This page contains an index of all of my Yinglet Space Facts posts so far, edited for display in a non-blog format.
Spherical Cows
Conventions
Spirals
Astrogation
Universal Structure
Shell Burning
As well as some miscellaneous information that didn't get a big writeup (yet):
As stars die, they fuse heavier and heavier elements. Because the number of protons in the core is relatively constant, there is less and less of any given element as it goes up the chain. Silicon burning happens last, and it only takes two weeks! It's rare that anything in space happens on a "normal" timescale.
The deal with iron being a starkiller is that the star needs to be constantly producing energy to prevent gravitational collapse. The thing about supernovae is that there is just an ABSURD amount of energy present, and the vast majority of it is pure excess. Most of this energy comes from the gravitational potential energy of the stellar atmosphere being converted into thermal and kinetic energy during the collapse! With all this extra energy around, the energy-consuming fusion pathways have absolutely no issues finding the energy they need to fuse all the way to uranium.
Most radio receivers (the bit that actually detects radiation) are effectively single "pixel". They're sampling a specific region of the sky, and output how bright that region is. This region is called the "beam" and it's usually a circle. HOWEVER. Many telescopes have multiple beams! This is usually from using multiple receivers slightly offset in the telescope and doing some extremely fancy math, it's really neat. Parkes in Australia has like... 9 beams? i think? CHIME in canada has 1024 beams and that's only part of why it's my favorite instrument. We can still generate images zhough! We map regions by sweeping the beam over a region and keeping track of how bright the beam is across the path. By doing enough sweeps and slowly filling out a rectangle or circle or what have you, and doing some more fancy math on the result, we can put togezher a "black and white" image of the region. By doing this for multiple frequencies, and coloring each frequency map a different color instead of white, we can make very pretty false color images of zhe radio sky.
Regarding possible alien visible wavelengths:
Stars generally glow as what we call "black bodies" - a physics term that just means "hot things glow just because they're hot". In practice, for the range of star temperatures you'll get a peak output somewhere between near IR (with dim output in optical) all the way to UV (with extremely strong output in optical) but every star produces pretty much everything in this range. What's more interesting to consider with possible alien vision is atmosphere composition - we see optical wavelengths because the atmosphere is relatively transparent to them, and so I'd imagine somezhing similar to whatever planet the aliens evolved on. Most matter is transparent to radio waves, so i wouldn't expect vision in that range just because it wouldn't be terribly helpful. Microwaves, maybe. Infrared almost definitely not if their atmosphere is anything like ours, though nearIR and near UV is very possible.
Interferometry requires an absurd amount of data and very very precise timing! It's cool and can be used with any telescopes that can observe the same wavelengths. The black hole pictures telescope, the EHT, has to physically send entire racks of hard drives across the world for data combination because anything over the internet would be far too slow.
Regarding killing stars via throwing iron at them: (speculative)
It's possible that, since iron would sink directly to the hottest part of the core, you could maybe push fusible material far enough out of the core such that it isn't hot enough for fusion anymore? Though my gut says almost certainly not. what's more likely to happen is forced shell burning, it wouldn't destabilize but also it would turn the sun into a giant of some description. After a certain point you'd just instigate an immediate collapse black hole which would certainly be exciting!
Pulsar timing has historically been done using python libraries, TEMPO and TEMPO2. Currently in development (and my preferred library) is a replacement known as PINT. One of the reasons I like it so much: PINT stands for "PINT Is Not Tempo3"
