RR Coronae Borealis (RR CrB, HD 140297, HIP 76844) is a M3-type semiregular variable

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

located in the constellation

Corona Borealis Corona Borealis is a small constellation in the Northern Celestial Hemisphere. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Its brightest stars form a sem ...

with a

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

of 2.93mas being a distance of . It varies between magnitudes 7.3 and 8.2 over 60.8 days. Located around 1228 light-years distant, it shines with a

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

approximately 2180 times that of the Sun and has a surface temperature of 3309 K. In 1907 it was announced that

Williamina Fleming Williamina Paton Stevens Fleming (15 May 1857 – 21 May 1911) was a pioneering Scottish astronomer, who made significant contributions to the field despite facing gender biases. She was a single mother hired by the director of the Harvard Co ...

had discovered that the star, listed then as BD +39° 2901, is a

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

. She had determined that from the examination of 26

photographic plate Photographic plates preceded film as the primary medium for capturing images in photography. These plates, made of metal or glass and coated with a light-sensitive emulsion, were integral to early photographic processes such as heliography, d ...

s taken from 1892 to 1907. It was given its

variable star designation In astronomy, a variable-star designation is a unique identifier given to variable stars. It extends the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in whic ...

, RR Coronae Borealis, in 1908.

References

Corona Borealis Semiregular variable stars M-type giants Coronae Borealis, RR 140297 076844 Durchmusterung objects {{var-star-stub