And now apparently China has one flying over it!

Heat-seeking is the old tech. The current ones also have radar and communications with the launching plane.

The sidewinder might have locked on to the reflection of the sun on a balloon. But kind of sus that the planes avionics were impaired by the object but the missile avionics managed a kill. I've posted some links to two common types of air-air missiles.

https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104557/aim-9-sidewinder/

AIM-9X is the newest variant of Sidewinder. The AIM-9X has the same rocket motor and warhead as the AIM-9M. Major physical changes from previous versions of the missile include fixed forward canards, and smaller fins designed to increase flight performance. The guidance section has been redesigned and features an imaging infrared seeker. The propulsion section now incorporates a jet-vane steering system for enhanced post-launch agility. The X model is also compatible with the Joint Helmet-Mounted Cueing System, which is designed for ease of target acquisition and decreased aircrew workload.

https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104576/aim-120-amraam/

AMRAAM is a follow-on to the AIM-7 Sparrow missile series. The missile is faster, smaller and lighter, and has improved capabilities against low-altitude targets. It incorporates active radar with an inertial reference unit and micro-computer system, which makes the missile less dependent upon the fire-control system of the aircraft. Once the missile closes on a target, its active radar guides it to intercept. This enables the pilot to aim and fire several missiles simultaneously at multiple targets. The pilot may then perform evasive maneuvers while the missiles guide themselves to their targets.