The size of astronomical objects are so large and the distances are so great that they quickly exceed human comprehension.
Inner planets of the solar system. These planets are the most dense in the solar system and, with the exception of Pluto, closest to the sun.
Our sun is a middle aged average sized star that has been around for about 5 billion years. it will use up all its fuel in another 4.5 Billion years.
The size of our sun (smallest sphere in the lower left) compared to other nearby stars:
Some of the still larger stars. Note that there life span is extremely short (millions of years) compared to our sun because they must burn hydrogen fuel at a prodigious rate to to balance against the incredibly strong gravitational force trying to compact the star because of their huge masses.