Simplify the following text for a Grade 9 native English-speaking person.
Original: A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and , as such , forms part of the Hubble sequence .
Simplified: The spiral galaxy as a type was first described by Edwin Hubble in his 1936 work The Realm of the Nebulae .