Would you mind giving a source for your tale of globular formation and evolution? I've never heard any such thing, and I'm working on my Ph.D. in astronomy.
Globulars are indeed old. But 40-50 billion years would make them about 25-35 billion years older than the universe itself. We thought we had issues when they appeared to be a couple billion years older, but even astrophysicists can't ignore 30 billion years.
I'll assume that that was a typo, though. Globulars, according to all I have studied, formed around our galaxy. Either with it or shortly before it started to form. What would a quasar have to do with this? Quasars, sexy as they are, are only big black holes on a binge of eating. These are not the kinds of places you form clusters of stars.
Finally, when a globular passes through the Milky Way's disk, nothing really happens. You can tell because almost all globulars are on disk-crossing orbits. They have to be, since most are orbit nearer the galactic center than we do (this is how Shapley worked out where the galactic center was, after all). And since they've made quite a few orbits in their lives and since they are still around, clearly passing through the disk isn't terribly disruptive. And it shouldn't be expected to be: stars don't collide when galaxies pass through each other. This is easy to understand because galaxies are made of mostly empty space. Stars can find their orbits disrupted, but they seldom collide.
I'd be curious to see where you heard all of this.
Brown dwarfs actually have spectral classes: L and T. (For some reason, the voices in my head are saying there's an M, too. But they also told me to buy dotcom stock.) They don't really evolve much in time, since there is little or no fusion occuring. They just kind of cool.
The difference is exactly that: how we think they formed. Stars form in a gas cloud collapse, whereas giant planets form by first accreting a core from an accretion disk around a forming star. To the best of our current understanding, anyway.
As it turns out, the same people who research brown dwarf atmospheres are also the ones who have a lot to say about exoplanet atmospheres. Moral: in terms of what we can observe, brown dwarfs are basically the same a giant planets.
The reason why not? Moving parts. There is a taboo on moving parts, in as far as they can be avoided. Moving parts can jam in the most inconvient places, rendering an instrument useless. In this case, if a wiper got caught midwipe, all the subsequent pictures would have that wiper in the middle of the image. Sort of like fingers in vacation photos, but way more expensive.
Sorry, but nope. Several asteroids where are now in the belt are massive enough to be spherical (that's a self-gravity effect) and be differentiated, Ceres and Vesta amoung them. Since we get metallic and stony meteorites on Earth, we know that some large asteroids which were differentiated must have existed only to be blown appart in a large collisions. Since we know that this erosion has been happening, there is no real reason to assume that the current asteroids are the largest that have ever existed. In fact, I can see a case that it is unlikely that Ceres is the largest asteroid to ever inhabit the asteroid belt. (Without knowing how much destruction has happened, I couldn't say off-hand.)
Why emilinate a larger asteroid? The asteroid belt constantly has collisions and destruction of the objects. It's actually easy to imagine that there were once much larger asteroids in the belt, and they have since been shattered.
I find it easier to believe than to believe that a rock was blasted off of Mercury and then somehow made it to Earth's orbit.
If you really want to know where it came from, we'll need a close look at Mercury. Last I heard, the European Space Agency's Mercury mission included a lander, so we might be in luck.
Speaking as someone who has Mathematica installed on his laptop as well as his workstation (and has it currently, actively working on both machines at the moment), I have to disagree with your review, if only in the light in which you cast MMA.
Mathematica (aka MMA) is a life-saver for some kinds of symbolic manipulations and is great for plotting up formulae. But it has a lot of weak flanks. I refuse to use it for writing things, [La]TeX is much better for that. You might lose a bit of WYSIWYG, yes, but MMA gets really slow after a few pages of serious 2D mathematics. And it's a lot easier to type straight text.
MMA also is far from ideal for data plotting and manipulation. While I knew MMA long before IDL (from RSI), I have long since started doing all of my data I/O, plotting and manipulation in IDL.
Finally, MMA is pretty slow about serious number crunching. Much has been made about doing modelling in MMA, but my observation and my experience is that if you want to use commercial software (as opposed to writing your own C/FORTRAN/whatever code), Matlab and even Maple are better than MMA.
Still, Mathematica is very strong in its niche. I'm not sure it's worth $700+, which is the usual cost. But since I'm still a graudate student, I got my copy for $150 or so. It's been worth that.
All that said, this far from proves that Wolfram has a clue about anything other than MMA.
To capture something into orbit, you need to get rid of some of its energy. One way to do that is to use gas drag in the atmosphere. Earth's atmosphere is too small for that to be a viable option. (This tricky probably doesn't work after the solar system forms much anyway.)
The other route is to collide with a pre-existing object already in orbit. The collision will dissipate energy and let the new moon settle in. Earth, having just one Moon, isn't a good candidate for this technique. Also, our domain of graviational dominance (over the Sun's gravity) is much, much smaller than Jupiter's. So capture is hard for us.
Someone who was on one of the moon-hunting teams worried about that to me about a year ago. I compiled a list of 50 names of nurses and paramours of Jupiter with a simply search, so I'm not quite worried, yet. Another 11 and we'll need to get concerned.
Your first guess is correct: the price paid to fix Hubble's flawed optics was the loss of that corner. Worth it, I suppose. And it gives HST images a unique fingerprint to make them easy to spot.
Darwin's (no, George Darwin, Charles's son) idea about planetary fission to form the Moon doesn't work. There's insufficent angular momentum in the system to make it work. The giant impact model is the ONLY model that makes sense right now. (The tidal locking of the Moon causing it to show us one face at all times has nothing to do with anything.)
In fact, the original poster is correct: if the Moon formed in a giant impact, it appears that it should be almost all rock akin to Earth's mantle. The iron and other metallic elements would have sunk into the interior of the Earth, being lost to the disk of debris what would go on to form the Moon.
If you want to use geothermal energy, you need active geologic activity at the surface. The Moon doesn't have that, based on the many, many observations we've made of the surface. If there is a molten core at all, it's a tiny fraction of the volume, deep in the interior.
The Moon appears to once have had a magnetic field, but if our theories of field generation are right, it's rotating too slowly now to have any real field.
It depends on where the peak emission is at. That, in turn, is temperature dependent. For a stove at a several hundred Kelvin, the peak is in the IR, so you're perfectly correct about the main radiative energy coming from IR.
The warmth you feel from the sun is infrared radiation.
Not true. About half of the energy you feel as "warmth" from the Sun is from visible light alone. If you added in the near IR and near UV to get what is often called "shortwave radiation" (as opposed to longwave infrared, like most of what Earth and you and I emit), you get the overwelming bulk of the energy that heats you up when you lie in the sun. For some reason, it's come to be a common misconception that IR warms you, and visible doesn't. The association is probably because we think of hot bodies (like people) with IR. But the Sun is just a very hot body, so the physics is all the same.
The atmosphere won't have snowed out by 2014. Remember, Pluto orbits very slowly.
In actuality, it is looking rather UNLIKELY that the atmosphere will snow out at all. Larry Esposito, who was competing with Alan Stern for this mission, found out in his research that the models that predicted this appear out of date and that newer models do not indicate that the atmosphere will solidify. Unfortunately, it's a cool idea and people have a hard time letting go of it.
Given that $500 million will buy you approximately 1 shuttle launch at current rates, and that the ISS is already getting around $5 billion annually, $500 million for a mission to explore a heretofore unexplored part of our solar system isn't so much, is it? In fact, it's a vertiable bargin, given how much more good science will come out of this than the ISS (which has been almost totally gutted of scientific worth).
The mechanism held responsible for this isn't capture, it's more akin to the "giant impact" model of the formation of Earth's Moon and Pluto's Charon. Capturing requires dissipation of energy, you're right. And without an atmosphere, asteroids and KBOs probably can't manage that. But if you bounce something loose off the surface, you can actually get a moon.
Actually, Jupiter emits most of its radiation in the IR. It's just blackbody emission, after all. Most of the nifty radio emission is tied to the magnetosphere, which is an entirely different kettle of fish. The internal heating is probably due to continued contraction (to expand on what you said).
As for capturing moons... it's really, really, really tough. You're right. You can't just capture a moon by having a body sling by and get caught. You need a dissipation to remove energy from the system (well, get it out of the graviational/kinetic forms). If you're a gas giant or a very young terrestrial planet, gas drag near the planet might work. KBOs and asteroids probably never were able to manage that and aren't really old enough for their moons to have been formed at an early epoch anyway.
The theory I've heard bandied about over the past year or two is that these moons are the result of an impact with the main body. The impact can toss material up into orbit around the object, creating a small moon. I don't think I've seen this put forth in any papers yet. (A quick search on ADS didn't show any hits, either. But my search-engine luck is pretty low.)
Simple, you come around behind it just like you do at Jupiter. Slingshotting has nothing to do with where in the solar system you are, it's just a matter of robbing momentum from the planet.
The Galileo and Cassini probes both used Venus and Earth slingshots to get to the outer solar system.
Both Voyagers were launched in 1977, the article made a typo (notice the "as well" in there). Voyager II did leave a few months earlier, but it took a slower route, so it got to the outer planets after its older brother. The trade-off to being the second child and travelling slower is that it got to say a big "Howdy!" to Uranus and Neptune, in a glorious mission extension.
It's not quite that bad. If you do a couple of gravity assists off of Earth and Venus (and you can do that no matter what year you launch) and snag Jupiter on your way out, you can get a pretty good velocity up. A big reason the Voyager alignment was so special is that they actually got to go to all 4 giant planets. If Neptune had been on the opposite side of the Sun from Jupiter, gravity assist or not, we'd have been sunk. Pioneers 10 and 11 didn't use the outer 3 giant planets, and they're doing a pretty good clip, too.
Still, you're right that we'd be short some of that Voyager delta-v! If memory serves (which is does at its own conviences, the punk), Voyagers overtook their Pioneer cousins a while ago.
Re:They should learn lessons, but use money elsewh
on
Voyager Keeps on Trucking
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· Score: 4, Insightful
The cost of checking in with Voyager every now and again is minimal. Far, far less than the costs of building even New Horizons, let alone another Voyager-class mission. And since Voyager is heading for the the heliopause and quite probably will get through it before it dies off or we lose contact, that will be a great scientific benefit. Right now, we don't really know where the heliopause is, exactly. To miss this chance to encounter it would be foolish, especially since our next chance wouldn't come for at least 20 more years, if we launched a mission right now.
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Would you mind giving a source for your tale of globular formation and evolution? I've never heard any such thing, and I'm working on my Ph.D. in astronomy.
Globulars are indeed old. But 40-50 billion years would make them about 25-35 billion years older than the universe itself. We thought we had issues when they appeared to be a couple billion years older, but even astrophysicists can't ignore 30 billion years.
I'll assume that that was a typo, though. Globulars, according to all I have studied, formed around our galaxy. Either with it or shortly before it started to form. What would a quasar have to do with this? Quasars, sexy as they are, are only big black holes on a binge of eating. These are not the kinds of places you form clusters of stars.
Finally, when a globular passes through the Milky Way's disk, nothing really happens. You can tell because almost all globulars are on disk-crossing orbits. They have to be, since most are orbit nearer the galactic center than we do (this is how Shapley worked out where the galactic center was, after all). And since they've made quite a few orbits in their lives and since they are still around, clearly passing through the disk isn't terribly disruptive. And it shouldn't be expected to be: stars don't collide when galaxies pass through each other. This is easy to understand because galaxies are made of mostly empty space. Stars can find their orbits disrupted, but they seldom collide.
I'd be curious to see where you heard all of this.
Brown dwarfs actually have spectral classes: L and T. (For some reason, the voices in my head are saying there's an M, too. But they also told me to buy dotcom stock.) They don't really evolve much in time, since there is little or no fusion occuring. They just kind of cool.
The difference is exactly that: how we think they formed. Stars form in a gas cloud collapse, whereas giant planets form by first accreting a core from an accretion disk around a forming star. To the best of our current understanding, anyway.
As it turns out, the same people who research brown dwarf atmospheres are also the ones who have a lot to say about exoplanet atmospheres. Moral: in terms of what we can observe, brown dwarfs are basically the same a giant planets.
The reason why not? Moving parts. There is a taboo on moving parts, in as far as they can be avoided. Moving parts can jam in the most inconvient places, rendering an instrument useless. In this case, if a wiper got caught midwipe, all the subsequent pictures would have that wiper in the middle of the image. Sort of like fingers in vacation photos, but way more expensive.
Sorry, but nope. Several asteroids where are now in the belt are massive enough to be spherical (that's a self-gravity effect) and be differentiated, Ceres and Vesta amoung them. Since we get metallic and stony meteorites on Earth, we know that some large asteroids which were differentiated must have existed only to be blown appart in a large collisions. Since we know that this erosion has been happening, there is no real reason to assume that the current asteroids are the largest that have ever existed. In fact, I can see a case that it is unlikely that Ceres is the largest asteroid to ever inhabit the asteroid belt. (Without knowing how much destruction has happened, I couldn't say off-hand.)
:-)
Note: I am an astronomer
Why emilinate a larger asteroid? The asteroid belt constantly has collisions and destruction of the objects. It's actually easy to imagine that there were once much larger asteroids in the belt, and they have since been shattered.
I find it easier to believe than to believe that a rock was blasted off of Mercury and then somehow made it to Earth's orbit.
If you really want to know where it came from, we'll need a close look at Mercury. Last I heard, the European Space Agency's Mercury mission included a lander, so we might be in luck.
The Journal Nature ran an article on this book, mainly on the reactions its getting (both good and bad):
http://www.nature.com/cgi-taf/DynaPage.taf?file=/Speaking as someone who has Mathematica installed on his laptop as well as his workstation (and has it currently, actively working on both machines at the moment), I have to disagree with your review, if only in the light in which you cast MMA.
Mathematica (aka MMA) is a life-saver for some kinds of symbolic manipulations and is great for plotting up formulae. But it has a lot of weak flanks. I refuse to use it for writing things, [La]TeX is much better for that. You might lose a bit of WYSIWYG, yes, but MMA gets really slow after a few pages of serious 2D mathematics. And it's a lot easier to type straight text.
MMA also is far from ideal for data plotting and manipulation. While I knew MMA long before IDL (from RSI), I have long since started doing all of my data I/O, plotting and manipulation in IDL.
Finally, MMA is pretty slow about serious number crunching. Much has been made about doing modelling in MMA, but my observation and my experience is that if you want to use commercial software (as opposed to writing your own C/FORTRAN/whatever code), Matlab and even Maple are better than MMA.
Still, Mathematica is very strong in its niche. I'm not sure it's worth $700+, which is the usual cost. But since I'm still a graudate student, I got my copy for $150 or so. It's been worth that.
All that said, this far from proves that Wolfram has a clue about anything other than MMA.
To capture something into orbit, you need to get rid of some of its energy. One way to do that is to use gas drag in the atmosphere. Earth's atmosphere is too small for that to be a viable option. (This tricky probably doesn't work after the solar system forms much anyway.)
The other route is to collide with a pre-existing object already in orbit. The collision will dissipate energy and let the new moon settle in. Earth, having just one Moon, isn't a good candidate for this technique. Also, our domain of graviational dominance (over the Sun's gravity) is much, much smaller than Jupiter's. So capture is hard for us.
Someone who was on one of the moon-hunting teams worried about that to me about a year ago. I compiled a list of 50 names of nurses and paramours of Jupiter with a simply search, so I'm not quite worried, yet. Another 11 and we'll need to get concerned.
Your first guess is correct: the price paid to fix Hubble's flawed optics was the loss of that corner. Worth it, I suppose. And it gives HST images a unique fingerprint to make them easy to spot.
Yes, exactly. This rotation is thought to be too slow to support a strong field, particularly in a body with such a small, if any, core.
Darwin's (no, George Darwin, Charles's son) idea about planetary fission to form the Moon doesn't work. There's insufficent angular momentum in the system to make it work. The giant impact model is the ONLY model that makes sense right now. (The tidal locking of the Moon causing it to show us one face at all times has nothing to do with anything.)
In fact, the original poster is correct: if the Moon formed in a giant impact, it appears that it should be almost all rock akin to Earth's mantle. The iron and other metallic elements would have sunk into the interior of the Earth, being lost to the disk of debris what would go on to form the Moon.
If you want to use geothermal energy, you need active geologic activity at the surface. The Moon doesn't have that, based on the many, many observations we've made of the surface. If there is a molten core at all, it's a tiny fraction of the volume, deep in the interior.
The Moon appears to once have had a magnetic field, but if our theories of field generation are right, it's rotating too slowly now to have any real field.
It depends on where the peak emission is at. That, in turn, is temperature dependent. For a stove at a several hundred Kelvin, the peak is in the IR, so you're perfectly correct about the main radiative energy coming from IR.
The warmth you feel from the sun is infrared radiation.
Not true. About half of the energy you feel as "warmth" from the Sun is from visible light alone. If you added in the near IR and near UV to get what is often called "shortwave radiation" (as opposed to longwave infrared, like most of what Earth and you and I emit), you get the overwelming bulk of the energy that heats you up when you lie in the sun. For some reason, it's come to be a common misconception that IR warms you, and visible doesn't. The association is probably because we think of hot bodies (like people) with IR. But the Sun is just a very hot body, so the physics is all the same.
The atmosphere won't have snowed out by 2014. Remember, Pluto orbits very slowly.
In actuality, it is looking rather UNLIKELY that the atmosphere will snow out at all. Larry Esposito, who was competing with Alan Stern for this mission, found out in his research that the models that predicted this appear out of date and that newer models do not indicate that the atmosphere will solidify. Unfortunately, it's a cool idea and people have a hard time letting go of it.
Given that $500 million will buy you approximately 1 shuttle launch at current rates, and that the ISS is already getting around $5 billion annually, $500 million for a mission to explore a heretofore unexplored part of our solar system isn't so much, is it? In fact, it's a vertiable bargin, given how much more good science will come out of this than the ISS (which has been almost totally gutted of scientific worth).
The mechanism held responsible for this isn't capture, it's more akin to the "giant impact" model of the formation of Earth's Moon and Pluto's Charon. Capturing requires dissipation of energy, you're right. And without an atmosphere, asteroids and KBOs probably can't manage that. But if you bounce something loose off the surface, you can actually get a moon.
Actually, Jupiter emits most of its radiation in the IR. It's just blackbody emission, after all. Most of the nifty radio emission is tied to the magnetosphere, which is an entirely different kettle of fish. The internal heating is probably due to continued contraction (to expand on what you said).
As for capturing moons... it's really, really, really tough. You're right. You can't just capture a moon by having a body sling by and get caught. You need a dissipation to remove energy from the system (well, get it out of the graviational/kinetic forms). If you're a gas giant or a very young terrestrial planet, gas drag near the planet might work. KBOs and asteroids probably never were able to manage that and aren't really old enough for their moons to have been formed at an early epoch anyway.
The theory I've heard bandied about over the past year or two is that these moons are the result of an impact with the main body. The impact can toss material up into orbit around the object, creating a small moon. I don't think I've seen this put forth in any papers yet. (A quick search on ADS didn't show any hits, either. But my search-engine luck is pretty low.)
Simple, you come around behind it just like you do at Jupiter. Slingshotting has nothing to do with where in the solar system you are, it's just a matter of robbing momentum from the planet.
The Galileo and Cassini probes both used Venus and Earth slingshots to get to the outer solar system.
Both Voyagers were launched in 1977, the article made a typo (notice the "as well" in there). Voyager II did leave a few months earlier, but it took a slower route, so it got to the outer planets after its older brother. The trade-off to being the second child and travelling slower is that it got to say a big "Howdy!" to Uranus and Neptune, in a glorious mission extension.
It's not quite that bad. If you do a couple of gravity assists off of Earth and Venus (and you can do that no matter what year you launch) and snag Jupiter on your way out, you can get a pretty good velocity up. A big reason the Voyager alignment was so special is that they actually got to go to all 4 giant planets. If Neptune had been on the opposite side of the Sun from Jupiter, gravity assist or not, we'd have been sunk. Pioneers 10 and 11 didn't use the outer 3 giant planets, and they're doing a pretty good clip, too.
Still, you're right that we'd be short some of that Voyager delta-v! If memory serves (which is does at its own conviences, the punk), Voyagers overtook their Pioneer cousins a while ago.
The cost of checking in with Voyager every now and again is minimal. Far, far less than the costs of building even New Horizons, let alone another Voyager-class mission. And since Voyager is heading for the the heliopause and quite probably will get through it before it dies off or we lose contact, that will be a great scientific benefit. Right now, we don't really know where the heliopause is, exactly. To miss this chance to encounter it would be foolish, especially since our next chance wouldn't come for at least 20 more years, if we launched a mission right now.