麻豆传媒

[Excerpt from STScI-PR2011-15] - Though the universe is filled with billions upon billions of stars, NASA's Hubble Space Telescope has been trained on a single variable star that in 1923 altered the course of modern astronomy. The star goes by the inauspicious name of Hubble variable number one, or V1, and resides two million light-years away in the outer regions of the neighboring Andromeda galaxy, or M31. V1 is a special class of pulsating star called a Cepheid variable that can be used to make reliable measurements of large cosmic distances. The star helped Edwin Hubble show that Andromeda lies beyond our galaxy. Prior to the discovery of V1 many astronomers, including Harlow Shapley, thought spiral nebulae, such as Andromeda, were part of our Milky Way galaxy. Others weren't so sure. But it took Edwin Hubble's discovery just a few years later to settle the debate. In commemoration of this landmark observation, astronomers with the Space Telescope Science Institute's Hubble Heritage Project partnered with the American Association of Variable Star Observers (AAVSO) to study the star. AAVSO observers followed V1 for six months, producing a plot, or light curve, of the rhythmic rise and fall of the star's light. Based on this data, the Hubble Heritage team scheduled Hubble telescope time to capture Wide Field Camera 3 images of the star at its dimmest and brightest light levels. The observations were presented on May 23, 2011, at the meeting of the American Astronomical Society in Boston, Mass. Edwin Hubble's observations of V1 became the critical first step in uncovering a larger, grander universe. He went on to measure the distances to many galaxies beyond the Milky Way by finding Cepheid variables within them. The velocities of those galaxies, in turn, allowed him to determine that the universe is expanding. The space telescope that bears his namesake continues using Cepheids to refine the expansion rate of the universe and probe galaxies far beyond Edwin Hubble's reach.