| Constellations (8) | |
|---|---|
| Caelum, Columba, Dorado, Horologium, Hydrus, Pictor, Reticulum, Volans | |
| Nomenclature | |
| Abbreviation | Sel |
| Genitive | Selachimorphi |
| Pronunciation | Name: /'sel•a•chē•mōr•fis/ Genitive: /'sel•a•chē•mōr•fī/ |
| Symbolism | the shark |
| Geometry | |
| Midpoint right ascension | 04h 35.25m |
| Midpoint declination | −54° 32.68' |
| Northernmost border | −27° 01.49' |
| Southernmost border | −82° 03.87' |
| Westernmost border | 00h 06.13m |
| Easternmost border | 09h 04.38m |
| Quadrant | SQ1 |
| Crossed by | Summer meridian |
| Bordering caelregios | Araneus (N) Hippocampus (NW) Malus (E) Simianus (SE) Solarium (S/W) |
| Segments | 46 |
| Area | 1568.171 sq. deg. (11th) |
| Proportion of the sky | 38.014‰ |
| Average constellation area | 261.362 sq. deg. (11th) |
| Stars | |
| Named stars | 3 |
| Stars in the figure | 3 |
| Naked eye stars (m < 6.50) |
175 |
| BF stars | 180 |
| Bright stars (m < 3.00) |
3 |
| Brightest star | Alpha Columbae (2.60m) |
| Nearby stars (D < 10.00 pc, 32.62 ly) |
5 |
| Nearest star | GJ 1061 (3.66 pc, 11.99 ly) |
| Messier objects | 0 |
| Visibility | |
| Full visibility range | 7°N–90°S |
| Partial visibility range | 62°N–7°N |
| Midnight culmination date | November 30 |
Selachimorphus is a caelregio located in the first quadrant of the southern hemisphere at its midpoint, but it extends into the second quadrant. Selachimorphus is the smallest caelregio with an area of 1568 square degrees, covering about 38‰ of the sky. Selachimorphus is divided into eight constellations (listed in the infobox).
Selachimorphus doesn't contain many bright stars and interesting features. But this caelregio does contain two famous deep sky objects: the Large Magellanic Cloud (LMC) and its embedded nebula: the Tarantula Nebula (NGC 2070). This caelregio also contains R136a1, the most massive star known.
Name and symbolism[]
Selachimorphus is named after the Latin word for shark, which is a type of fish like a component constellation Dorado (swordfish), and unrelated water snake (Hydrus). It is also imagined that shark, swordfish, water snake, dove (Columba), and flying fish (Volans) are drawn on an easel (Pictor) within the time limit using the clock (Horologium). If the drawing is completed before time runs out, a reticle (Reticulum) is awarded, but if time runs out, an easel would be broken apart using a chisel (Caelum).
Notable stars[]
Bright stars[]
A B-type subgiant Phact is the Selachimorphus' brightest star at a magnitude of 2.60, located in Columba.
Selachimorphus contains just two other bright stars with magnitudes less than 3.00: a G-type main sequence Beta Hydri (2.82m), and an F-type subgiant Head of Hydrus (2.91m).
Nearby stars[]
A red dwarf GJ 1061 is the Selachimorphus' nearest star at a distance of 11.99 light-years (3.66 parsecs), located in Horologium.
Another interesting nearby star is Kapteyn's Star in Pictor, which is also a red dwarf but variable of BY Draconis type, given the variable star designation VZ Pictoris. With the proper motion about 8 arcseconds per year, it is the second highest proper motion star known, after Barnard's Star located in Tarandus. Elemental abundances indicate that this star was part of the Omega Centauri globular cluster that is remnant of a dwarf galaxy that collided into the Milky Way. It is the nearest halo star known at a distance of 12.77 ly (3.92 pc). This star was discovered by a Dutch astronomer Jacobus Kapteyn in 1898.
R136a1[]
The most massive star known is R136a1, massing 265 solar masses. This blue hypergiant star is located in the super star cluster R136 in the LMC to be mentioned below, located in Dorado. It is also the most luminous star known at 8.7 million times more luminous than our sun.
Variable stars[]
Gamma Doradus is a prototype variable star that varies in brightness by less than tenth of a magnitude caused by pulsations owing to nonradial gravity wave oscillations. The variability period is about 18 hours.
Another prototype variable star is S Doradus. This star is located in the LMC. The variability exhibits long, slow changes in brightness, punctuated by occasional outburst. S Dor variable can be considered as a class of Luminous Blue Variable (LBV).
R Doradus, which is a Mira-type variable, varies from 4.8 to 6.6 in magnitude. The visual magnitude is 5.73, but in infrared light, it is one of the brightest stars in the night sky. With an angular diameter of 57.5 mas, it is apparently the largest star seen from Earth other than the Sun.
Binary stars[]
Zeta Reticuli is a binary system comprising of two solar analogs. The two stars are separated by 5.2 arcminutes or 3750 AU at a distance of 12.1 parsecs, which is wide enough to be resolved with the unaided eye under a dark sky. Component A is speculated to have six planets while component B has five.
Planetary systems[]
As of 2015, there are nearly half a hundred exoplanets known around approximately 25 stars in Selachimorphus.
HD 40307 (P8 Sel) in Pictor has six super-Earths, all within the orbit of Venus, five within the orbit of Mercury. Beta Pictoris in Pictor has a massive planet named Midas (Beta Pictoris b, P301) which was detected by direct imaging.
Located in Hydrus, HD 10180 (P11 Sel) has seven confirmed planets, two unconfirmed planets, and three hypothetical planets. The innermost planet, Moneta (HD 10180 b, P455), was the first mid-Earth exoplanet known. It masses 1.75 M⊕ and sizing at 1.19 R⊕. Moneta takes just 28 hours to orbit the star at a distance of about 1⁄48 the Earth–Sun distance. Also there are speculatively three super-Earths, six midplanets and two sub-Jupiters in the HD 10180 system.
Located in Dorado, Gliese 163 (P22 Sel) contains three planets, the innermost planet is a midplanet (13.11 M⊕), the middle planet is a super-Earth (8.67 M⊕) in the habitable zone, and the outermost planet is a sub-Jupiter (0.15 MJ). The two inner planets have densities of a shade over 5 g/cm3 while the outer has a density of 1½ g/cm3.
Notable deep sky objects[]
Selachimorphus contains the famous Large Magellanic Cloud (LMC), which is a Milky Way's satellite galaxy located in Dorado with some of it stretching into Mensa, which is in Solarium. The LMC is an irregular galaxy with great deal of star formation. The LMC in Dorado contains the spectacular Tarantula Nebula (NGC 2070, C103), which is the largest known emission nebula in the universe. Within that nebula, there is R136, which is a super star cluster containing the most massive star known mentioned above. Also in the LMC, the supernova took place in 1987, which was observed by modern astronomers and spectators, even with their naked eyes. It was the first supernova visible to the naked eye since 1604 when the supernova last took place in the Milky Way. The supernova remnant is now designated SN 1987A.
In Carina, there is NGC 3532 (also known as the Wishing Well Cluster), which is an open cluster. In Reticulum, there is the Topsy Turvy Galaxy (NGC 1313), which is a barred spiral galaxy. This galaxy had a recent collision with another galaxy as evidenced from scattered patches of stars in its arms.
In Dorado, there is the Southern Seagull Nebula, which comprises of several objects including NGC 2035, NGC 2029, and NGC 2032. NGC 2020 is the small oblong "hole" toward the right in the image. The bulbous structure to the right of NGC 2020, whose tendrils appear like a supernova remnant, is not designated yet.
Gallery[]
 The Large Magellanic Cloud (LMC) |
 The Tarantula Nebula (NGC 2070, C103), located in the LMC |
 The super star cluster R136, located in the Tarantula Nebula |
  The Topsy Turvy Galaxy (NGC 1313) |
  |
Visibility[]
In the northern hemisphere, Selachimorphus can be visible throughout spring into summer. A significant portion of this caelregio can easily be visible from the north tropics and in the southern hemisphere, however at least a small portion can be visible up to 62°N. But north of 50°N such as in London and Moscow, only two northernmost constellations of this caelregio are visible –– Caelum and Columba. In Antarctica, the entire caelregio can be seen rotating around the south pole in counterclockwise direction, completing a revolution in one sidereal year at a given time.
Selachimorphus is the faintest caelregio as it contains only three stars of less than 3.00m, meaning that from the urban areas, Selachimorphus would only been seen as the triangle of faint stars and a smudge of the Large Magellanic Cloud.
Zodiac[]
Since the Sun never crosses Selachimorphus, this is not a zodiacal caelregio.