Circinus is a small, faint constellation in the southern sky, first defined in 1756 by the French astronomer Nicolas-Louis de Lacaille. Its name is Latin for compass, referring to the drafting tool used for drawing circles. Its brightest star is Alpha Circini, with an apparent magnitude of 3.19. Slightly variable, it is the brightest rapidly oscillating Ap star in the night sky. AX Circini is a Cepheid variable visible with the unaided eye, and BX Circini is a faint star thought to have been formed from the merger of two white dwarfs. Two sun-like stars have planetary systems: HD 134060 has two small planets, and HD 129445 has a Jupiter-like planet. Supernova SN 185 appeared in Circinus in 185 AD and was recorded by Chinese observers. Two novae have been observed more recently, in the 20th century.
HD 2638 is a ternary star system system in the equatorial constellation of Cetus. The pair have an angular separation of 0.53″ along a position angle of 166.7°, as of 2015. This is system too faint to be visible to the naked eye, having a combined apparent visual magnitude of 9.44; a small telescope is required. The distance to this system is 179.5 light years based on parallax, and it is drifting further away with a radial velocity of +9.6 km/s. The magnitude 7.76 star HD 2567 forms a common proper motion companion to this pair at projected separation 839″.
101 Aquarii is a star in the equatorial constellation of Aquarius. 101 Aquarii is the Flamsteed designation, although it also bears the Bayer designation b3 Aquarii. The combined apparent visual magnitude of the pair is 4.71, which is bright enough to be seen with the naked eye from the suburbs. The distance of this star from Earth is estimated as 290 light-years based upon parallax measurements.
Omicron Capricorni is a wide binary star system in the constellation Capricornus. The brighter component has an apparent visual magnitude of +5.94, which is near the lower limit on stellar brightness that still can be seen with the naked eye. Based upon an annual parallax shift of 15.07 mas as seen from Earth, this system is located roughly 220 light years from the Sun. Large but uncertain discrepancies in the parallax measurements from Hipparcos may indicate, weakly, that there is a third, unseen companion in the system.
HD 73389 is a binary star system in the constellation Carina. It has the Bayer designation e2 Carinae; HD 73389 is the identifier from the Henry Draper Catalogue. This system is visible to the naked eye as a point of light with a combined apparent visual magnitude of +4.84. Based on parallax measurements, it is located at a distance of approximately 225 light years from the Sun. The system is drifting further away with a radial velocity of +25.6 km/s.
HR 4177, also called t² Carinae, is a double star in the southern constellation of Carina. It is faintly visible to the naked eye with a combined apparent visual magnitude of +4.77. The two components are HD 92397 and HD 92398. The primary component is located at a distance of approximately 1,600 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +11 km/s. It has a peculiar velocity of 24.3+9.9
−16.1 km/s and may be a runaway star. The star is a member of the BH 99 cluster.
HD 175740 is a single star in the northern constellation of Lyra. This object has an orange hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.46. It is located at a distance of approximately 266 light years from the Sun based on parallax, and has an absolute magnitude of 0.89. The star is drifting closer with a radial velocity of −9.5 km/s, and is predicted to come as close as 31.7 light-years in around 8 million years.
HD 156846 is a binary star system in the equatorial constellation of Ophiuchus, positioned a degree SSE of Messier 9. It has a yellow hue and is just barely bright enough to be visible to the naked eye with an apparent visual magnitude of 6.5. The system is located at a distance of 156 light years from the Sun based on parallax. It is drifting closer with a radial velocity of −68.5 km/s, and is predicted to come to within 85.0 light-years in about 476,000 years.
HD 41004 is a visual binary star system in the southern constellation of Pictor. It is too faint to be visible to the naked eye, having a combined apparent visual magnitude of 8.65. The two components have a magnitude difference of 3.7, and share a common proper motion with an angular separation of 0.30″, as of 2018. The distance to this system is approximately 136 light years based on parallax. It is drifting further away from the Sun with a radial velocity of +42.5 km/s, having come to within 44.5 ly some 831,000 years ago.
HD 109749 is a binary star about 206 light years away in the constellation of Centaurus.
HD 2767 is the primary component of a double star located 115 parsecs (380 ly) away in the constellation Andromeda. It is a red giant with a spectral type of K1III and an apparent magnitude of 5.88, thus is visible by the naked eye under favourable conditions.
HD 222093 is a double star in the equatorial constellation of Aquarius. It has an orange hue and is visible to the naked eye with an apparent visual magnitude of 5.68. The system is located at a distance of approximately 293 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −13 km/s.
DV Aquarii is a binary star system in the zodiac constellation of Aquarius. It has a peak apparent visual magnitude of 5.89, which is bright enough to be visible to the naked eye. The distance can be estimated from its annual parallax shift of 11.2 mas, yielding a separation of 291 light years.
HD 220766 is a double star in the equatorial constellation of Aquarius. The primary is a K-type giant star with a stellar classification of K0III and an apparent magnitude of 6.44. It has a faint, magnitude 12 companion, located at an angular separation of 5.0″ along a position angle of 132°.
HD 157661 is the Henry Draper Catalogue designation for a likely triple star in the southern constellation of Ara. With a measured annual parallax of 5.13 mas, is located at a distance of approximately 640 light-years from Earth. The combined apparent visual magnitude of the stars is 5.29, which means it is faintly visible to the naked eye.
HR 3082 is a double star in the northern circumpolar constellation of Camelopardalis. It is faintly visible to the naked eye with an apparent visual magnitude of 5.39. The system is moving closer to the Sun with a heliocentric radial velocity of +2.7 km/s. It is currently at a distance of around 323 light years, based upon an annual parallax shift of 10.10±0.24 mas.
HD 3 is a single, white-hued star in the northern constellation Andromeda. With an apparent visual magnitude of 6.71, it is below the nominal brightness limit for visibility with the typical naked eye but may still be visible by some observers under ideal viewing conditions. Based upon an annual parallax shift of 5.89±0.35 mas, it is located roughly 550 light years away. The star is moving closer with a heliocentric radial velocity of −18 km/s, and will make perihelion in around 2.9 million years at a separation of around 351 ly (107.71 pc).
HD 125628 is a binary star system in the constellation Centaurus. It is faintly visible to the naked eye with a combined apparent visual magnitude of 4.76. The distance to this system is approximately 380 light years based on parallax. It is drifting further away from the Sun with a radial velocity of +15 km/s. The absolute magnitude is −0.55.
HD 24071 and HD 24072 form a binary or possibly a triple star system in the equatorial constellation of Eridanus. It is visible to the naked eye, with component HD 24071 having an apparent visual magnitude of 5.25 and HD 24072 a magnitude of 4.72. As of 2009, the pair had an angular separation of 8.40″ along a position angle of 216°. The annual parallax shift of HD 24071 is 19.0 mas, which provides a distance estimate to the system of 172 light years. The pair are members of the Tucana-Horologium moving group, a 45 million year old set of stars that share a common motion through space.
52 Hydrae is a triple star system in the constellation Hydra. It has the Bayer designation l Hydrae; 52 Hydrae is the Flamsteed designation. This system is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude of 4.97. It is a probable member of the Sco OB2 moving group of stars, and is moving away from the Earth with a heliocentric radial velocity of 5 km/s.
