hip-64906

Its story

21 Canum Venaticorum —also known as BK CVn— is a silicon star of the Alpha-2 Canum Venaticorum class: a peculiar variable type whose brightness shifts slightly as chemical patches rotate across its surface. Its variability —just 0.04 magnitudes over 18.4 hours— was discovered in 1984 by Juraj Zverko. A blue subgiant 277 light-years away with nearly three solar masses, it spins fast and shows how a star's magnetic imperfections can paradoxically become its most recognisable signature.