Ciro Santilli likes to learn astronomy a bit like he learns geography: go down some lists of "stuff that seems most relevant in some criteria to us!", possibly at different size scales e.g.:
We can't see individual stars outside of the Milky Way: https://earthsky.org/tonight/can-we-see-stars-outside-our-milky-way-galaxy/.
The Large Magellanic Cloud stands out as the brightest thing we can see from outside the Milky Way by far!
A fancy name for astronomy ;-)
Surely You're Joking, Mr. Feynman chapter An Offer You Must Refuse (a play on words on The Godfather (1972)) has an interesting historical mention from the early 1950s while at Caltech:
The next day, I had the greatest luck in making a decision. God must have set it up to help me decide. I was walking to my office, and a guy came running up to me and said, "Hey, Feynman! Did you hear what happened? Baade found that there are two different populations of stars! All the measurements we had been making of the distances to the galaxies had been based on Cephid variables of one type, but there's another type, so the universe is twice, or three, or even four times as old as we thought!"I knew the problem. In those days, the earth appeared to be older than the universe. The earth was four and a half billion, and the universe was only a couple, or three billion years old. It was a great puzzle. And this discovery resolved all that: The universe was now demonstrably older than was previously thought. And I got this information right away - the guy came running up to me to tell me all this.
The existence of this is quite mind blowing.
It is basically perfectly black-body radiation, with a very faintly by measurable anisotropy (slightly less or slightly more some regions) due to quantum fluctuations of the early universe.
The ansiotropies of CMB are likely the best astronomical compass we will ever have, as it is the thing with the least proper motion.
What an awesome list the dude compiled. Contains many of the features we care the most about of the sky, since of course, apparent magnitude is a big determinant of that.
Cover up the entire sky in a compatible way with the traditional constellations. They are also very square, the boundaries consisting only of vertical and horizontal lines on the sphere.
Basically a mini-Constellation.
Some major ones:https://noirlab.edu/public/images/noao-m49/?nocache=true also lists: M58, M59, M60, M61, M84, M85, M86, M87, M88, M89, M90, M91, M98, M99, and M100 so lots of large and easily observable galaxies in the area.
Many Andromeda satellite galaxies are simply numbered Andromeda II, Andromeda III and so on.
As described on Wikipedia, the observational history of Andromeda is fascinating. Little by little, people noticed that it had a different nature to many other objects observed on the sky, and the hypothesis that there are other galaxies like ours grew in force.
Part of our fascination with Andromeda is due to how similar in size and shape and close it is to the Milky Way.
It is clearly the only thing so large and so close.
Andromeda is, without a doubt, our sister galaxy.
Another important one to know is the
It is so close that we can notice its proper motion, and its distance to us will vary significantly across a few tens of thousands of years!
Some notable ones:
As usual, blame the Russians.
The term "visible life" refers to multicellular from before people knew there was life in the proterozoic.
It ends together with the pleistocene.
Agriculture is not the official definition of the age. But it is good enough. Likely related to the official end of glaciations thing.
No life, earth too hot, until formation of water.
Made up mosty of calcium carbonate.
Not done yet as of 2020! Will be done one day for sure.
The first planet not known since anitquity.
Quite cool how it was discoverd by the perturbation of Uranus' orbit.