Supernova remnants (SNRs) play key roles in the final evolution of stars, reshaping and heating interstellar medium, and the birth of the high-energy cosmic rays. Reliable distances to SNRs are essential to constrain their physical parameters like age, physical size, the expansion velocity and the explosion energy of the progenitor supernovae which reveal the evolutionary process of SNRs. However, it is a really challenging job to obtain reliable distances of SNRs. Distance measurements of SNRs usually depend on specific conditions, for examples, the SNRs might interact with the molecular clouds or be associated with the OB stars or pulsars. 

Recently, the researchers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC) have applied a universal method via the red clump stars and measured the distances of 47 SNRs. The red clump (RC) stars are low mass stars in the early stage of core He-burning. They are used as standard candles and extinction probes to build the optical extinction – distance relation in each direction of SNRs with known extinction. Combining the Bayesian method, the distances of 15 SNRs are well determined. Among them, the distances of G65.8-0.5, G66.0-0.0 and G67.6+0.9 are given for the first time. We also obtain 32 upper/lower limits of distances, and the distances to G5.7-0.1, G15.1-1.6, G28.8+1.5 and G78.2+2.1 are constrained.

The study has been published by Astrophysical Journal Supplement Series (APJs, https://doi.org/10.3847/1538-4365/aae07a). The authors are S.S. Shan, H. Zhu,  W.W. Tian, M.F. Zhang, H.Y. Zhang,  D. Wu, and A.Y. Yang. This work was supported jointly by National Science Foundation of China and Chinese Academy of Sciences.

Fig.15: Supernova remnants are distributed in two dimensions on the spiral arms of the galaxy. The distance parameter is obtained from the work. The red dots indicate the sun, and the green dots represent supernova remnants. Background maps are galactic art maps based on existing observations, cited from NASA/JPL-Caltech/R.Hurt (SSC-Caltech).