounding images taken from ground-based telescopes by the European Southern Observatory. Interestingly, features on the different maps do match up - which definitely shows that they're real feature, and not random camera artefacts.

The European Southern Observatory in Munich, Germany

The original evidence for the fine structure constant changing are now in question with recent observations released this year. New limits put tighter constraints on the constant further back in time.

A good summary can be found here with the recent press release here.

mh

I am somewhat involved with the European version of these missions (the Darwin mission, to be launched around 2014), so I might clear some things up.

Goal: to detect earth-like planets around other starts. Extra-solar planets detected thus far are usually 'hot Jupiters': big planets that orbit the star in a few days. These are relatively easy to detect. Detecting an earth-like planet (which have not been found yet) is far more difficult. It is usually compared to detecting the light of a firefly (reflection of the planet) flying very close to a lighthouse (the star). Measurements need to be done in the far infrared because there the ratio between the planet and the starlight is the highest (but still only 1:10^6 !!). With some luck they might find traces of ozone and CO2 in the spectrum that might be an indication for life.

Methods:
-Coronography: Simply put it is just a conventional big (~10 meter) telescope with a shadow mask that blocks the light of the star. The light of the planet should get past the mask on the detector.

-Interferometry: Somewhat similar to the techniques used in radio astronomy. The resolution of a telescope improves by increasing its size. The trick is to combine several small telescopes. The resolution should then be comparable to the resolution of one big telescope that is as wide as the separation between the small ones. With radio interferometry you can do the 'beam combination' by computer. In optics however you have to physically combine the beams of the different telescopes. This requires flying satellites in formation with stabilities on the order of nanometers!! Current schemes are limited to several hundred meters. There are also some attemps to do this on earth.

There is quite a lot of politics going on between NASA and ESA at the moment about how they should cooperate. First ideas where to do an interferometry mission together, but now NASA has decided to go for coronography and postpone interferometry to 2020. ESA is sticking to interferometry.

Check out the ESO's Overwhelmingly Large Telescope .. 100 meter diameter .. resolution of 1 milliarcsecond .. should be able to image the Lunar Lander on the moon when it's built.

http://www.eso.org/projects/owl/
-Johan

Hubble is our most powerful telescope

Actually no. Using adaptive optics with large ground based scopes (Keck, VLT) you can get some amazing images. Not that Hubble is in any way bad. It's just not the most "powerful" scope we have.

The Hubble is a 2.4m mirror. The Keck is a 10m, and the VLT is 4 8m mirrors. Adaptive Optics is really quite good at reducing atmospheric noise in images.

NO! Read my other post and get your names correct before you start going on about "knowing nothing about astronomy".

The VLA is the Very Large Array, a RADIO telescope run by the american National Radio Astronomy Observatory (or NRAO). It is certainly NOT run by ESO, which is the European Southern Observatory, the organisation that runs the 4 8m Very Large Telescope (VLT) telescopes in chile.

There is no other complete solution to avoid atmospheric turbulence (i.e. seeing and scintillation) other than going to space. A *partial* solution is to use deformable mirrors in an adaptive optics to attempt to correct the problem.

Even with multiple-conjugate adaptive optics (which use multiple laser guide stars to improve performance), you will NOT get diffraction-limited images on an 8m telescope.

Crisper images taken from space will only be better if the diffraction limit of hte telescope is better than what can be obtained by a ground-based system using AO or MCAO. Although nobody has a working MCAO system yet.

sorry, sounds a bit much like a rant, but might add some helpful info into the discussion...

NO! Read my other post and get your names correct before you start going on about "knowing nothing about astronomy".

The VLA is the Very Large Array, a RADIO telescope run by the american National Radio Astronomy Observatory (or NRAO). It is certainly NOT run by ESO, which is the European Southern Observatory, the organisation that runs the 4 8m Very Large Telescope (VLT) telescopes in chile.

There is no other complete solution to avoid atmospheric turbulence (i.e. seeing and scintillation) other than going to space. A *partial* solution is to use deformable mirrors in an adaptive optics to attempt to correct the problem.

Even with multiple-conjugate adaptive optics (which use multiple laser guide stars to improve performance), you will NOT get diffraction-limited images on an 8m telescope.

Crisper images taken from space will only be better if the diffraction limit of hte telescope is better than what can be obtained by a ground-based system using AO or MCAO. Although nobody has a working MCAO system yet.

sorry, sounds a bit much like a rant, but might add some helpful info into the discussion...

Apparently a variety of infrared images of Titan at different wavelengths have been taken from the European Southern Observatory. These different wavelengths allow features at different depths in the atmosphere to be visualized, revealing dynamic and asymmetric atmospheric features, one dubbed the Southern Smile.

As I understand it, in the visible wavelengths we have something better down here. New telescopes with actively controlled lenses are claimed to be achieving as good results as Hubble, with all the advantages of ground basing and at a fraction of the cost.

It is in the infra-red, which cannot get through the atmosphere (well, some near-infra-red can) where you need space based telescopes. And while Hubble can do infra-red work, I don't think it is optimised for it. Which is why the Webb telescope will be an infra-red instrument.

A Hubble refit mission would probably cost something $250 million. For perhaps three times that, you could have this, which stikes me as even more exciting.

Safety may be the main reason but it was always risky to do work in space. Perhaps we understand the risk better now and have rethought our risk:reward ratio. Comments on other points:

The Hubble wasn't state of the art when it was launched. Nothing launched is state of the art; by the time it is designed and built with space-hardened parts, it is already out of date, not to mention the actual delay involved in launching and on-orbit activation.

Hubble was flawed when it was launched. Luckily there was a servicing mission or it would have been a practically useless telescope, though today we have deconvolution software which goes a long way toward correcting this and other optical flaws, whether or not you know how it is flawed or camera is moving, etc.

While adaptive optics can compensate for the atmosphere in some ways it cannot compensate in all ways; there are limitations and more limitations, even of multi-conjugate AO. Telescopes in orbit or on the Moon will always have some advantages.

Compared to new ground-based telescopes, the Hubble is a technically inferior telescope. But it still gets much better images because it doesn't have the atmosphere. It's not just because it "must be cooler" because it's space-based. No amount of telescope can make up for the atmosphere.

Replacement - The replacement for the HST is due to go up in 2012, so there's a relatively small window with no orbital telescope (at least, if all goes well)

Exactly. As an astronomer let me assure you that all of these are absolutely worthless, and all scientific progress will cease once this horribly-redesigned-to-justify-a-manned-shuttle, wasn't-even-built-right-by-political-contractees turkey that's reached the end of its operative lifetime.

Actually, it is a shame in a purely emotional way. Just like when MIR was deorbited. But it's still the right call.

And I don't mean to demean the astronauts who at risk to their own lives got that POS in something like working order, and finally gave everyone some pretty pictures.

Come on, I can't believe none of you AC's noticed... First, please use these links instead:

Science with 100m telescopes - PDF Version
Science with 100m telescopes - HTML Version

Second, the AC modded as Troll is using a web redirect for the second link, which explains the confusion about whether he's posting a goatse image or not. Sometimes, it points to one, other times it doesn't. By the way, the first link of the parent was broken and corrected now.

No need to say again the reasons why this isn't feasible (yet) the way you say. Just wanted to show a link to another interferometer: the VLTI

That machine is so delicate that we weren't allowed to walk near the tunnels (you see them on the picture) when I was visiting the site.

Cheers...

If you're going to spend a $1B on a telescope, aren't you reaching the point where the money would be better spent to put one in space away from the atmosphere and associated debris rather than sticking it on terra firma?

No, putting a project into space something in space is like going for the "I'd like an inch-thick gold-plate finish with diamond encrusting" when purchasing a car. Consider this: the Hubble Space Telescope cost $1.5 billion in the 1980s, for a 2.4m diameter primary mirror. If we were to scale the cost based on the diameter of the mirror, then a 100m space telescope would cost $62.5 billion, over an order of magnitude more than the proposed ground-based facility.

And don't think that ground-based telescopes are the poor cousins of space-based ones. The European Southern Observatory's Very Large Telescope (VLT) can achieve resolutions better than Hubble, even if the latter had been built without the optical problems, and the VLT cost 1/10th of what Hubble did.

If you're going to spend a $1B on a telescope, aren't you reaching the point where the money would be better spent to put one in space away from the atmosphere and associated debris rather than sticking it on terra firma?

No, putting a project into space something in space is like going for the "I'd like an inch-thick gold-plate finish with diamond encrusting" when purchasing a car. Consider this: the Hubble Space Telescope cost $1.5 billion in the 1980s, for a 2.4m diameter primary mirror. If we were to scale the cost based on the diameter of the mirror, then a 100m space telescope would cost $62.5 billion, over an order of magnitude more than the proposed ground-based facility.

And don't think that ground-based telescopes are the poor cousins of space-based ones. The European Southern Observatory's Very Large Telescope (VLT) can achieve resolutions better than Hubble, even if the latter had been built without the optical problems, and the VLT cost 1/10th of what Hubble did.

A paper on the $1b telescope (called the Effelsberg telescope, after a 18th century astronomer) can be acquired here. Also the HTML version is here if you don't want to bother downloading the PDF or if you don't have a reader.

I'd paste the whole text here, but it's too long.

I'm talking about the fact that there are several ground-based observatories that consist of multiple telescopes (Keck, Magellan, VLT, LBT), and that one of the goals of this design is interferometry. None of these telescopes is currently planning on doing optical interferometry, because it's just too hard. They're all working on infrared interferometry, and even that is very difficult to accomplish. Especially with mirrors mounted independently, as all except the LBT are.

30 metres? Ha! So you want big? I'll give you big. Link goes to a page about a proposed 100 metre telescope!

When scientists look for life out side the solar system, why don't they focus on moons of Jupiter like planets instead of finding Earth like planets.

Actually, they have looked for moons around extrasolar planets that eclipse their star. The main example (so far) of the "transiting technique" is HD 209458b, a hot Jupiter in a 3-day period. This transit has been observed using Hubble, with a sensitivity that would allow one to detect Saturn-like rings or moons as small as twice the size of Earth. None were found. More information here.

Of course, a 3-day period planet's moon would still be unable to harbor life as we know it (too hot). But these are the first steps being taken to look for such objects. As more transiting planets are detected, this technique will tell us a lot about moon systems around these planets.

Moons of giant planets in temperate zones may indeed be the key to finding life-sustaining bodies. Our own Moon stabilizes the rotational axis of the Earth, which prevents many extreme climatic changes. Compare this to Mars, which has no large moons (only two small ones) that lead to the same stability. A giant planet would have a similar affect on the dynamics. This is just one example of how a second body (in our case, the Moon) aids the development of life. One can ponder how much the probability of life drops off if such a body does not exist, though I'm not sure anyone has a convincing answer, yet.

We can barely image planets that are twice the size of Jupiter and you are suggesting we should image MOONS!?

So far, scientists have been unable to image any extra-solar planets at all. The planets have been detected indirectly--by looking at the effects of the planet on the star. An overview of these techniques. Astronomers have directly imaged brown dwarfs, which are somewhat like both planets and stars. We can't yet image exoplanets, but we can still learn a lot about them.

Direct imaging of planets may be made with the Keck Interferometer in Nulling Mode (a similar setup is being designed for the LBTI in Arizona, and the European VLTI), or with "Extreme Adaptive Optics", or finally with the Terrestrial Planet Finder.

Earth-based telescopes are not necessarily limited.

The VLT Array in Chile, when fully operational, will produce images with greater resolution than Hubble, using adaptive optics and interferometry.

The downside is that you are more limited in where you can point it; however, most of the more interesting astronomical stuff is visible from the southern hemisphere anyway.

I hope this is not too OT, but here is the sound of a pulsar

Actually, according to the link xi Hydrae is not a pulsar. It is a large star (about 10 times that of the Sun) that is getting ready to start expanding into a red giant. They are converting the changing radial velocity of the solar upper atmospheric layers into sound. Not a pulsar at all, but it does have a good dance beat...

MP3 version.

I hope this is not too OT, but here is the sound of a pulsar

Actually, according to the link xi Hydrae is not a pulsar. It is a large star (about 10 times that of the Sun) that is getting ready to start expanding into a red giant. They are converting the changing radial velocity of the solar upper atmospheric layers into sound. Not a pulsar at all, but it does have a good dance beat...

MP3 version.

Enjoy some truly cosmic drum 'n bass!

Enjoy some truly cosmic drum 'n bass!

Peter,

I am not usually this relentless, but as an employee at STScI, your accusation of fraud really annoys me.

Anyway, I am prepared to prove you wrong. Please examine the animated GIF image I have placed at the following URL:
http://www.stsci.edu/~jharris/sombrero.gif

In the image, I have stacked the HST image and the VLT image on top of each other, and I am displaying each with the same scale and orientation. The first frame shows the HST image, the second frame shows the VLT image. You may need to set your browser to "loop" animated GIFs, or save it to disk and use a tool like gifview.

The rotation and scale are not perfectly matched, but it's good enough to see correspondence between the images.

Oh, wait. I think I see what you are on about. The "missing" stars are all in the dusty disk, right? If you look closely, they aren't gone in the HST image, just much fainter. The reason is simple: the intervening dust absorbs blue light much more than red light. These disappearing-objects are not foreground stars, they are probably star clusters in the galaxy.

If you read the technical data about each image:
ESO, HST, you'll see that the ESO image was taken through redder filters than the HST image (V,R,I compared to B,V,R), so it's no suprise that the ESO image is going to see through dust better!

(I posted this on metafilter, but it bears a mention on slashdot.)

That should be European Southern Observatory (www.eso.org).

As some astronomer pointed out at the time, the repair mission for the Hubble cost more than all the proposed ground-based observatories put together, like the Very Large Telescope and the California Extremely Large Telescope.

NASA - The government version of Hollywood.

You should also mention ESO's VLTI here, the Very Large Telescope Interferometer at Mt. Paranal, which is just taking its first shots...

You should also mention ESO's VLTI here, the Very Large Telescope Interferometer at Mt. Paranal, which is just taking its first shots...