The Chamaeleon complex is a large star forming region (SFR) at the surface of the

Local Bubble The Local Bubble, or Local Cavity, is a relative superbubble, cavity in the interstellar medium (ISM) of the Orion Arm in the Milky Way. It contains the List of nearest stars and brown dwarfs, nearest stars and brown dwarfs and, among others, the ...

that includes the Chamaeleon I, Chamaeleon II, and Chamaeleon III dark clouds. It occupies nearly all of the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Chamaeleon Chamaeleon () is a small constellation in the deep southern sky. It is named after the chameleon, a kind of lizard. It was first defined in the 16th century. History Chamaeleon was one of twelve constellations created by Petrus Plancius f ...

and overlaps into

Apus Apus is a small constellation in the Southern Celestial Hemisphere, southern sky. It represents a bird-of-paradise, and its name means "without feet" in Greek language, Greek because the bird-of-paradise was once wrongly believed to lack feet. ...

Musca is a small constellation in the deep southern sky. It was one of 12 constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman, and it first appeared on a celestial globe in diameter p ...

Carina Carina may refer to: Places Australia * Carina, Queensland, a suburb in Brisbane * Carina Heights, Queensland, a suburb in Brisbane * Carina, Victoria, a locality in Mildura Serbia * Carina, Osečina, a village in the Kolubara District ...

and

Octans Octans is a faint constellation located in the deep southern celestial hemisphere, Southern Sky. Its name is Latin for the eighth part of a circle, but it is named after the octant (instrument), octant, a navigational instrument. Devised by kingd ...

. The mean density of X-ray sources is about one source per square degree.

Chamaeleon I dark cloud

The Chamaeleon I (Cha I) cloud is one of the nearest active star formation regions at ~160 pc. It is relatively isolated from other star-forming clouds, so it is unlikely that older pre-main sequence (PMS) stars have drifted into the field. The total stellar population is 200–300. The Cha I cloud is further divided into the North cloud or region and South cloud or main cloud. Star-formation began 3-4 Myrs in the southern region and 5-6 Myr ago in the northern region. The stars have a median age of about 2 Myrs. The age was later revised to 1-2 Myr. HD 97300 emits X-rays, illuminates the reflection nebula IC 2631 and is one of the highest mass members of the Cha I cloud,

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

B9V, a

Herbig Ae/Be star A Herbig Ae/Be star (HAeBe) is a pre-main-sequence star – a young () star of spectral types A or B. These stars are still embedded in gas-dust envelopes and are sometimes accompanied by circumstellar disks. Hydrogen and calcium emission lines ...

without emission lines. Cha Helpha 1 is an object of spectral type M8 in the Chamaeleon I dark cloud that was determined in 1998 to be an X-ray source and as such is the first X-ray emitting

brown dwarf Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...

found. There are some seventy to ninety X-ray sources in the Chamaeleon I star forming region. The Uhuru X-ray source (4U 1119–77) is within the Chamaeleon I cloud. This source region within the Chamaeleon I dark cloud was observed by

ROSAT ROSAT (short for Röntgensatellit; in German X-rays are called Röntgenstrahlen, in honour of Wilhelm Röntgen) was a German Aerospace Center-led satellite X-ray telescope, with instruments built by West Germany, the United Kingdom and the Un ...

on February 9 at 22:14:47 UTC to February 18, 1991, 17:59:12 UTC, and on March 6, 1991, from 09:12:19 to 13:05:13 UTC. This cloud contains both "weak" T Tauri (WTT) stars and "classical" T Tauri (CTT) stars. Chamaeleon I X-ray ROSAT source 66 is at RA 11^h 17^m 36.4-37.9^s Dec -77° 04' 27-50", is a CTT, Chamaeleon I No. T56, aka CTT star HM 32. The Chamaeleon I dark cloud was observed with the Imaging Proportional Counter (IPC) on board the

Einstein Observatory Einstein Observatory (HEAO-2) was the first fully imaging X-ray telescope put into space and the second of NASA's three HEAO Program, High Energy Astrophysical Observatories. Named HEAO B before launch, the observatory's name was changed to ho ...

for 2.5 h on January 23–24, 1981, identifying some 22 X-ray sources. None of these sources was closer than 8' to 4U 1119–77. A survey of stars in Chamaeleon I with VLT/SPHERE showed that 13 out of 20 systems showed a

protoplanetary disk A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion disk; while the two are sim ...

in polarized scattered light. Systems such as HD 97048, SZ Chamaeleontis, and the WW Chamaeleontis showed morphological structures. HD 97048 also shows a kink in its carbon monoxide gas disk structure, which was interpreted with the presence of a

protoplanet A protoplanet is a large planetary embryo that originated within a protoplanetary disk and has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometer-sized planetesimals that gravitatio ...

inside around the star and inside the disk. Another notable member of Chamaeleon I is

OTS 44 OTS 44 is a free-floating planetary-mass object or brown dwarf located at in the constellation Chamaeleon near the reflection nebula IC 2631. It is among the lowest-mass free-floating substellar objects, with approximately 11.5 ti ...

, which is a

planetary-mass object A planetary-mass object (PMO), planemo, or planetary body (sometimes referred to as a world) is, by geophysical definition of celestial objects, any celestial object massive enough to achieve hydrostatic equilibrium, but not enough to sustain c ...

surrounded by a disk. Other notable objects are Cha J11110675-7636030, which has a mass of 3-6 and might be surrounded by a protoplanetary disk, and

Cha 1107−7626 Cha 1107−7626 (Cha J11070768−7626326) is a free-floating planetary-mass object in the Chamaeleon I star-forming region, about distant from the Solar System. It is the lowest-mass object with hydrocarbons detected in its disk (as of ...

(6-10 ), which also is surrounded by a disk.

Chamaeleon II dark cloud

Chamaeleon II contains the Uhuru source 4U 1302–77. It is close to RXJ 1303.1-7706 at RA 13^h 03^m 04.70^s Dec -77° 06' 55.0", a K7-M0 new WTT. The Chamaeleon II dark cloud contains some 40 X-ray sources. Observation in Chamaeleon II was carried out from September 10 to 17, 1993. Source RXJ 1301.9-7706, a new WTTS candidate of

K1, is closest to 4U 1302–77. Stars in Chamaeleon II have a mean age of 2-6 Myr. This age was later revised to 1-2 Myr. Cha II stars have a larger disk fraction than Cha I in this study. A study with

ALMA Alma or ALMA may refer to: Arts and entertainment * ''Alma'' (film), a 2009 Spanish short animated film * ''Alma'', an upcoming film by Sally Potter * ''Alma'' (Oswald de Andrade novel), 1922 * ''Alma'' (Le Clézio novel), 2017 * ''Alma'' ( ...

detected 22 disks around stars in Cha II in continuum. There are also candidate planetary-mass objects in Cha II that are surrounded by disks.

Chamaeleon III dark cloud

"Chamaeleon III appears to be devoid of current star-formation activity." There are two particularly prominent nebulae associated with this area. The smaller is commonly known as the Thumbprint Nebula and the larger The Talon Nebula.

Extended definition

The cloud is sometimes extended with an eastern part, and together with the distinctively long Dark Doodad Nebula (or Musca nebula) to the north the complex is called the ''Musca-Chamaeleonis Molecular Cloud''. Two foreground associations are found near the Chamaeleon dark clouds. These are named after ε Chamaeleontis (3-5 Myr, distance 110 parsec) and η Chamaeleontis (4-8 Myr, distance 97 parsec). The proper motion of these associations are distinct from Chamaeleon I and II, but it is unclear whether the associations are physically connected to the dark clouds. One notable member of the ε Chamaeleontis association is WISEA J120037.79-784508.3, which is one of the closest brown dwarfs that is surrounded by a disk.

Gallery

File:The Ominous Chamaeleon I Dark Cloud (noirlab2519a).jpg, Middle and south of Cha I in visible light with the

Víctor M. Blanco telescope The Víctor M. Blanco Telescope, also known as the Blanco 4m, is a 4-metre aperture telescope located at the Cerro Tololo Inter-American Observatory, Chile on the summit of Mt. Cerro Tololo. Commissioned in 1974 and completed in 1976, the telescop ...

. This view does not contain the northern part of Cha I. File:A cosmic master of disguise (potw2329a).jpg, Infrared view ( VIRCam) of the north of Cha I (reflection nebula IC 2631) File:An infrared view of the IRAS 11051-7706 object in Chamaeleon (eso2307e).jpg, Infrared view (VIRCam) of the middle of Cha I, with Ass Cha T 2-21 (top) and Ced 110 IRS 4 (middle) File:An infrared view of the HH 909 A object in Chamaeleon (eso2307d).jpg, Infrared view (VIRCam) of the south of Cha I, including HD 97048, DI Chamaeleontis (both at the upper left) and Cha IRN (bright nebula at the lower right) File:Chamaeleon (32041290740).png, Another view of the south of Cha I, this time with Hubble File:Ced 110 IRS 4 (IRAS 11051-7706).png, Detailed view of the two disks of Ced 110 IRS4 (center) and the surrounding nebula with JWST File:Variable Star DI Cha.jpg, DI Chamaeleontis nebula in detail with Hubble File:Light Cones of the Cha IRN (24109069837).png, Detail of the young star Cha IRN with HH909A, with Hubble File:Coalsack and Dark Doodad Dark Nebulae.jpg, The distinctively thin Doodad nebula can be seen south of the large

Coalsack nebula The Coalsack Nebula (Southern Coalsack, or simply ''the'' Coalsack) is a dark nebula, which is visible to the naked eye as a dark patch obscuring part of the Milky Way east of Acrux (Alpha Crucis) in the constellation of Crux (constellation), Cru ...

at the top. File:Chamaeleon I cloud.png, This is a

false-color image in X-rays between 500 eV and 1.1 keV of the Chamaeleon I dark cloud. The contours are 100 μm emission from dust measured by the

IRAS The Infrared Astronomical Satellite (Dutch language, Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a astronomical survey, survey of the entire night sky at infrared wavelengths. Launched on 25 Janu ...

satellite.

References