On January 15, 2025, scientists commemorated the centennial of Edwin Hubble's discovery of the Cepheid variable star V1 in the Andromeda galaxy, a pivotal moment in astronomy that reshaped humanity's understanding of the universe.
Located 2.2 million light-years away, V1 is 1/100,000th the brightness of the faintest star visible to the naked eye. Hubble's detection of this star using the 100-inch Hooker Telescope at Mount Wilson Observatory in California in 1923 provided the first evidence that the Milky Way is just one of countless galaxies.
Prior to Hubble's findings, many astronomers believed the Milky Way encompassed the entirety of the universe. Hubble's discovery proved otherwise, revealing the vastness of space and leading to the birth of modern cosmology. His observation indicated that the universe is expanding, a concept later formalized into Hubble-Lemaître's law, which correlates the distance of galaxies with their redshift.
Hubble's work laid the groundwork for the Hubble Space Telescope, which has since expanded our knowledge of the cosmos by observing galaxies over ten times farther than Hubble could. The telescope's findings have confirmed the universe's expansion is accelerating, a phenomenon attributed to dark energy.
As astronomers continue to explore the implications of Hubble's legacy, the upcoming NASA Roman Space Telescope aims to deepen our understanding of dark matter and dark energy, potentially refining measurements of the Hubble constant.
Hubble's initial observation of V1 opened a Pandora's box of cosmic mysteries, fundamentally altering our perception of humanity's place in the universe.