A Star Cluster is a cluster of stars found within a galaxy or the intergalactic medium, and they don't usually have supermassive black hole centers or spiral arms. Star clusters contain around a thousand stars, compared to the Milky Way's 300 billion stars. In short, a galaxy is not classified as a star cluster.
A galaxy.
It is called R136a1. It is in a star cluster in a nearby galaxy.
A nebula galaxy does not exist.
Universe, Cluster, Galaxy, Star, Planet NB: Some stars are smaller than planets.
Eta Carinae.
That is called a globular cluster.
Could be a Star Cluster or a galaxy.
We will never know the largest star in the Universe. The biggest star in our Galaxy is VY Canis Majoris.
A solar system is smaller. There are billions of solar systems in a single galaxy.Each star is a solar system. (some have planets, some don't)When you look at the sky at night, every star is a solar system and all of them are part of the Milky Way galaxy.A galaxy cluster is a group of galaxies.
A globular cluster contains hundreds of thousands of starsAn open cluster contain less than a few hundred stars.A galaxy contains billions of stars.
Constellation or "asterism". The difference is that "constellations" are officially recognized by the International Astronomical Union, while an "asterism" is any other pattern or grouping of stars.
It's impossible to be precise, but I would guess all of them. The galaxy is so large.