There's no hard evidence that it was an actual physical (massive) object. There is evidence (mostly testimonial) that it was visible to radar, infrared and vis

There's no hard evidence that it was an actual physical (massive) object. There is evidence (mostly testimonial) that it was visible to radar, infrared and visible light sensors and the human eye. Is there anything that has those characteristics and is not an object ? Yes, plasma phenomena are one example.