John Baez
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Nice article! But you need oxygen to burn methane, right?
Jonathan Langdale
Shared publicly -Lonely gas stations
It's pretty "cool" that they've found the coolest Y class ultra cold brown dwarf (or free-floating planet) known as WISEPA 1828+2650 (left image). And it's not really that far away at 37 light years. It has a spectral class rating of >Y2.
As for age, it might be anywhere from 100 million to 10 billion years old. Wiki says that due to it's high tangential velocity, it might be between 2-4 billion years old and between ~3-6 times the mass of Jupiter.
It's really hard for me to call this a star since it is said to be cool enough that it emits no visible light. Therefore, I'm going to call it a free-floating gas giant planet.
The temperature range is 250—400 K (-23—127 °C / -10—260 °F).
Paper:
http://arxiv.org/abs/1301.1669
http://en.wikipedia.org/wiki/WISEPA_J182831.08%2B265037.8
I'm interested in this because I had previously heard that these really old brown ultra cold dwarfs might be old enough to have significant accumulations of methane. If you have liquid (cold) methane under pressure, it will burn and can be used as a rocket fuel.
The next warmest brown dwarf is a T spectral class. SCR 1845-6357 B (right image) is a companion T-5.5±1 brown dwarf star at 4.1 AU from his main red dwarf star A, which has a mass which might be perhaps 7% of our Sun. This binary system is about 12.6 light years away.
SCR 1845-6357 B has a mass 40 to 50 times that of Jupiter at a temperature of 950K. It's age is thought to be between 100 million years and up to 10 billion years old.
The cool thing about it is that they were able to determine that it's a companion by using simultaneous differential imaging (SDI), which consists of 3 filters used to identify the presence of methane for such a brown dwarf of that magnitude and at that distance. It's the first T-dwarf discovered around a low mass star.
Biller (2006)
http://arxiv.org/pdf/astro-ph/0601440v3.pdf
http://en.wikipedia.org/wiki/SCR_1845-6357
http://www.eso.org/public/images/eso0611d/
http://www.universetoday.com/100682/wise-nabs-the-closest-brown-dwarfs-yet-discovered/
This is a NASA rocket engine that runs off methane:
https://plus.google.com/109667384864782087641/posts/LpE7JUfjUeV
But how could you get it off the high gravity gas giant? Our closest example is Jupiter. Jupiter is about (by mass) 75% hydrogen, 24% helium, and maybe 3000 ppm methane along with 260 ppm ammonia. It has wind speed of between 40 and 150 m/s. The higher the pressure the hotter things get. So the outer most layer of Jupiter's atmosphere has ammonia crystals. Ammonia easily liquifies with hydrogen, but freezes at 195.45 K (-77.7 C or -107.86F) into white crystals.
If you take methane gas and cool it under 3.6 psi to about -162 C or -260 F, you can condense it into liquid methane.
If you take Jupiter's mass and increase it by above 1.6 it's current mass, it's interior would become sufficiently compressed due to gravity that this would cause the planet's volume to decrease despite the additional mass. So, at ~3-6 Jupiter's mass, WISEPA 1828+2650 might have a smaller diameter than Jupiter?
We measure Jupiter's atmosphere at the point where the pressure is 10 times that of Earth or less. Therefore, Jupiter's atmosphere is 5000km high using this criteria. Within this range there are ammonia crystal clouds and possibly ammonium hydrosulfide. However, the outer cloud layer is only about 50km thick. Underneath this it might be possible that there's a thin layer of water clouds.
So if methane is a heavier compound, why doesn't it sink?
The general idea here is that the hotter interior is composed of hot metallic hydrogen. The cooler heavier gases which later fell onto Jupiter were heated to gas form & prevented from cooling into a more dense liquid form. And a higher pressure equates to a hotter gas. Therefore, if you take some of the outer gas off a large gas giant and move it to a lower pressure, it will cool, condense & liquify causing gravity to pull it down. This is how precipitation works.
In a crude way, to get methane off such a giant we'd be doing something similar to trying to capture rain from a hot Earth by moving steam into space.
This then raises a similar comparison with an Earth-water habitable zone and a liquid-Methane habitable zone. This zone happens to be eerily similar to Jupiter's Moon, Titan which has rivers of liquid methane/ethane. Titan is at -179C where water can't exist a liquid. Water freezes at 0 C, which means that if WISEPA 1828+2650 is between -23—127 °C, it could have a layer of water clouds & liquid rain.
http://www.universetoday.com/90945/is-there-a-methane-habitable-zone/
Methane clathrates are stable at higher temperature than liquid methane (–20 C vs –162 C). This would be the likely methane rain form along with methane ice crystals. Getting methane clathrate would be getting both methane and water.
On Earth, methane clathrate can be found in deep sea sediments where it's been trapped or dissolved in water ice formed under this high pressure.
http://en.wikipedia.org/wiki/Methane_clathrate
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It's pretty "cool" that they've found the coolest Y class ultra cold brown dwarf (or free-floating planet) known as WISEPA 1828+2650 (left image). And it's not really that far away at 37 light years. It has a spectral class rating of >Y2.
As for age, it might be anywhere from 100 million to 10 billion years old. Wiki says that due to it's high tangential velocity, it might be between 2-4 billion years old and between ~3-6 times the mass of Jupiter.
It's really hard for me to call this a star since it is said to be cool enough that it emits no visible light. Therefore, I'm going to call it a free-floating gas giant planet.
The temperature range is 250—400 K (-23—127 °C / -10—260 °F).
Paper:
http://arxiv.org/abs/1301.1669
http://en.wikipedia.org/wiki/WISEPA_J182831.08%2B265037.8
I'm interested in this because I had previously heard that these really old brown ultra cold dwarfs might be old enough to have significant accumulations of methane. If you have liquid (cold) methane under pressure, it will burn and can be used as a rocket fuel.
The next warmest brown dwarf is a T spectral class. SCR 1845-6357 B (right image) is a companion T-5.5±1 brown dwarf star at 4.1 AU from his main red dwarf star A, which has a mass which might be perhaps 7% of our Sun. This binary system is about 12.6 light years away.
SCR 1845-6357 B has a mass 40 to 50 times that of Jupiter at a temperature of 950K. It's age is thought to be between 100 million years and up to 10 billion years old.
The cool thing about it is that they were able to determine that it's a companion by using simultaneous differential imaging (SDI), which consists of 3 filters used to identify the presence of methane for such a brown dwarf of that magnitude and at that distance. It's the first T-dwarf discovered around a low mass star.
Biller (2006)
http://arxiv.org/pdf/astro-ph/0601440v3.pdf
http://en.wikipedia.org/wiki/SCR_1845-6357
http://www.eso.org/public/images/eso0611d/
http://www.universetoday.com/100682/wise-nabs-the-closest-brown-dwarfs-yet-discovered/
This is a NASA rocket engine that runs off methane:
https://plus.google.com/109667384864782087641/posts/LpE7JUfjUeV
But how could you get it off the high gravity gas giant? Our closest example is Jupiter. Jupiter is about (by mass) 75% hydrogen, 24% helium, and maybe 3000 ppm methane along with 260 ppm ammonia. It has wind speed of between 40 and 150 m/s. The higher the pressure the hotter things get. So the outer most layer of Jupiter's atmosphere has ammonia crystals. Ammonia easily liquifies with hydrogen, but freezes at 195.45 K (-77.7 C or -107.86F) into white crystals.
If you take methane gas and cool it under 3.6 psi to about -162 C or -260 F, you can condense it into liquid methane.
If you take Jupiter's mass and increase it by above 1.6 it's current mass, it's interior would become sufficiently compressed due to gravity that this would cause the planet's volume to decrease despite the additional mass. So, at ~3-6 Jupiter's mass, WISEPA 1828+2650 might have a smaller diameter than Jupiter?
We measure Jupiter's atmosphere at the point where the pressure is 10 times that of Earth or less. Therefore, Jupiter's atmosphere is 5000km high using this criteria. Within this range there are ammonia crystal clouds and possibly ammonium hydrosulfide. However, the outer cloud layer is only about 50km thick. Underneath this it might be possible that there's a thin layer of water clouds.
So if methane is a heavier compound, why doesn't it sink?
The general idea here is that the hotter interior is composed of hot metallic hydrogen. The cooler heavier gases which later fell onto Jupiter were heated to gas form & prevented from cooling into a more dense liquid form. And a higher pressure equates to a hotter gas. Therefore, if you take some of the outer gas off a large gas giant and move it to a lower pressure, it will cool, condense & liquify causing gravity to pull it down. This is how precipitation works.
In a crude way, to get methane off such a giant we'd be doing something similar to trying to capture rain from a hot Earth by moving steam into space.
This then raises a similar comparison with an Earth-water habitable zone and a liquid-Methane habitable zone. This zone happens to be eerily similar to Jupiter's Moon, Titan which has rivers of liquid methane/ethane. Titan is at -179C where water can't exist a liquid. Water freezes at 0 C, which means that if WISEPA 1828+2650 is between -23—127 °C, it could have a layer of water clouds & liquid rain.
http://www.universetoday.com/90945/is-there-a-methane-habitable-zone/
Methane clathrates are stable at higher temperature than liquid methane (–20 C vs –162 C). This would be the likely methane rain form along with methane ice crystals. Getting methane clathrate would be getting both methane and water.
On Earth, methane clathrate can be found in deep sea sediments where it's been trapped or dissolved in water ice formed under this high pressure.
http://en.wikipedia.org/wiki/Methane_clathrate
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Yea. The methane clathrate has 5 something mole H2O to every 1 mole of methane CH4. And if we see methane absorption lines in spectrum, that might meant more methane emission than consumption, using up any water leaving free methane crystals.
Maybe with a good power source, you can split the H2O with electrolysis?
How much LOX is needed?
Maybe with a good power source, you can split the H2O with electrolysis?
How much LOX is needed?
I guess the hope is gravitational potential energy from the right mass or sized (shrinking) ultra cold dwarf can be transferred and stored into clathrate, pressurized liquid water that forms with methane somehow and freezes. Maybe clathrate hail?
So if we go 100,000 km/hr then it will only take 301,000 years of hibernation in interstellar space to go 28 light years and refuel.
John Baez
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Clathrates have methane in water ice, but my hunch is that splitting water into hydrogen and oxygen and then using that oxygen to burn methane is a losing proposition, energy-wise.
We can figure this out, at least at standard temperature and pressure, by looking up the heats of combustion:
CH4 + 2 O2 → CO2 + 2 H2O + 891 kJ
H2 + (1/2) O2 → H2O + 286 kJ
Hmm. So it takes 286 kilojoules to split a mole of water into hydrogen and oxygen, and you get half a mole of O2. Letting two moles of O2 burn methane produces 891 kilojoules. But that means letting half a mole of oxygen burn methane will produce 1/4 as much energy: 891/4 = 222.75 moles. So when we combine both these reactions, the net loss of energy is 286 - 222.75 = 63.25 moles.
So, you can't power a spaceship by this reaction. At best you can use solar power or something to split the water before you launch the rocket, then burn the methane with the resulting oxygen to power the rocket.
We can figure this out, at least at standard temperature and pressure, by looking up the heats of combustion:
CH4 + 2 O2 → CO2 + 2 H2O + 891 kJ
H2 + (1/2) O2 → H2O + 286 kJ
Hmm. So it takes 286 kilojoules to split a mole of water into hydrogen and oxygen, and you get half a mole of O2. Letting two moles of O2 burn methane produces 891 kilojoules. But that means letting half a mole of oxygen burn methane will produce 1/4 as much energy: 891/4 = 222.75 moles. So when we combine both these reactions, the net loss of energy is 286 - 222.75 = 63.25 moles.
So, you can't power a spaceship by this reaction. At best you can use solar power or something to split the water before you launch the rocket, then burn the methane with the resulting oxygen to power the rocket.
Brian Fitzgerald
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Does that analysis assume that there are no catalysts?
That makes sense. Ideally, you'd want to find binary systems with an actual star for some extra photon energy. That is probably more rare though.
The other part of the problem is extraction energy cost to get anything in an orbit. It still seems to assume there is more energy stored by way of heavier compound rest-mass created by conversion of gravitational potential.
The hydrogen you get is also useful. It makes more sense to figure out a self-sustaining mechanism. If there was a source to obtain catalysts, it might be an opportunistic adaptation one might be able to take advantage of, but you might not want to expect that you can produce them. Nor would you want to bring a potentially non-rewable dependency, not to mention having to push it through space by ejecting rocket fuel.
The other part of the problem is extraction energy cost to get anything in an orbit. It still seems to assume there is more energy stored by way of heavier compound rest-mass created by conversion of gravitational potential.
The hydrogen you get is also useful. It makes more sense to figure out a self-sustaining mechanism. If there was a source to obtain catalysts, it might be an opportunistic adaptation one might be able to take advantage of, but you might not want to expect that you can produce them. Nor would you want to bring a potentially non-rewable dependency, not to mention having to push it through space by ejecting rocket fuel.
Brian Fitzgerald
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Our present petrochemical industry depends largely on the production and use of synthetic zeolites. http://en.wikipedia.org/wiki/Zeolite
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