Rowling posted the new writing on the Pottermore website, giving an insight into the character who resembles Shirley Bassey in 'both looks and style'.
The Harry Potter author offers a detailed backstory to the 'Singing Sorceress', who is only briefly mentioned in the books, revealing her to have been a member of the Hogwarts house Gryffindor, Welsh and someone who frequently appeared with a chorus of backing banshees.
She also discusses her inspiration for the obscure character, saying the name Celestina came from an Amnesty International colleague.
As well as the biography, an accompanying music video including original lyrics was published entitled "You Stole My Cauldron but You Can't Have My Heart", the first song to be posted on the Pottermore website.
The addition to the popular Pottermore website, first launched in 2011, comes after other recent elaborations on the Harry Potter universe from J.K. Rowling including the previous "Dumbledore's Army Reunites", a 1500-word piece focusing on an aging 34-year-old Harry.