Transient astronomy is the study of phenomena that lasts for a limited amount of time, e.g., compared to a human lifetime, such as when the appearance of an object changes, perhaps temporarily. The term transient astronomical event is used for such phenomena. Examples:
The challenge is to know when and where to start looking and catching it early to observe as much of the phenomena as possible. Surveys are now carried out to look for changes, rechecking the same area and looking for changes. Examples:
When a change is discovered, other telescopes can be used to follow up in the direction of the changes.