why can we not see a comet when it is far away from the sun
We cannot see a comet when it is far away from the Sun because comets are mainly made up of ice and dust. When a comet approaches the vicinity of the Sun, the heat causes the ice to evaporate, creating a glowing coma around the nucleus. This glowing coma, along with the tail formed by the solar wind, reflects sunlight and becomes visible from Earth. However, when a comet is far away from the Sun, it is too dim to be seen with the naked eye because there is not enough sunlight to reflect and make it visible.
To observe a comet when it is far away, astronomers often use powerful telescopes and sensitive instruments that can detect faint light. They track the position and movement of comets to predict when they will come closer to the Sun and become visible from Earth. Additionally, professional astronomers and space agencies like NASA deploy spacecraft to study and capture close-up images of comets as they journey through the solar system.