FEBRUARY 2019 OBSERVING Celestial Calendar by S. N. Johnson-Roehr Echoes from a Variable Star RS Puppis continues to delight astronomers more than 120 years after its true nature was discovered. The thick cloak of nebulosity that surrounds RS Puppis makes the star unique among Cepheid variables. These dust clouds reveal "light echoes" of the star's pulsations. The echoes have to travel farther, so they arrive at Earth later than does the starlight. 48 FE B RUA RY 2 019 * SK Y & TELESCOPE