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 cavity in the interstellar medium (ISM) of the Orion Arm in the Milky Way. It contains the closest of celestial neighbours and among others, the Local Interstellar Cloud (which contains the S ...

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

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 sky. It represents a bird-of-paradise, and its name means "without feet" in Greek because the bird-of-paradise was once wrongly believed to lack feet. First depicted on a celestial globe by Petrus ...

Musca 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 ...

, Carina and

Octans Octans () is a faint constellation located in the deep Southern Sky. Its name is Latin for the eighth part of a circle, but it is named after the octant, a navigational instrument. Devised by French astronomer Nicolas Louis de Lacaille in 1752 ...

. 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. 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 th ...

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 a ...

without emission lines. IC 2631-Eso1605a-crop

Cha Halpha 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 (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen (hydrogen-1, 1H) into helium in their cores, unlike a main sequence, main-sequence star. Instead, they have ...

found. There are some seventy to ninety X-ray sources in the Chamaeleon I star forming region. The

Uhuru Uhuru (a Swahili word meaning ''freedom'') may refer to: People * Uhuru Hamiter (born 1973), American football player * Uhuru Kenyatta (born 1961), President of Kenya since 2013 Places *Uhuru (Tanzanian ward), an administrative ward in the Dodoma ...

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 Uni ...

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 High Energy Astrophysical Observatories. Named HEAO B before launch, the observatory's name was changed to honor Albert E ...

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.

Chamaeleon II dark cloud

Chamaeleon II contains the

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.

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 The Dark Doodad Nebula is a dark nebula near the globular cluster NGC 4372, much closer than the centre of the galaxy and in the galactic plane, having a length of nearly three degrees of arc. Although officially unnamed, this long molecular clo ...

(or Musca nebula) to the north the complex is called the ''Musca-Chamaeleonis Molecular Cloud''. Coalsack and Dark Doodad Dark Nebulae

References

{{DEFAULTSORT:Chamaeleon complex Star-forming regions

Chamaeleon I dark cloud

Chamaeleon II dark cloud

Chamaeleon III dark cloud

Extended definition

See also

References