LTT 3780

{{Short description|Star system in the constellation Hydra}} {{Starbox begin | name = LTT 3780 }} {{Starbox observe | epoch = J2000 | constell = [[Hydra (constellation)|Hydra]] | ra = {{RA|10|18|35.137}}<ref name=GaiaDR3/> | dec = {{DEC|−11|43|00.24}}<ref name=GaiaDR3/> | appmag_v = 13.07{{±|0.015}}<ref name=Cloutier2020/> }} {{Starbox character | type = | class = {{nowrap|M3.5 V + M5.0 V}}<ref name=Nowak2020/> | appmag_1_passband = B | appmag_1 = 14.678 | appmag_2_passband = G | appmag_2 = 11.8465{{±|0.0005}}<ref name=Cloutier2020/> | appmag_3_passband = J | appmag_3 = 9.007{{±|0.030}}<ref name=Cloutier2020/> | variable = }} {{Starbox astrometry | radial_v = {{val|0.27|0.34}}<ref name=GaiaDR3/> | prop_mo_ra = −341.537 | prop_mo_dec = −247.747 | pm_footnote = <ref name=GaiaDR3/> | parallax = 45.3972 | p_error = 0.0301 | parallax_footnote = <ref name=GaiaDR3/> | absmag_v = 11.36{{±|0.02}}<ref name=Cloutier2020/> }} {{Starbox relpos | reference = <ref name=Nowak2020/> | epoch = J2015.5 | primary = LTT 3780 | component = LP 729-55 | angdistsec = 15.81{{±|0.150}} | posang = 96.9{{±|0.2}} | projsep = 348{{±|3}} }} {{Starbox detail | component1 = LTT 3780 | mass = 0.363{{±|0.008}}<ref name=Weisserman2026/> | radius = 0.375{{±|0.011}}<ref name=Weisserman2026/> | luminosity = {{val|0.0165|0.0021}}<ref name="Bonfanti2024"/> | gravity = 4.85{{±|0.03}}<ref name=Weisserman2026/> | temperature = {{val|3358|92|fmt=commas}}<ref name="Bonfanti2024"/> | metal_fe = {{val|0.06|0.14}}<ref name=Weisserman2026/> | rotation = 104{{±|15}}<ref name=Cloutier2020/> | rotational_velocity = < 1.3<ref name=Cloutier2020/> | age_gyr = {{val|3.10|6.20|0.98}}<ref name="Bonfanti2024"/> | component2 = LP 729-55 | mass2 = 0.136{{±|0.004}}<ref name=Cloutier2020/> | radius2 = 0.173{{±|0.005}}<ref name=Cloutier2020/> }} {{Starbox catalog | names = {{odlist | G=162-44 | LTT=3780 | NLTT=23974 | 2MASS=J10183516-1142599 | LP=729-54 | TOI-732}}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = TOI-732 | NSTED = TOI-732 }} {{Starbox end}}

'''LTT 3780''', also known as '''TOI-732''' or LP 729-54, is the brighter component of a wide [[visual binary]] [[star]] system in the constellation [[Hydra (constellation)|Hydra]]. This star is host to a pair of orbiting [[exoplanet]]s. Based on [[stellar parallax|parallax]] measurements, it is located at a distance of 72 [[light year]]s from the Sun. LTT 3780 has an [[apparent visual magnitude]] of 13.07,<ref name=Cloutier2020/> requiring a telescope to view.

The [[stellar spectrum|spectrum]] of LTT 3780 presents as a small [[M-type main-sequence star]], a [[red dwarf]], with a [[stellar classification]] of M3.5 V. It is spinning very slowly, with a [[rotation period]] of 104 days.<ref name=Cloutier2020/> The abundance of iron, an indicator of the star's [[metallicity]], appears higher than in the Sun.<ref name=Nowak2020/> The star is inactive, showing a negligible level of [[magnetic activity]] in its [[chromosphere]].<ref name=Cloutier2020/> It has about 40% of the mass and 37% of the radius of the Sun. The star is radiating just 17% of the Sun's luminosity from its [[photosphere]] at an [[effective temperature]] of 3,331.<ref name=Cloutier2020/>

Collectively designated LDS 3977, the two stars in this system share a [[common proper motion]] and have an [[angular separation]] of {{val|15.8|ul=arcsecond}}, which corresponds to a (physical) [[projected separation]] of {{val|348|ul=AU}}.<ref name=Nowak2020/> At this separation, the [[orbital period]] would be ~9,100 years.<ref name=Cloutier2020/> The fainter member is a red dwarf with a class of M5.0 V.<ref name=Nowak2020/> It has 14% of the mass of the Sun and 17% of the Sun's radius.<ref name=Cloutier2020/>

== Planetary system == In 2020, an analysis carried out by a team of astronomers led by astronomer Ryan Cloutier of the [[Transiting Exoplanet Survey Satellite|TESS project]] confirmed the existence of two planets on mildly eccentric orbits, the inner being a [[super-Earth]] and the outer a [[Gas dwarf|small gas planet]] about half the mass of [[Uranus]].

===LTT 3780 b=== The inner planet, LTT 3780 b, is an [[ultra-short period planet|ultra-short period]] rocky super-Earth. [[James Webb Space Telescope]] observations published in 2025 are consistent with the planet being a bare rock with no atmosphere; [[carbon dioxide|CO<sub>2</sub>]] atmospheres with a surface pressure of at least 0.01 [[bar (unit)|bar]] can be ruled out.<ref name=Allen2025/>

===LTT 3780 c=== Astronomers utilizing the [[Gemini Observatory|Gemini South 8.1-meter telescope]] performed an atmospheric survey of LTT 3780 c through high-resolution [[transmission spectroscopy]]. From observations during a single [[Astronomical transit|transit]], they detected tentative signs of [[methane]] in the atmosphere but found no traces of [[ammonia]], even though it is highly detectable in a cloud-free, [[hydrogen]]-rich atmosphere.<ref name="Cabot2024"/> A later study with [[James Webb Space Telescope|JWST]] found stronger evidence for methane along with moderate to strong signs of either heavier [[hydrocarbon]]s or [[sulfur]]-bearing molecules. This study also put constraints on the atmospheric abundance of water vapor, [[Carbon monoxide|CO]] and [[Carbon dioxide|CO<sub>2</sub>]].<ref>{{cite arXiv |last1=Rigby |first1=Frances E. |last2=Madhusudhan |first2=Nikku |last3=Sarkar |first3=Subhajit |last4=Pica-Ciamarra |first4=Lorenzo |last5=Holmberg |first5=Måns |last6=Moses |first6=Julianne I. |title=A JWST Transmission Spectrum of the Temperate Sub-Neptune TOI-732 c |date=2025 |class=astro-ph.EP |eprint=2512.15844}}</ref>

[[File:Ltt3780bc.jpg|thumb|Size comparison of the two known planets of LTT 3780 (''artistic concept'') with Earth]]

{{OrbitboxPlanet begin | table_ref = <ref name="Bonfanti2024"/> }} {{OrbitboxPlanet | exoplanet = b | mass_earth = {{val|2.34|0.10}}<ref name=Weisserman2026/> | radius_earth = {{val|1.31|0.05}}<ref name=Weisserman2026/> | period = {{val|0.7683793|(4)}} | semimajor = {{val|0.01195|0.00028|0.00029}} | eccentricity = 0 | inclination = {{val|86.10|0.92|0.68}} }} {{OrbitboxPlanet | exoplanet = c | mass_earth = {{val|7.89|0.26}}<ref name=Weisserman2026/> | radius_earth = {{val|2.39|0.10|0.11}} | period = {{val|12.252284|(13)}} | semimajor = {{val|0.0757|0.0018}} | eccentricity = {{val|0.024|0.032|0.017}} | inclination = {{val|88.958|0.074|0.068}} }} {{Orbitbox end}}

== See also == * [[List of extrasolar planets]] * [[List of multiplanetary systems]]

== References == {{Reflist|refs=

<ref name="Bonfanti2024">{{cite journal | title=Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley | last1=Bonfanti | first1=A. | last2=Brady | first2=M. | last3=Wilson | first3=T. G. | last4=Venturini | first4=J. | last5=Egger | first5=J. A. | last6=Brandeker | first6=A. | last7=Sousa | first7=S. G. | last8=Lendl | first8=M. | last9=Simon | first9=A. E. | last10=Queloz | first10=D. | last11=Olofsson | first11=G. | last12=Adibekyan | first12=V. | last13=Alibert | first13=Y. | last14=Fossati | first14=L. | last15=Hooton | first15=M. J. | last16=Kubyshkina | first16=D. | last17=Luque | first17=R. | last18=Murgas | first18=F. | last19=Mustill | first19=A. J. | last20=Santos | first20=N. C. | last21=Van Grootel | first21=V. | last22=Alonso | first22=R. | last23=Asquier | first23=J. | last24=Bandy | first24=T. | last25=Bárczy | first25=T. | last26=Barrado Navascues | first26=D. | last27=Barros | first27=S. C. C. | last28=Baumjohann | first28=W. | last29=Bean | first29=J. | last30=Beck | first30=M. | last31=Beck | first31=T. | last32=Benz | first32=W. | last33=Bergomi | first33=M. | last34=Billot | first34=N. | last35=Borsato | first35=L. | last36=Broeg | first36=C. | last37=Collier Cameron | first37=A. | last38=Csizmadia | first38=Sz. | last39=Cubillos | first39=P. E. | last40=Davies | first40=M. B. | last41=Deleuil | first41=M. | last42=Deline | first42=A. | last43=Delrez | first43=L. | last44=Demangeon | first44=O. D. S. | last45=Demory | first45=B.-O. | last46=Ehrenreich | first46=D. | last47=Erikson | first47=A. | last48=Fortier | first48=A. | last49=Fridlund | first49=M. | last50=Gandolfi | first50=D. | last51=Gillon | first51=M. | last52=Güdel | first52=M. | last53=Günther | first53=M. N. | last54=Heitzmann | first54=A. | last55=Helling | first55=Ch. | last56=Hoyer | first56=S. | last57=Isaak | first57=K. G. | last58=Kasper | first58=D. | last59=Kiss | first59=L. L. | last60=Lam | first60=K. W. F. | last61=Laskar | first61=J. | last62=Lecavelier des Etangs | first62=A. | last63=Magrin | first63=D. | last64=Maxted | first64=P. F. L. | last65=Mordasini | first65=C. | last66=Nascimbeni | first66=V. | last67=Ottensamer | first67=R. | last68=Pagano | first68=I. | last69=Pallé | first69=E. | last70=Peter | first70=G. | last71=Piotto | first71=G. | last72=Pollacco | first72=D. | last73=Ragazzoni | first73=R. | last74=Rando | first74=N. | last75=Rauer | first75=H. | last76=Ribas | first76=I. | last77=Scandariato | first77=G. | last78=Ségransan | first78=D. | last79=Seifahrt | first79=A. | last80=Smith | first80=A. M. S. | last81=Stalport | first81=M. | last82=Stefánsson | first82=G. | last83=Steinberger | first83=M. | last84=Stürmer | first84=J. | last85=Szabó | first85=Gy. M. | last86=Thomas | first86=N. | last87=Udry | first87=S. | last88=Villaver | first88=E. | last89=Walton | first89=N. A. | last90=Westerdorff | first90=K. | last91=Zingales | first91=T. | display-authors=1 | journal=Astronomy & Astrophysics | volume=682 | article-number=A66 | page= | date=2024 | arxiv=2311.12577 | bibcode=2024A&A...682A..66B | bibcode-access=free | doi=10.1051/0004-6361/202348180 | doi-access=free }}</ref>

<ref name="Cabot2024">{{cite journal | title=High-resolution Spectroscopic Reconnaissance of a Temperate Sub-Neptune | last1=Cabot | first1=Samuel H. C. | last2=Madhusudhan | first2=Nikku | last3=Constantinou | first3=Savvas | last4=Valencia | first4=Diana | last5=Vos | first5=Johanna M. | last6=Masseron | first6=Thomas | last7=Cheverall | first7=Connor J. | display-authors=1 | journal=The Astrophysical Journal Letters | volume=966 | issue=1 | article-number=L10 | page= | date=2024-05-01 | arxiv=2403.18891 | bibcode=2024ApJ...966L..10C | bibcode-access=free | doi=10.3847/2041-8213/ad3828 | doi-access=free }}</ref>

<ref name=Weisserman2026>{{cite journal |last=Weisserman |first=Drew |last2=Gromek |first2=Nicole |last3=Cloutier |first3=Ryan |last4=Bali |first4=Komal |last5=Cadieux |first5=Charles |last6=Plotnykov |first6=Mykhaylo |last7=L'Heureux |first7=Alexandrine |last8=Srivastava |first8=Avidaan |last9=Carmona |first9=Andres |title=Super-Earth masses and stellar abundances from NIRPS reveal tentative evidence for water-rich formation around M dwarfs |date=2026-04-08 |arxiv=2604.07447 |journal=Astronomy & Astrophysics }}</ref>

<ref name=Cloutier2020>{{cite journal | title=A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780 | last1=Cloutier | first1=Ryan | last2=Eastman | first2=Jason D. | last3=Rodriguez | first3=Joseph E. | last4=Astudillo-Defru | first4=Nicola | last5=Bonfils | first5=Xavier | last6=Mortier | first6=Annelies | last7=Watson | first7=Christopher A. | last8=Stalport | first8=Manu | last9=Pinamonti | first9=Matteo | last10=Lienhard | first10=Florian | last11=Harutyunyan | first11=Avet | last12=Damasso | first12=Mario | last13=Latham | first13=David W. | last14=Collins | first14=Karen A. | last15=Massey | first15=Robert | last16=Irwin | first16=Jonathan | last17=Winters | first17=Jennifer G. | last18=Charbonneau | first18=David | last19=Ziegler | first19=Carl | last20=Matthews | first20=Elisabeth | last21=Crossfield | first21=Ian J. M. | last22=Kreidberg | first22=Laura | last23=Quinn | first23=Samuel N. | last24=Ricker | first24=George | last25=Vanderspek | first25=Roland | last26=Seager | first26=Sara | last27=Winn | first27=Joshua | last28=Jenkins | first28=Jon M. | last29=Vezie | first29=Michael | last30=Udry | first30=Stéphane | display-authors=1 | journal=The Astronomical Journal | year=2020 | volume=160 |issue=1 | page=3 | doi=10.3847/1538-3881/ab91c2 | doi-access=free | arxiv=2003.01136 | bibcode=2020AJ....160....3C | s2cid=211817805 }}</ref>

<ref name=Nowak2020>{{cite journal | title=The CARMENES search for exoplanets around M dwarfs. Two planets on the opposite sides of the radius gap transiting the nearby M dwarf LP 729-54 | last1=Nowak | first1=G. | last2=Luque | first2=R. | last3=Parviainen | first3=H. | last4=Pallé | first4=E. | last5=Molaverdikhani | first5=K. | last6=Béjar | first6=V. J. S. | last7=Lillo-Box | first7=J. | last8=Rodríguez-López | first8=C. | last9=Caballero | first9=J. A. | last10=Zechmeister | first10=M. | last11=Passegger | first11=V. M. | last12=Cifuentes | first12=C. | last13=Schweitzer | first13=A. | last14=Narita | first14=N. | last15=Cale | first15=B. | last16=Espinoza | first16=N. | last17=Murgas | first17=F. | last18=Zapatero Osorio | first18=M. R. | last19=Pozuelos | first19=F. J. | last20=Aceituno | first20=F. J. | last21=Amado | first21=P. J. | last22=Barkaoui | first22=K. | last23=Barrado | first23=D. | last24=Bauer | first24=F. F. | last25=Benkhaldoun | first25=Z. | last26=Caldwell | first26=D. A. | last27=Casasayas Barris | first27=N. | last28=Chaturvedi | first28=P. | last29=Chen | first29=G. | last30=Collins | first30=K. A. | display-authors=1 | journal=Astronomy & Astrophysics | year=2020 | volume=A173 | page=642 | doi=10.1051/0004-6361/202037867 | s2cid=211818198 | arxiv=2003.01140 | bibcode=2020A&A...642A.173N }}</ref>

<ref name=SIMBAD>{{cite simbad | title=LTT 3780 | access-date=2020-03-06 }}</ref>

<ref name=Allen2025>{{cite journal |last1=Allen |first1=Natalie H. |last2=Espinoza |first2=Néstor |display-authors=etal |date=August 2025 |title=Hot Rocks Survey IV: Emission from LTT 3780 b is consistent with a bare rock |journal=[[The Astronomical Journal]] |volume= 170|issue= 4|page=240 |doi= 10.3847/1538-3881/adfc51|doi-access=free |arxiv=2508.14210 |bibcode=2025AJ....170..240A }}</ref>

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[[Category:M-type main-sequence stars]] [[Category:Planetary systems with two confirmed planets]] [[Category:Planetary transit variables]]  [[Category:Hydra (constellation)]] [[Category:TESS Objects of Interest|732]]