The title somewhat sounds like the image was taken in some random night but that is probably many years of data contributing to that image. They have a similar image [1] from more than 20 years of data. The article is from 2010, they started collecting data in 1996, depending on how much the image predates the article this might be up to 14 years worth of data. According to this paper [2] they expect to observe about ten solar neutrinos per day.
News to me too. I found a site. The answer is longish but begins this way:
A photon of light can take 100,000 years from the core of the Sun to get to the surface.
the density of the core is incredibly high — 150 times greater than water. So all the atoms are jammed up against each other.
Let's look at a pair of hydrogen atoms that have fused together to make a helium atom — and released a lot of energy, in the form of gamma rays. The gamma rays can travel only a few millimeters, before they're absorbed by an atom, and then re-radiated.
Over and over again, they are absorbed, and then re-radiated. So, very slowly, the gamma-rays that have been generated by nuclear burning work their way up from the dense core.
After thousands upon thousands of years, they make their way into what's called the 'radiative zone'. The radiative zone is huge — it stretches up from the outer core (that's at the 24 per cent mark) to about 70 per cent of the way to the surface.
It's called the radiative zone, because here, energy travels by radiation. The gamma rays are still being absorbed and re-radiated, but each time they're being re-radiated at longer wavelengths.They gradually get converted from gamma rays down to visible light.
I'm no physicist but this is weird to me; it implies that the sun's light originates at the core, instead of for example the glowing plasma at the surface. Or is it in addition to? That is, photons originate all throughout the mass of the sun, some of which bounce around for 100K years before coming out at the surface?
Yes it is both, photons are emitted everywhere in the sun. The photons emitted on the surface will come directly to us, but those emitted in the core will take thousands of years to get out.
But... if the process of "taking thousands of years to get out" involves getting absorbed and re-emitted a whole bunch of times, doesn't that mean it's not the same photon any more? So technically only the surface photons come directly to us?
yeah this is simplified a lot. What it truly means is that some of the energy emitted at the core takes thousands of years to get "out". The energy is converted multiple times, getting released as photons, then absorbed again, etc.
There’s a lot of stuff in the photon’s path “out”. from NASA[0]:
> Once a photon of light is born, it travels at a speed of 300,000 km/sec until it collides with a charged particle and is diverted in another direction. Because the density of the sun decreases by tens of thousands of times from its lead-dense core to its tenuous photosphere, the typical distance a photon can travel between charged particles changes from 0.01 cm at the core to 0.3 cm near the surface.
I’ve always been bothered by this reasoning. Wouldn’t it be a different photon since a photon in the core is being absorbed and reemitted many many times through charged particles? So while the reaction that is providing the power is a long distance from the surface, the photons you’re seeing are from the surface and give you no information other than what’s happening on the surface of the sun.
Also, has anyone though of how mind-numbingly wasteful solar fusion is? All that energy, and only a tiny fraction makes it to Earth with the rest getting dumped wastefully into space. Seems like an area that's ripe for disruption by a startup.
> Also, has anyone though of how mind-numbingly wasteful solar fusion is? All that energy, and only a tiny fraction makes it to Earth with the rest getting dumped wastefully into space. Seems like an area that's ripe for disruption by a startup.
That energy can be captured by a Dyson sphere:
> A Dyson sphere is a hypothetical megastructure that encompasses a star and captures a large percentage of its solar power output
>> Also, has anyone though of how mind-numbingly wasteful solar fusion is? All that energy, and only a tiny fraction makes it to Earth with the rest getting dumped wastefully into space. Seems like an area that's ripe for disruption by a startup.
> EEVblog 1637: Solar Freakin' Space Mirrors! - Reflect Orbital DEBUNKED [1]
That seems like a kludge because space mirrors are still going leave lots of energy dumped wastefully into space. But even if we could collect all the Sun's energy, there's no way we could use it all and it'd just fry the planet.
The kind of disruption I was thinking about was re-engineering the Sun so it only produces the energy the Earth needs. There are great monetization opportunities, because the technology would almost certainly allow for charging subscription fees for sunlight.
Deep down in the sun photons are absorbed almost as soon as they are created. In a sense the photons at the surface of the sun are the result of nuclear reactions thousands of years back. However neutrinos escape pretty fast and so can be used to gauge the status of nuclear reactions now.
Light emitted from the core of the sun is re-absorbed by the stellar plasma/matter many, many times before the energy finally, as the result of a random walk, is expressed close enough to the surface that its mean free path is on the order of the distance to Earth. However, since neutrinos are not affected by the charged matter, they are free to leave far more easily and thus, rather than a random walk lasting thousands of years, they simply "flit" right through the intervening material until they hit our detectors (extremely rarely).
The issue a lot of people have with this is that they think of the Sun as a big ball of fire, where the activity is happening on the surface of a big flammable mass.
They Might Be Giants has two songs about this exact misunderstanding.
In the first song, "Why Does The Sun Shine?" they sing (incorrectly):
>The Sun is a Mass of Incandescent Gas
>A gigantic nuclear furnace.
In their next song, "Why Does The Sun Really Shine?", they sing:
>The sun is a miasma
>Of incandescent plasma
>The sun's not simply made out of gas
>No, no, no
>The sun is a quagmire
>It's not made of fire
>Forget what you've been told in the past
Most of the photos that create sunlight are born at the core of the Sun. The Sun is one gigantic nuclear reaction. The activity isn't at the surface, there's hot energetic plasma (and other exotic states of matter) all the way down to the core.
Photons from the core have to make their way through a unfathomably massive sea of matter and energy before they can escape into space. From core to surface, a photon takes about 30,000 years to make it's way through all of that.
What's crazy is that our Sun is an orange dwarf star which is quite small compared to some of the other stars in our Galaxy. A photon born in a hypergiant star with much greater mass and core density could take millions of years to escape.
But a single photon isn’t making its way ever from the core to the surface is it? Wouldn’t all the photons in the core be absorbed by all the charged particles and reemitted as new photons and thus the photons you see are photons being emitted from the surface?
Quantum theory makes it extremely [understated!] unlikely that a photon emitted from the surface of the sun originated in the core. Photons blink into/out of existence for all practical purposes instantaneously. Otherwise Josephson junctions, quantum tunneling and modern electronics would be DOA.
[1] https://www-sk.icrr.u-tokyo.ac.jp/en/sk/about/research/
[2] https://link.springer.com/article/10.1140/epjc/s10052-019-67...