Castor is the second-brightest object in the zodiac constellation of Gemini. It has the Bayer designation α Geminorum, which is Latinised to Alpha Geminorum and abbreviated Alpha Gem or α Gem. With an apparent visual magnitude of 1.58, it is one of the brightest stars in the night sky. Castor appears singular to the naked eye, but it is actually a sextuple star system organized into three binary pairs. Although it is the 'α' (alpha) member of the constellation, it is half a magnitude fainter than 'β' (beta) Geminorum, Pollux.
Epsilon Geminorum or ε Geminorum, formally named Mebsuta, is a star in the constellation of Gemini, on the outstretched right 'leg' of the twin Castor. The apparent visual magnitude of +3.06 makes it one of the brighter stars in this constellation. The distance to this star is determined at 860 light-years.
Eta Geminorum, formally named Propus, is a triple star system in the constellation of Gemini. It is a naked-eye variable star around 380 light years from the Sun.
Mu Geminorum or μ Geminorum, formally named Tejat, is a single star in the northern constellation of Gemini. From parallax measurements obtained during the Hipparcos mission, it is roughly 230 light-years distant from the Sun. The position of the star near the ecliptic means that it is subject to lunar occultations.
37 Geminorum is a solitary Sun-like star located at the northwest part of the northern constellation of Gemini, about three degrees to the east of the bright star Epsilon Geminorum. The apparent visual magnitude of 37 Geminorum is 5.74, which is just bright enough to be visible to the naked eye on a dark night. It is located at a distance of 57 light years from the Sun based on parallax. This star is drifting closer with a radial velocity of −15 km/s, and is predicted to come as near as 13.8 light-years in approximately a million years. It is positioned close enough to the ecliptic to be subject to lunar occultations, such as happened on April 8, 1984.
1 Cancri is a single star in the zodiac constellation of Cancer, positioned near the border with Gemini at a distance of around 467 light years from the Sun. It is barely visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 5.97. The object is moving further from the Earth with a heliocentric radial velocity of +14 km/s.
Lambda Geminorum, Latinized from λ Geminorum, is a candidate multiple star system in the constellation Gemini. It is visible to the naked eye at night with a combined apparent visual magnitude of 3.57. The distance to this system is 101 light years based on parallax, and it is drifting closer with a radial velocity of –7.4 km/s. It is a member of what is suspected to be a trailing tidal tail of the Hyades Stream.
Tau Geminorum, Latinized from τ Geminorum, is a star in the northern zodiac constellation of Gemini. It has the apparent visual magnitude of +4.42, making it visible to the naked eye under suitably good seeing conditions. This star is close enough to the Earth that its distance can be measured using the parallax technique, which yields a value of roughly 392 light-years.
Delta Piscium is a solitary, orange-hued star in the zodiac constellation of Pisces. It has an apparent visual magnitude of +4.4, so it is bright enough to be faintly visible to the naked eye. Based upon an annual parallax shift of 10.86 mas, it is around 300 light-years from the Sun. The visual magnitude of the star is diminished by an interstellar absorption factor of 0.08 due to interstellar dust.
Upsilon Geminorum, Latinized from υ Geminorum, is a star in the constellation Gemini. It has an apparent visual magnitude of 4.04, which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 12.88 mas, it is around 253 light years from the Sun. There is a visual companion: a magnitude 13.20 star located at an angular separation of 55.20″ along a position angle of 40°, as of 2008.
Rho Geminorum is a star system that lies 59 light-years away in the constellation of Gemini, about 5 degrees west of Castor. The system consists of a primary bright enough to be seen with the naked eye, a faint secondary which has rarely been observed even professionally, and a distant, somewhat bright tertiary which requires telescopic equipment for observation.
10 Lacertae is a star in the constellation Lacerta. With an apparent magnitude of 4.9, it is located around 550 parsecs (1,800 ly) distant in the small Lacerta OB1 association. It is a hot blue main-sequence star of spectral type O9V, a massive star that is currently fusing its core hydrogen. It is a suspected Beta Cephei variable star.
Pi Leonis, Latinised from π Leonis, is a single star in the zodiac constellation Leo. It is a red-hued star that is visible to the naked eye with an apparent visual magnitude of 4.70. This object is located at a distance of some 410 light-years from the Sun based on parallax, and is drifting further away with a radial velocity of +22 km/s. Because the star lies near the ecliptic it is subject to occultations by the Moon.
X Cancri is a variable star in the northern constellation of Cancer. It has a red hue and is visible to the naked eye at its brightest. The distance to this object is approximately 1,860 light years based on parallax measurements, but is drifting closer with a radial velocity of −5 km/s. It lies very close to the ecliptic and so is subject to lunar occultations.
3 Piscis Austrini, also known as HD 201901 or simply 3 PsA, is an astrometric binary located in the southern constellation Microscopium. It was once part of Piscis Austrinus, the southern fish. The system has a combined apparent magnitude of 5.39, making it faintly visible to the naked eye under ideal conditions. Gaia DR3 parallax measurements imply a distance of 404 light years and it is currently approaching the Solar System with a heliocentric radial velocity of −46.2 km/s. At its current distance, 3 PsA's brightness is diminished by 0.12 magnitudes due to extinction from interstellar dust and it has an absolute magnitude of +0.19.
3 Geminorum is a blue supergiant star in the constellation Gemini. It is a small amplitude pulsating variable and a close double star, with a mean combined apparent visual magnitude of about 5.7.
6 Geminorum is a variable star in the zodiac constellation of Gemini, located roughly 5,800 light years away from the Sun. It has the variable star designation BU Geminorum; 6 Geminorum is the Flamsteed designation. At its brightest this reddish hued star is barely visible to the naked eye but is readily visible with binoculars, found southeast of M 35, just to the south of WY Geminorum. It is moving further from the Earth with a heliocentric radial velocity of +27 km/s. The star is a member of the Gemini OB1 association.
HD 114533, also known as HR 4976, is a solitary star located in the southern circumpolar constellation Chamaeleon. It has an apparent magnitude of 5.84, making it faintly visible to the naked eye. The system is located relatively far at a distance of roughly 2,100 light years based on Gaia DR3 parallax measurements but is drifting closer with a heliocentric radial velocity of −18 km/s. At its current distance, HD 114533A's brightness is diminished by 0.74 magnitudes due to interstellar dust. It has an absolute magnitude of −2.0.
72 Tauri is a possible binary star in the zodiac constellation of Taurus. It is faintly visible to the naked eye with an apparent visual magnitude of +5.5, although only 0.29° from the brighter υ Tauri. Based upon an annual parallax shift of 7.9 mas seen from Earth, it is around 410 light years from the Sun.
HD 37320 is a star located in the constellation Orion. It is an evolved blue giant star, based on its spectral type of B8III. The distance to HD 37320 is calculated at 285.5 parsecs, based on a parallax from Gaia EDR3. The apparent magnitude of the star is 5.852, which is above the limiting magnitude for naked-eye vision (6.5m), making it faintly visible to the naked eye.
