An unknown celestial body is called an unidentified object in the realm of astronomy and space science. It refers to a cosmic object that hasn't been previously observed or recognized by astronomers, and cannot be associated with any known celestial bodies or astrophysical phenomena.

There are countless unidentified celestial objects in the vast expanse of the universe, and astronomers are constantly striving to discover and categorize these mysterious objects. These could be a new kind of asteroid, a distant planet, a comet, or an entirely new class of celestial body that defies current scientific understanding.

The discovery of any new celestial body provides valuable insights into the workings of the universe and offers new clues for astronomers to further our understanding of the cosmos. However, identifying and categorizing unknown bodies is a challenging task that requires a great deal of expertise, advanced technology, and a deep understanding of astronomy and astrophysics.

Observations of unidentified objects are typically conducted using various ground-based and space-based telescopes, as well as specialized instruments like spectrometers and imagers. The data gathered from these observations is analyzed meticulously to determine the properties, composition, and overall characteristics of the object in question.

For instance, spectroscopic observations enable astronomers to determine the chemical composition of an object by analyzing the light it emits or absorbs, which can provide valuable clues about its origins and evolution. Similarly, imaging techniques can reveal detailed pictures of the object that may contain telltale signs of its nature and history.

Identification of an unknown celestial body requires careful analysis of the gathered data and correlation with existing astronomical knowledge. This process can take months or even years, and in many cases, may remain unresolved indefinitely due to the object's distant location, elusive nature, or unusual properties that defy current scientific understanding.

In conclusion, the study of unidentified celestial objects is an exciting and ongoing endeavor that continues to unravel the mysteries of our vast universe. While the discovery of any new object poses challenges for astronomers, the potential rewards of expanding our understanding of the cosmos are invaluable.