SOFIA Sees Jupiter's Ancient Heat 59
astroengine writes "The flying telescope SOFIA took its maiden flight on Wednesday, and its 'first light' images have already been released. The cool thing about SOFIA is that it flies high enough (integrated inside a converted 747, taking it to an altitude of 41,000 ft) to carry it above 99% of the atmosphere's infrared-absorbing water vapor. This means it can collect 80% of the IR radiation that hits orbital telescopes (like NASA's Spitzer) but without the huge cost of being launched into space. Also, SOFIA is expected to last 20 years, many times the operational lifespan of space missions. Already, SOFIA has returned stunning results, including the observation of heat leaking through Jupiter's clouds, heat that was generated billions of years ago when the gas giant was forming."
20 years is "many times"? (Score:2)
Really? I could swear the hubble has been up for 20 years.
Re:20 years is "many times"? (Score:5, Informative)
Also, infrared instruments usually need to be actively cooled, which means that the spacecraft needs a supply of coolant, such as liquid nitrogen. The coolant usually runs out long before anything on the spacecraft breaks down. So, the lifespans of space-based infrared telescopes tend to be limited by the amount of coolant that can be stored onboard. Sofia does not have that problem because it can refill its tanks every time it finished flying.
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It's pretty cold in space. The James Webb telescope will operate at 40 K with just a sun shield.
Re:20 years is "many times"? (Score:4, Informative)
No, it's not. If you're in view of the sun it's incredibly hot. And even when it's cold there's no medium to absorb your waste heat. In the same way that water cools you faster than air because water is denser, a void won't cool you at all beyond what you can naturally radiate away.
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I was explicitly talking about not being in view of the Sun, because of a sunshield. You are naturally radiating away to a very cold sink. Without exposure to the Sun it will get very cold, although at the Earth's distance from the Sun I expect there is some minor back radiation from the Sun's extended atmosphere, plus some conduction from those thin gases. Anyhow, the James Webb is supposed to be at 40 K, which I consider cold, even if perhaps not as cold as SOFIA will be.
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It doesn't matter how cold it is if there's no medium to suck up your heat. Again, there's a reason 80F air feels warmer than 80F water: water is thicker and so transmits radiation (eg, heat) more efficiently. A void won't transmit any heat at all, unless you're pushing it out.
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What? How do you think the Sun's heat gets to Earth through the void? The only "pushing" the Sun is doing is being hotter than the Earth, just as the James Webb telescope is hotter than deep space, which if you're far enough out to get beyond local effects is at about 3 K.
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The Sun is throwing photons at us, which is how both light and heat get's here.
And that is the problem. Yes, things in space will cool down, however, the only way this occurs is through what is called "black body radiation", that is, the emission of photons. Cooling down this way is slower than being cooled by air, water or some other substance.
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A void won't transmit any heat at all, unless you're pushing it out.
So you have an explination on why the "day" side of the moon is about 390 k and the "night" side is around 100 k then?
You think it magically heats up and then cools down for no reason? By your reasoning wouldn't everything that gets any sunlight just keep heating up in space as long as it's in the light? That's ignoring the part about the sun actually being able to heat up things through a void in the first place though. Right?
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Read the other response down below, from MrZilla. His contains a great explanation for how this happens.
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The temperature of space is 2.7 kelvin, the temperature of the cosmic microwave background radiation. Getting the temperature below that would require some form of active cooling.
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Yes. The universe is actively only supplying 2.7 kelvin to your space-borne object -- so it's not being heated much. However said object carries heat with it from its home on Earth, and cannot shed that heat very quickly. In a few years, centuries, maybe millenia, it will finally manage to slowly bleed away the excess heat via radiation only, not convection, and reach 2.7 kelvin. Maybe.
Re:20 years is "many times"? (Score:4, Informative)
I could swear the hubble has been up for 20 years.
Indeed. But Hubble's optics and instruments are optimized for operating in the near-ultraviolet and visible ranges. The more recent Spitzer telescope operates in infra-red (3 micron to 180 micron), so it is a more salient comparison. Spitzer's operational life is limited by its coolant supply of 360 liters of liquid helium http://www.spitzer.caltech.edu/technology/cryostat.shtml [caltech.edu], unlike Hubble, which does not need cryogenics.
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The Hubble can operate
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Yes, for all the bad press NASA may have received in its past, there have been at least a few outstanding feats achieved by the program, the Hubble being one of these.
In 1990 the Hubble space telescope was launched and put successfully into orbit, and with a few extremely successful "service missions" has allowed us insight to the universe in many ways we might have not seen otherwise (at least for a while!): We have gained understanding how are universe is expanding and the rate at which it is expanding
Vibration isolation (Score:5, Informative)
Re:Vibration isolation (Score:4, Interesting)
Well, according to the WP page on clear air turbulence [wikipedia.org]: "Clear air turbulence[1] weather, sometimes colloquially referred to as "air pockets", is the erratic movement of air masses in the absence of any visual cues, such as clouds. Clear-air turbulence is caused when bodies of air moving at widely different speeds meet; at high altitudes of around 7,000-12,000 metres (23,000-39,000 ft)". I guess at 41000 feet this means they pass above most turbulence. Having been aboard some jumbojets I must say they appear very stable under normal flight, you probably need more stabilizers than on the ground but even there it's windy and such.
Re:Vibration isolation (Score:5, Informative)
The telescope is mounted on a spherical bearing with gyroscopic stabilization and image feedback to correct for drift. This takes care of rotations. For translations, there is a damped spring mechanism holding the whole kaboodle to the support bulkhead (the image doesn't care if the telescope is translated, as it is "inifinitely" far away; however sudden translations can cause the telescope to flex, moving the image plane). And the pilots are very, very skilled at keeping constant and very precise attitudes. It's remarkably stable.
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Re:Vibration isolation (Score:4, Insightful)
Adaptive optics can deal with atmospheric image distortion, but they can't do anything about absorption. As I understand it, the key advantage of SOFIA (and space telescopes, of course) is that it can pick up wavelengths that are absorbed before reaching ground level.
Cheaper astronomy (Score:3, Interesting)
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IT never fails to amaze me that NASA does not send a balloon to 100,000 feet and load it up with all kinds of scientific equipment. That way, they would have advantages of being almost in space, but for a fraction of the cost of sending anything in space.
They do. Sometimes they break. [space.com]
Re:Cheaper astronomy (Score:4, Insightful)
With that large payload you'd need a balloon the size of Milwaukee.
Re:Cheaper astronomy (Score:4, Funny)
I'm not familiar with the size of Milwaukee, can I get that in football-fields?
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American or European?
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For infrared/sub-mm astronomy see, for example:
http://en.wikipedia.org/wiki/BLAST_(telescope) [wikipedia.org]
http://en.wikipedia.org/wiki/BLAST!_(movie) [wikipedia.org]
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NASA launches several balloon missions every year. They are cheaper than space telescopes, but they have some severe limitations, such as very short life spans and size-mass restrictions. Sometimes you get more science per dollar spent by flying a telescope in space.
Re:Cheaper astronomy (Score:4, Informative)
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EU is all about no proof and ignoring experiment (Score:4, Insightful)
Personally I am attracted to the alternative Electric Universe theory because they recognize a need to back up their statements with laboratory experiments, and with theories that do have a great deal of proof behind them, such as the behavior of plasma.
LOL.
Electric Universe holds that the solar wind is caused by the sun's electric charge, creating a current of protons outward.
Actual experiment indicates that the solar wind is comprised of roughly equal amounts of protons and electrons traveling outward from the sun. With no net movement of charge there is no current, and Coulomb's Law says an electric field cannot move oppositely charged particles in the same direction, both indicating (though it's really one thing, the Theory of Electromagnetism) that the Sun has no net charge.
As one would expect from the well-verified theory of plasma behavior, the majority of which are quasi-neutral, with those that aren't being necessarily non-dense.
So, yeah, they ignore experiments that prove their most basic premises wrong, and don't even understand the well-established theory their ideas are allegedly based on.
But hey, I can't tell you who you should be attracted to.
20 years? Hubble's done that (Score:2)
It obviously does have advantages so far as costs go, though only time will tell just how many observing hours it clocks up
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Well, hubble had a few repair missions, each of which was A LOT more expensive than this whole project.
It's the potential energy that's old (Score:2)
Jupiter's heat is not billions of years old - the planet keeps shrinking, and thus keeps producing heat.
Why Not Put It on a U-2? (Score:1)
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At those altitudes, the U-2 barely has enough lift to carry it's own weight, let alone carry a telescope with liquid cooling system.
Another reason for choosing a 747 is the size of the telescope. It's roughly half a U-2 long, and more than double as wide.
CO2 versus H20? (Score:1, Offtopic)
So, CO2 is now (however wrongheadedly) officially a "pollutant". How is it that water vapor, a much stronger greenhouse gas, isn't considered such?
If you think human produced water vapor isn't an issue, I suggest you research the historical humidity record in erstwhile dry spots like Phoenix, AZ and inland southern CA.
The true answer is neither is a pollutant, and the human contribution to any warming of the Earth is negligible. The odds favor a cooling trend for a few decades regardless.