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First Observation Of Aurora On Jupiter
Doctor Fishboy writes: "Aurora are not restricted to our planet -- BBC news reports the sighting of Aurora on Jupiter for the first time. It looks as if it was a happy coincidence that the Hubble Space Telescope was looking at Jupiter when the aurora happened."
Soon, we will have another sun, and we will finally have peace with the Russians ( and Chinese ).
Aurora have been visible on jupiter for a long time, at least galileo has been imaging them for 5 years. Furthemore ground based te4lescopes have observed the aurora - although not in the same detail as the HST.
What's really interesting is the observation of a flash in the images lasting about 5 minutes and having an estimated energy of ~10^17 - 10^18 joules - 20 -200 megatonnes. This story neglects to mention this observation, but I've seen it elsewhere. Some people think this is an auroral flare, while others think it make be a small meteor impact (it'd have to be really small - impact energies at jupiter are huge)
That's a pretty image, but it doesn't really make sense since every object in the universe has an infinitely large magnetic field.
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Mod up a post Rob doesn't like and you'll never mod again
Good article on the science behind the aurorae. Take a look here.
Wrong from both a theoretical and a practical perspective. In theory, any magnetic field stretches potentially to infinity. But the carrier particle of electromagnetism, the photon, has a finite velocity and, as such, takes an infinite amount of time to travel an infinite distance.
From a practical perspective it's wrong because there are a lot of other magnetic fields out there in the cosmos, and at some point an object's magnetic field is always overwhelmed by the presence of another's.
The photon is the carrier particle of light,, not electromagnetism.
:)
:) The first measurements of the speed of light were done by measuring differences between expected occultations of Jupiter and the experimental times; it turned out that they could only be reconciled if light had a finite, although large, velocity. Currently, we've found that light travels 299,792,458 m/s, or just about three hundred thousand kilometers per hour--or roughly 186,000mph.
:)
James Clerk Maxwell disagrees with you, as well as Einstein. Light is nothing more nor less than a waveparticle which varies in both electric field strength and magnetic field strength. Radio waves are carried by photons; so is visible light; so is hard gamma and X-rays. All these are located at different frequencies along the electromagnetic spectrum.
Electromagnetism is one of the four fundamental forces (three if, like me, you're a pedant who says electromagnetism is just a low-temperature case of the electroweak force). Look it up. It's interesting.
Photons have infinite velocity.
We've known better than this for a few hundred years.
It takes sunlight a few million years to get from the Sun's stellar core to the surface; but once it escapes, it's got a short trip to Earth of some eight-and-change minutes.
Next time you go about casting aspersions on people, please take the time to get your own facts straight first. Thanks.
Apology accepted. :) But hey, you never know--some people probably do think photons just carry light, or that it travels infinitely fast.
:)
At any rate, the best way to handle people yanking your chain, I've found, is to just let them do it and not blow your stack. Let's face it; it's no fun to troll someone who doesn't get angry over it.
Very good question! Let's take a look at how we know the Earth has a metallic core; after all, we've never been there, either, have we?
Well, let's see. How did we first measure the Earth's size, and how did we learn it was round? A Greek mathematician (Eratosthenes?) looked down a well at noon on a particular day and discovered the sun cast no shadow in the well; i.e., it was directly overhead. The next year, he did the same experiment in a different city; lo and behold, the sun cast a shadow in the well. Eratosthenes had a good idea (based on other evidence I won't go into) that all rays from the sun were parallel; so, if the sun cast no shadow in the well of one city, but did in another, that meant the Earth had to be curved.
And thus, Eratosthenes measured the size of the Earth, with remarkable accuracy, by watching rays from the sun, paying attention, and knowing basic geometry.
Then, Sir Isaac Newton invented Newtonian physics a few thousand years later. (Newton didn't invent physics; Eratosthenes, for instance, was one hell of an experimental physicist!) With Newton came the Newtonian Theory of Gravity, which correlated mass to gravitational force.
Then a lot of other physicists began figuring out what that gravitational force was. The numeric term, as it turns out, is 6.67*10^-11, if I remember correctly--so weak that it was hell to measure. But they did measure it, and before long they measured it accurately.
Now that they knew how strong the Earth's gravitational field was (Galileo demonstrated this by rolling balls down an inclined plane), and how much gravitational energy was present per unit mass/distance-squared, and how large the Earth was, they were able to compute the mass of the Earth.
(Do the math for yourself. The force of gravity is 9.8033m/s^2. The gravitational constant's numerical term is 6.67 * 10^-11. The radius of the Earth is 6.378 * 10^6 meters. The equasion is
- Gf = (Gc * M1 * M2) / (d^2),
... where Gf is the gravitational force, Gc is the gravitational constant, M1 and M2 are the masses being attracted to each other, and d is the distance between them. The algebra involved is left as an exercise for the reader.)... Doing this equasion by hand takes about five minutes. Less if you're handy with exponentials. When all is said and done, you have the Earth's mass: 5.98 * 10^24 kilograms.
Now, assuming the Earth is a sphere (it's not, but close enough), it has a volume given by pi multiplied by the cube of the radius. Do the math, and divide the mass by the volume to get the density of the Earth.
You get about 7.3 metric tons per cubic meter.
Now go out and get yourself a box a cubic meter on a side. Pick up a shovel and start digging, throwing everything you find into the box until it's full. Now weigh it. You get much, much less than 7.3 metric tons per cubic meter.
Conclusion: what's deep inside the Earth must be much,
And then you share your results with the chemists.
And soon, after a few more back-of-the-paper-napkin calculations, you're able to show that the center of the earth possesses a metallic core--either that, or else something else extremely exotic which would provide the mass you need. And since the simple explanations tend to be the correct ones (Occam's Razor), the vast majority of scientists today believe the earth has a metal core.
Now, what did you need to do all this, to come to all these conclusions in which you have so much confidence?
- Geometry had to be invented.
- Eratosthenes had to look down a well.
- Newton had to invent calculus.
- Newton had to invent the theory of gravity.
- Somebody had to measure the gravitational constant.
... That's it.That's the beauty of science. Just by thinking logically, by searching and striving for the simplest answer, you can come to absolutely breathtaking discoveries about the world using nothing more than your brain and a couple of discoveries from other people.
Free your mind... and the Cosmos will follow.
every object in the universe has an infinitely large magnetic field Not actually true. Yes, a magnetic dipole in isolated free space will have a magnetic field that should go to infinity, assuming there's nothing else there. Except the real world isn't as simplified as E&M textbook problems would have you think - there are other objects and other fields out there, with the effect that a magnetic dipole (like the Earth or Jupiter) doesn't have a field which extends to infinity. Rather, it goes out to some finite distance at which point it is stopped by the Sun's much stronger field. The shock between the two is known as the magnetopause, and the finite-sized region inside of it is called the magnetosphere.
Item 5 above is "measure the gravity of the planet." For Earth that's easy to do - drop something. For Jupiter, we can do it by measuring the orbit of something going around Jupiter. It's got a whole mess of moons which are nice and visible, so this is relatively straightforward. But you can get *much* better data if you send a spacecraft there. As the spacecraft flys by or orbits the planet, its course will be deflected by Jupiter's gravity. Carefully measuring the spacecraft's course (which you do anyway for navigation purposes) lets you measure the gravity of Jupiter, and more importantly, how it differs from place to place
Turns out Jupiter is not a sphere. None of the planets are - they all spin, so they're all flattened by rotation. (Take a look at pictures of Jupiter - it's *visibly* about 10% wider than it is tall. Spinning a planet 320 times larger than the Earth around once every 10 hours will do that to ya.) Now maybe you've heard of a physics theorem that if you have a spherical object, its gravity is the same as that of a point source at the center. You couldn't figure out the internal structure of a sphere based on its gravity because it's so symmetric. But Jupiter's not a sphere, and so the gravitational potential varies from place to place in such a way that you can calculate backwards from it and get the densities at different places inside of the planet. Voila, we know it's mostly atmosphere, turns to metallic hydrogen a few thousand km down, and probably has a rocky core about 6-10 times larger than the Earth.
I'm not a physics student/professor/etc. so others might be able to give better info on this effect than others.
The aurora effect seen in nature is essentially the same physics used in flouressent lights. Solar winds carrying charged particles are channeled into the northern and southern polar regions due to the planet's magnetic field(Earth, Jupiter whatever). The particles strike molucules in the upper atmosphere which excites them to a new energy state and light is emmited when they return to their original energy state.
What is physicist have known for awhile is that different gasses emmit different wavelengths of light in this kind of situations(neon lights etc). Recording an aurora effect this large is interesting because there is a possiblity of catching a glimpse of the chemestry in the upper Jovian atmosphere or possibly a different/rare physical reaction(can you excite hydrogen to the point of doing something new?). Hopefully they'll pull some interesting science out of their lucky observations.
A lot of science is theory and logic. A piece of it is also being lucky and at the right place at the right times.
a solid ball of mostly metal
This reminds me of a few lines from an ST:TNG episode some years ago. My apologies for the paraphrasing...
Alien on viewscreen: Ugly bags of mostly water!
Riker (or Picard, maybe): [something indicating displeasure at the insult]
Data: Well, he's right about the "bags of mostly water" part....
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>And how exactly do people know all this stuff?
>No-one has been inside Jupiter, so in fact all that is
>pure speculation.
While nothing is set in stone, many aspects of this are quite likely to be accurate. The internal structure of a massive object can be deduced from several things:
- simple physics : put together a massive ball of 75% Hydrogen, 24% Helium and 1% "stuff" and you can calculate quite well what it would be like.
- gravitational effects : a ball the size of Jupiter that is totally uniform inside will have a different effect on orbiting objects than a non-uniform one, these differences can be measured and an estimate can be made of the density variations required to produce the effects
- Occam's razor : meaning : if multiple explanations are possible and you have no known way of choosing between them, choose the simplest explanation. In this case, a layer of metallic Hydrogen is the simplest explanation for the existence of such a huge magnetic field.
To learn more about all this, you might check out some Nasa websites, they have tons of info on this.
Aurorae have been observed on Jupiter for years (Even Voyager detected them 25 years ago!). Galileo and Hubble have been taking pictures of them for years now.
What is new is the observation of an auroral "flare", a sudden and significant increase in auroral activity. Such flares are quite rare on earth, and probably on Jupiter too, so it's quite a lucky streak for Hubble to be observing at just the right time.
In fact, only a couple of months ago, Astronomy Picture of the Day released this:
http://antwrp.gsfc.nasa.gov/apod/ap001219.html
Bart Declercq
Jupiter has the largest magnetic field of any object in the solar system (except the sun). It is so large that if it were visible in the sky, it would stretch some 20-30 times the diameter of the moon. Jupiter itself is layered, consisting of a thick outer layer of gas (predominantly Hydrogen & Helium) about 35.000km thick, within this, there is a "liquid" zone (although at the incredible pressures there, the distinction between liquid and gas is somewhat (pardon the pun) hazy.) This zone is about 25.000km thick. Inside this there is a solid ball of mostly metal which is about 20.000km in diameter. The magnetic field is actually produced in the liquid layer, parts of which are in a state called "metallic hydrogen", where hydrogen behaves as a conducting metal, creating one ginormous electromagnet.
Jupiter, gas ball with a whole bunch of different gasses than the Earth, Probably has a whole different spectrum of colours within it's Aurora. I wonder if our eyes can pick up the wonders of that one without digital enhancement. I, for one, would like to see colour pics, without touchups, of the whole thing just to see the differences.
DanH
Cav Pilot's Reference Page
Cav Pilot's Reference Page
UNIX - Not just for Vestal Virgins anymore
Are you sure this is the first observation of Aurora on Jupiter? I mean when I worked as a research assistant in the Space Physics lab, I spent a fair amount of time doing image analysis on things that looked like aurora on Jupiter, and that was about ten years ago now. Infact, what I was looking at were maps of spectral emmissons coming of the plant. I also worked with images of ultraviolet light being emitted from the planet. If this wasn't an aurora, I don't know what is.
I think BBC got their terms confused. There's a fine book on the Jovian outer atmosphere and magentosphere called Time Variant Phenomenon in the Jovian System. While technical, this book is way cool and has some great images. Anyway, this is sort of a reference for researchers and grad students who study Jupiter. I believe it's out of print, but can be found at a decent University Library. It was self publisched by NASA and NSF. The point here is that aurora on Jupiter are familar phenomenon that have been studied for a quite a while. I'm not saying anyone understands it, but that's why they study it.
I wish my institution still had access to Nature so I could check the primary source. I think the news here is that a flare was observed. Maybe the big news is that the Hubble imaged it. I dunno. The project I worked on was based off a sounding rocket. It was a pretty cool setup. We'd put a telescope in the nose of small rocket. I think it was a Redstone, but I'm probably wrong. The thing would fly in a ballistic trajectory briefly leaving the atmosphere. During that brief time, our module would find the disk of Jupiter, focus on it, and record the spectra.
Waitaminute. Go to Nature and read the little write up they have. The BBC misreported it. This flare is wholly unlike anything yet seen. Different wavelength--visible! And, it's huge! Dang, that's impressive. The news here is that whatever is going on is not related to the well observed interation between Jupiter and IO. This event is due to an entirely different mechanism. It warms my heart to see an old prof of mine as a coauthor on the report.
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Does anyone actually have a Java program designed to control air traffic, or for the operation of a nuclear facility?
Other non-terrestrial auroras can be found:
Neptune's aurorae occur near its equator, due to the alignment of that planet's magnetic field... I couldn't find a definite page or photograph of aurorae on Uranus, although I did find an AAS paper that discusses auroral emissions.
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Scott Robert Ladd
Master of Complexity
Destroyer of Order and Chaos
All about me
Timothy, timothy, timothy -- do you actually read articles before you publish them? Once again, you've shown an disturbing lack of knowledge when reporting a scientific topic...
The BBC article you referenced is about the discover of an auroral flare -- a phenomena hitherto unseen in Jovia aurorae. Aurorae have, however, been photographed on Jupiter for several years, by Galileo, Hubble, and other devices. Here, for example, is a 1996 article about related observations by Hubble. I spent a whole ten seconds checking my facts on Google; you might want to try it sometime!
I appreciate Slashdot's commitment to science -- but a core principle of science is accurate observation and reporting... and when you publish erroneous stories, it destroys both your reputation and Slashdot's value.
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Scott Robert Ladd
Master of Complexity
Destroyer of Order and Chaos
All about me
He has a point, there is NO reason for this besides the fact of learning something new (which I have to say, is a decent reason but still). The money could be put to better uses, such as say.. helping third world countries. I mean really, Why should we be focusing on something that is uh, let me check my math Why educate ourselves on something 588,000,000 kilometers away (at minimum) when there are children and even adults in third-world countries that can't even do basic arithmetic??
To hell with karma.
Turn off your computers at night! Don't assume they can't read lips! Beware the second sun!
My other sig is extremely clever...
For some great pictures and a more detailed explanation, try here.
--Shoeboy
--Shoeboy
(posting anonymously to preserve my precious karma)
Scientific American
In the distance you hear an ominous moo.
Not a correction, really; just so people don't walk away from this post thinking that the number 320 represents Jupiter's diameter. The quote above refers to Jupiter's mass. Its diameter is about 11 times greater than Earth's.
here..
Sex is heriditary, if your parents didn't have it chances are good you won't either.
Maybe they need to rethink the actual composition of a planet's core.
".. If I put soy oil into my diesel engine, and my diesel engine still runs -- wait, my engine is running? I didn't put diesel fuel in? Impossible. The fuel must be diesel, our math is wrong. Case closed."
I propose a physics/astrophysics/theoretical etc 'school' be established whose only purpose is to refute currently-accepted laws and theories -- NOT by examining the current theories, but by examining the properties they define; abstract everything and ask ourselves the questions once more. Please, at least once a century this needs to happen. How often, during the development of a program (especially one that is many thousands of years old. ;)) do you trash it all and, in 20% of the time it took to create the original, come up with something 200% better?
Some good reading that can incite both in-depth discussion and controversy: http://www.hollowplanets.com - nothing I actively advocate, but a few chapters and subjects are mind-openers (I prefer the physics and astrophysics-related topics, personally.)
Jason
SOMEBODY SET US UP THE IONS!
Interesting. Anyway, for more info on this go here. At this site, they identify it as a mysterious light similar to our Aurora lights.
Diplomacy is the art of letting people have your way