Final answer:
The object in question is a slide armed indicator on an airplane door, illuminating white to show that the emergency slide is armed and will deploy if the door opens.
Step-by-step explanation:
The object being described in the question seems to be a safety feature found on airplanes, specifically an indicator light that is part of an emergency exit. The object in question is a slide armed indicator on an airplane door, illuminating white to show that the emergency slide is armed and will deploy if the door opens. This light is known as a slide armed indicator.
It's located in the window of an aircraft's door and illuminates white to indicate that the emergency slide has been armed. This means that if the door were to open, the slide would automatically deploy to aid in an emergency evacuation. As such, it is a critical component of an aircraft's safety systems. It serves as a visual cue to the flight attendants and passengers, communicating the status of the emergency slide.