While a couple of hundred million years is a reasonable timescale for a galaxy like the Milky Way, it is important to realize that galaxies typically rotate differentially and in the case of ellipticals without a single well defined rotation axis. Spiral galaxies like the Milky Way have "flat" rotation curves such that the velocities are constant no matter the radial distance, so it takes stars at larger radial distances much longer to orbit around than stars closer in. Individual stars in sprial galaxies to not all rotate together with a fixed pattern speed.
Galaxy formation is a much trickier business. This particular "galaxy" is very tiny compared to to the Milky Way (think more like the Magellanic Clouds). It may just be a small galaxylet that will, in its future, merge with other similar pieces to form a larger galaxy. In such a heirarchical scenario it can be difficult to define a single time of formation. In some sense the size/mass of the galaxy and the age of the universe provide constraints to test formation models.
OK, I shoulf go prepare my real lecture for today on the Doppler effect.
The James Web Telescope specs are converging, but not yet finished. A lot of the capability will be in the infraread (counting near-infrared that overlaps what Hubble does sometimes, all the way to the mid infrared), but it will not have blue or ultraviolet capability for sure. We're going to lose that. Ground-based telescopes will NEVER EVER EVER be able to see in the ultraviolet the way Hubble can. Current AO operates in the infrared, NOT in the optical -- certain science requires optical or UV observations. When Hubble dies, we lose capability we won't have again for a very long time.
Meteorite impacts as well as other phenomena can cause seismic motions. The moon is a pretty stable platform overall though, very much so compared to earth, but space in principle is more stable (X-ray interferometry will be possible in space over very long baselines, e.g., the proposed MAXIM mission). I am an astronomer but would want to check some hard numbers before making a strong argument on this point (and it would depend on things like the size of the telescope, wavelength of operation, available technologies, etc.).
Probably a larger issue is that the moon has a month-long day, more or less. From space, you can look pretty much anywhere anytime (not strictly true with a LEO space telescope like Hubble but close enough). You can monitor a source daily for a month. You can't do that on the moon unless you put your telescope at a pole, and then you lose the other hemisphere. The problem goes away if you put half a dozen lunar telescopes on the moon spread over the entire surface, but then you've multiplied expense and problems by six.
The far side of the moon would be an ideal location for radio telescopes since the moon would block interference. Some cell phone systems are an issue now with radio telescopes like the VLA, and even with governments setting aside frequencies for astronomers, guess who loses when the mulit-billion dollar companies want their bandwidth?
Not quite true. While the budget for the James Webb Telescope has been a moving target, it'll probably come in at around a billion dollars, factors of at least several times more expensive than a servicing mission. We've also built instruments already for Hubble that were to go on during the next servicing mission, at a price tag on order of the cost of the mission itself, that will go to waste.
The official NASA line is indeed this, to make sure the money flows to the telescope and it can be launched ASAP, but we're still talking a couple of years after Hubble will be dead.
This is one thing I think bugged a lot of astronomers, myself included. Throughout last year the community assembled a report on the future of Hubble, in terms of what astronomers desired, weighing pros and cons in light of what Hubble could continue to provide. There are certain transient events, like supernovae gamma ray bursts, for which it is very desireable to have a space-based telescope available. The community worked hard to make the case that Hubble should continue to fly until the James Webb Telescope was launched and then, bam!, no biscuit. I'm not saying that there isn't a case to be made for not keeping Hubble (there are costs and risks involved), but the community was blind-sided.
Yes, we could put a telescope on the moon (not so easily and probably not for many many years, and there are problems there, too, with vibration issues for instance), but that isn't really the point here. The issue is about whether or not to keep an operating telescope in operation until its replacement is flying. Hubble servicing missions have upgraded it from 1980s (or even 1970s) technology to 1990s technology (instruments, computers, solar panels, etc., get upgrades), so that's not a valid criticism.
OK, this is a little shameless self-promotion, but John Wright's series is among the "also bought" books on amazon.com for my novel STAR DRAGON. I confess I haven't read his serious, although it looks interesting. Has anyone read them and also my novel (also from Tor, Oct 2003) and can compare them? Any similarities in theme, style, substance, etc? I expect I'll get to them, but between my faculty job and my work on the next novel my reading time is limited. Thanks!
What the hell do you mean? It is working to its original specs? Are you stupid? Have you seen the images following the repair mission? Do you understand all new instruments have been built to compensate for the Hubble optics as installed? If you bought a car that was initially out of whack and ran OK but not well, took it in for a tune-up and then it ran as well as it should have before, what wou you call that? Fundamentally broken? I think not. You're a not very droll troll.
I'm a professional astronomer and have used the Hubble Space Telescope for many projects, including imaging with 2nd generation instruments. Things that are fundamentally broken do not produce ground-breaking science.
No Hubble is not fundamentally broken. There are high precision optics that correct for the flawed shape of the mirror, so image resolution is essentially what it was intended to be. It's about as good as it gets for a large mirror in space, and it is already in space, not on the drawing board.
Also, we DO put new technologies on Hubble! That is a major point of the servicing missions that are now cancelled. The new instruments to be installed on SM4 were going to do some great new space-breaking work.
There is a next generation space telescope being developed (The James Webb Telescope) that will be bigger and better than Hubble, but why not desire to keep Hubble flying until that one is up (around 2010)? We won't be able to follow up on supernovas, gamma ray bursts, and other transient phenomena until then.
Not true!!! OK, yes the missions are expensive (few hundred million), but the largest ground-based observatories cost on order of 100 million each (e.g., Keck, VLT, etc.) with a few million per year in supporting costs. And as for "propsed" large ground-based telescopes put together -- that is ALSO quite false. There are several 30-100 meter telescopes at various levels of development and these are going to cost much more than Keck or the VLT telescopes.
There was also a study done concerning the scientific impact per dollar spent on different astronomical missions/facilities. Despite Hubble's few billion dollar price tag it was rated as the best science per dollar spent. And if we've already spent a few billion, what's a few hundred million to keep it going?
Finally, we ARE putting up a new one. Cancelling SM4 and any other servicing missions makes sure that Hubble will be gone at least several YEARS before the next one goes up. Most astronomers want to keep Hubble, but only until there is an alternative.
The astronomical community has spent much effort in the past year reaching a consensus opinion, and conveying this opinion, to NASA and the government. Astronomers are in favor of continuing support and service for Hubble at least until the NGST (James Webb Telescope) is up and flying. Hubble does some things that cannot be done from the ground at all and has been a huge success. Despite the cost, Hubble has been evaluated to have provided the best science per dollar of all astronomy facilities.
Hubble Space Telescope proposals for the next year of observations are due THIS Friday, Jan. 23. I assume we will go on with the current observing cycle, but probably not the one beyond. But we don't know yet. The timing here is shocking.
I also have a lot of friends who work on Hubble Instruments that were due to be installed on SM4 -- their jobs will vanish as the funding is cut and we'll have a flood of unemployed astronomers (we are a small field and this will have a relatively large immediate impact). Many astronomers were looking forward to some spectacular new science capabilities. Those won't happen now (the Webb Telescope is being optimized for infrared work, so we will be losing general UV capability entirely).
The American Astronomical Society is maintaining an informational webpage at http://www.aas.org/policy/CurrentIssues.html that should help us determine just how this is going to affect us.
I served on the Hubble Space Telescope science review panel last year to determine what projects would be done. This was just after the shuttle accident, and there was speculation at the time that this could happen. We knew then that a Hubble-mission could not abort to ISS in the event of a problem and that this might curtail things like SM4. I don't think anyone there really believed it would happen though, at least not this abruptly at this time.
The universe doesn't care what you believe! Seriously though, this isn't a valid argument. First, we certainly do butt up against an "edge in time" as we peer back -- the universe has certainly evolved, with things smaller, hotter, and closer together in the distant past. *That* is really the crux of the Big Bang. The actual value of the age isn't relevent to basics of the theory itself. Google up "Ned Wright cosmology tutorial" for an excellent set of pages and FAQs regarding common misconceptions.
I've collaborated with Paul Francis myself in the past, and he's a good scientist. Good scientists get turned down for telescope all the time, for good projects -- there is a lot of competition. Those judgment calls are tough, and Paul and his collaborators may have failed to make a strong enough case to get high enough ranked against the competition, or he might have simply had the bad luck of having a too-skeptical reviewer on the panel. That happens, too. Depending on which telescope, the panel may have to evaluate up to a hundred proposals in their "spare" time and they aren't getting paid to do it either (astronomers serve on such panels for the experience and as a service to the community). Still, I've bashed panels myself when they've turned down my super-duper fantastic proposal for clearly the wrong reasons! Best response I ever heard about was an older, rich grad student who built his own telescope when his first proposal was turned down.
The narrow bands aren't so narrow that the small redshifts of nearby objects (ie. in the galaxy or nearby galaxies) would get shifted out of the band. When working on higher redshift targets, yes, astronomers use filters centered on longer wavelengths as appropriate. For a narrow-band image of a galaxy centered on say, Hydrogen alpha, that line in much more distant galaxies in the image would not be in the filter. This effect is actually used to survey for things like star formation at particular redshifts and can be regarded as a feature rather than a problem. As an aside, there are also "tunable filters" out there using a variety of technologies. The HST tunable filter is called a linear ramp filter, and is centered on a different wavelength in different parts of the image.
OK, I do spend part of my life processing HST Images (and Chandra images, VLA images, etc.). cynicalmoose is sort of on the right track but the explanation is muddled, confusing spectroscopy with imaging. HST takes no true color images as you would get with color film, for instance. Yes, images are digital with an array of numbers, but so what? An individual image is a simple intensity map *taken through a single color filter*. HST has a pile of filters, some colors like blue, red, etc., even infrared and ultraviolet (so you do need false color for these). Some are narrow-band filters centered on particular emission lines to pick out particular elemental emission (e.g., useful when studying nebulas). You can make a so-called "true-color" image by mixing together several of the individual images taken in different filters, and this can be pretty close to true. The emission-line filters high-light colors in a false but useful way. UV and IR do require false color (and Hubble cannot see X-rays). Sometimes "black and white" single-color images are rendered with a color map that permits subtle detail to be more easily seen (this is pretty common actually, and I have done it myself for press releases, since you rarely pick out filters for the creation of true-color images as there isn't a lot of science in that).
Slashdot Mirror
While a couple of hundred million years is a reasonable timescale for a galaxy like the Milky Way, it is important to realize that galaxies typically rotate differentially and in the case of ellipticals without a single well defined rotation axis. Spiral galaxies like the Milky Way have "flat" rotation curves such that the velocities are constant no matter the radial distance, so it takes stars at larger radial distances much longer to orbit around than stars closer in. Individual stars in sprial galaxies to not all rotate together with a fixed pattern speed. Galaxy formation is a much trickier business. This particular "galaxy" is very tiny compared to to the Milky Way (think more like the Magellanic Clouds). It may just be a small galaxylet that will, in its future, merge with other similar pieces to form a larger galaxy. In such a heirarchical scenario it can be difficult to define a single time of formation. In some sense the size/mass of the galaxy and the age of the universe provide constraints to test formation models. OK, I shoulf go prepare my real lecture for today on the Doppler effect.
The James Web Telescope specs are converging, but not yet finished. A lot of the capability will be in the infraread (counting near-infrared that overlaps what Hubble does sometimes, all the way to the mid infrared), but it will not have blue or ultraviolet capability for sure. We're going to lose that. Ground-based telescopes will NEVER EVER EVER be able to see in the ultraviolet the way Hubble can. Current AO operates in the infrared, NOT in the optical -- certain science requires optical or UV observations. When Hubble dies, we lose capability we won't have again for a very long time.
Meteorite impacts as well as other phenomena can cause seismic motions. The moon is a pretty stable platform overall though, very much so compared to earth, but space in principle is more stable (X-ray interferometry will be possible in space over very long baselines, e.g., the proposed MAXIM mission). I am an astronomer but would want to check some hard numbers before making a strong argument on this point (and it would depend on things like the size of the telescope, wavelength of operation, available technologies, etc.). Probably a larger issue is that the moon has a month-long day, more or less. From space, you can look pretty much anywhere anytime (not strictly true with a LEO space telescope like Hubble but close enough). You can monitor a source daily for a month. You can't do that on the moon unless you put your telescope at a pole, and then you lose the other hemisphere. The problem goes away if you put half a dozen lunar telescopes on the moon spread over the entire surface, but then you've multiplied expense and problems by six. The far side of the moon would be an ideal location for radio telescopes since the moon would block interference. Some cell phone systems are an issue now with radio telescopes like the VLA, and even with governments setting aside frequencies for astronomers, guess who loses when the mulit-billion dollar companies want their bandwidth?
Not quite true. While the budget for the James Webb Telescope has been a moving target, it'll probably come in at around a billion dollars, factors of at least several times more expensive than a servicing mission. We've also built instruments already for Hubble that were to go on during the next servicing mission, at a price tag on order of the cost of the mission itself, that will go to waste. The official NASA line is indeed this, to make sure the money flows to the telescope and it can be launched ASAP, but we're still talking a couple of years after Hubble will be dead.
This is one thing I think bugged a lot of astronomers, myself included. Throughout last year the community assembled a report on the future of Hubble, in terms of what astronomers desired, weighing pros and cons in light of what Hubble could continue to provide. There are certain transient events, like supernovae gamma ray bursts, for which it is very desireable to have a space-based telescope available. The community worked hard to make the case that Hubble should continue to fly until the James Webb Telescope was launched and then, bam!, no biscuit. I'm not saying that there isn't a case to be made for not keeping Hubble (there are costs and risks involved), but the community was blind-sided.
Yes, we could put a telescope on the moon (not so easily and probably not for many many years, and there are problems there, too, with vibration issues for instance), but that isn't really the point here. The issue is about whether or not to keep an operating telescope in operation until its replacement is flying. Hubble servicing missions have upgraded it from 1980s (or even 1970s) technology to 1990s technology (instruments, computers, solar panels, etc., get upgrades), so that's not a valid criticism.
OK, this is a little shameless self-promotion, but John Wright's series is among the "also bought" books on amazon.com for my novel STAR DRAGON. I confess I haven't read his serious, although it looks interesting. Has anyone read them and also my novel (also from Tor, Oct 2003) and can compare them? Any similarities in theme, style, substance, etc? I expect I'll get to them, but between my faculty job and my work on the next novel my reading time is limited. Thanks!
PLONK!
What the hell do you mean? It is working to its original specs? Are you stupid? Have you seen the images following the repair mission? Do you understand all new instruments have been built to compensate for the Hubble optics as installed? If you bought a car that was initially out of whack and ran OK but not well, took it in for a tune-up and then it ran as well as it should have before, what wou you call that? Fundamentally broken? I think not. You're a not very droll troll. I'm a professional astronomer and have used the Hubble Space Telescope for many projects, including imaging with 2nd generation instruments. Things that are fundamentally broken do not produce ground-breaking science.
No Hubble is not fundamentally broken. There are high precision optics that correct for the flawed shape of the mirror, so image resolution is essentially what it was intended to be. It's about as good as it gets for a large mirror in space, and it is already in space, not on the drawing board. Also, we DO put new technologies on Hubble! That is a major point of the servicing missions that are now cancelled. The new instruments to be installed on SM4 were going to do some great new space-breaking work. There is a next generation space telescope being developed (The James Webb Telescope) that will be bigger and better than Hubble, but why not desire to keep Hubble flying until that one is up (around 2010)? We won't be able to follow up on supernovas, gamma ray bursts, and other transient phenomena until then.
Not true!!! OK, yes the missions are expensive (few hundred million), but the largest ground-based observatories cost on order of 100 million each (e.g., Keck, VLT, etc.) with a few million per year in supporting costs. And as for "propsed" large ground-based telescopes put together -- that is ALSO quite false. There are several 30-100 meter telescopes at various levels of development and these are going to cost much more than Keck or the VLT telescopes. There was also a study done concerning the scientific impact per dollar spent on different astronomical missions/facilities. Despite Hubble's few billion dollar price tag it was rated as the best science per dollar spent. And if we've already spent a few billion, what's a few hundred million to keep it going? Finally, we ARE putting up a new one. Cancelling SM4 and any other servicing missions makes sure that Hubble will be gone at least several YEARS before the next one goes up. Most astronomers want to keep Hubble, but only until there is an alternative.
The astronomical community has spent much effort in the past year reaching a consensus opinion, and conveying this opinion, to NASA and the government. Astronomers are in favor of continuing support and service for Hubble at least until the NGST (James Webb Telescope) is up and flying. Hubble does some things that cannot be done from the ground at all and has been a huge success. Despite the cost, Hubble has been evaluated to have provided the best science per dollar of all astronomy facilities. Hubble Space Telescope proposals for the next year of observations are due THIS Friday, Jan. 23. I assume we will go on with the current observing cycle, but probably not the one beyond. But we don't know yet. The timing here is shocking. I also have a lot of friends who work on Hubble Instruments that were due to be installed on SM4 -- their jobs will vanish as the funding is cut and we'll have a flood of unemployed astronomers (we are a small field and this will have a relatively large immediate impact). Many astronomers were looking forward to some spectacular new science capabilities. Those won't happen now (the Webb Telescope is being optimized for infrared work, so we will be losing general UV capability entirely). The American Astronomical Society is maintaining an informational webpage at http://www.aas.org/policy/CurrentIssues.html that should help us determine just how this is going to affect us. I served on the Hubble Space Telescope science review panel last year to determine what projects would be done. This was just after the shuttle accident, and there was speculation at the time that this could happen. We knew then that a Hubble-mission could not abort to ISS in the event of a problem and that this might curtail things like SM4. I don't think anyone there really believed it would happen though, at least not this abruptly at this time.
Good answer, Doug. I know these guys but skipped Atlanta this year.
The universe doesn't care what you believe! Seriously though, this isn't a valid argument. First, we certainly do butt up against an "edge in time" as we peer back -- the universe has certainly evolved, with things smaller, hotter, and closer together in the distant past. *That* is really the crux of the Big Bang. The actual value of the age isn't relevent to basics of the theory itself. Google up "Ned Wright cosmology tutorial" for an excellent set of pages and FAQs regarding common misconceptions.
I've collaborated with Paul Francis myself in the past, and he's a good scientist. Good scientists get turned down for telescope all the time, for good projects -- there is a lot of competition. Those judgment calls are tough, and Paul and his collaborators may have failed to make a strong enough case to get high enough ranked against the competition, or he might have simply had the bad luck of having a too-skeptical reviewer on the panel. That happens, too. Depending on which telescope, the panel may have to evaluate up to a hundred proposals in their "spare" time and they aren't getting paid to do it either (astronomers serve on such panels for the experience and as a service to the community). Still, I've bashed panels myself when they've turned down my super-duper fantastic proposal for clearly the wrong reasons! Best response I ever heard about was an older, rich grad student who built his own telescope when his first proposal was turned down.
The narrow bands aren't so narrow that the small redshifts of nearby objects (ie. in the galaxy or nearby galaxies) would get shifted out of the band. When working on higher redshift targets, yes, astronomers use filters centered on longer wavelengths as appropriate. For a narrow-band image of a galaxy centered on say, Hydrogen alpha, that line in much more distant galaxies in the image would not be in the filter. This effect is actually used to survey for things like star formation at particular redshifts and can be regarded as a feature rather than a problem. As an aside, there are also "tunable filters" out there using a variety of technologies. The HST tunable filter is called a linear ramp filter, and is centered on a different wavelength in different parts of the image.
OK, I do spend part of my life processing HST Images (and Chandra images, VLA images, etc.). cynicalmoose is sort of on the right track but the explanation is muddled, confusing spectroscopy with imaging. HST takes no true color images as you would get with color film, for instance. Yes, images are digital with an array of numbers, but so what? An individual image is a simple intensity map *taken through a single color filter*. HST has a pile of filters, some colors like blue, red, etc., even infrared and ultraviolet (so you do need false color for these). Some are narrow-band filters centered on particular emission lines to pick out particular elemental emission (e.g., useful when studying nebulas). You can make a so-called "true-color" image by mixing together several of the individual images taken in different filters, and this can be pretty close to true. The emission-line filters high-light colors in a false but useful way. UV and IR do require false color (and Hubble cannot see X-rays). Sometimes "black and white" single-color images are rendered with a color map that permits subtle detail to be more easily seen (this is pretty common actually, and I have done it myself for press releases, since you rarely pick out filters for the creation of true-color images as there isn't a lot of science in that).