Categorize this text into one of the three topic.
The researchers studied planets outside our solar system and compared it to planets orbiting close to stars.
Topic: Astronomy/ Space Science
Complete the following task based on the instruction and optional input provided.### Instruction:
Categorize this text into one of the three topic.

### Input:
The researchers studied planets outside our solar system and compared it to planets orbiting close to stars.

### Output:
Topic: Astronomy/ Space Science