In astronomical terms, what is a conjunction?

Question

What device, a tool for studying astronomical phenomena, uses the fact that when a material is heated to incandescence it emits light that is characteristic of the atomic makeup of the material?

Answer 1

An apparent meeting or passing of two or more bodies in space
Conjunction, in astronomy, is an apparent phenomenon caused by the observer's perspective. It occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, usually as observed from Earth.