NASA's NuSTAR Observatory Pinpoints Hottest Spots on the Sun:
Every day, astronomers learn more about the stars spread around the cosmos, but there's still plenty to learn about the star closest to Earth. NASA has released a new composite image of the Sun featuring data from the NuSTAR space telescope. It reveals some of the hottest areas of the Sun, which may help scientists unravel a stellar mystery that has remained unsolved for decades.
[...] NASA believes the NuSTAR data could help scientists understand why the Sun's corona is so hot. While the Sun's surface is a toasty 5,500 degrees Celsius, the corona reaches scorching temperatures of more than 1 million degrees Celsius. The Sun's heat radiates out from the core, so no one is certain how the star's atmosphere ends up so much hotter than the surface. Solar flares don't happen often enough to keep the corona so hot, but nanoflares might be the key. That's what you're seeing in the blue regions above.
Individual nanoflares, small eruptions originating deep inside the Sun, are too faint compared with the blazing brightness of the Sun to appear in today's instruments. However, NuSTAR can detect the high-energy output when multiple nanoflares occur close together. This could help physicists determine how often nanoflares happen and how much energy they release.
(Score: 2) by JoeMerchant on Wednesday February 22, @10:02PM (8 children)
So, fusion happens deep down under high pressure, but... are there other nuclear reactions that only take place once the material is "released" into space? I mean, chemically, Helium is pretty chill, but if you have any leftover matter-energy conversion that happens up above the surface, it has a relatively tiny mass to heat with all that energy so temperatures could rise impressively fast.
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(Score: 2) by RS3 on Wednesday February 22, @10:26PM (2 children)
Even more stellar ignorance here, but pure guessing: most earthly fusion designs involve creating a plasma (ionized stuff), then clobbering it with huge magnetic field to squeeze it and cause fusion. So, my hunch is, when the stuff is ejected from the sun's core, it causes huge magnetic fields that squeeze other stuff and ignite some more fusion.
(Score: 2) by JoeMerchant on Wednesday February 22, @11:49PM (1 child)
>huge magnetic fields that squeeze other stuff and ignite some more fusion.
Sounds good to me, and the large scale thermodynamics works. Starting the fuel out at 5000C as ionized plasma (easily manipulated by the magnetic fields) probably helps.
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(Score: 4, Interesting) by RS3 on Thursday February 23, @05:28AM
There are many things that I occasionally dabble in, notice something, pay attention, etc. Like most of us here and most tech / science types. Anyway, I remember seeing videos of huge "storms" on the sun, and large loops of plasma. It comes up out of the "surface" and immediately forms a quite circular loop and heads back in. Knowing it's plasma which is quite electrically active / conductive (I've done some welding and other experiments with sparks and plasma) and knowing that looping shows magnetic field, it stands to reason there are huge currents, huge magnetic fields, which likely (must?) cause more fusion within those unimaginable forces. Forces greater than 200,000 elephants standing on a Roman coin, for reference. :)
The more interesting one is "sun spots" - areas of much lower temperature. My feeble mind always thought those are where the opposite happens- for reasons beyond my understanding (or interest) there are areas of lesser magnetism, or opposing (N to N or S to S) magnetism, or just a large uniform area of N, or S, and no great force happens, so no fusion at the "surface".
(Score: 1) by khallow on Thursday February 23, @01:34AM (4 children)
Probably not. It's actually cooler than in the deep interior of the Sun and the density is way, way lower. You need that density in order to have enough opportunities for things to hit each other. For example, a key fusion reaction in the heart of the Sun is a triple proton [wikipedia.org] collision - two protons wack together and then run into a third proton before the pair falls apart. You need a high density in order for this to work. My guess is that it falls off as the square of the density with an order of magnitude drop resulting in two orders of magnitude less fusion reactions assuming temperature doesn't change.
(Score: 1) by khallow on Thursday February 23, @01:43AM (3 children)
(Score: 2) by JoeMerchant on Thursday February 23, @11:14AM (2 children)
Chat GPT is a little less word salady:
In the Sun's atmosphere, the plasma is made up of hydrogen and helium ions and electrons. When the plasma is subjected to high temperatures and pressures, the hydrogen ions can undergo fusion reactions, where they combine to form helium and release energy.
The fusion process in the Sun's core is facilitated by a phenomenon known as the proton-proton chain. In this process, four hydrogen nuclei (protons) combine to form a helium nucleus, releasing two positrons (positively charged electrons), two neutrinos, and energy in the form of gamma rays. The gamma rays are absorbed and re-emitted many times by the surrounding plasma before they can escape from the core and reach the Sun's surface.
At the surface of the Sun, the temperature and pressure are much lower, and fusion reactions are much less common. However, magnetic reconnection can still occur in regions where plasma is compressed or accelerated by the magnetic fields. During magnetic reconnection, the magnetic field lines break and rejoin, releasing energy in the process. This energy can heat the plasma and accelerate charged particles to high speeds.
The acceleration of charged particles during magnetic reconnection is governed by the laws of electromagnetism. As the magnetic field lines break and rejoin, they create electric fields that can accelerate charged particles. The particles can also be deflected by the magnetic field, leading to the formation of electric currents and the generation of magnetic fields.
In the context of solar storms, the energy released by magnetic reconnection can ionize particles in the Sun's atmosphere and accelerate them to high speeds. This can cause a burst of X-rays and ultraviolet radiation, as well as a stream of charged particles known as the solar wind. When the solar wind interacts with Earth's magnetic field, it can cause magnetic reconnection at the magnetopause - the boundary between the Earth's magnetic field and the solar wind. This can lead to the formation of auroras and other space weather phenomena.
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(Score: 1) by khallow on Friday February 24, @02:22PM (1 child)
It's actually six protons or four protons plus a helium nuclei (alpha particle). Two protons blob together (spitting off that positron and neutrino to form deuterium) and then run into a third proton before they decay. That forms helium 3 which apparently can loiter in the Sun for centuries under present conditions. Then helium 3 eventually runs into helium 3 or 4 nuclei and fuses producing one or two helium 4 nuclei (with two protons in the case of the first fusion reaction and requiring another proton to turn the beryllium 7 intermediate into two helium 4). Helium 3 plus proton apparently doesn't happen much (otherwise helium 3 wouldn't stick around) and deuterium plus deuterium (the only other four proton fusion of interest) is extremely rare (like many orders of magnitude rarer than anything else mentioned so far).
(Score: 2) by JoeMerchant on Friday February 24, @06:15PM
>It's actually six protons or four protons plus a helium nuclei (alpha particle).
Chat GPT can't code for shit, either. It will make stuff up as examples that look good, but don't compile because it's assuming that libraries contain functions that they don't.
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