A century ago, Edwin Hubble's discovery of the variable star V1 in the Andromeda Galaxy revealed a vast, expanding universe, becoming a turning point in our understanding of the cosmos.

To mark the 100th anniversary of Edwin Hubble’s discovery of a Cepheid variable star, named V1, in the neighboring Andromeda galaxy, astronomers collaborated with the American Association of Variable Star Observers (AAVSO) to study the star. AAVSO observers followed V1 for six months, creating a graph—or light curve—that records the star’s periodic rise and fall in brightness. Based on this data, the Hubble Space Telescope was scheduled to observe the star during its faintest and brightest hours. Credit: NASA, ESA, Hubble Heritage Project (STScI, AURA), Robert Gendler.
To mark the 100th anniversary of the discovery of a Cepheid variable star, called V1, in the neighboring Andromeda galaxy by astronomer Edwin Hubble, astronomers collaborated with the American Society of Variable Star Observers (AAVSO) to study the star. The society's observers followed V1 for six months, recording its rhythmic rises and falls in starlight. Based on this data, the Hubble Space Telescope was designed to image the star at its brightest and dimmest moments.
A cosmic landmark that opened the realm of galaxies
At the beginning of the 20th century, astronomers were faced with a cosmic puzzle. The night sky was filled with more than 100 nebulous objects, classified in the late 18th century by the French astronomer Charles Messiaen. Most of them were identified as star clusters, nebulae, supernova remnants, or glowing gas clouds.
However, 40 of these objects were different. Their mysterious spiral shapes, called "spiral nebulae," were seen scattered across the sky. Astronomer Wes Stu Slipper revealed, through spectroscopy, that the light from these nebulae was red-shifted, suggesting that they were moving away from Earth.
Edwin Hubble hypothesized that spiral nebulae were not part of the Milky Way, but galaxies far away. To prove this, he needed precise distance measurements. He looked for Cepheid variable stars within these nebulae. Cepheids are unique stars that pulsate at a constant rate related to their intrinsic brightness, allowing astronomical distances to be calculated.
When Hubble measured the distance to a Cepheid star in the Andromeda galaxy, called V1, he found that it was more than 2 million light-years away—far beyond the boundaries of the Milky Way. This discovery settled a scientific debate: spiral nebulae are not just clouds of gas, but entire galaxies.
A discovery that changed the perception of the universe
Hubble's discovery changed humanity's perception of the universe. He proved that the Andromeda Galaxy is 20 times larger than the Milky Way, and discovered that galaxies are moving away from us in all directions. This meant that the universe is not eternal, but has a finite age and an expanding structure.
Hubble's discovery, a century ago, was a turning point in human knowledge, revealing a universe rich in distant galaxies. Over the next century, astronomers explored new frontiers with ever more advanced instruments. The Hubble Space Telescope, a major technological achievement, built on this legacy with precise measurements that revealed the age of the universe—13.8 billion years—through observations of distant Cepheid stars.
To humans, the most important star is undoubtedly our Sun. But another star, located deep in the Andromeda Galaxy, holds extraordinary significance. The star, located 2.2 million light-years away, is so faint that it is only 1/100,000th as bright as the faintest star visible to the naked eye.
However, a century ago, its discovery by Edwin Hubble opened humanity's eyes to the true size of the universe. The discovery showed that the Milky Way is just one galaxy among hundreds of billions of galaxies.
Today, NASA's Roman Space Telescope, named after Nancy Roman, the founding mother of space telescopes, is expected to provide new insights into dark energy and the structure of the universe through wide-ranging cosmic surveys. Hubble's discoveries a century ago were the beginning of a journey to understand the vast, expanding universe.
Today, the Hubble Space Telescope continues to illuminate the universe, revealing new discoveries about galaxies, stars, and cosmic phenomena, and deepening our understanding of the origin and structure of the universe. The legacy left by Edwin Hubble continues to shape the future of space exploration and inspire generations to come.
More of the topic in Hayadan: (Beresheet is the Hebrew name for the book of Genesis)
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The revelations explain that we are small and the world is big. So what?
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