Cepheid variable stars
A Cepheid variable is a type of star that pulsates radially, changing in both size and temperature as it grows brighter and dimmer in a regular cycle. These pulsations typically occur over periods of 1–100 days. Cepheids are crucial for astronomy because there is a direct relationship between how luminous a Cepheid is and how long its pulsation cycle lasts. By measuring the pulsation period, astronomers can determine the star's true brightness, and by comparing that to how bright it appears from Earth, they can calculate its distance. This discovery by Henrietta Leavitt in 1908 became a fundamental tool for measuring distances to other galaxies and helped Edwin Hubble prove that distant galaxies exist beyond our Milky Way, ultimately leading to our understanding that the universe is expanding.
Sources
- en.wikipedia.org: “A Cepheid variable is a type of variable star that pulsates radially, varying in both diameter and temperature.”
- en.wikipedia.org: “It changes in brightness, with a well-defined stable period (typically 1–100 days) and amplitude.”
- en.wikipedia.org: “Cepheids are important cosmic benchmarks for scaling galactic and extragalactic distances; a strong direct relationship exists between a Cepheid variable's luminosity and its pulsation period.”
- en.wikipedia.org: “This characteristic of classical Cepheids was discovered in 1908 by Henrietta Swan Leavitt when she studied thousands of variable stars in the Magellanic Clouds.”
- en.wikipedia.org: “In 1924, Edwin Hubble established the distance to classical Cepheid variables in the Andromeda Galaxy, until then known as the "Andromeda Nebula" and showed that those variables were not members of the Milky Way.”