How big is universe? Pulsing stars could help solve mystery
Recent research indicates that the study of pulsating Cepheid variable stars, such as RS Puppis, could provide a new method for measuring the universe. These stars undergo a cycle of changing brightness over a six-week period, displaying specific luminosity patterns. The Velocities of Cepheids (VELOCE) project utilized advanced spectrography observations, to study hundreds of Cepheids with remarkable precision.
The role of the VELOCE project in understanding Cepheid stars
The VELOCE project gathered data from 2010 to 2022, employing the Swiss Euler telescope and the Flemish Mercator telescope. High-resolution spectrographs on both telescopes, enabled astronomers to separate as well as measure wavelengths of starlight, and also capture shifts in brightness. Astrophysicist Richard I. Anderson, the lead author of the study from the Swiss Federal Institute of Technology Lausanne (EPFL), stressed the importance of grasping the nature and physics of Cepheids.
Radial velocity measurements uncover unexpected variations
The team used Doppler effect to measure the velocity at which stars expand and contract along the telescopes' line of sight, a phenomenon known as radial velocity. Giordano Viviani, a Ph.D. student at EPFL and co-author of the study said, "The pulsations lead to changes in the line-of-sight velocity of up to 70km per second, or about 250,000km per hour." The VELOCE team collected over 18,000 highly accurate radial velocity measurements of 258 Cepheids, revealing unexpected variations in their pulsations.
New data to enhance understanding of Cepheid stars
The VELOCE team identified several Cepheid stars belonging to a binary system where two stars orbit each other. Henryka Netzel, a co-author of the study, stated, "This suggests that there are more intricate processes occurring within these stars, such as interactions between different layers of the star, or additional (non-radial) pulsation signals." This data will assist astronomers in determining whether changes seen in the stars' brightness are due to their individual structure or because of potential interactions with companion stars.
