The surface temperature of a star can be estimated based on the stars?

One way in which a scientist can determine the surface temperature of a star is by:

Step 1: launching a rocket to space

Step 2: Ensure they have a thermometer with them.

Note: The thermometer must be at least 20m long so as to reach the star whilst the scientist remain in the rocket

Step 3: After having landed on planet Mars, the scientists open the shuttle of the rocket

Note: they must be tied to the rocket so they don't fly out and get stranded/lost in outer space ( there safety must be ensured so that they do not get abducted by aliens)

Step 4: The scientists hold out the thermometer towards the nearest star and measure it's temperature in degrees Celsius