Simianus

Simianus is a caelregio located in the third quadrant of the at its midpoint, but it extends into the second and fourth quadrants. Simianus is the third smallest caelregio after Selachimorphus and Malus with an area of 2963 square degrees, covering about 72‰ of the sky. Simianus is divided into eleven s (listed in the infobox), including three famous constellations:, , and.

Simianus contains the nearest star system to Earth as well as the, which is the most recognizable  in the southern sky. This caelregio also contains few recognizable doubles and multiples, as well as a couple of famous s.

Name and symbolism
Simianus is named after the Latin word for. Simianus contains component constellations with symbolisms of animals occupying same habitat as monkeys, such as (Lupus), s (Chamaeleon), s (Scorpius), and  (Musca).

Former name
Vexilius the was the former name for Simianus until December 2010.

Bright stars
A   is the Simianus' brightest star and is also the fourth brightest overall at a  of −0.01.

is the brightest star in Scorpius at a magnitude of 1.09. It is a containing a companion star. Antares is one of the four brightest stars within 5° of the, the others are in Noctua,  in Felis, and  in Araneus.

is an  located in Scorpius. Its magnitude is 1.86.

is a giant located in. Its magnitude is 1.93.

The Southern Cross
is a B-type main sequence 25,000 times more luminous than our Sun. Acrux is the Crux's brightest star and is the twelfth brightest star in the night sky at a magnitude of 0.77. Also Acrux is the southernmost first magnitude star of the sky. Acrux is the leading pointer to the south pole.

is a B-type. Its magnitude is 1.30, the second brightest star in Crux and 19th brightest star in the night sky.

is the nearest star at a distance of 89 light-years. Its magnitude is 1.63, the third brightest star in Crux. Gacrux is 30% more massive than our Sun but it is 84 times larger than our Sun. It is 1500 times more luminous than our Sun and is enriched with.

is a B-type subgiant 10,000 times more luminous than our Sun. It is the faintest member of the Southern Cross at a magnitude of 2.78.

Variable stars
In Scorpius, the  is an unique  star that it turns on and off caused by inclination changes by the gravity of a tertiary star. Antares is a type LC star varying between 0.88 and 1.16 in magnitude.

Multiple stars
Alpha Centauri is a tertiary star system. It comprises of G-type, K-type, and M-type stars. The M-type star is the nearest star to the Sun at a  of 4.24 s (1.30 s). The separation between components A and B ranges from 11.2 to 35.6 AU with an orbital period of 79.91 years. Proxima Centauri orbits the binary at a distance of 13,000 AU with a period between 100,000 to 500,000 years. Despite that closest approach in binary system, the s (region around the star where liquid water is stable on the planet's surface) around both stars should be stable.

Another notable star system is Acrux, which is a comprising of α$th$ and α$th$ Crucis. One of the pair α$undefined$ is a with a period of 76 days at a separation of about 1 AU. The binary period is at least 1500 years at a minimum distance of 430 AU, and may be much longer. Another nearby companion α$1$ Crucis at 90 s away from the binary pair may be just an optical closeness but not gravitationally bound. The suggest that α$2$ is moving further away from the main binary pair. α$1$ may be twice as distant as the main binary pair.

Double stars
Scorpius has a beautiful :. ζ$3$ is a while ζ$3$ is an  and is the brighter of the pair, thus ζ$3$ is 19.5 times more distant than ζ$1$, 2573 vs. 132 light-years. ζ$2$ is a member of the open cluster.

Another double star is. This can be resolved using just the with the separation of 0.66°, a bit more separated than the  of the. ξ$1$ is twice as distant as ξ$2$, 467 vs. 221 light-years.

Solar twin
The most known is. 18 Scorpii is similar to the Sun in terms of mass, radius, temperature, luminosity, metallicity, age, rotation period, and spectral type. The prospects for are very good. I spectulate that 18 Scorpii has 11 planets, three more than our Sun, including a forest planet located in its.

Planetary systems
As of 2015, there are about 80 s known around nearly 60 stars in Simianus. The first example is (P1 Sim) in Scorpius, which hosts the third oldest known planet at 12.7 billion years old that survived the  explosion. This planet, named Methuselah (, P11), orbits at a distance of 23 AU, placing between the orbits of and  in our own.

Another notable planetary system is (P4 Sim), which has four planets with the innermost is a midplanet and the outer three are mid-Jupiters. In Centaurus, (P11 Sim) is the first  known to have a planet (named Lerna (, P115)) which has mass 4.22  and orbits at a distance of 41.

In Scorpius, (P35 Sim) contains two planets, including the habitable planet Cresphontes (, P677). In Ara, (P36 Sim) contains four planets, the inner two are rocky or watery while the outer two are gaseous. (P46 Sim) contains three confirmed planets, one super-Earth and two midplanets, all orbiting within 0.5 AU from the star. It is speculated that 47 Lupi contains 14 planets, six more planets than our solar system with the outermost planet orbiting at 50 AU, beyond the orbit of.

(P49 Sim) contains the nearest known exoplanet, Ixionidae (, P832). The planet masses 1.28 M$1$, making it the lowest-mass planet yet discovered with the. The planet induces stellar wobble at just 51 cm/s, the lowest value ever measured with. Ixionidae takes just 3.236 days to orbit the star at an average distance of 6.261 s. Although right now the planet is unconfirmed.

Notable deep sky objects
Simianus contains two famous s: (7) in Scorpius and  ( 5139, 80) in Centaurus. Crux contains the (NGC 4755), which is an.

In Scorpius, there is the less famous globular cluster. This was the first globular cluster to have its stars resolved and is competing with in Ara for the nearest globular clusters to the Solar System.

In Ara, there is the open cluster (also known as the Ara Cluster) visible to a large. This cluster contains a lot of massive, blue stars including some 24 s. In fact, it is the most compact young not just in the  but the entire  of galaxies. In, there is the (NGC 6087, C89), which is a  open cluster with the variable star  being the brightest member.

Scorpius contains the : the  (NGC 6302, C69); and it also contains the  (NGC 6357), which is a, which contains the open cluster  which is home to several massive stars.

Centaurus contains the (also known as the Bow Tie Nebula), which is a. In this nebula, the temperature is only one kelvin above, which is the coldest known place in the. Also in this constellation, there is the. In Norma, there is the bipolar nebula. This nebula glows red caused by the ultraviolet radiation from the massive central star ionizing hydrogen gas. This nebula is shaped by the star's magnetic field and fast rotation.

Yet another interesting nebula in Centaurus is the ( 2948), which is a   where new stars form. Embedded within the nebula made of glowing reddish cloud of gas is the energetic young star cluster. Also in this constellation, there is the open cluster and emission nebula (also called the Lambda Centauri Nebula) (IC 2944, C100) featuring s called  with sites of active star formation.

Crux contains the (C99), which is a. Coalsack is the largest dark in the sky. It masses 3500 Suns and stretches dozens of light-years.

In Scorpius, the (NGC 6334), which is a red-colored emission nebula caused by ionized hydrogen, can be seen using a small telescope. Located in, we find planetary nebulae, the (MyCn 18) and the  (NGC 5189). The  is a  planetary nebula located in.

Also in Scorpius, there is the, which is a complex. The blue star marking the eye is the multiple star system. This complex includes the prominent blue reflection nebula.

In, there is the (also known as the Tornado Nebula) ( 49/50), which is an unusually tube-shaped emission nebula. It is about 0.3 light-year or 2 trillion miles long, located about 480 light-years away in the star-formation region. Jets of particles emitted from young stars colliding with interstellar clouds in the presence of magnetic fields create this unique tubular spiral shape as seen in the image below. This Herbig-Haro object was discovered on January 12, 2006.

, which is an unique, and (NGC 5128, C77), which is a   or  with unusual dust lane, can be found in Centaurus. It is the only galaxy with opposite rotations between inner and outer arms relative to the observer.

In Lupus, was a  seen from Earth in the year 1006. With a peak magnitude of −7.5, it was the brightest supernova in recorded history. The supernova was approximately 7200 light-years from Earth.

Visibility
In the northern hemisphere, Simianus can be visible from late winter till the dawn of summer. About half of this caelregio can be visible from mid-northern latitudes but all of it can only be visible from very low northern latitudes and in the southern hemisphere. For the Southern Cross (Crux) and the nearest star (α Cen) to be seen, it can only be viewed from south of 35°N, that means that the Southern Cross and α Cen would never be visible from places like Europe, northern and central Asia, and northern half of North America.

The Southern Cross is useful for to southern observers because it points to the south  especially when the bright south pole star is not present, contrasting the bright north pole star  located in Avis.

Zodiac
The appears to briefly cross Simianus from November 23 till November 29: it crosses the only constellation. This al caelregio is located between Noctua to the west and Tarandus to the east.

Simianus was formerly in the from October 24 till November 22.