Using Analog Stars to Decipher Early Galaxy Shapes
Observations show that galaxies formed shortly after the Big Bang display morphologies that differ markedly from the orderly spirals and ellipticals seen today. To uncover the reasons, a team from the University of Utah launched a survey that treats certain stars in nearby galaxies as stand‑ins for the first stellar populations.
The program, called the Treasury of Extremely Metal‑Poor O Stars (TEMPOS), measures the ultraviolet emission of these stars with the Cosmic Origins Spectrograph installed on the Hubble Space Telescope. The selected O‑type stars contain very low abundances of elements heavier than helium, reproducing the chemical environment of the early cosmos.
By analysing the UV spectra researchers derive the stars’ temperatures, metallicities and ionising photon fluxes. These properties determine how the surrounding interstellar gas is heated and shaped, which in turn influences the way galaxies assemble and evolve.
The data collected by TEMPOS are used to test theoretical models that aim to explain the clumpy, irregular appearances of high‑redshift galaxies. Future work will expand the sample and refine the link between stellar characteristics and galactic structure.