The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.
The Centre de Données astronomiques de Strasbourg (CDS; English translation: Strasbourg Astronomical Data Center) is a data hub which collects and distributes astronomical information.
A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices.
Hydrogen is a chemical element with symbol H and atomic number 1.
Perseus is a constellation in the northern sky, being named after the Greek mythological hero Perseus.
A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses) in a late phase of stellar evolution.
A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.