To Touch the Sun · 10:17pm Aug 14th, 2019
Georg’s latest story: The Golden Alicorn of the Sun is a brilliant surreal scific adventure describing a voyage to touch down on the sun itself. It was inspired by the equally crazy 1953 short story by Ray Bradbury.
The idea of flying a rocket to the sun, touching the surface, and scoping a sample of solar matter to take home is pure fiction. But is the idea even conceivable to a modern physicist or engineer?
We can appreciate the motivation. An astronomer might joking dismiss the sun as merely one of hundreds of billions of stars in a galaxy, which is only one of hundreds of billions in the universe. But this one star has played a key role in almost everything of interest on the Earth. We really want to understand what it is made of, how it works, and how it, and the planets around it formed.
It is believed the outer layer of the sun has the same composition as the early solar nebula from which the planets formed. By measuring the precise composition different nuclear isotopes, and comparing these to measurements of samples on Earth or other planets, we can help to construct a model of how the solar system formed.
To a human (or pony) eye, the sun is best viewed from a distance of at least 150 million kilometres, on a planet with an atmosphere to absorb harmful radiation, and a magnetic field to deflect the charged particles it throws at us in the solar wind. Even then you should never look directly at the sun. However our eyes only see a narrow range of wavelengths. If we build a robot with eyes to see the ultra-violet spectrum, and send it on a rocket to fly above the atmosphere and you can see the sun in further glory. This was done by the SOHO satellite, and more recently the Solar Dynamics Observatory, which took these amazing images of our star.
Looking at the sun, we see physical processes on scales we can’t hope to reproduce on Earth. The beautiful patterns in the sun’s atmosphere are shaped by magnetohydrodynamics. The magnetic field directs the movement of the particles in the plasma so we are literally looking at magnetic field lines. The movement of charged particles will in turn shape the magnetic field. We can see surface activity including coronal mass ejections and solar flares. Particles from these storms can reach the Earth leading to what we call space weather, producing beautiful arora, but potentially disrupting power and communication systems.
But could we build a probe to fly to and touch the sun? That is the stated goal of the Parker Solar Probe, launched last year, which will pass within 6.2 million kilometres. Not quite at the solar radius (measured by SOHO as just under 700,000 km) but still prettty impressive. Mercury, the closest planet, orbits at an average of 58 million kilometres. The probe has a 10cm thick heat shield to protect it from the expected 1,400 °C temperature. Perhaps the data from the probe will help answer one of the big questions of solar research: why is the corona surrounding the sun hundreds of times hotter than its surface?
This probe will not return a sample to the Earth. The closest to that has been the Genesis sample-return probe, which collected samples of particles from the solar wind and returned a capsule to Earth. Unfortunately the samples were contaminated when it crash landed in Utah in 2004, yet it was still possible to extract interesting results, including the ratio of the abundance of different nuclear isoptopes of light elements including neon, argon, nitrogen, and oxygen. This has provided key pieces which are helping to fit together the puzzle of the origin of our world.
Theoretically a Clockwork Hafnium OxyGraphene probe could reach the surface before sublimating, but if it could be made reflective it would be able to impact?
Then again, if you wanted an impactor, you just needed a snowball big enough?
Pushing Ice. but thats another story.
But this story, is about how to write a Story, not how to do the job.
I actually got to see the remains of the genesis probe in person as part of a school trip. One of our guides basically looked at the other, shrugged, and said it was probably okay to take us through the room where it was laid out on a table.
Well hey, that’s really cool.
It astounds me that only 10cm of heat shield hold up to 1,400 °C. Like, dang.
The concept of 'surface' with the sun is somewhat nebulous. Something inside my rational brain hiccuped with the original Bradbury story where the ship had a giant hand with a cup that dipped up some of the surface.
Let me explain (in my own fumble-fingered way)
The Earth has a surface. Actually, several. The gas atmosphere extends out, thinner and thinner, until the solar wind pushes up against it and flows around the magnetic lines of force. So dipping a 'cup' of Earth's atmosphere is questionable, without a really huge cup. There's a liquid surface at ocean level, and an irregular solid surface further down (for 4/5th of the planet at least). So if an alien ship were to scoop a bit of the Earth's 'surface' they would get big rocks and mud.
So let's look at a Jovian. No, let's look at a Superjovian. They're more fun. Mesklin from Hal Clement's Mission of Gravity 600g at the poles, 3g at the equator. Vast seas of methane that boil off when the planet makes its closest approach to the sun. Intelligent life forms that look like 1/3meter centipedes. Ice that comes with numbers attached (Ice-2, Ice-3, Ice-4...) Surface? Depends on the time of year, but you better land at the equator to get your cup of liquid methane or you're going to get crushed.
Now the sun. A mere 28g compared to Mesklin, but that's because the 'surface' is made up of hydrogen plasma at 5,700K (Water boils at 370K, iron melts at 1,800K, Tungsten at 3,600K, ty Wikipedia) so it's bloated like a balloon. In particular, a balloon without the rubber. Gravity holds it together just like the... well, not *quite* like the Earth's atmosphere, but you get the picture, only with huge arcs of plasma that could swallow the Earth without even noticing, flung up into the 'sky' by magnetic lines of force that would likewise fry a ship like a microwave with induced current. Yeah, I knew all that as a kid when I read the story. I was a weird kid. FYI: Mission of Gravity was written in 1953, the same year The Golden Apples of the Sun was published. A golden era.
I haven't ready Bradbury's story, but I've read another not quite as crazy-sounding story about an expedition into the sun: David Brin's Sundiver. He isn't that specific about all the technology in his character's ship, but it's cooled by a powerful "Refrigerator Laser".
(It's also a very fun book with inventive worldbuilding, if you're interested.)
5106154
I have no idea what a Hafnium OxyGraphene probe is. I don't think any solid material could survive for long on the 6000 degree surface of the sun.
5106264
That's very cool. Where was that?
5106299
NASA does have experience with carbon composite heat shields for the shuttle, and other probes. The design sounds like an interesting physics exercise - I'll have to see if I can adapt it for my students.
5106335
The solar radius does have a precise definition as it is used as a standard unit to judge the size of stars. You measure it by timing the transit of planets. And indeed, when you look closely at the images from SDO, you see the surface is not such a stable phase boundary as the Earth's surface. The Earth is already in the Sun's atmosphere. To collect its sample, Genesis only had to get away from the Earth's magnetic field.
Meskin was a fun game, playing around with the physics to see what might be possible. Another great classic story.
5106415
I'm not sure a "refrigerator laser" is possible, but that does sound like a fun story.
5106435
Being a physics major at my school in Colorado included a mini summer semester where the physics students got to take tours of a couple local aerospace companies (and in our case see the genesis probe), run some high vacuum experiments, learn LaTex and Mathematica, play with thin film deposition... that sort of thing. It was a blast, but the regular semester classes that followed were incredibly grueling.
They should send the probe at night.
5106538 In Equestria, depending on your model of its physics, that might be a valid suggestion.
5106538
How would they see where they were going?
5106966
Ooh, good point. I hadn't thought of that.
5106966 5107005 Headlights, duh.