R Coronae Australis

R Coronae Australis (R CrA) is a variable binary system in the constellation Corona Australis. It has varied between magnitudes 10 and 14.36. A small reflection/emission nebula NGC 6729 extends from the star towards SE. It is also the brightest feature of the Coronet Cluster, therefore sometimes called R CrA Cluster.

This star is moving toward the Solar System with a radial velocity of 36 km s−1. It was previously believed that in roughly 222,000 years, this system could have approached within 1.77 ly of the Sun. However, the estimate had a considerable margin of error in it. With the release of Gaia DR2, the star was determined to be 4 times further from the Sun than initially believed, constraining the approach to only 111 +/-. Examination of other objects known to be in the same star-forming region gives a distance of $-36$, suggesting an error in the Gaia parallax for R CrB itself.

A companion to the star was proposed in 2019 with a mass between 0.1 and 1 Solar masses, depending on the characteristics of the stellar environment, orbiting the primary in 43–47 years. The companion was later directly observed to be a red dwarf with a mass between and. It has also been proposed that the primary component is itself a close binary.