Sensor beam
A sensor beam was a focused beam of particles produced by a starship's sensors. At the point of impact, the beam would interact with the subject, thus revealing information about it. 

In 2265, Lieutenant Commander Spock activated this beam as the  approached the galactic barrier. As the beam passed through the barrier, the sensors reported that it didn't exist. Density, radiation, and energy had negative readings. After passing through this barrier, the sensor beam was deactivated. ()
Sensor technology