The Little Cepheid that Stopped

Cepheid Variable Star. Credit: Hubble Space Telescope

When Hubble first discovered a Cepheid variable in the galaxy M31, the universe grew. Previously, many astronomers had held that the fuzzy “spiral nebulae” were small patches of gas and dust within our own galaxy, but through the Period-Luminosity relationship which allowed him to determine the distance, Hubble demonstrated that these were “island universes”, or galaxies in their own right.

Soon after, Hubble (as well as other astronomers) began searching other fuzzy patches for Cepheids. Among them was the spiral galaxy M33 in which he discovered 35 Cepheids. Among them was V19 which had a 54.7 day period, an average magnitude of 19.59 ± 0.23 M_B, and an amplitude of 1.1 magnitudes. But according to recent work revealed at the recent American Astronomical Society meeting, V19 no longer seems to be pulsating as a Cepheid.