What term describes the moment when objects collide with the Earth's atmosphere?

The moment when objects collide with the Earth's atmosphere is referred to as a meteor. This term specifically describes the phenomenon that occurs when a meteoroid—a small rocky or metallic body in space—enters the Earth's atmosphere and produces a visible streak of light due to the intense heat generated by friction with the atmospheric gases. As the meteoroid travels at high speeds, it heats up and glows, creating what is commonly known as a "shooting star" or meteor.

In contrast, the term meteoroid denotes the object itself before it enters the atmosphere, while an asteroid is a much larger space rock that orbits the Sun, typically found in the asteroid belt between Mars and Jupiter. An astronaut refers to a human who is trained to travel and work in space, which does not pertain to the concept of objects entering the atmosphere. Each of these terms has distinct meanings related to space and atmospheric entry, making "meteor" the accurate choice for the question asked.