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|Aquila, Hercules, Ophiuchus, Sagitta, Sagittarius, Scutum|
|Pronunciation|| Name: /'tər•an•dis/|
|Midpoint right ascension||18h 13.62m|
|Midpoint declination||+02° 01.40'|
|Northernmost border||+51° 19.46'|
|Southernmost border||−45° 16.65'|
|Westernmost border||15h 48.50m|
|Easternmost border||20h 38.74m|
|Crossed by|| Ecliptic|
|Bordering caelregios|| Avis (N)|
|Area||3882.439 sq. deg. (7th)|
|Proportion of the sky||94.113‰|
|Average constellation area||647.073 sq. deg. (3rd)|
|Stars in the figure||4|
| Naked eye stars|
(m < 6.50)
| Bright stars|
(m < 3.00)
|Brightest star||Altair (0.77m)|
| Nearby stars|
(D < 10.00 pc, 32.62 ly)
|Nearest star||Barnard's Star (1.83 pc, 5.98 ly)|
|Full visibility range||44°N–38°S|
|Partial visibility range|| 90°N–44°N|
|Midnight culmination date||June 24|
Tarandus is a caelregio located in the fourth quadrant of the northern hemisphere at its midpoint, but it extends into the southern hemisphere and into the third quadrant. Tarandus is divided into six constellations (listed in the infobox), including Hercules, Ophiuchus, and Sagittarius.
Tarandus is located in the rich star fields because it points near the center of our galaxy. Because of this, this caelregio contains many examples of nebulae, star clusters, and star clouds but very few galaxies. Tarandus also contains the second nearest star system to Earth, which is the red dwarf Barnard's Star, and is also the highest proper motion star known.
Name and symbolism Edit
Tarandus is named after the Latin word for reindeer. This caelregio can also be called Rangifer since it also means reindeer in Latin. It is imagined that reindeer, although a holiday creature, does share little relationship with eagle (Aquila). Reindeer wears the shield (Scutum) for protection as worn by Heracle (Hercules), especially from arrows (Sagitta).
Notable stars Edit
Bright stars Edit
An A-type main sequence Altair is the Tarandus' brightest star at a magnitude of 0.77, located in Aquila. Altair is one of the stars that make up the Summer Triangle, the other two are Vega and Deneb, both located in the neighboring caelregio Avis.
The other notable bright stars in Tarandus are Kaus Australis (a 1.80m B-type giant located in Sagittarius), Rasalhague (a 2.08m A-type giant located in Ophiuchus), and Kaus Borealis (a 2.83m K-type subgiant located in Sagittarius).
Nearby stars Edit
Barnard's Star is the Tarandus' nearest star at a distance of 5.98 light-years (1.83 parsecs), located in Ophiuchus. It is also the second nearest star system overall after the Alpha Centauri system in Simianus. Barnard's Star is a red dwarf with the highest known proper motion, moving at 10.3 arcsec/year. Barnard's Star can sometimes be referred as Proxima Ophiuchi. This star was discovered by the American astronomer E.E. Barnard in 1916. Barnard's Star was claimed to have planets but further observations find no evidence for planets. However, Barnard's Star is speculated to have three sub-Earth planets all orbiting within 0.105 AU. The innermost planet orbits only 0.008 AU from the star, taking 17 hours to orbit. Yet the planet's temperature is just 664 K (735°F, 390°C), cooler than Mercury and Venus and it is a lava planet caused by the intense tidal forces from its parent star.
Another notable nearby star is 70 Ophiuchi, which was claimed to have the first ever extrasolar planet discovered in 1855, but subsequent observations gradually ruled out the planet's existence. However, 70 Oph is speculated to have eight planets, four orbit component A and four orbit component B. 70 Oph is a K-type main sequence star located 16.58 light-years away. Yet another nearby star speculated to have planets is 12 Ophiuchi, which is a K-type star speculated to contain nine planets, one more than in our solar system.
Variable stars Edit
Multiple stars Edit
36 Ophiuchi is a triple star system, all are K-type stars. Star C is separated from the A-B pair by about 700 arcseconds, which itself separated by 4.6 arcseconds at minimum. 36 Ophiuchi speculatively contains eight planets, two around Star A, one around Star B, and five around Star C.
Double stars Edit
The two stars of Xi Sagittarii are separated by 0.46° which is more easily resolvable with the naked eye. ξ2 is nearly 52⁄3 times further away from the observer than ξ1, 2069 vs. 365 light-years.
Planetary systems Edit
As of 2015, there are nearly a hundred exoplanets identified orbiting more than 80 stars in Tarandus. A notable example is HD 154345 (P12 Tar) in Hercules, which has a Jupiter-twin Alpheus (HD 154345 b, P170). HD 154345 also contains six speculative planets, four of them are terrestrials. Also in Hercules, HD 164922 (P15 Tar) has a long-period saturnian planet named Diomedes (HD 164922 b, P182) along with two speculative smaller planets closer to the star.
14 Herculis (P1 Tar) has two long-period planets: Cerenytis (14 Her b, P20) and Eurystheus (14 Her c, P163). 14 Her also has two speculative planets orbiting closer than the two known planets: 14 Herculis d and 14 Herculis e. 14 Her e is in a 1:4 resonance with Cerenytis while Cerenytis is in a 1:4 resonance with Eurystheus. So this puts three outer planets in a 1:4:16 laplacian resonance, which would dynamically make 14 Herculis a very interesting planetary system.
But the most famous example of a planetary system in Tarandus is GJ 1214 (P35 Tar) in Ophiuchus, which has a super-Earth exoplanet detected by transit. This planet, named Shesha (GJ 1214 b, P385), is a mini-Neptune with a hydrogen-helium atmosphere. Despite this planet has a relatively cool temperature of 516 K compared with all other transiting exoplanets, it has one of the closest orbits to the star than any other exoplanets. The planet's distance from the star is only 1⁄70 the Earth–Sun distance and takes just 38 hours to orbit the star. The reason why this planet is so cool is because the parent star's radiation is only about 1⁄300 as strong as the Sun.
Another star with a transiting planet is HD 149026 (P9 Tar, in Hercules), which has a planet named Augean (HD 149026 b, P151). Based on its density, the core makes up merely 70% the mass of this planet. The mass of this planet is 0.36 MJ and the density 0.81 g/cm3.
Notable deep sky objects Edit
Tarandus contains a lot of notable deep sky objects. The Lagoon Nebula (M8, NGC 6523), which is an interstellar cloud, and Trifid Nebula, which is an HII region, are located in Sagittarius. The Omega Nebula (also known as the Swan Nebula, Horseshoe Nebula, Checkmark Nebula or the Lobster Nebula) (M17, NGC 6618) is an HII region also located in Sagittarius. Also in this constellation, there is Sagittarius A, which is a supermassive black hole at the center of our galaxy.
There is the Sagittarius Star Cloud (M24, IC 4715). This star cloud does contain the open cluster NGC 6603. Sagittarius also contains the nearest barred irregular galaxy Barnard's Galaxy (NGC 6822, C57) located just 1.6 million light-years from the Milky Way. This galaxy is similar in structure and composition to the Small Magellanic Cloud (SMC).
The Twin Jet Nebula (M2-9) is a planetary nebula located in Ophiuchus. Also in this constellation, there is the Little Ghost Nebula (NGC 6369). There is the Hercules Globular Cluster (M13, NGC 6205), which is a bright globular cluster visible to the naked eye in Hercules. Sagitta contains the Necklace Nebula, which is a planetary nebula dotted with dense, bright knots of gas that resemble diamonds in a necklace.
The Rho Ophiuchi cloud complex is a group of objects in Ophiuchus south of the star Rho Ophiuchi. It contains two globular clusters in the upper right, one reflection nebula from above to the upper left, and one dark nebula to the upper left in the image.
There is a globular cluster in Sagittarius: M22 (also known as the Sagittarius Cluster) (NGC 6656), which is the first known globular cluster discovered in 1665 (possibly earlier). This globular cluster is the third brightest in the sky after Omega Centauri and 47 Tucanae and before M13 just mentioned. This cluster is even more notable because it contains a planetary nebula. Sagittarius contains another globular cluster: M55 (NGC 6809). This cluster appears more grainy than nebulous, which is more akin to an open cluster than a globular cluster. Sagittarius contains yet another globular cluster: M70 (NGC 6681). This globular cluster is located close to the center of our galaxy and is visible through a small telescope. This constellation contains yet another globular cluster: M54 (NGC 6715), which was the first globular cluster found outside of our galaxy belonging to the Sagittarius Dwarf Elliptical Galaxy. However this cluster was previously thought to belong to our galaxy until 1994 after it was discovered by Charles Messier in 1778.
Ophiuchus contains Kepler's Supernova Remnant SN 1604 located in our galaxy after the progenitor star exploded in 1604. This supernova was seen by Johannes Kepler. It was the first naked-eye supernova since 1572 and the next naked-eye supernova would not take place until 1987.
In Sagittarius, there is a rare example of triple merger of galaxies appearing like a bird: the Tinker Bell Triplet (also dubbed 'The Bird'). This triplet is composed of two massive spiral galaxies and an irregular galaxy. In Ophiuchus, there is the Starfish Galaxy (NGC 6240), which is a remnant of a merger between two smaller galaxies and is a nearby ultraluminous infrared galaxy.
In the northern hemisphere, Tarandus can be visible from late fall till mid winter. Since the area of Tarandus is extremely similar between northern and southern hemispheres, observers at the north pole and south pole would see about equal proportions of Tarandus. The north pole observer would find that the northern half of Tarandus appears to circumnavigate clockwise along the horizon, and the southern half would never rise. The south pole observer would see that the southern half of Tarandus appears to circumnavigate counterclockwise along the horizon, and the northern half would never rise.
Sagittarius contains the "Teapot" asterism which the main stars make up the prominent arrow we see in the sky.
The Sun appears to cross Tarandus from November 30 till February 15: it crosses the constellations Ophiuchus (November 30 till December 17), Sagittarius (December 18 till January 18), and then Capricornus (January 19 till February 15). This zodiacal caelregio is located between Simianus to the west and Hippocampus to the east.
Tarandus was formerly in the sign of zodiac from November 23 till January 20.