SS 433 is one of the most exotic star systems observed. It is located in the Milky Way galaxy, and is an eclipsing X-ray binary system, with the primary being a stellar-mass black hole. The spectrum of the secondary companion star suggests that it is a late A-type star. SS 433 is the first discovered microquasar. It is at the centre of the supernova remnant W50.
Gamma Velorum is a quadruple star system in the constellation Vela. This name is the Bayer designation for the star, which is Latinised from γ Velorum and abbreviated γ Vel. At a combined magnitude of +1.7, it is one of the brightest stars in the night sky, and contains by far the closest and brightest Wolf–Rayet star. It has the traditional name Suhail al Muhlif and the modern name Regor, but neither is approved by the International Astronomical Union.
Gamma Volantis, Latinized from γ Volantis, is a wide binary star system in the southern constellation of Volans. Based upon parallax measurements, it is approximately 133 light years from Earth. It is bright enough to be seen with the naked eye and can be found around 9° to the east-southeast of the Large Magellanic Cloud.
Phi Aquilae, Latinized from φ Aquilae, is the Bayer designation of a binary star system in the equatorial constellation of Aquila. It has an apparent visual magnitude of +5.28 and is visible to the naked eye. With an annual parallax shift of 14.198 mas, this star is located at a distance of approximately 230 light-years from Earth. It is drifting closer with a radial velocity of –27 km/s. Based on its motion through space, this system is considered a possible member of the nearby Argus association of co-moving stars, although it may be too old.
Gamma Delphini, which is Latinized from γ Delphini, is a wide binary star system in the northern constellation of Delphinus. The star marks one corner of the asterism "Job's Coffin". The pair can be split with a modest amateur telescope and have been described as "one of the prettier pairs in the sky", with their contrasting colors said to be orange and lime in appearance. Together, the system is visible to the naked eye with a combined apparent visual magnitude of 3.87.
HD 10307 is a spectroscopic binary star in the constellation Andromeda. The primary is similar to the Sun in mass, temperature and metal content. situated about 42 light-years from Earth Its companion, HR 483 B, is a little-studied red dwarf.
The Tolman–Oppenheimer–Volkoff limit is an upper bound to the mass of cold, non-rotating neutron stars, analogous to the Chandrasekhar limit for white dwarf stars. If the mass of a neutron star reaches the limit it will collapse to a denser form, most likely a black hole.
LS I +61 303 is a microquasar, a binary system containing a massive star and a compact object. The compact object is a pulsar and the system is around 7,000 light-years away.
Beta Crateris, Latinized from β Crateris, is a binary star system in the southern constellation of Crater. It is visible to the naked eye with an apparent visual magnitude of 4.46. Based upon an annual parallax shift of 9.59 mas as seen from Earth, it is located around 340 light years from the Sun.
PSR J1302−6350 is a pulsar and member of an eclipsing binary star system with the blue O9.5Ve-class star LS 2883. The pair has an eccentric orbit that is inclined to the line of sight from Earth by about 36°, leading to a 40-day-long eclipse each time the pulsar passes behind the star. The pulsar has a period of about 48 ms and a luminosity of 8.3 × 1035 erg/s. It emits very high energy gamma rays that vary on a time scale of several days.
4U 1700-37 is one of the stronger binary X-ray sources in the sky, and is classified as a high-mass X-ray binary. It was discovered by the Uhuru satellite. The "4U" designation refers to the fourth Uhuru catalog.
Gamma Circini, Latinized from γ Circini, is a star system in the constellation Circinus. It was noted as a double star by Herschel in 1835, who estimated the separation as 1 arc second. It is visible to the naked eye with an apparent visual magnitude of 4.51. Based upon an annual parallax shift of 7.27 mas, it is about 450 light-years away.
Gamma Sagittae, Latinized from γ Sagittae, is the brightest star in northern constellation of Sagitta. A single star, it is visible to the naked eye with an apparent visual magnitude of +3.47. Based upon an annual parallax shift of 12.62 mas as seen from Earth, it is located about 288 light-years from the Sun. It is moving closer to the Sun with a radial velocity of −34 km/s.
Chi1 Hydrae is a binary star in the equatorial constellation of Hydra. It originally received the Flamsteed designation of 9 Crateris before being placed in the Hydra constellation. Based upon an annual parallax shift of 22.8 mas as seen from Earth, it is located about 143 light years from the Sun. It is visible to the naked eye with a combined apparent visual magnitude of 4.94.
Tau1 Hydrae is a triple star system in the equatorial constellation of Hydra. Based upon the annual parallax shift of the two visible components as seen from Earth, they are located about 18 parsecs (59 ly) from the Sun. The system has a combined apparent visual magnitude of +4.59, which is bright enough to be visible to the naked eye at night.
Gamma2 Normae, Latinized from γ2 Nor, is the brightest star in the southern constellation of Norma. Its apparent magnitude is 4.02 – making it a faint star but visible to the naked eye. Based upon an annual parallax shift of 25.33 mas as seen from Earth, this star is located roughly 129 light years from the Sun. It is moving closer to the Sun with a radial velocity of −29 km/s.
HD 85622 is a binary star system in the southern constellation of Vela. It is visible to the naked eye with an apparent visual magnitude of 4.58. The distance to HD 85622 can be estimated from its annual parallax shift of 4.3 mas, yielding a value of 750 light years. It is moving further from the Earth with a heliocentric radial velocity of +8 km/s.
Gamma Mensae, Latinized from γ Mensae, is an orange-hued star system in the southern constellation of Mensa. The apparent visual magnitude of 5.19 indicates it is dimly visible to the naked eye. Based upon an annual parallax shift of 7.70 mas as seen from the Earth, it is about 102 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.033 due to interstellar dust. The system shows the high velocity kinematic properties of a population II star, but has Sun-like abundances of most elements.
Gustavo E. Romero is a professor of Relativistic Astrophysics at the University of La Plata and Superior Researcher of the National Research Council of Argentina. Currently, he is Director of the Argentine Institute of Radio Astronomy (IAR). He is past President of the Argentine Astronomical Society and currently he is the leader of GARRA research group and a Helmholtz International Fellow. Romero has been honored with several award for his achievements in scientific research, including the award of the Argentine Academy of Sciences, the Houssay Prize and the Konex Award 2023.
AP Librae is a BL Lacertae object located at a distance of 700 million light years in the southern constellation of Libra. In the visual band it is one of the most active blazars known. AP Lib is surrounded by an extended source with a spectrum characteristic of a red-shifted giant elliptical galaxy. The derived visual magnitude of this region is 15.0, and it follows a radially decreasing brightness that is characteristic of an elliptical. Seven fainter galaxies are visible within an angular radius of 9′, suggesting it is the brightest member of a galactic cluster.
