Ophiuchus

Ophiuchus or Ophiuchus (the carrier of the snake or Serpentarium), also known as "The hunter of serpents", is one of the 88 modern constellations and one of the 48 listed by Ptolemy. It can be seen in both hemispheres between the months of April to October because it is located on the celestial equator.

To the north of Ofiuco is Hercules, to the southwest Sagittarius (Sagittarius) and to the southeast Scorpion (Scorpius); to the east are the Serpent's Head (Serpens Caput) and Libra, while to the west are the Eagle (Aquila), Sobieski's Shield (Scutum) and the Serpent's Tail (Serpens Cauda). The constellation is flanked by the Head and the Tail of the Serpent, which can be considered as a single constellation: Serpent (Serpens), which crosses it. The resulting set is a man surrounded by a snake.

Notable features

Ophiuchus AlltheSky.com constellation.

The brightest star in the constellation is α Ophiuchi, which is called Rasalhague or Ras Alhague, a white subgiant of spectral type A5IVnn, 25 times more luminous than the Sun and 48 light-years distant. Next in brightness is η Ophiuchi, known as Sabik, a binary composed of two main-sequence white stars of spectral type A2.5V and A3V; What is unusual about the system is the great eccentricity of the orbit (ε = 0.95), which makes the separation between the components oscillate between 2 AU and 65 AU, with an orbital period of 88 years.

The third brightest star, ζ Ophiuchi, is a very luminous and massive blue star of type O9V —74,000 times more luminous than the Sun and 20 times more massive— considered a runaway star, that is, it is thought to have been ejected from a star system by the explosion of a companion star. Yed Prior —official name of δ Ophiuchi— has contrasting characteristics, a cold red giant of type M0.5III and an effective temperature of 3811 K.

Location of the Star of Barnard—star closest to the solar system after α Centauri—in the night sky

In this constellation are located several of the closest stars to our solar system. Thus, Barnard's Star is, after the three components of Alpha Centauri, the closest star to the Sun, being located just under 6 light years. It is a red dwarf of spectral type M4.0V that has approximately 16% of the solar mass and a radius equal to 19% of that of the Sun. Its bolometric luminosity—including emitted infrared light—is 3.5/1,000 times that of the Sun. With an age between 7 and 12 billion years, Barnard's Star is considerably older than the Sun, and could be among the oldest stars in the Milky Way.

Also in Ofiuco are the 70 Ophiuchi and 36 Ophiuchi systems, made up of orange dwarfs —stars similar to the Sun although cooler and fainter—, both less than 20 light-years away. The two components of 70 Ophiuchi, of type K0V and K4V, have an eccentric orbit (ε = 0.499), which causes their separation to fluctuate between 11.6 and 34.8 au along their orbital period of 88.4 years. It is 16.64 light years from the solar system. For its part, 36 Ophiuchi is a triple system, where the two main components, of type K0V and K1V, also move in a remarkably eccentric orbit (ε = 0.922), varying the separation between them from 7 to 169 AU; a third orange dwarf —type K5V— orbits this binary at a distance between 4,370 and 5,390 AU.

Distant 18.7 light-years, Gliese 644 is a quintuple star system, the system of its characteristics closest to Earth, all of its components being red dwarfs. In the first instance, Gliese 644 is a visual binary with an orbital period of 627 days, but in addition, one of the components is a spectroscopic binary with a period of 2.96 days. The system is completed by two other stars much more distant, visually at 72 and 220 arcseconds, respectively.

Among the variables of the constellation, it is worth mentioning RS Ophiuchi, a recurring nova whose last outburst took place on February 12, 2006. Likewise, in 1604 the Kepler supernova (SN 1604) appeared in this constellation, the last supernova observed in our own galaxy at a distance of no more than 6 kiloparsecs. It was a Type Ia supernova visible to the naked eye that at its brightest outgrew any other star in the night sky.

Several stars with exoplanets are known in Ophiuchus. Around Gliese 628 (Wolf 1061), a red dwarf of spectral type M3.5V, orbit three planets with masses low enough to be rocky planets, although their sizes and densities are currently unknown. One of these is a "super-Earth" hovering near the inner edge of the star's habitable zone. Around another red dwarf, GJ 1214, another super-Earth with a diameter 2.68 times larger than the Earth's diameter has also been discovered. Another star with an extrasolar planet is Rosalíadecastro, the official name of HD 149143, a yellow subgiant of type G0IV whose planet, called Riosar, has a diameter 5% larger than that of Jupiter. Its separation from its star is only 0.053 AU.

Image of the M62 globular cluster obtained with the Hubble space telescope

In Ophiuchus is the M2-9 nebula, also known as the Twin Jets nebula, a planetary nebula located about 2,100 light-years away. It is a bipolar nebula with two lobes of material emitted by the binary star at its center. The outer shell is estimated to be about 1,200 years old. NGC 6369 is another planetary nebula, also called the Little Spirit Nebula or Little Ghost Nebula, as it appears as a small ghostly cloud surrounding the dim central star. Images from the Hubble Space Telescope show how the stellar remnant at its center radiates ultraviolet light into the surrounding gas.

Several globular clusters of the constellation can be observed with binoculars. M9 is one of the closest globular clusters to the nucleus of the Milky Way, at a distance of 5,500 light-years from it and 25,800 light-years from our solar system. M10 and M12 are also clusters of this type, distant 14,300 and 16,000 light years respectively; the latter is characterized by having very few low-mass stars. For its part, M19 is one of the most flattened globular clusters known, which may be due to its proximity to the center of the galaxy; it is a rich and dense cluster, as well as considerably concentrated. M62, an irregular globular cluster, is also close to the galactic nucleus —5,500 light-years away— and is one of the most massive and luminous clusters in our galaxy.

Main Stars

• α Ophiuchi (Ras Alhague or Rasalhague), the brightest constellation with magnitude 2,09 and white; located near Ras Algethi (α Herculis) north of the constellation.
• β Ophiuchi (Cebalrai), orange giant type K2III and magnitude 2,77, also located north of the constellation.
• γ Ophiuchi, white star of magnitude 3,75 where a circumestelar disc of dust has been detected.

γ Ophiuchi, a fugitive star that travels 24 km/s and creates a shock wave in front of it

• δ Ophiuchi (Yed Prior), of magnitude 2,73 and red, located south of the constellation and near the head of the snake.
• ε Ophiuchi (Yed Posterior), very close to Yed Prior and of magnitude 3.23, a giant yellow star.
• γ Ophiuchi, the third brightest of constellation (magnitude 2.54), star of the rare spectral type O (dark blue).
• η Ophiuchi (Sabik), the second most brilliant with magnitude 2,43, white binary star of the main sequence.
• θ Ophiuchi, hot subgigante blue of magnitude 3.25.
• κ Ophiuchi, orange giant of magnitude 3,20.
• λ Ophiuchi (Marfik), triple star located in the elbow of Ofiuco.
• μ Ophiuchi, mercury-manganese star of magnitude 4,62.
• Ophiuchi, an orange giant accompanied by two brown dwarfs.
• ρ Ophiuchi, binary star surrounded by a nebula of reflection.
• υ Ophiuchi, star Am and binaria spectroscopic magnitude 4.63.
• φ Ophiuchi, yellow giant of magnitude 4,29.
• χ Ophiuchi, star Be of magnitude 4,42.
• Ophiuchi, an orange giant of magnitude 4,49.

Image of interferometry and radio waves of RS Ophiuchi obtained days after its 2006 burst.

• 45 Ophiuchi (d Ophiuchi), giant or subgross white-yellow of magnitude 4,29.
• 51 Ophiuchi, star Herbig Ae/Be surrounded by a circum-stellar disk of gas and dust.
• 58 Ophiuchi, distant white-yellow star 57 light years.
• 67 Ophiuchi, blue supergiant of magnitude 3,97 that is part of the star cluster Collinder 359.
• 70 Ophiuchi and 36 Ophiuchi, star systems close to Earth, the first to 16.6 light years and the second to 19.5 light years.
• 72 Ophiuchi, white subgiant of magnitude 3.72.
• U Ophiuchi, stellar system whose main component is an eclipsing binary of magnitude 5.72.
• X Ophiuchi, binary system composed of a Mira variable and an orange giant separated about 0.5 seconds of arc.
• And Ophiuchi, cefeida of average magnitude 6,18 whose period is 17,1241 days.
• RS Ophiuchi, a recurring nova formed by a red giant and a white dwarf.
• TW Ophiuchi, carbon star and semi-regular variable of average magnitude 8.20.
• V2129 Ophiuchi, young star T Tauri of magnitude 11,2.
• V2292 Ophiuchi, yellow dwarf of magnitude 6.64 distant 55 light years.
• V2388 Ophiuchi, one of the most brilliant contact binaries in the sky with magnitude 6.26.

Rest of the Kepler supernova, whose light came to Earth in 1604.

• Star of Barnard, the second star closest to the solar system to 5,96 light years, a dark red dwarf not visible to the naked eye. It owes its name to astronomer Edward Emerson Barnard, who in 1916 discovered that it is the star with a greater apparent movement (10.3 seconds of arc per year).
• Rosaliadecastro (HD 149143), a star with a mass superior to that of the Sun, which has an extrasolar planet called Riosar that orbits it. Names chosen by popular vote in Spain under the grant of the NameExoWorlds project by the International Astronomical Union (IAU).
• Gliese 628 (Wolf 1061), red dwarf at 13,81 light years of the solar system.
• Gliese 644 (Wolf 630), the near-Earth quadruple Star System, distant 18.7 light years.
• Gliese 673, 12 Ophiuchi (V2133 Ophiuchi) and Gliese 688, orange dwarfs at 25.2, 31.9 and 34.9 light years respectively.
• Gliese 653 and Gliese 654, a large binary system at 34.7 light years of the solar system.
• GJ 1214, red dwarf with an extrasolate planet.
• G 21-15, system formed by three white dwarfs, one of the few known of these characteristics.
• SN 1604 (Supernova de Kepler), supernova that took place in 1604.

Deep Sky Objects

Image of the M2-9 nebula (also known as a nebula of the Twin Chorros or nebula Butterfly Wings).

• M9, globular cluster of magnitude 7,7, one of the closest to the galactic core. Thirteen variables have been found in this cluster and the brightest stars are 13.5.
• M10 and M12 globular clusters north of the constellation, both yellowed by the giant red and orange stars.
• M19 is a globular cluster slashed only 5200 light years from the center of the galaxy.
• M62, another cluster in the boundary with Scorpion characterized by its irregular shape. It has up to 89 recognized variables, many of them RR Lyrae variables.
• M107, the latter near the galactic plane at a distance of about 20 000 light years; like M9, it is located south of the constellation.
• Nebula M2-9 (also known as a nebula of the Twin Chorros and nebula Butterfly Wings), a bipolar planetary nebula in whose center is a binary star.
• LDN 1773, obscure nebula also known as Pipa nebula.
• NGC 6240, light galaxy in the infrared, remnant of the fusion of two smaller galaxies.
• NGC 6369, planetary nebula also known as the nebula of the Little Spirit or the Little Ghost.

Mythology

Ofiuco at the Atlas Coelestis of John Flamsteed.

In Greek mythology, Ophiuchus corresponds to Asclepius, son of the god Apollo and the mortal Coronide. He developed such skill in medicine that it was said that he was even able to raise the dead. Very offended by this, Hades asked Zeus to kill him for violating the natural order of things, to which Zeus agreed. However, as a tribute to his worth, he decided to place him in the sky surrounded by the serpent, a symbol of renewed life.

Another version tells that Heracles killed Iphytus, son of Eurytus and grandson of Melanius, king of Ecalia, while he was his guest. Zeus, angry, sent him bad dreams that did not let him sleep. Heracles consulted the oracle at Delphi how he could get rid of them; the pythoness Jenodea told him: You murdered your guest. I have no oracles for those like you! Heracles was enraged and carried off the temple's offerings and even the tripod on which Jenodea sat. Apollo was outraged by this and fought Heracles, Zeus intervened in the dispute and they finally became friends again; Heracles returned what he had stolen and the pythoness gave him the following oracle: To get rid of your affliction you must be sold as a slave for a whole year, and the price you get must be delivered to the sons of Iphytus. Heracles was bought by Omphale, queen of Lydia, to be her lover. Heracles bore him several sons; he also chased away bandits from the region. Among other things he killed a gigantic snake that killed men and ruined crops. Zeus created the constellation Ophiuchus to commemorate this victory over the serpent, and Omphale, who finally discovered Heracles' true identity, released him and sent him to Tiryns loaded with gifts.