{{Short description|Star in the constellation Chamaleon}} {{Starbox begin | name = CT Chamaeleontis }} {{Starbox image | image = 250 px | caption = CT Chamaeleontis and its companion (faint object on the upper right near the star) | credit=NASA/ESA/CSA JWST; Ya-Lin Wu et al.; processing: Meli_thev }} {{Starbox observe | epoch = J2000.0 | constell = Chamaeleon<ref name=constellation/> | ra = {{RA|11|04|09.0989}}<ref name="Gaia DR3"/> | dec = {{DEC|−76|27|19.330}}<ref name="Gaia DR3"/> | appmag_v={{nowrap|11.7 to 12.9<ref name=vsx/>}} }} {{Starbox character | type=pre-main sequence<ref name=Sheehan2019/> | class = K7 Ve<ref name = Torres2006/> | variable = T Tauri<ref name=vsx/> }} {{Starbox astrometry | radial_v = {{val|15.13|0.09}}<ref name = Nguyen2012/> | prop_mo_ra = {{val|−22.223}} | prop_mo_dec = {{val|+0.019}} | pm_footnote = <ref name="Gaia DR3"/> | parallax = 5.2645 | p_error = 0.0116 | parallax_footnote = <ref name="Gaia DR3"/> | absmag_v = }} {{Starbox detail | source = | mass = {{val|0.85|0.02}} or {{Val|0.96|0.02}}<ref name=Premnath2020/> | radius = {{val|2.06|0.05}}<ref name=Sheehan2019/> | gravity = {{val|3.66|0.01}}<ref name=Swastik2021/> | temperature= {{val|4403|6|10|fmt=commas}}<ref name=Swastik2021/> | luminosity= {{val|1.41|0.17|0.16}}<ref name=Sheehan2019/> | metal_fe = {{Val|-0.56|0.01}}<ref name=Swastik2021/> | rotational_velocity = {{Val|13.97|0.10|0.15}}<ref name=Swastik2021/> | age_myr = {{val|1.26|0.41|0.23}}<ref name=Sheehan2019/> or {{val|1.41|0.38|0.30}}<ref name=Sheehan2019/><ref name=Lazzoni2026/> }} {{Starbox catalog | names = CT Cha, 2MASS J11040909−7627193, IRAS 11027−7611, NSV 5081, WDS J11042−7627AB }} {{Starbox reference | Simbad = CT+Cha|sn=CT Cha | Simbad2 = CT+Cha+B|sn2=CT Cha b }} {{Starbox end}}
'''CT Chamaeleontis''' ('''CT Cha''') is a T Tauri star in the constellation of Chamaeleon.<ref name=sb0 /> The star belongs to Chamaeleon I, which is part of the Chamaeleon complex.<ref name=Ginski2024/> It has an apparent visual magnitude which varies between 11.7 and 12.9.<ref name=vsx/>
==Characteristics== {{Easy CSS image crop |image = Planet-forming discs in the Chamaeleon cloud (eso2405d).jpg |desired_width = 120 |crop_left_perc = 5.5 |crop_right_perc = 80.5 |crop_top_perc = 70.5 |crop_bottom_perc = 14.5 |alt = CT Cha |caption = Disk around CT Cha with VLT/SPHERE |align =left }} CT Chamaeleontis has a spectral type of K7Ve,<ref name = Torres2006/> indicating that it is a late K-type star with emission lines and a main sequence luminosity class, although it has not yet reached this stage of evolution yet, with an age likely between one and two million years.<ref name=Sheehan2019/> The star's mass has been obtained dynamically using the Keplerian rotation of its protoplanetary disk, yielding two values of {{val|0.85|0.02}} and {{Val|0.96|0.02|ul=solar mass}}.<ref name=Premnath2020/> It has a radius 2.06 times that of the Sun ({{solar radius}}) and is radiating 1.4 times the Sun's luminosity ({{solar luminosity}}) from its photosphere<ref name=Sheehan2019/> at an effective temperature of 4,403 K. The star's iron-to-hydrogen abudance is equivalent to only 27.5% that of the Sun.<ref name=Swastik2021/>
Observations with JWST MIRI did show that the disk around CT Cha A does not contain any carbon molecules. Emission lines of water and OH were identified. The low energy emission by water comes from cold (≲{{convert|200|K|C F}}) water.<ref name=Cugno2025/> The disk around the star was directly imaged with ALMA<ref name="Wu2020"/> and VLT/SPHERE.<ref name=Ginski2024/> {{clear left}} == Planetary system == [[File:CTChaLightCurve.png|thumb|left|250px|A visual band light curve for CT Chamaeleontis, plotted from ASAS data<ref name=ASASServer/>]] In 2006 and 2007, a faint companion was observed 2.7 arcseconds away from {{nowrap|CT Chamaeleontis}}, using the Very Large Telescope at the European Southern Observatory. Since the object shares common proper motion with {{nowrap|CT Chamaeleontis}}, it is believed to be physically close to the star, with a projected separation of approximately 440 astronomical units. The companion has been either designated as {{nowrap|CT Chamaeleontis b}}<ref name=exoplanet/> or as {{nowrap|CT Chamaeleontis B}}, sometimes erroneously as low-mass star.<ref name=SIMBAD/>
The companion's mass was estimated at {{Val|17|6|u=Jupiter masses}} ({{jupiter mass}}) in 2008<ref name=Schmidt2008/> and at {{Val|14|-|24|u=Jupiter mass}} in 2015.<ref name=Wu2015/> Since these values are likely to be above the deuterium burning limit, {{nowrap|CT Cha b}} was considered to be likely a brown dwarf rather than an exoplanet.<ref name=Schmidt2008/><ref name=Wu2015/> These mass estimates rely on the host star's age, which was estimated to be {{Val|2|2}} million years in 2008<ref name=Schmidt2008/> and between one and five million years in 2015.<ref name=Wu2015/> However, the age was later revised downwards, ranging from {{Val|1.26|0.41|0.32}} to {{Val|1.77|0.60|0.49}} million years.<ref name=Sheehan2019/> A recent value of {{Val|1.41|0.38|0.30}} implies a mass of {{val|9.7|1.2|1.1|u=Jupiter mass}}, which is well within the planetary-mass regime.<ref name=Lazzoni2026/>
Already during the discovery evidence of accretion from a gas-rich circumplanetary disk was suspected from emission by Paβ.<ref name=Schmidt2008/> Later it was found that the emission in the r-band is overluminous, indicating Hα emission. This team estimated an accretion rate of ~6 × 10<sup>−10</sup> {{solar mass}}/yr.<ref name=Wu2015/> A search with ALMA failed to detect the disk around the companion.<ref name=Wu2020/> Observations with JWST MIRI medium resolution spectroscopy found that the disk is rich in carbon chemistry. Seven carbon-bearing molecules were found inside the disk.<ref name=Cugno2025/> The following molecules were identified: acetylene (C<sub>2</sub>H<sub>2</sub>, <sup>13</sup>CCH<sub>2</sub>), ethane (C<sub>2</sub>H<sub>6</sub>), propyne (C<sub>3</sub>H<sub>4</sub>), diacetylene (C<sub>4</sub>H<sub>2</sub>), benzene (C<sub>6</sub>H<sub>6</sub>), hydrogen cyanide (HCN) and carbon dioxide (CO<sub>2</sub>).<ref name=HITRANonline/><ref name=Cugno2025/><ref name=ESApress/> This carbon-rich disk is similar to disks around isolated planetary-mass objects and other low-mass objects that show a transition from oxygen-rich disk to carbon-rich disk in their lifetime. This result will give insights into the formation of exomoons around giant planets.<ref name=Cugno2025/> {{clear left}} {{OrbitboxPlanet begin}} {{OrbitboxPlanet disk | disk = protoplanetary disk<ref name=Sheehan2019/> | periapsis = 6.1 | apoapsis = 9.3 | inclination = {{val|54.0|1.0|0.9}} }} {{OrbitboxPlanet disk | disk = protoplanetary disk<ref name = Ginski2024/> | apoapsis = {{val|64.6|4.2}} | inclination = {{val|45.7|5.0}} }} {{OrbitboxPlanet | exoplanet = b | mass = {{val|9.7|1.2|1.1}}<ref name=Lazzoni2026/> | semimajor = {{Val|500|320|150}}<ref name=Lazzoni2026/> | eccentricity = {{Val|0.59|0.28|0.34}}<ref name=Lazzoni2026/> | radius = {{val|2.20|0.81|0.60}}<ref name=Schmidt2008/> }} {{Orbitbox end}}
==References== {{Reflist|refs=
<ref name=constellation>{{cite constellation|CT Cha}}</ref>
<ref name="Gaia DR3">{{Cite Gaia DR3|5201360671411974912}}</ref>
<ref name=SIMBAD>{{cite simbad| title=CT Cha b| access-date=October 1, 2008 }}</ref>
<ref name=vsx>{{Cite web |title=VSX : Detail for CT Cha |url=https://vsx.aavso.org/index.php?view=detail.top&oid=9357 |access-date=2026-05-06 |website=vsx.aavso.org}}</ref>
<ref name=exoplanet>{{Cite web |title=Planet CT Cha b |url=https://exoplanet.eu/catalog/ct_cha_b--502/ |access-date=2024-08-20 |website=Encyclopaedia of exoplanetary systems / Exoplanet.eu}}</ref>
<ref name=Swastik2021>{{Cite journal |last1=Swastik |first1=C. |last2=Banyal |first2=Ravinder K. |last3=Narang |first3=Mayank |last4=Manoj |first4=P. |last5=Sivarani |first5=T. |last6=Reddy |first6=Bacham E. |last7=Rajaguru |first7=S. P. |date=March 2021 |title=Host Star Metallicity of Directly Imaged Wide-orbit Planets: Implications for Planet Formation |bibcode=2021AJ....161..114S |journal=The Astronomical Journal |language=en |volume=161 |issue=3 |pages=114 |doi=10.3847/1538-3881/abd802 |doi-access=free |arxiv=2012.13694 |issn=0004-6256}}</ref>
<ref name=Premnath2020>{{Cite journal |last1=Premnath |first1=Pranav H. |last2=Wu |first2=Ya-Lin |last3=Bowler |first3=Brendan P. |last4=Sheehan |first4=Patrick D. |date=July 2020 |title=Dynamical Masses of Young Stars Inferred from Two Transitions of CO with ALMA |journal=Research Notes of the American Astronomical Society |language=en |volume=4 |issue=7 |pages=100 |doi=10.3847/2515-5172/aba125 |doi-access=free |arxiv=2012.12690 |bibcode=2020RNAAS...4..100P |issn=2515-5172}}</ref>
<ref name=Lazzoni2026>{{Cite arXiv |last1=Lazzoni |first1=Cecilia |last2=Zurlo |first2=Alice |last3=Desidera |first3=Silvano |last4=Bernardi |first4=Andrea |last5=Pérez |first5=Sebastian |last6=Mesa |first6=Dino |last7=Barbato |first7=Domenico |last8=Nogueira |first8=Pedro Henrique |last9=Dasgupta |first9=Anuroop |date=2026-03-25 |title=SaNDi-SHoP: Searching for Satellites'N'Disks with a Star-Hopping Program I. Analysis of the close surroundings of DI companions |eprint=2603.24796 |class=astro-ph.EP}}</ref>
<ref name=Wu2015>{{cite journal|arxiv=1501.01396|year=2015|title=New Extinction and Mass Estimates from Optical Photometry of the Very Low Mass Brown Dwarf Companion CT Chamaeleontis B with the Magellan AO System|doi=10.1088/0004-637X/801/1/4|last1=Wu|first1=Ya-Lin|last2=Close|first2=Laird M.|last3=Males|first3=Jared R.|last4=Barman|first4=Travis S.|last5=Morzinski|first5=Katie M.|last6=Follette|first6=Katherine B.|last7=Bailey|first7=Vanessa|last8=Rodigas|first8=Timothy J.|last9=Hinz|first9=Philip|last10=Puglisi|first10=Alfio|last11=Xompero|first11=Marco|last12=Briguglio|first12=Runa|journal=The Astrophysical Journal|volume=801|issue=1|page=4|bibcode=2015ApJ...801....4W|s2cid=96467798}}</ref>
<ref name=Sheehan2019>{{cite journal|arxiv=1903.00032|year=2019|title=High Precision Dynamical Masses of Pre-Main Sequence Stars with ALMA and Gaia|doi=10.3847/1538-4357/ab09f9|last1=Sheehan|first1=Patrick D.|last2=Wu|first2=Ya-Lin|last3=Eisner|first3=Josh A.|last4=Tobin|first4=John J.|journal=The Astrophysical Journal|volume=874|issue=2|page=136|bibcode=2019ApJ...874..136S|s2cid=119218828 |doi-access=free }}</ref>
<ref name=Schmidt2008>{{cite journal |arxiv=0809.2812 |doi=10.1051/0004-6361:20078840 |title=Direct evidence of a sub-stellar companion around CT Chamaeleontis |year=2008 |last1=Schmidt |first1=T. O. B. |last2=Neuhäuser |first2=R. |last3=Seifahrt |first3=A. |last4=Vogt |first4=N. |last5=Bedalov |first5=A. |last6=Helling |first6=Ch. |last7=Witte |first7=S. |last8=Hauschildt |first8=P. H. |journal=Astronomy & Astrophysics |volume=491 |issue=1 |pages=311–320 |bibcode=2008A&A...491..311S |s2cid=17161561 }}</ref>
<ref name=ASASServer>{{cite web |title=ASAS All Star Catalogue |url=https://www.astrouw.edu.pl/asas/?page=aasc |publisher=The All Sky Automated Survey |access-date=8 December 2021}}</ref>
<ref name=sb0>{{cite simbad |title=CT+Cha |access-date=October 1, 2008 }}</ref>
<ref name=Torres2006>{{cite journal | last1 = Torres | first1 = C. A. O. | last2 = Quast | first2 = G. R. | last3 = da Silva | first3 = L. | last4 = de la Reza | first4 = R. | last5 = Melo | first5 = C. H. F. | last6 = Sterzik | first6 = M. | title = Search for associations containing young stars (SACY) | journal = Astronomy & Astrophysics | date = 12 September 2006 | volume = 460 | issue = 3 | pages = 695–708 | issn = 0004-6361 | eissn = 1432-0746 | doi = 10.1051/0004-6361:20065602 | bibcode = 2006A&A...460..695T | doi-access = free | arxiv = astro-ph/0609258 }}</ref>
<ref name=Nguyen2012>{{cite journal | last1 = Nguyen | first1 = Duy Cuong | last2 = Brandeker | first2 = Alexis | last3 = van Kerkwijk | first3 = Marten H. | last4 = Jayawardhana | first4 = Ray | title = Close Companions to Young Stars. I. A Large Spectroscopic Survey in Chamaeleon I and Taurus-Auriga | journal = The Astrophysical Journal | date = 6 January 2012 | volume = 745 | issue = 2 | page = 119 | issn = 0004-637X | eissn = 1538-4357 | doi = 10.1088/0004-637X/745/2/119 | bibcode = 2012ApJ...745..119N | arxiv = 1112.0002 | doi-access = free}}</ref>
<ref name=Ginski2024>{{cite journal |last1=Ginski |first1=C. |last2=Garufi |first2=A. |last3=Benisty |first3=M. |last4=Tazaki |first4=R. |last5=Dominik |first5=C. |last6=Ribas |first6=á. |last7=Engler |first7=N. |last8=Birnstiel |first8=T. |last9=Chauvin |first9=G. |last10=Columba |first10=G. |last11=Facchini |first11=S. |last12=Goncharov |first12=A. |last13=Hagelberg |first13=J. |last14=Henning |first14=T. |last15=Hogerheijde |first15=M. |last16=van Holstein |first16=R. G. |last17=Huang |first17=J. |last18=Muto |first18=T. |last19=Pinilla |first19=P. |last20=Kanagawa |first20=K. |last21=Kim |first21=S. |last22=Kurtovic |first22=N. |last23=Langlois |first23=M. |last24=Manara |first24=C. |last25=Milli |first25=J. |last26=Momose |first26=M. |last27=Orihara |first27=R. |last28=Pawellek |first28=N. |last29=Pinte |first29=C. |last30=Rab |first30=C. |last31=Schmidt |first31=T. O. B. |last32=Snik |first32=F. |last33=Wahhaj |first33=Z. |last34=Williams |first34=J. |last35=Zurlo |first35=A. |title=The SPHERE view of the Chamaeleon I star-forming region: The full census of planet-forming disks with GTO and DESTINYS programs |journal=Astronomy & Astrophysics |date=May 2024 |volume=685 |pages=A52 |arxiv=2403.02149 |doi=10.1051/0004-6361/202244005 |bibcode=2024A&A...685A..52G}}</ref>
<ref name=Cugno2025>{{cite arXiv|last1=Cugno |first1=Gabriele |last2=Grant |first2=Sierra L. |eprint=2509.15209|title=A carbon-rich disk surrounding a planetary-mass companion |date=2025 |class=astro-ph.EP }}</ref>
<ref name=HITRANonline>{{Cite web |title=HITRANonline line-by-line search: 1. Select Molecules |url=https://hitran.org/lbl/ |access-date=2024-12-10 |website=hitran.org}}</ref>
<ref name=Wu2020>{{Cite journal |last1=Wu |first1=Ya-Lin |last2=Bowler |first2=Brendan P. |last3=Sheehan |first3=Patrick D. |last4=Andrews |first4=Sean M. |last5=Herczeg |first5=Gregory J. |last6=Kraus |first6=Adam L. |last7=Ricci |first7=Luca |last8=Wilner |first8=David J. |last9=Zhu |first9=Zhaohuan |date=May 2020 |title=ALMA 0.88 mm Survey of Disks around Planetary-mass Companions |journal=The Astronomical Journal |language=en |volume=159 |issue=5 |pages=229 |arxiv=1903.00032 |bibcode=2019ApJ...874..136S |doi=10.3847/1538-3881/ab818c |doi-access=free |issn=0004-6256}}</ref>
<ref name=ESApress>{{Cite web |date=2025-09-29 |title=Webb studies moon-forming disc around massive planet |url=https://www.esa.int/Science_Exploration/Space_Science/Webb/Webb_studies_moon-forming_disc_around_massive_planet |access-date=2025-09-29 |website=www.esa.int |language=en}}</ref>
}}
{{Stars of Chamaeleon}}
Category:Chamaeleon Category:K-type pre-main-sequence stars Category:T Tauri stars Category:Planetary systems with one confirmed planet Chamaeleontis, CT 11027−7611