Malus

Malus is a caelregio located in the second quadrant of the at its midpoint. Malus is the second smallest caelregio after Selachimorphus with an area of 2127 square degrees, covering about 52‰ of the sky. Malus is divided into five s (listed in the infobox).

Malus contains, which is one of the most luminous stars known. This caelregio also contains couple of notable spectroscopic binaries, a recurrent nova, and a supernova remnant.

Name and symbolism
is directly named after the where it was part of Argo Navis to be mentioned below where it is now incorporated into Pyxis. Malus is originally named after the Latin word for, a component of the .

Argo Navis
The component constellations, , and are all splitted from the formerly largest constellation , which had an area of 1667 square degrees, which is about 364 square degrees or 28% larger than the present-day largest constellation. If Argo Navis never split, then it would make up merely 78% of the total area of Malus, while the remaining 22% would be two other Malus' constellations and  that were never part of that former constellation. Then Argo Navis would be the only constellation in the entire sky to occupy most of the caelregio's area. The present-day largest constellation proportion of a caelregio would be Hydra which occupy just 32% of the total area of Felis.

Bright stars
An   is the Malus' brightest star at a  of −0.72, located in Carina. It is also the second brightest star in the sky after in Araneus. The second brightest star is (1.75$th$), which contains a  and an  supergiant. The third brightest is (2.25$th$) in Puppis, which is an O-type supergiant 360,000 times more luminous (21,000 times brighter) than our Sun.

Nearby stars
A  is the Malus' nearest star and the third nearest star overall at a  of 6.60 s (2.02 s), located in Vela. Prior to the discovery of brown dwarf in 2013, a  was previously the Malus' nearest star at a  of 13.17 s (4.04 s), located in Antlia.

Variable stars
This caelregio contains one of the most luminous stars known: with five million times the solar luminosity and 7600 light-years away. Eta Carinae is a so-called (LBV). During the 1840s, Eta Carinae was the second brightest star in the sky after after a brief brightening outburst. As of March 2011, it has an apparent magnitude of 4.47.

is a that reaches a peak magnitude of 6.4 every 12 to 25 years. The usual magnitude of T Pyx is 15.5.

Multiple stars
is a quadruple containing two sets of s. The primary star is a  plus an, bringing the total number of stars in this system to six. δ Vel is the brightest known eclipsing binary but has a deeper minimum.

Gamma Velorum is a sextuple star system containing a between a Wolf-Rayet star and an O-type supergiant. The spectroscopic binary period is 78.5 days at a separation of 1. Another companion, a, is 41.2 away from the binary, easily resolvable with. This star system also contains three  stars.

Planetary systems
As of 2015, there are more than 40 s identified around more than 30 stars in Malus. Three notable examples of planetary systems are (P6 Mal) in Puppis,  (P12 Mal), and  (P24 Mal) in Vela.

HD 70642 has a planetary companion named Lusus (HD 70642 b, P106) which has mass 2.96 in a 6.11-year orbit. HD 70642 also has four speculated planets, two inner and two outer planets relative to Lusus.

99 Puppis has three midplanets, all within the orbit of, an , and a speculated super-Jupiter orbiting at -like distance from the star.

Gliese 370 contains the Mors (, P558). Mors is an massing 14.5  orbiting at 0.26 AU from its star, which is similar in mass to  and  in our. Gliese 370 also contains eight hypothetical planets, two orbit closer to the star than Mors and the rest orbit further away.

(P29 Mal) has a planet directly imaged in Carina. It is a 4.5 M$undefined$ super-Jupiter orbiting at 56 AU and an orbital period of 332 years. The parent star is just 14 million years old. After this planet formed, it migrated outward to explain the planet orbiting so far from the A-type star.

Notable deep sky objects
Malus contains several interesting deep sky objects. The, located in the (Gum 12), which is an  in Vela, was created when the progenitor star exploded about 11000 years ago and the first farmers may have seen this supernova with their s. In that remnant, there is the  (NGC 2736), which may have formed as part of the shockwave that created the whole remnant. The ( 3372, 92) is a  located in Carina, which contains the. This nebula is shined by the luminous blue variable Eta Carinae mentioned above. Also in this constellation, there are the, which means this windblown nebula is shaped by a Wolf-Rayet star at its center, and , which is an emission nebula.

In Vela, there is the (NGC 3132, C74), which is a  that can only be seen using a. Because of the appearance, this nebula is considered to be the southern hemisphere's equivalent of the (M57) located in the northern constellation  in Avis, that's why amateur astronomers often referred to this as the Southern Ring Nebula.

Puppis contains several notable s. These include, , , , and. In Carina,, which is a beautiful young open cluster, can be seen using a. Westerlund 2 contains a dozen O-type stars. In Vela, the ( 2391, C85), which is a beautiful open cluster containing about 30 stars, most of them are blue. This cluster can be seen using just the. Carina also contains the open cluster. At the center is the young cluster, comprising of nine stars.

In Antlia, there is the bright, which can be visible using binoculars. The galaxy's core is surrounded by a hot giant cloud of ionized hydrogen gas.

Visibility
In the northern hemisphere, Malus can be visible during winter, but all of Malus can only be seen from south of 14°N. Although part of Malus can be seen from south of 78°N. From south of 78°S in Antarctica, the entire caelregio appears to rotate counterclockwise around the south pole making one complete trip in a at a given time.

Zodiac
Since the never crosses Malus, this is not a al caelregio.