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 The Coronet Cluster, also known as the R Coronae Australis, R CrA cluster after its best-known member, is a small open cluster located about 170 parsecs away in the southern constellation Corona Australis, isolated at the edge of the Gould Belt. T ...

, therefore sometimes called R CrA Cluster. This star is moving toward the Solar System with a

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the rate of change of the distance or range between the two points. It is equivalent to the vector projection ...

of . It was previously believed that in roughly 222,000 years, this system could have approached within of the Sun. However, the estimate had a considerable

margin of error The margin of error is a statistic expressing the amount of random sampling error in the results of a survey. The larger the margin of error, the less confidence one should have that a poll result would reflect the result of a census of the en ...

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 . Examination of other objects known to be in the same star-forming region gives a distance of , 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 mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass o ...

es, 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 ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave (TV channel), Dave since 2009, gaining a ...

with a mass between and . It has also been proposed that the primary component is itself a close

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that ta ...

References

{{Stars of Corona Australis A-type giants Corona Australis Coronae Australis, R 093449 Durchmusterung objects Herbig Ae/Be stars