Circinus in the context of "PSR B1509−58"

Pyxis is a small and faint constellation in the southern sky. Abbreviated from Pyxis Nautica, its name is Latin for a mariner's compass (contrasting with Circinus, which represents a draftsman's compasses). Pyxis was introduced by Nicolas-Louis de Lacaille in the 18th century, and is counted among the 88 modern constellations.

The plane of the Milky Way passes through Pyxis. A faint constellation, its three brightest stars—Alpha, Beta and Gamma Pyxidis—are in a rough line. At magnitude 3.68, Alpha is the constellation's brightest star. It is a blue-white star approximately 880 light-years (270 parsecs) distant and around 22,000 times as luminous as the Sun.

AX Circini is a binary star system in the southern constellation of Circinus. It has a nominal magnitude of 5.91, which is bright enough to be visible to the naked eye. Based upon an annual parallax shift of 1.7 mas, it is located roughly 1,900 light-years from the Earth. The system is moving closer with a heliocentric radial velocity of −21 km/s.

This is a spectroscopic binary with an orbital period of 17.88 years and an eccentricity of 0.19. A binary companion was first suspected in 1960, as the spectrum was considered to be composite and there is an ultraviolet excess. The companion was confirmed in 1982, and it was resolved using long baseline interferometry in 2014 and 2015. The system has an a sin i value of 6.05 AU, where a is the semimajor axis and i is the (unknown) orbital inclination.

BX Circini is a star in the constellation Circinus. Its variability was discovered in 1995, with its apparent magnitude ranging from 12.57 to 12.62 over a period of 2 hours 33 minutes. It is currently classified as a PV Telescopii variable star, but has been put forward as the prototype of a new class of pulsating star—the BX Circini variables—along with the only other known example, V652 Herculis. This class of star is rare, possibly because this is a brief stage of stellar evolution. Its mass has been calculated to be around 40 percent that of the Sun, but the radius is a few times larger than that of the Sun. The average surface temperature is high, and has been measured at 23,390 ± 90 K using optical spectra, but 1750 K cooler if analysing it in both the visual and ultraviolet. The temperature appears to vary by 3450 K.

This star has an extremely low proportion of hydrogen, which was first noticed in 1980. In fact, over 99% of its composition appears to be helium, qualifying it as an extreme helium star. Its origin is unclear, but thought to be a result of the merger of a helium white dwarf with a carbon/oxygen one. The two merge violently, with material from the lighter helium white dwarf forming the outer envelope. The resulting star expands and shines as a yellow giant, its outer helium shell igniting and undergoing fusion as material continues to be accreted from the lighter star. The size of the star is maintained by the weight upon the helium shell, and once that has become light enough and the helium is exhausted, the star begins heating and shrinking, becoming the smaller blue star now observed.

HD 134060, also known by its Gould designation of 38 G. Circini, is a star in the southern constellation of Circinus. It is near the lower limit of stars visible to the naked eye, having an apparent visual magnitude of 6.29. The distance to HD 134060, as determined using an annual parallax shift measurement of 41.6 mas, is 78.4 light years. It is moving further away with a heliocentric radial velocity of 43.5 km/s, having come within 34.6 ly some 439,000 years ago.

During the NStars project, Grey et al. (2006) found a stellar classification of G0 V Fe+0.4 for this star, matching a Sun-like G-type main-sequence star with an overabundance of iron in its outer atmosphere. However, an older classification of G3 IV is still used, which would suggest it is instead a more evolved subgiant star. HD 134060 has an estimated 1.07 times the mass of the Sun and 1.15 times the Sun's radius. It is radiating 1.63 times the Sun's luminosity from its photosphere at an effective temperature of about 5,965 K.

NGC 5315 is a planetary nebula in the southern constellation Circinus. Of apparent magnitude 9.8 around a central star of magnitude 14.2, it is located 5.2 degrees west-southwest of Alpha Circini. It is only visible as a disc at magnifications over 200-fold. The nebula was discovered by astronomer Ralph Copeland in 1883. The central star has a stellar class of WC4 and is hydrogen deficient with an effective temperature of 76-79 kK. The distance to this nebula is not known accurately, but is estimated to be around 6.5 kilolight-years.

This planetary nebular has a slightly elliptical form, a complex structure, and a ring that is somewhat broken. It shows a typical abundance of carbon and a slightly enhanced nitrogen abundance. Radial velocity studies indicate that the star may be a member of a binary system. The nebula does not show enrichment of s-process elements. This suggests that the star's asymptotic giant branch stage may have been truncated by interaction with the companion. Alternatively, the star may be low in mass and did not undergo third dredge-up, or the star's s-process elements were heavily diluted by the envelope during the AGB phase.