One night three months ago, Rosa Castro finished her dinner, opened her laptop, and uncovered a novel object that was neither planet nor star. Therapist by day and amateur astronomer by night, Castro joined the NASA-funded Backyard Worlds: Planet 9 citizen science project when it began in February — not knowing she would become one of four volunteers to help identify the project’s first brown dwarf, formally known as WISEA J110125.95+540052.8.