Old-Aged Primary Distance Indicators

Rachael L. Beaton, Giuseppe Bono, Vittorio Francesco Braga, Massimo Dall’Ora, Giuliana Fiorentino, In Sung Jang, Clara E. Martínez-Vázquez, Noriyuki Matsunaga, Matteo Monelli, Jillian R. Neeley, Maurizio Salaris

Research output: Contribution to journalReview articlepeer-review

39 Citations (Scopus)


Old-aged stellar distance indicators are present in all Galactic structures (halo, bulge, disk) and in galaxies of all Hubble types and, thus, are immensely powerful tools for understanding our Universe. Here we present a comprehensive review for three primary standard candles from Population II: (i) RR Lyrae type variables (RRL), (ii) type II Cepheid variables (T2C), and (iii) the tip of the red giant branch (TRGB). The discovery and use of these distance indicators is placed in historical context before describing their theoretical foundations and demonstrating their observational applications across multiple wavelengths. The methods used to establish the absolute scale for each standard candle is described with a discussion of the observational systematics. We conclude by looking forward to the suite of new observational facilities anticipated over the next decade; these have both a broader wavelength coverage and larger apertures than current facilities. We anticipate future advancements in our theoretical understanding and observational application of these stellar populations as they apply to the Galactic and extragalactic distance scale.

Original languageEnglish
Article number113
JournalSpace Science Reviews
Issue number8
Publication statusPublished - 1 Dec 2018
Externally publishedYes


  • Distance scale
  • Old stars
  • Population II stars
  • RR Lyrae
  • Standard candles
  • Tip of the red giant branch
  • Type II Cepheids
  • Variable stars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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