Ophiuchus and Serpens

Ophiuchus /ɒfiˈjuːkəs/ is a large constellation located around the celestial equator. Its name is from the Greek Ὀφιοῦχος "serpent-bearer", and it is commonly represented as a man grasping the snake that is represented by the constellation Serpens. Ophiuchus was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. It was formerly referred to as Serpentarius /sɜrpənˈtɛəriəs/ and Anguitenens. ... Ophiuchus is located between Aquila, Serpens and Hercules, northwest of the center of the Milky Way. The southern part lies between Scorpius to the west and Sagittarius to the east. In the northern hemisphere, it is best visible in summer. It is located opposite Orion in the sky. Ophiuchus is depicted as a man grasping a serpent; the interposition of his body divides the snake constellation Serpens into two parts, Serpens Caput and Serpens Cauda, which are nonetheless counted as one constellation. ... Stars. The brightest stars in Ophiuchus include α Ophiuchi, called Ras Alhague ("head of the serpent charmer"), at magnitude 2.07, and η Ophiuchi, known as Sabik ("the preceding one"), at magnitude 2.43. Other bright stars in the constellation include β Ophiuchi, Cebalrai ("heart of the shepherd") and λ Ophiuchi, or Marfik ("the elbow"). RS Ophiuchi is part of a class called recurrent novae, whose brightness increase at irregular intervals by hundreds of times in a period of just a few days. It is thought to be at the brink of becoming a type-1a supernova. Barnard's Star, one of the nearest stars to the Solar System (the only stars closer are the Alpha Centauri binary star system and Proxima Centauri), lies in Ophiuchus. It is located to the left of β and just north of the V-shaped group of stars in an area that was once occupied by the now-obsolete constellation of Taurus Poniatovii (Poniatowski's Bull). ... Deep-sky objects. Ophiuchus contains several star clusters, such as IC 4665, NGC 6633, M9, M10, M12, M14, M19, M62, and M107, as well as the nebula IC 4603-4604. ... The unusual galaxy merger remnant and starburst galaxy NGC 6240 is also in Ophiuchus. [Ophiuchus. Wikipedia] Serpens ("the Serpent", Greek Ὄφις) is a constellation of the northern hemisphere. One of the 48 constellations listed by the 2nd century astronomer Ptolemy, it remains one of the 88 modern constellations defined by the International Astronomical Union. It is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput (Serpent's Head) to the west and Serpens Cauda (Serpent's Tail) 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 μ Ser in Serpens Caput and ν Ser in Serpens Cauda. The brightest star in Serpens is Unukalhai or Cor Serpentis "Serpent's Heart", with an apparent magnitude of 2.63. Part of the Milky Way passes through Serpens Cauda, which is thus rich in deep-sky objects, such as the Eagle Nebula (IC 4703) and its associated star cluster Messier 16. The nebula measures 70 light-years by 50 light-years and contains the Pillars of Creation, three dust clouds that became famous for the image taken by the Hubble Space Telescope. Located in Serpens Caput are Seyfert's Sextet, one of the densest galaxy clusters known, and Arp 220, the prototypical ultraluminous infrared galaxy. ... Serpens is unique among the 88 modern constellations in that it is split into two separate parts: Serpens Caput and Serpens Cauda, the head and tail respectively. The constellation is also one of the only ones that is dependent on another constellation for context; specifically, it is being held by the Serpent Bearer Ophiuchus. Serpens Caput is bordered by Libra to the south, Virgo and Boötes to the east, Corona Borealis to the north, and Ophiuchus and Hercules to the west; Serpens Cauda is bordered by Sagittarius to the south, Scutum and Aquila to the east, and Ophiuchus to the north and west. ... The International Astronomical Union (IAU) adopted the three-letter abbreviation "Ser" for the constellation in 1922. ... Stars. Since Serpens is regarded as one constellation despite being split into two halves, the ordering of Bayer and Flamsteed designations go roughly in order of brightness among both halves (i.e. there is only one Alpha, one Beta, etc. in the entire constellation). Only one star in Serpens is brighter than third magnitude, so the constellation is not easy to perceive. Head stars. The brightest star in Serpens, Alpha Serpentis, also known as Unukalhai, is a red giant of spectral type K2III located approximately 22.68 parsecs (74.0 ly) away which marks the snake's heart. With a visual magnitude of 2.63... Located near Alpha is Lambda Serpentis, a magnitude 4.42 star rather similar to the Sun... Another solar analog in Serpens is the primary of Psi Serpentis, a binary star located slightly further away at approximately 14.64 parsecs (47.7 ly). Beta, Gamma, and Iota Serpentis form a distinctive triangular shape marking the head of the snake, with Kappa Serpentis being roughly midway between Gamma and Iota. The brighest of the four with an apparent magnitude of 3.67, Beta Serpentis is a white main-sequence star roughly 155.0 parsecs (506 ly) distant. ... The Mira variable R Serpentis, located between Beta and Gamma, is visible to the naked eye at its maximum brightness of 5.16, but, typical of Mira variables, it can fade to below magnitude 14. Gamma Serpentis itself is an F-type subgiant located only 11.25 parsecs (36.7 ly) distant and thus is quite bright, being of magnitude 3.84. The star is known to show solar-like oscillations. Delta Serpentis, forming part of the body of the snake between the heart and the head, is a multiple star system located 69.93 parsecs (228.1 ly) light-years from Earth. Consisting of four stars, the system has a total apparent magnitude of 3.79... The primary, an white subgiant, is a Delta Scuti variable with an average apparent magnitude of 4.23. Located very near Delta, both in the night sky and likely in actual space at an estimated distance of 70.87 parsecs (231.1 ly), is the barium star 16 Serpentis. Another notable variable star visible to the naked eye is Chi Serpentis, an Alpha2 Canum Venaticorum variable located midway between Delta and Beta which varies from its median brightness of 5.33 by 0.03 magnitudes over a period of approximately 1.5 days. ... Tail stars. The brightest star in the tail, Eta Serpentis, is similar to Alpha Serpentis' primary in that it is a red giant of spectral class K. This star, however, is known to exhibit solar-like oscillations over a period of approximately 2.16 hours. ... The other two stars in Serpens Cauda forming its asterism are Theta and Xi Serpentis. Xi, where the asterism crosses over to Mu Serpentis in the head, is a triple star system located approximately 105.2 parsecs (343 ly) away. Two of the stars, with a combined apparent magnitude of 3.54, form a spectroscopic binary... Theta, forming the tip of the tail, is also a multiple system, consisting of two A-type main-sequence stars with a combined apparent magnitude of 4.10 separated by almost half an arcminute. Lying near the boundary with Ophiuchus are Zeta (23.55 parsecs (76.8 ly) distant), Nu (209.3 parsecs (683 ly) distant), and Omicron Serpentis (173.1 parsecs (565 ly) distant). All three are 4th-magnitude main-sequence stars, with Nu and Omicron being of spectral type A and Zeta being of spectral type F. Nu is a binary star with a secondary component of magnitude 9.3, while Omicron is a Delta Scuti variable with amplitude variations of 0.01 magnitudes. ... The star system 59 Serpentis, also known as d Serpentis, is a triple star system. The primary system is a spectroscopic binary consisting of an A-type star and an orange giant, while the secondary is another orange giant. The system shows irregular variations in brightness between magnitudes 5.17 and 5.2. [Serpens. Wikipedia]