Wouldn't it make sense that, these black holes out there would eventually all converge together, gaining mass and 'size', presumably even increasing escape velocity?
The right answer is that space is almost empty, so the black hole cannot grow quickly. (but see below for more)
A black hole has the same gravitational pull as a star of the same mass would. So, if our Sun miraculously became a black hole, it could not suck in the Earth. Black holes are special because you can get really close to them. Since gravity decreases as the distance squared, small distance equals strong gravity.
Radiation is not a significant factor. Only very small black holes radiate significantly enough to matter. A solar-mass black hole would take 10^67 years to evaporate... alienmole had it right above.
In a high-density environment, black holes do grow. Namely, in the center of galaxies we see black holes that can be like a million or 10 million times the mass of the Sun. Ones which are actively feeding (on gas clouds, stars, etc) may explain quasars (the brightest sustained light sources in the universe).
The Milky Way almost certainly has a pretty decent sized black hole in the center, so our galaxy may once have hosted a quasar.
Just for fun, when the Fred Moody article came out, I calculated how long it would take a Brookhaven-style mini black hole to consume the Earth (calculations summarized here.
It takes about 10^59 years to consume one atom, let alone the whole Earth!
If it wasn't in the ecliptic, it would not have much to interact with.
Not true. The solar system is only flat (i.e. disk-like) out to about 100 AU or so - the outer edge of the Kuiper Belt. Beyond that, the Oort cloud is a spherical shell likely containing billions of proto-comets. Since these comet cores are arranged pretty much uniformly in 3 dimensions, the hypothetical planet would not need to be in the ecliptic to slingshot the comets towards the inner solar system.
I think what you're thinking of is that one of Saturn's moons (Phoebe) orbits backwards (or retrograde) around Saturn. The thought is that this irregular-shaped, small moon is an asteroid captured by Saturn's gravity well. It is notable that Phoebe is Saturn's outermost moon (number 18 as of 1994).
Jupiter also has four retrograde moons: Ananke, Carme, Pasiphae and Sinope, also the outermost moons of the planet (numbers 13-16 as of 1994)
I hacked a Java gravity simulator I wrote last year to show the hypothetical Planet 10 slingshotting comets into the inner solar system. The physics is quite realistic, but the scenario is very simplistic. I did just as a tool to show how knowing the trajectory of a number of comets can hint at the orbit of a perturbing body.
Please send comments/complaints by email instead of posting.
P.S. if you want a pretty accurate simulation of the solar system, crank the timstep down to a few days, zoom in and turn on the planets (options screen).
There was no telescope involved. This hypothetical planet has not been seen.
The comets in question have had their trajectories computed (there are difficult, but well-known procedures to calculate the 3D orbits of comets/asteroids/etc from their 2D positions in the sky - one was invented by Gauss). Once the trajectories are known (in the form of elliptical orbits around the Sun), you can figure out where in the sky the furthest point from the sun lies (called the aphelion). This is the point at which the comet was ejected from the Oort cloud at the fringes of our solar system.
My understanding of this potential disocvery is that the 13 must all have aphelia which lie in a line in the outer solar system. This line would then indicate the trajectory of the perturbing body (our hypothetical planet in question) and yield a preliminary orbit.
The high probability that this is not coincidence (1 in 1700) probably comes from the authors' calculations of whether the aphelia lie in the same region by chance or not. This calculation would take into account the uncertainty of the 3D location of the aphelia (since we couldn't have *seen* each comet at its aphelion - we can just extrapolate their orbits out to that point).
I don't think it could be a brown dwarf. If it were, at 30,000 AU it would be visible to the naked eye (about 6th mag apparent), and significantly brighter than Neptune or Uranus.
Here's how to set up your Unix machine to try out the Dvorak layout. You need X windows to do this.
First, print out a picture of the Dvorak layout. A GIF and a PDF version are on Marcus Brooks' page.
Now, follow these instructions IN ORDER (or you'll have trouble changing back to Qwerty). Download the following xmodmap scripts: Qwerty and Dvorak
Then, make an alias to change back and forth easily:
% alias asdf 'xmodmap ~/dvorak.xmodmap' % alias aoeu 'xmodmap ~/qwerty.xmodmap'
I chose the alias so the same four keys are typed in either Qwerty or Dvorak mode. So just type "asdf" to toggle between them. Then you can decide for yourself and avoid all the flame-ridden commotion.:)
Forget disposable - Try flexible and accessible!
on
Disposable Computers
·
· Score: 1
Everyone is making a stink about how bad it is to make disposable electronics (landfills, bad chemicals, etc.). Sure I agree that this is bad stuff. But read the article ignoring the disposable part of it. After all, you don't *have* to throw it out.
It's describing very thin, flexible substrates. If it becomes reality, you can bring your computer to bed and read it like a newspaper. That's the cool aspect of this technology. And if it's cheap, then great! The cheaper the hardware gets, the more important free software becomes.
Leave it to marketers to read "inexpensive" as "disposable" instead of "practical" and "accessible to the masses"
It is true that cosmologists are discussing the possibility of a non-zero cosmological constant (Einstein's lambda), but the subtlety of the effect is way to small to be evident on the scale of the solar system and masses like the Sun's. The realm where lambda may be relevent is in very high densities, like just after the the Big Bang, or over very large distances (like the diameter of the observable universe).
Anyway, if lambda (or any odd theory of gravity) could affect Pioneer, then we would likely see it in the orbit of the outer planets, I would think... It seems MUCH more likely to me that something peculiar to the spacecraft (like directional heat dissipation) could cause the effect.
Contrary to mettw's post, the speed of outer stars in a galaxy does not in any way constitute a discrepency in any theory of gravity.
[This is mostly background to redirect many of the wild posts regarding dark matter attached to this article]
When you measure the velocity at which stars orbit the center of a spiral galaxy (mostly external galaxies like Andromeda, but also in more difficult work on our own galaxy), you see that the stars near the center orbit in a pattern which mimics the pattern of stars we see in that galaxy. That is, if we count the stars in the center and calculate what their mass should be, it matches with the velocity at which the stars orbit (that is, gravity is balanced by centripedal force: called Keplerian rotation). But further out from the center of many galaxies, stars orbit faster than what you would predict by counting all the mass from all the stars you can see. If they are going faster than the gravity must be stronger than what you originally predicted. If all the stars you can see can't make enough gravity, then what? Throw out the theory of gravity which has proved so very successful in the past, or postulate that there must be some matter which you can't see, that is, dark matter.
Most astronomers believe the latter. They think there is not enough eveidence to toss the whole theory. Instead, they assume that galaxies are more complicated that we first thought. What causes this dark matter? Well, it must be something that gives off less light than stars. Some folks have suggested that "ordinary" matter (planets and brown dwarfs) make up the difference. Others suggest "strange" matter (stuff not discovered yet). Finally, the flippant sort of people commonly attribute the extra mass to interstellar Volkswagens (i.e. they don't care what it is just yet; they just want to measure the effect for now).
Why am I saying all of this? I just want people to be a little more informed when the term "dark matter" gets thrown into the discussion.
BTW, the "1/r^2" that the previous poster refers to is the pattern of density of dark matter needed in many galaxies to explain the patter of stellar orbits you see. That is, as you go further out from the center of a galaxy, the density of dark matter decreases by the square of the distance. This is NOT a factor thrown into a gravitational equation. It is a feature added to a density model of a galaxy that helps to explain its rotation curve. It's like needing to account for the mass of the passengers when computing the acceleration of a car. It's NOT a feature of physics.
I disagree that your CPU would interfere significantly with your cordless phone. The phone uses an amplified signal powered through an antenna while the CPU is not amplified and (hopefully) has no antenna other than its own wiring. I can foresee that the phone might negatively influence the CPU (although it should be designed to resist interference regardless of its specific frequency), but the CPU interfering with the phone seems much less likely.
There was a recent Slashdot article about deliberately generating a transmission with your system, but apparently it isn't simple!
No, near UV light has been imaged since the early days of film photography. But I believe this is a significant advance in the direct electronic detection of UV light. As someone else said, UV light is usually detected electronically by fluorescence: take one UV photon, and use an absorptive chemical film to convert that into two visible light photons. (That's what Tide laundry soap does to make "whites whiter!" etc.)
The energies discussed are definitely "near-UV". That is, wavelengths of 200-400 nanometers (the human eye can see from about 400 (blue) to 700 (red) nm. Far UV (about 100 nm) and Extreme UV (less than 100 nm) are not included in this technology. X-rays (1 nm and shorter) are definitely out (but actually, CCDs are used on the new Chandra X-Ray satellite in funky ways). Down to about 100 nm (or maybe lower?) you can use conventional lenses, but they must be made out of magnesium-fluoride (MgF) instead of glass. It's not really until X-rays that you have to use bizarre techniques to focus light (like nested grazing-incidence foil mirrors).
This is new technology to do a better job of old science (at least from the astronomical point of view).
Currently the majority of visible and near-visible astronomy is done with CCD cameras (same technology as typical digital cameras and camcorders) which have peak sensitivity in the red or even IR. This makes it rather hard to study blue stars. The further blue you go, the less transmissive the atmosphere is and the brighter scattered moonlight appears (y'know, the sky is blue and all). So, having a camera that has poor sensitivity in the blue is doubly bad.
On a less technological and more historical note, prior to the 1980s (or so), photographic film was the dominant technology for astronomical imaging. Since most film has higher sensitivity in the *blue*, there was a lot of astronomy done at that end of the spectrum. Using CCDs today, it can be hard to compare to the blue work of the past. With new cameras specializing on blue and UV light, better comparisons with previous work can be made.
So it's quite wrong to say that new UV cameras will open up a new window in astronomy. In fact they will reopen an old window!
It's cool that NASA is supporting Linux. But it is certainly true that the field of astronomy has been very Unix oriented for a long time (that is, for those who have given up their VAX systems already.:) )
Anotheuinr interesting thing about astronomy is the emphasis on open source software. Two of the most popular astronomical data analysis packages in the USA have been open source from the start.
The IRAF project (supported by the NSF) has been open source since it started in the early-mid 80's. It's primarily used for optical and infrared imaging and spectroscopy for ground-based and space-based observation, but it is also used for X-ray astronomy. Nearly all of the Hubble data is processed in IRAF.
Radio astronomers use the AIPS software, which is also open source and has been since its origin in 1978.
Both have supported Linux since about the time RedHat first appeared on the scene. Neither of these packages are recommended for non-specialists, but they are examples of free software which dominate a discipline.
It's undoubtably super news that there is an aspect of the satellite that may prove useful. Having any telescope in space, even one as small as this spotting scope is astonishly great for calibrating ground-based telescope observations which need to be made through miles of crud in our atmosphere.
But while this is a small improvement on what would have been a total loss, it is certainly not going to be free. For every active satellite (or even any active ground-based telescope to a lesser extent), there is a substantial expenditure in maintainance and data processing. For a satellite a large part of the price comes from ground operations, including issuing commands and maintaining a downlink station to receive the data as it comes in.
More information for the confused: Why is a tiny telescope (2 inch diameter) in space such a big deal? After all, anyone could pay about $200 and buy a telescope from a department store with equivalent light collection power. The key is that any telescope in orbit is above terrestrial weather. Measuring stellar brightness and color (which in turn yield info about a star's age, mass, distance, etc) is difficult from the ground because the atmosphere is not transparent. Weather makes the transparency change on short timescales, so a star's brightness appears to change rapidly. This is especially difficult for an astronomer who wants to study stars which have intrinsically variable brightness.
In short, a little satellite-borne telescope is a stable instrument for consistent work, like all those 386's running Linux and serving web pages out there.
As said by many others, the key is trust. I trust Cmdr Taco, Hemos, etc to filter my tech news for me because I've enjoyed the articles they've chosen.
But for the scientific articles I choose to read (which affect my career, unlike Slashdot which is entertainment for me), I need a deeper level of trust. A 100 year old journal with an editor who I have met is more worthy of trust (IMO) than a few-years-old abstract/preprint server run by people I know nothing about.
I do hope that an open source type scheme is attempted, but it may take time to build the level of faith that we place in the established journals.
In astronomy, there is a very popular preprint server at Los Alamos where many people submit electronic copies of papers they expect to get published.
However, I usually don't peruse this server. I instead read journal tables of contents (often sorted by topic) or (even better!) newsletters focusing on my particular subfield (star formation). This is for the same reason that I read Slashdot: I don't have the time/energy to peruse everything. Instead, I put my trust in a "portal" of some nature to pre-filter my reading material for me.
I do think it is very valuable to have large archives of electronic materials for reference research (like the NASA/ADS abstract and article service) which is much more effecient than a trip to the library. But I believe the parallel between open source software and scientific reporting breaks down at the bleeding-edge. "Beta" versions of scientific papers are either not worth much (for lack of credibility) or even dangerous (as "bugs" may propagate in the literature).
1) there is not really any evidence that supernovae typically result in black holes. While theory does *predict* black holes, they are notoriously hard to detect. In fact most theories predict neutron stars and many have been been found in supernova remnants, including the Crab Pulsar in the remnant of the 1054 AD supernova.
2) LBVs are thought to be of order 70-100 solar masses, as opposed to the 30 or 40 suggested.
Yes, you are right. Eta Car's total luminosity is about 10^5 times that of the Sun. This star is about as bright as any stable star can get. Any brighter, and the photons trying to escape the core of the star start knocking off the outer layers of the star's atmosphere (this is what one of the previos commenters called luminosity pressure).
What's surprising about the admission of ignorance is that the media allowed it! The whole point of science is to explore the limits of our ignorance. We astronomers always admit our vast ignorance, it just usually doesn't make the newspaper when we do.
Slashdot Mirror
It's not my math that's in error. I simply misworded. I meant 1.1e-64 collisions per orbit. So that's 1e64 orbits/collision.
Sorry. The web page is fixed. Thanks for the fix.
Wouldn't it make sense that, these black holes out there would eventually all converge together, gaining mass and 'size', presumably even increasing escape velocity?
The right answer is that space is almost empty, so the black hole cannot grow quickly. (but see below for more)
A black hole has the same gravitational pull as a star of the same mass would. So, if our Sun miraculously became a black hole, it could not suck in the Earth. Black holes are special because you can get really close to them. Since gravity decreases as the distance squared, small distance equals strong gravity.
Radiation is not a significant factor. Only very small black holes radiate significantly enough to matter. A solar-mass black hole would take 10^67 years to evaporate... alienmole had it right above.
In a high-density environment, black holes do grow. Namely, in the center of galaxies we see black holes that can be like a million or 10 million times the mass of the Sun. Ones which are actively feeding (on gas clouds, stars, etc) may explain quasars (the brightest sustained light sources in the universe).
The Milky Way almost certainly has a pretty decent sized black hole in the center, so our galaxy may once have hosted a quasar.
M87 has a somewhat active one now. See http://antwrp.gsfc.nasa.gov/a pod/index/blackhole.html for more observational evidence of black holes.
Just for fun, when the Fred Moody article came out, I calculated how long it would take a Brookhaven-style mini black hole to consume the Earth (calculations summarized here.
It takes about 10^59 years to consume one atom, let alone the whole Earth!
If it wasn't in the ecliptic, it would not have much to interact with.
Not true. The solar system is only flat (i.e. disk-like) out to about 100 AU or so - the outer edge of the Kuiper Belt. Beyond that, the Oort cloud is a spherical shell likely containing billions of proto-comets. Since these comet cores are arranged pretty much uniformly in 3 dimensions, the hypothetical planet would not need to be in the ecliptic to slingshot the comets towards the inner solar system.
I think what you're thinking of is that one of Saturn's moons (Phoebe) orbits backwards (or retrograde) around Saturn. The thought is that this irregular-shaped, small moon is an asteroid captured by Saturn's gravity well. It is notable that Phoebe is Saturn's outermost moon (number 18 as of 1994).
Jupiter also has four retrograde moons: Ananke, Carme, Pasiphae and Sinope, also the outermost moons of the planet (numbers 13-16 as of 1994)
I hacked a Java gravity simulator I wrote last year to show the hypothetical Planet 10 slingshotting comets into the inner solar system. The physics is quite realistic, but the scenario is very simplistic. I did just as a tool to show how knowing the trajectory of a number of comets can hint at the orbit of a perturbing body.
The href is http://www.astro.wisc. edu/~dolan/java/planet10/Planet10.html
Please send comments/complaints by email instead of posting.
P.S. if you want a pretty accurate simulation of the solar system, crank the timstep down to a few days, zoom in and turn on the planets (options screen).
There was no telescope involved. This hypothetical planet has not been seen.
The comets in question have had their trajectories computed (there are difficult, but well-known procedures to calculate the 3D orbits of comets/asteroids/etc from their 2D positions in the sky - one was invented by Gauss). Once the trajectories are known (in the form of elliptical orbits around the Sun), you can figure out where in the sky the furthest point from the sun lies (called the aphelion). This is the point at which the comet was ejected from the Oort cloud at the fringes of our solar system.
My understanding of this potential disocvery is that the 13 must all have aphelia which lie in a line in the outer solar system. This line would then indicate the trajectory of the perturbing body (our hypothetical planet in question) and yield a preliminary orbit.
The high probability that this is not coincidence (1 in 1700) probably comes from the authors' calculations of whether the aphelia lie in the same region by chance or not. This calculation would take into account the uncertainty of the 3D location of the aphelia (since we couldn't have *seen* each comet at its aphelion - we can just extrapolate their orbits out to that point).
I don't think it could be a brown dwarf. If it were, at 30,000 AU it would be visible to the naked eye (about 6th mag apparent), and significantly brighter than Neptune or Uranus.
Here's the official web site with pictures: http://oposite.stsci.edu/pub info/pr/1999/34/index.html
In general, you can get the best scoop from the Lastest Hubble News page.
Here's how to set up your Unix machine to try out the Dvorak layout. You need X windows to do this.
:)
First, print out a picture of the Dvorak layout. A GIF and a PDF version are on Marcus Brooks' page.
Now, follow these instructions IN ORDER (or you'll have trouble changing back to Qwerty). Download the following xmodmap scripts:
Qwerty and Dvorak
Then, make an alias to change back and forth easily:
% alias asdf 'xmodmap ~/dvorak.xmodmap'
% alias aoeu 'xmodmap ~/qwerty.xmodmap'
I chose the alias so the same four keys are typed in either Qwerty or Dvorak mode. So just type "asdf" to toggle between them. Then you can decide for yourself and avoid all the flame-ridden commotion.
Everyone is making a stink about how bad it is to make disposable electronics (landfills, bad chemicals, etc.). Sure I agree that this is bad stuff. But read the article ignoring the disposable part of it. After all, you don't *have* to throw it out.
It's describing very thin, flexible substrates. If it becomes reality, you can bring your computer to bed and read it like a newspaper. That's the cool aspect of this technology. And if it's cheap, then great! The cheaper the hardware gets, the more important free software becomes.
Leave it to marketers to read "inexpensive" as "disposable" instead of "practical" and "accessible to the masses"
It is true that cosmologists are discussing the possibility of a non-zero cosmological constant (Einstein's lambda), but the subtlety of the effect is way to small to be evident on the scale of the solar system and masses like the Sun's. The realm where lambda may be relevent is in very high densities, like just after the the Big Bang, or over very large distances (like the diameter of the observable universe).
Anyway, if lambda (or any odd theory of gravity) could affect Pioneer, then we would likely see it in the orbit of the outer planets, I would think... It seems MUCH more likely to me that something peculiar to the spacecraft (like directional heat dissipation) could cause the effect.
Contrary to mettw's post, the speed of outer stars in a galaxy does not in any way constitute a discrepency in any theory of gravity.
[This is mostly background to redirect many of the wild posts regarding dark matter attached to this article]
When you measure the velocity at which stars orbit the center of a spiral galaxy (mostly external galaxies like Andromeda, but also in more difficult work on our own galaxy), you see that the stars near the center orbit in a pattern which mimics the pattern of stars we see in that galaxy. That is, if we count the stars in the center and calculate what their mass should be, it matches with the velocity at which the stars orbit (that is, gravity is balanced by centripedal force: called Keplerian rotation). But further out from the center of many galaxies, stars orbit faster than what you would predict by counting all the mass from all the stars you can see. If they are going faster than the gravity must be stronger than what you originally predicted. If all the stars you can see can't make enough gravity, then what? Throw out the theory of gravity which has proved so very successful in the past, or postulate that there must be some matter which you can't see, that is, dark matter.
Most astronomers believe the latter. They think there is not enough eveidence to toss the whole theory. Instead, they assume that galaxies are more complicated that we first thought. What causes this dark matter? Well, it must be something that gives off less light than stars. Some folks have suggested that "ordinary" matter (planets and brown dwarfs) make up the difference. Others suggest "strange" matter (stuff not discovered yet). Finally, the flippant sort of people commonly attribute the extra mass to interstellar Volkswagens (i.e. they don't care what it is just yet; they just want to measure the effect for now).
Why am I saying all of this? I just want people to be a little more informed when the term "dark matter" gets thrown into the discussion.
BTW, the "1/r^2" that the previous poster refers to is the pattern of density of dark matter needed in many galaxies to explain the patter of stellar orbits you see. That is, as you go further out from the center of a galaxy, the density of dark matter decreases by the square of the distance. This is NOT a factor thrown into a gravitational equation. It is a feature added to a density model of a galaxy that helps to explain its rotation curve. It's like needing to account for the mass of the passengers when computing the acceleration of a car. It's NOT a feature of physics.
I disagree that your CPU would interfere significantly with your cordless phone. The phone uses an amplified signal powered through an antenna while the CPU is not amplified and (hopefully) has no antenna other than its own wiring. I can foresee that the phone might negatively influence the CPU (although it should be designed to resist interference regardless of its specific frequency), but the CPU interfering with the phone seems much less likely.
There was a recent Slashdot article about deliberately generating a transmission with your system, but apparently it isn't simple!
No, near UV light has been imaged since the early days of film photography. But I believe this is a significant advance in the direct electronic detection of UV light. As someone else said, UV light is usually detected electronically by fluorescence: take one UV photon, and use an absorptive chemical film to convert that into two visible light photons. (That's what Tide laundry soap does to make "whites whiter!" etc.)
The energies discussed are definitely "near-UV". That is, wavelengths of 200-400 nanometers (the human eye can see from about 400 (blue) to 700 (red) nm. Far UV (about 100 nm) and Extreme UV (less than 100 nm) are not included in this technology. X-rays (1 nm and shorter) are definitely out (but actually, CCDs are used on the new Chandra X-Ray satellite in funky ways). Down to about 100 nm (or maybe lower?) you can use conventional lenses, but they must be made out of magnesium-fluoride (MgF) instead of glass. It's not really until X-rays that you have to use bizarre techniques to focus light (like nested grazing-incidence foil mirrors).
This is new technology to do a better job of old science (at least from the astronomical point of view).
Currently the majority of visible and near-visible astronomy is done with CCD cameras (same technology as typical digital cameras and camcorders) which have peak sensitivity in the red or even IR. This makes it rather hard to study blue stars. The further blue you go, the less transmissive the atmosphere is and the brighter scattered moonlight appears (y'know, the sky is blue and all). So, having a camera that has poor sensitivity in the blue is doubly bad.
On a less technological and more historical note, prior to the 1980s (or so), photographic film was the dominant technology for astronomical imaging. Since most film has higher sensitivity in the *blue*, there was a lot of astronomy done at that end of the spectrum. Using CCDs today, it can be hard to compare to the blue work of the past. With new cameras specializing on blue and UV light, better comparisons with previous work can be made.
So it's quite wrong to say that new UV cameras will open up a new window in astronomy. In fact they will reopen an old window!
It's cool that NASA is supporting Linux. But it is certainly true that the field of astronomy has been very Unix oriented for a long time (that is, for those who have given up their VAX systems already. :) )
Anotheuinr interesting thing about astronomy is the emphasis on open source software. Two of the most popular astronomical data analysis packages in the USA have been open source from the start.
The IRAF project (supported by the NSF) has been open source since it started in the early-mid 80's. It's primarily used for optical and infrared imaging and spectroscopy for ground-based and space-based observation, but it is also used for X-ray astronomy. Nearly all of the Hubble data is processed in IRAF.
Radio astronomers use the AIPS software, which is also open source and has been since its origin in 1978.
Both have supported Linux since about the time RedHat first appeared on the scene. Neither of these packages are recommended for non-specialists, but they are examples of free software which dominate a discipline.
Why not repair the WIRE?
Because the Hubble repair missions go for at least $300M a shot, not including the new instruments they use for upgrades, beyond simple repairs.
Would you want to pay $300M to repair a $73M satellite?
It's undoubtably super news that there is an aspect of the satellite that may prove useful. Having any telescope in space, even one as small as this spotting scope is astonishly great for calibrating ground-based telescope observations which need to be made through miles of crud in our atmosphere.
But while this is a small improvement on what would have been a total loss, it is certainly not going to be free. For every active satellite (or even any active ground-based telescope to a lesser extent), there is a substantial expenditure in maintainance and data processing. For a satellite a large part of the price comes from ground operations, including issuing commands and maintaining a downlink station to receive the data as it comes in.
More information for the confused: Why is a tiny telescope (2 inch diameter) in space such a big deal? After all, anyone could pay about $200 and buy a telescope from a department store with equivalent light collection power. The key is that any telescope in orbit is above terrestrial weather. Measuring stellar brightness and color (which in turn yield info about a star's age, mass, distance, etc) is difficult from the ground because the atmosphere is not transparent. Weather makes the transparency change on short timescales, so a star's brightness appears to change rapidly. This is especially difficult for an astronomer who wants to study stars which have intrinsically variable brightness.
In short, a little satellite-borne telescope is a stable instrument for consistent work, like all those 386's running Linux and serving web pages out there.
As said by many others, the key is trust. I trust Cmdr Taco, Hemos, etc to filter my tech news for me because I've enjoyed the articles they've chosen.
But for the scientific articles I choose to read (which affect my career, unlike Slashdot which is entertainment for me), I need a deeper level of trust. A 100 year old journal with an editor who I have met is more worthy of trust (IMO) than a few-years-old abstract/preprint server run by people I know nothing about.
I do hope that an open source type scheme is attempted, but it may take time to build the level of faith that we place in the established journals.
In astronomy, there is a very popular preprint server at Los Alamos where many people submit electronic copies of papers they expect to get published.
However, I usually don't peruse this server. I instead read journal tables of contents (often sorted by topic) or (even better!) newsletters focusing on my particular subfield (star formation). This is for the same reason that I read Slashdot: I don't have the time/energy to peruse everything. Instead, I put my trust in a "portal" of some nature to pre-filter my reading material for me.
I do think it is very valuable to have large archives of electronic materials for reference research (like the NASA/ADS abstract and article service) which is much more effecient than a trip to the library. But I believe the parallel between open source software and scientific reporting breaks down at the bleeding-edge. "Beta" versions of scientific papers are either not worth much (for lack of credibility) or even dangerous (as "bugs" may propagate in the literature).
Very nice recap.
A couple minor points:
1) there is not really any evidence that supernovae typically result in black holes. While theory does *predict* black holes, they are notoriously hard to detect. In fact most theories predict neutron stars and many have been been found in supernova remnants, including the Crab Pulsar in the remnant of the 1054 AD supernova.
2) LBVs are thought to be of order 70-100 solar masses, as opposed to the 30 or 40 suggested.
Yes, you are right. Eta Car's total luminosity is about 10^5 times that of the Sun. This star is about as bright as any stable star can get. Any brighter, and the photons trying to escape the core of the star start knocking off the outer layers of the star's atmosphere (this is what one of the previos commenters called luminosity pressure).
What's surprising about the admission of ignorance is that the media allowed it! The whole point of science is to explore the limits of our ignorance. We astronomers always admit our vast ignorance, it just usually doesn't make the newspaper when we do.