IC 4756 | |
---|---|
Observation data (J2000 epoch) | |
Constellation | Serpens |
Right ascension | 18h 38m 31.2s [1] |
Declination | +05° 29′ 24″ [1] |
Distance | 1.3 kly (400 pc) |
Apparent magnitude (V) | 4.6 [1] |
Physical characteristics | |
Other designations | Cr 386, Mel 210 |
IC 4756 is a large bright open cluster in the constellation Serpens. Known as Graff's Cluster, it is bright enough to be seen with the naked eye and considered a fine cluster for binoculars or small telescopes. [2]
IC 4756 is also known as the Tweedledee Cluster (paired with NGC 6633 as Tweedledum), also as the Secret Garden Cluster. [3]
Metallicity of IC 4756 is similar to the Sun, at -0.02±0.01 dex. [4]
There are some noteworthy stars in the cluster. HD 172365 [5] is a likely post-blue straggler in the IC 4756 that contains a large excess of lithium. [6] HD 172189, also in IC 4756, is an Algol variable eclipsing binary [7] with a 5.70 day period. The primary star in the system is also a Delta Scuti variable, undergoing multiple pulsation frequencies, which, combined with the eclipses, causes the system to vary by around a tenth of a magnitude. [8]
Serpens is a constellation in the northern celestial hemisphere. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations designated by the International Astronomical Union. It is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput to the west and Serpens Cauda to the east. Between these two halves lies the constellation of Ophiuchus, the "Serpent-Bearer". In figurative representations, the body of the serpent is represented as passing behind Ophiuchus between Mu Serpentis in Serpens Caput and Nu Serpentis in Serpens Cauda.
Scutum is a small constellation. Its name is Latin for shield, and it was originally named Scutum Sobiescianum by Johannes Hevelius in 1684. It lies entirely in the southern celestial hemisphere and its four brightest stars form a narrow diamond shape. It is one of the 88 IAU designated constellations defined in 1922.
Perseus is a constellation in the northern sky, being named after the Greek mythological hero Perseus. It is one of the 48 ancient constellations listed by the 2nd-century astronomer Ptolemy, and among the 88 modern constellations defined by the International Astronomical Union (IAU). It is located near several other constellations named after ancient Greek legends surrounding Perseus, including Andromeda to the west and Cassiopeia to the north. Perseus is also bordered by Aries and Taurus to the south, Auriga to the east, Camelopardalis to the north, and Triangulum to the west. Some star atlases during the early 19th century also depicted Perseus holding the disembodied head of Medusa, whose asterism was named together as Perseus et Caput Medusae; however, this never came into popular usage.
NGC 2360 is an open cluster in the constellation Canis Major. It was discovered on 26 February 1783 by Caroline Herschel, who described it as a "beautiful cluster of pretty compressed stars near 1/2 degree in diameter”. Her notes were overlooked until her brother William included the cluster in his 1786 catalogue of 1000 clusters and nebulae and acknowledged her as the discoverer. The cluster lies 3.5 degrees east of Gamma Canis Majoris and less than one degree northwest of the eclipsing binary star R Canis Majoris; it has a combined apparent magnitude of 7.2. It is 13 arc minutes in diameter. By the western edge of the cluster is the unrelated star, 5.5-magnitude HD 56405.
35 Aquilae is a star in the equatorial constellation of Aquila. 35 Aquilae is its Flamsteed designation though it also bears the Bayer designation c Aquilae. The apparent visual magnitude of this star is 5.8, which means it is a faint star but visible to the naked eye from dark suburban or rural skies. It has an annual parallax shift of 16.34 mas that is caused by the Earth's orbit around the Sun. This yields a distance estimate of 200 light-years, give or take a 4 light-year margin of error. At this distance, the visual magnitude is diminished by 0.26 from extinction caused by interstellar gas and dust.
HD 92063 is a single star in the southern constellation of Carina. It has the Bayer designation t1 Carinae, while HD 92063 is the star's identifier from the Henry Draper Catalogue. This is a suspected variable star and is visible to the naked eye with an apparent visual magnitude of 5.08. The star is located at a distance of approximately 246 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −10 km/s. Although it appears at the edge of the Carina Nebula, it is much closer than the nebula. It is also not considered a member of the nearby Alessi 5 open cluster of stars.
NGC 6334, colloquially known as the Cat's Paw Nebula, Bear Claw Nebula, or Gum 64, is an emission nebula and star-forming region located in the constellation Scorpius. NGC 6334 was discovered by astronomer John Herschel in 1837, who observed it from the Cape of Good Hope in South Africa. The nebula is located in the Carina–Sagittarius Arm of the Milky Way, at a distance of approximately 5.5 kilolight-years from the Sun.
IC 2391 is an open cluster in the constellation Vela. The Persian astronomer Al Sufi may have first described it about 964. It was found by Abbe Lacaille and cataloged as Lac II 5.
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.
HD 65750, also known as V341 Carinae is a bright red giant star in the constellation Carina. It is surrounded by a prominent reflection nebula, known as IC 2220, nicknamed the Toby Jug Nebula.
IC 2488 is an open cluster in the constellation Vela. It was discovered by Nicolas-Louis de Lacaille in 1752. It is located approximately 3,700 light years away from Earth.
S Scuti is a carbon star located in the constellation Scutum. Parallax measurements by Hipparcos put it at a distance of approximately 1,300 light-years. Its apparent magnitude is 6.80, making it visible to the naked eye only under excellent conditions.
BB Phoenicis is a variable star in the constellation of Phoenix. It has an average visual apparent magnitude of 6.17, being visible to the naked eye with excellent viewing conditions. From parallax measurements by the Gaia spacecraft, it is located at a distance of 448 light-years from Earth. Its absolute magnitude is calculated at 0.6.
Rho Phoenicis is a variable star in the constellation of Phoenix. From parallax measurements by the Gaia spacecraft, it is located at a distance of 240 light-years from Earth.
HD 74423 is a heartbeat binary star and one component pulsates on only one hemisphere. This is caused by tidal interaction with its partner. The star is located in the Volans constellation.
AO Serpentis is an eclipsing binary star system in the Serpens Caput segment of the Serpens constellation. It is invisible to the naked eye with a typical apparent visual magnitude of 11.04. Variable star observers record a peak magnitude of 10.7, dropping to 12.0 during the primary eclipse and 10.8 from the secondary eclipse. The distance to this system is approximately 1,450 light years based on parallax measurements.
HR 3831, also known as HD 83368, is a binary star system in the southern constellation of Vela at a distance of 233 light years. This object is barely visible to the naked eye as a dim, blue star with an apparent visual magnitude of 6.232. It is approaching the Earth with a heliocentric radial velocity of 4.0±0.3 km/s.
HD 139319 is a ternary system composed of the binary Algol variable star known as TW Draconis, and a main-sequence companion star at a separation of 3 arcseconds. The system lies in the constellation of Draco about 540 light years away.
FG Virginis is a well-studied variable star in the equatorial constellation of Virgo. It is a dim star, near the lower limit of visibility to the naked eye, with an apparent visual magnitude that ranges from 6.53 down to 6.58. The star is located at a distance of 273.5 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of +16 km/s. Because of its position near the ecliptic, it is subject to lunar occultations.
RR Lyncis is a star system in the northern constellation of Lynx, abbreviated RR Lyn. It is an eclipsing binary of the Algol type; one of the closest in the northern sky at an estimated distance of approximately 263 light years based on parallax measurements. The system is faintly visible to the naked eye with a combined apparent visual magnitude of 5.53. During the primary eclipse the brightness drops to 6.03, while it decreases to magnitude 5.90 with the secondary eclipse. The system is drifting closer to the Sun with a radial velocity of −12 km/s.