19b

19b is a designation that can refer to several different entities. In astronomy, 19b is most commonly associated with exoplanets. For example, 55 Cancri b is also known as 19b, referring to a planet orbiting the star 55 Cancri. This particular exoplanet is a super-Earth, meaning it is more massive than Earth but less massive than ice giants like Uranus and Neptune. Its orbital period is very short, completing a revolution around its star in just under 2.8 days.

The designation may also appear in other contexts. In chemistry, it could potentially denote a specific isomer or compound, though this is less common without further context. In mathematics, "19b" might refer to a problem or theorem within a specific textbook or paper, such as problem 19b in a set of exercises. Without additional information, it is difficult to pinpoint the exact "19b" being referenced. However, the astronomical context, particularly the exoplanet 55 Cancri b, is a frequent and well-documented instance of this designation. It is important to consider the field or context in which "19b" is encountered to determine its precise meaning.