Chamaeleon complex#Extended definition

File:Planet-forming discs in the Chamaeleon cloud (eso2405d).jpg, showing protoplanetary disks imaged with SPHERE.]]

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.{{ cite journal |doi=10.1086/423613 |vauthors=Feigelson ED, Lawson WA |title=An X-ray census of young stars in the Chamaeleon I North Cloud |journal=Astrophys. J. |date=Oct 2004 |volume=614 |issue=10 |pages=267–83 |bibcode=2004ApJ...614..267F|arxiv = astro-ph/0406529 }} 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.{{Cite journal |last=Luhman |first=K. L. |date=2007-11-01 |title=The Stellar Population of the Chamaeleon I Star-forming Region* |url=https://iopscience.iop.org/article/10.1086/520114 |journal=The Astrophysical Journal Supplement Series |language=en |volume=173 |issue=1 |pages=104–136 |arxiv=0710.3037 |bibcode=2007ApJS..173..104L |doi=10.1086/520114 |issn=0067-0049}} The age was later revised to 1-2 Myr.{{Cite journal |last1=Galli |first1=P. A. B. |last2=Bouy |first2=H. |last3=Olivares |first3=J. |last4=Miret-Roig |first4=N. |last5=Sarro |first5=L. M. |last6=Barrado |first6=D. |last7=Berihuete |first7=A. |last8=Bertin |first8=E. |last9=Cuillandre |first9=J. -C. |date=2021-02-01 |title=Chamaeleon DANCe. Revisiting the stellar populations of Chamaeleon I and Chamaeleon II with Gaia-DR2 data |url=https://ui.adsabs.harvard.edu/abs/2021A&A...646A..46G/abstract |journal=Astronomy and Astrophysics |volume=646 |pages=A46 |arxiv=2012.00329 |bibcode=2021A&A...646A..46G |doi=10.1051/0004-6361/202039395 |issn=0004-6361}}

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 B9V, a Herbig Ae/Be star 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 found.

There are some seventy to ninety X-ray sources in the Chamaeleon I star forming region.{{ cite journal |vauthors=Feigelson ED, Casanova S, Montmerle T, Guibert J |title=ROSAT X-Ray Study of the Chamaeleon I Dark Cloud. I. The Stellar Population |journal=Astrophys. J. |date=Oct 1993 |volume=416 |issue=10 |pages=623–46 |bibcode=1993ApJ...416..623F |doi=10.1086/173264 }} 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 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 for 2.5 h on January 23–24, 1981, identifying some 22 X-ray sources.{{ cite journal |vauthors=Feigelson ED, Kriss GA |s2cid=121939381 |title=Soft X-ray observations of pre-main-sequence stars in the Chamaeleon dark cloud |journal=Astrophys. J. |date=Mar 1989 |volume=338 |issue=3 |pages=262–76 |bibcode=1989ApJ...338..262F |doi=10.1086/167196 |hdl=2060/19880002197 |hdl-access=free }} 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 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 inside around the star and inside the disk. Another notable member of Chamaeleon I is OTS 44, which is a planetary-mass object surrounded by a disk.{{cite journal |last1=Oasa |first1=Y. |last2=Tamura |first2=M. |last3=Sugitani |first3=K. |date=1999 |title=A Deep Near-Infrared Survey of the Chamaeleon I Dark Cloud Core |journal=The Astrophysical Journal |volume=526 |issue=1 |pages=336–343 |bibcode=1999ApJ...526..336O |doi=10.1086/307964 |doi-access=free}}{{cite journal |last1=Luhmann |first1=K. L. |last2=Peterson |first2=D. E. |last3=Megeath |first3=S. T. |date=2004 |title=Spectroscopic Confirmation of the Least Massive Known Brown Dwarf in Chamaeleon |journal=The Astrophysical Journal |volume=617 |issue=1 |pages=565–568 |arxiv=astro-ph/0411445 |bibcode=2004ApJ...617..565L |doi=10.1086/425228 |s2cid=18157277}}{{cite journal |last1=Joergens |first1=V. |last2=Bonnefoy |first2=M. |last3=Liu |first3=Y. |last4=Bayo |first4=A. |last5=Wolf |first5=S. |last6=Chauvin |first6=G. |last7=Rojo |first7=P. |date=2013 |title=OTS 44: Disk and accretion at the planetary border |journal=Astronomy & Astrophysics |volume=558 |pages=L7 |arxiv=1310.1936 |bibcode=2013A&A...558L...7J |doi=10.1051/0004-6361/201322432 |s2cid=118456052 |number=7}} Other notable objects are Cha J11110675-7636030, which has a mass of 3-6 {{Jupiter mass|link=true}} and might be surrounded by a protoplanetary disk,{{Cite journal |last1=Esplin |first1=T. L. |last2=Luhman |first2=K. L. |last3=Faherty |first3=J. K. |last4=Mamajek |first4=E. E. |last5=Bochanski |first5=J. J. |date=2017-08-01 |title=A Survey for Planetary-mass Brown Dwarfs in the Chamaeleon I Star-forming Region |journal=The Astronomical Journal |volume=154 |issue=2 |pages=46 |arxiv=1706.00058 |bibcode=2017AJ....154...46E |doi=10.3847/1538-3881/aa74e2 |doi-access=free |issn=0004-6256}} and Cha 1107−7626 (6-10 {{Jupiter mass}}), which also is surrounded by a disk.{{Cite arXiv |eprint=2505.13714 |last1=Flagg |first1=Laura |last2=Scholz |first2=Aleks |last3=Almendros-Abad |first3=V. |last4=Jayawardhana |first4=Ray |last5=Damian |first5=Belinda |last6=Muzic |first6=Koraljka |last7=Natta |first7=Antonella |last8=Pinilla |first8=Paola |last9=Testi |first9=Leonardo |title=Detection of Hydrocarbons in the Disk around an Actively-Accreting Planetary-Mass Object |date=2025 |class=astro-ph.EP }}

File:ESA Herschel Cha II+III.jpg

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.{{ cite journal |vauthors=Alcalá JM, Covino E, Sterzik MF, Schmitt JH, Krautter J, Neuhäuser R |title=A ROSAT pointed observation of the Chamaeleon II dark cloud |journal=Astron. Astrophys. |date=Mar 2000 |volume=355 |issue=3 |pages=629–38 |bibcode=2000A&A...355..629A }} Observation in Chamaeleon II was carried out from September 10 to 17, 1993. Source RXJ 1301.9-7706, a new WTTS candidate of spectral type K1, is closest to 4U 1302–77. Stars in Chamaeleon II have a mean age of 2-6 Myr.{{Cite journal |last1=Spezzi |first1=Loredana |last2=Alcalá |first2=Juan M. |last3=Covino |first3=Elvira |last4=Frasca |first4=Antonio |last5=Gandolfi |first5=Davide |last6=Oliveira |first6=Isa |last7=Chapman |first7=Nicholas |last8=Evans |first8=Neal J., II |last9=Huard |first9=Tracy L. |last10=Jørgensen |first10=Jes K. |last11=Merín |first11=Bruno |last12=Stapelfeldt |first12=Karl R. |date=2008-06-01 |title=The Young Population of the Chamaeleon II Dark Cloud |url=https://ui.adsabs.harvard.edu/abs/2008ApJ...680.1295S/abstract |journal=The Astrophysical Journal |volume=680 |issue=2 |pages=1295–1318 |arxiv=0802.4351 |bibcode=2008ApJ...680.1295S |doi=10.1086/587931 |issn=0004-637X}} 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 detected 22 disks around stars in Cha II in continuum.{{Cite journal |last1=Villenave |first1=M. |last2=Ménard |first2=F. |last3=Dent |first3=W. R. F. |last4=Benisty |first4=M. |last5=van der Plas |first5=G. |last6=Williams |first6=J. P. |last7=Ansdell |first7=M. |last8=Ribas |first8=Á. |last9=Caceres |first9=C. |last10=Canovas |first10=H. |last11=Cieza |first11=L. |last12=Hales |first12=A. |last13=Kamp |first13=I. |last14=Pinte |first14=C. |last15=Principe |first15=D. A. |date=2021-09-01 |title=Probing protoplanetary disk evolution in the Chamaeleon II region |url=https://ui.adsabs.harvard.edu/abs/2021A&A...653A..46V/abstract |journal=Astronomy and Astrophysics |volume=653 |pages=A46 |arxiv=2106.13847 |bibcode=2021A&A...653A..46V |doi=10.1051/0004-6361/202140496 |issn=0004-6361}} There are also candidate planetary-mass objects in Cha II that are surrounded by disks.{{Cite journal |last1=Allers |first1=K. N. |last2=Kessler-Silacci |first2=J. E. |last3=Cieza |first3=L. A. |last4=Jaffe |first4=D. T. |date=2006-06-01 |title=Young, Low-Mass Brown Dwarfs with Mid-Infrared Excesses |url=https://ui.adsabs.harvard.edu/abs/2006ApJ...644..364A/abstract |journal=The Astrophysical Journal |volume=644 |issue=1 |pages=364–377 |arxiv=astro-ph/0602249 |bibcode=2006ApJ...644..364A |doi=10.1086/503355 |issn=0004-637X}}

"Chamaeleon III appears to be devoid of current star-formation activity."{{ cite journal |vauthors=Yamauchi S, Hamaguchi K, Koyama K, Murakami H |title=ASCA Observations of the Chamaeleon II Dark Cloud |journal=Publ. Astron. Soc. Jpn. |date=Oct 1998 |volume=50 |issue=10 |pages=465–74 |bibcode=1998PASJ...50..465Y |doi = 10.1093/pasj/50.5.465 |doi-access=free }} There are two particularly prominent nebulae associated with this area. The smaller is commonly known as the Thumbprint Nebula{{cite journal |vauthors=Lehtinen K, Mattila K, Schnur G, Prusti T|title=The Thumbprint nebula: The distribution of molecular gas and dust in a regular BOK globule|journal=Astronomy and Astrophysics|date=1995|volume=295|pages=487–503|bibcode=1995A&A...295..487L }} and the larger The Talon Nebula.{{cite book |last1=Chadwick |first1=Stephen |last2=Cooper |first2=Ian |title=Imaging the Southern Sky |date=11 December 2012 |publisher=Springer |isbn=978-1461447498 |page=272}}

The cloud is sometimes extended with an eastern part,{{cite journal | last1=Bonne | first1=L. | last2=Bontemps | first2=S. | last3=Schneider | first3=N. | last4=Clarke | first4=S. D. | last5=Arzoumanian | first5=D. | last6=Fukui | first6=Y. | last7=Tachihara | first7=K. | last8=Csengeri | first8=T. | last9=Guesten | first9=R. | last10=Ohama | first10=A. | last11=Okamoto | first11=R. | last12=Simon | first12=R. | last13=Yahia | first13=H. | last14=Yamamoto | first14=H. | title=Formation of the Musca filament: evidence for asymmetries in the accretion flow due to a cloud–cloud collision | journal=Astronomy & Astrophysics | publisher=EDP Sciences | volume=644 | date=2020-11-26 | issn=0004-6361 | doi=10.1051/0004-6361/202038281 | page=A27| doi-access=free | arxiv=2010.12479 | bibcode=2020A&A...644A..27B }} and together with the distinctively long Dark Doodad Nebula (or Musca nebula) to the north the complex is called the Musca-Chamaeleonis Molecular Cloud.{{cite journal | last1=Hacar | first1=A. | last2=Kainulainen | first2=J. | last3=Tafalla | first3=M. | last4=Beuther | first4=H. | last5=Alves | first5=J. | title=The Musca cloud: A 6 pc-long velocity-coherent, sonic filament | journal=Astronomy & Astrophysics | publisher=EDP Sciences | volume=587 | date=2016-02-24 | issn=0004-6361 | doi=10.1051/0004-6361/201526015 | page=A97| doi-access=free | arxiv=1511.06370 | bibcode=2016A&A...587A..97H }}

Two foreground associations are found near the Chamaeleon dark clouds. These are named after ε Chamaeleontis (3-5 Myr, distance 110 parsec){{Cite journal |last1=Murphy |first1=Simon J. |last2=Lawson |first2=Warrick A. |last3=Bessell |first3=Michael S. |date=2013-10-01 |title=Re-examining the membership and origin of the ɛ Cha association |journal=Monthly Notices of the Royal Astronomical Society |volume=435 |issue=2 |pages=1325–1349 |arxiv=1305.4177 |bibcode=2013MNRAS.435.1325M |doi=10.1093/mnras/stt1375 |doi-access=free |issn=0035-8711}} and η Chamaeleontis (4-8 Myr, distance 97 parsec).{{Cite journal |last1=Mamajek |first1=Eric E. |last2=Lawson |first2=Warrick A. |last3=Feigelson |first3=Eric D. |date=1999-05-01 |title=The η Chamaeleontis Cluster: A Remarkable New Nearby Young Open Cluster |url=https://ui.adsabs.harvard.edu/abs/1999ApJ...516L..77M/abstract |journal=The Astrophysical Journal |volume=516 |issue=2 |pages=L77–L80 |bibcode=1999ApJ...516L..77M |doi=10.1086/312005 |issn=0004-637X}} 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.{{Cite journal |last1=Lopez Martí |first1=B. |last2=Jimenez Esteban |first2=F. |last3=Bayo |first3=A. |last4=Barrado |first4=D. |last5=Solano |first5=E. |last6=Rodrigo |first6=C. |date=2013-03-01 |title=Proper motions of young stars in Chamaeleon. I. A Virtual Observatory study of spectroscopically confirmed members |url=https://ui.adsabs.harvard.edu/abs/2013A&A...551A..46L/abstract |journal=Astronomy and Astrophysics |volume=551 |pages=A46 |arxiv=1302.7167 |bibcode=2013A&A...551A..46L |doi=10.1051/0004-6361/201220128 |issn=0004-6361}} 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.{{Cite journal |last1=Schutte |first1=Maria C. |last2=Lawson |first2=Kellen D. |last3=Wisniewski |first3=John P. |last4=Kuchner |first4=Marc J. |last5=Silverberg |first5=Steven M. |last6=Faherty |first6=Jacqueline K. |last7=Gagliuffi |first7=Daniella C. Bardalez |last8=Kiman |first8=Rocio |last9=Gagné |first9=Jonathan |last10=Meisner |first10=Aaron |last11=Schneider |first11=Adam C. |last12=Bans |first12=Alissa S. |last13=Debes |first13=John H. |last14=Kovacevic |first14=Natalie |last15=Bosch |first15=Milton K.D. |date=2020-08-04 |title=Discovery of a Nearby Young Brown Dwarf Disk |journal=The Astrophysical Journal |volume=160 |issue=4 |pages=156 |arxiv=2007.15735v2 |bibcode=2020AJ....160..156S |doi=10.3847/1538-3881/abaccd |issn=1538-3881 |s2cid=220920317 |doi-access=free |last16=Luca |first16=Hugo A. Durantini |last17=Holden |first17=Jonathan |last18=Hyogo |first18=Michiharu}}

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 at the top.

File:Chamaeleon_I_cloud.png|This is a ROSAT 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 satellite.

• Corona Australis Molecular Cloud
• List of nearby stellar associations and moving groups

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Category:Star-forming regions

Category:Chamaeleon