# LTT 3780

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Star system in the constellation Hydra

LTT 3780 Observation data Epoch J2000 Equinox J2000 Constellation Hydra Right ascension 10h 18m 35.137s[1] Declination −11° 43′ 00.24″[1] Apparent magnitude (V) 13.07±0.015[2] Characteristics Spectral type M3.5 V + M5.0 V[3] Apparent magnitude (B) 14.678 Apparent magnitude (G) 11.8465±0.0005[2] Apparent magnitude (J) 9.007±0.030[2] Astrometry Radial velocity (Rv) 0.27±0.34[1] km/s Proper motion (μ) RA: −341.537 mas/yr[1] Dec.: −247.747 mas/yr[1] Parallax (π) 45.3972±0.0301 mas[1] Distance 71.85 ± 0.05 ly (22.03 ± 0.01 pc) Absolute magnitude (MV) 11.36±0.02[2] Position (relative to LTT 3780)[3] Component LP 729-55 Epoch of observation J2015.5 Angular distance 15.81±0.150″ Position angle 96.9±0.2° Projected separation 348±3 AU Details LTT 3780 Mass 0.363±0.008[4] M☉ Radius 0.375±0.011[4] R☉ Luminosity 0.0165±0.0021[5] L☉ Surface gravity (log g) 4.85±0.03[4] cgs Temperature 3,358±92[5] K Metallicity [Fe/H] 0.06±0.14[4] dex Rotation 104±15[2] Rotational velocity (v sin i) < 1.3[2] km/s Age 3.10+6.20 −0.98[5] Gyr LP 729-55 Mass 0.136±0.004[2] M☉ Radius 0.173±0.005[2] R☉ Other designations G 162-44, LP 729-54, LTT 3780, NLTT 23974, 2MASS J10183516-1142599[6] Database references SIMBAD data Exoplanet Archive data

**LTT 3780**, also known as **TOI-732** or LP 729-54, is the brighter component of a wide [visual binary](/source/Visual_binary) [star](/source/Star) system in the constellation [Hydra](/source/Hydra_(constellation)). This star is host to a pair of orbiting [exoplanets](/source/Exoplanet). Based on [parallax](/source/Stellar_parallax) measurements, it is located at a distance of 72 [light years](/source/Light_year) from the Sun. LTT 3780 has an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 13.07,[2] requiring a telescope to view.

The [spectrum](/source/Stellar_spectrum) of LTT 3780 presents as a small [M-type main-sequence star](/source/M-type_main-sequence_star), a [red dwarf](/source/Red_dwarf), with a [stellar classification](/source/Stellar_classification) of M3.5 V. It is spinning very slowly, with a [rotation period](/source/Rotation_period) of 104 days.[2] The abundance of iron, an indicator of the star's [metallicity](/source/Metallicity), appears higher than in the Sun.[3] The star is inactive, showing a negligible level of [magnetic activity](/source/Magnetic_activity) in its [chromosphere](/source/Chromosphere).[2] 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](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 3,331.[2]

Collectively designated LDS 3977, the two stars in this system share a [common proper motion](/source/Common_proper_motion) and have an [angular separation](/source/Angular_separation) of 15.8[″](/source/Second_of_arc), which corresponds to a (physical) [projected separation](/source/Projected_separation) of 348 [AU](/source/Astronomical_unit).[3] At this separation, the [orbital period](/source/Orbital_period) would be ~9,100 years.[2] The fainter member is a red dwarf with a class of M5.0 V.[3] It has 14% of the mass of the Sun and 17% of the Sun's radius.[2]

## Planetary system

In 2020, an analysis carried out by a team of astronomers led by astronomer Ryan Cloutier of the [TESS project](/source/Transiting_Exoplanet_Survey_Satellite) confirmed the existence of two planets on mildly eccentric orbits, the inner being a [super-Earth](/source/Super-Earth) and the outer a [small gas planet](/source/Gas_dwarf) about half the mass of [Uranus](/source/Uranus).

### LTT 3780 b

The inner planet, LTT 3780 b, is an [ultra-short period](/source/Ultra-short_period_planet) rocky super-Earth. [James Webb Space Telescope](/source/James_Webb_Space_Telescope) observations published in 2025 are consistent with the planet being a bare rock with no atmosphere; [CO2](/source/Carbon_dioxide) atmospheres with a surface pressure of at least 0.01 [bar](/source/Bar_(unit)) can be ruled out.[7]

### LTT 3780 c

Astronomers utilizing the [Gemini South 8.1-meter telescope](/source/Gemini_Observatory) performed an atmospheric survey of LTT 3780 c through high-resolution [transmission spectroscopy](/source/Transmission_spectroscopy). From observations during a single [transit](/source/Astronomical_transit), they detected tentative signs of [methane](/source/Methane) in the atmosphere but found no traces of [ammonia](/source/Ammonia), even though it is highly detectable in a cloud-free, [hydrogen](/source/Hydrogen)-rich atmosphere.[8] A later study with [JWST](/source/James_Webb_Space_Telescope) found stronger evidence for methane along with moderate to strong signs of either heavier [hydrocarbons](/source/Hydrocarbon) or [sulfur](/source/Sulfur)-bearing molecules. This study also put constraints on the atmospheric abundance of water vapor, [CO](/source/Carbon_monoxide) and [CO2](/source/Carbon_dioxide).[9]

Size comparison of the two known planets of LTT 3780 (*artistic concept*) with Earth

The LTT 3780 planetary system[5] Companion (in order from star) Mass Semimajor axis (AU) Orbital period (days) Eccentricity Inclination (°) Radius b 2.34±0.10[4] M🜨 0.01195+0.00028 −0.00029 0.7683793(4) 0 86.10+0.92 −0.68 1.31±0.05[4] R🜨 c 7.89±0.26[4] M🜨 0.0757±0.0018 12.252284(13) 0.024+0.032 −0.017 88.958+0.074 −0.068 2.39+0.10 −0.11 R🜨

## See also

- [List of extrasolar planets](/source/List_of_extrasolar_planets)

- [List of multiplanetary systems](/source/List_of_multiplanetary_systems)

## References

1. ^ [***a***](#cite_ref-GaiaDR3_1-0) [***b***](#cite_ref-GaiaDR3_1-1) [***c***](#cite_ref-GaiaDR3_1-2) [***d***](#cite_ref-GaiaDR3_1-3) [***e***](#cite_ref-GaiaDR3_1-4) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D3767281845873242112%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Cloutier2020_2-0) [***b***](#cite_ref-Cloutier2020_2-1) [***c***](#cite_ref-Cloutier2020_2-2) [***d***](#cite_ref-Cloutier2020_2-3) [***e***](#cite_ref-Cloutier2020_2-4) [***f***](#cite_ref-Cloutier2020_2-5) [***g***](#cite_ref-Cloutier2020_2-6) [***h***](#cite_ref-Cloutier2020_2-7) [***i***](#cite_ref-Cloutier2020_2-8) [***j***](#cite_ref-Cloutier2020_2-9) [***k***](#cite_ref-Cloutier2020_2-10) [***l***](#cite_ref-Cloutier2020_2-11) [***m***](#cite_ref-Cloutier2020_2-12) [***n***](#cite_ref-Cloutier2020_2-13) Cloutier, Ryan; et al. (2020). ["A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780"](https://doi.org/10.3847%2F1538-3881%2Fab91c2). *The Astronomical Journal*. **160** (1): 3. [arXiv](/source/ArXiv_(identifier)):[2003.01136](https://arxiv.org/abs/2003.01136). [Bibcode](/source/Bibcode_(identifier)):[2020AJ....160....3C](https://ui.adsabs.harvard.edu/abs/2020AJ....160....3C). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/ab91c2](https://doi.org/10.3847%2F1538-3881%2Fab91c2). [S2CID](/source/S2CID_(identifier)) [211817805](https://api.semanticscholar.org/CorpusID:211817805).

1. ^ [***a***](#cite_ref-Nowak2020_3-0) [***b***](#cite_ref-Nowak2020_3-1) [***c***](#cite_ref-Nowak2020_3-2) [***d***](#cite_ref-Nowak2020_3-3) [***e***](#cite_ref-Nowak2020_3-4) Nowak, G.; et al. (2020). "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". *Astronomy & Astrophysics*. **A173**: 642. [arXiv](/source/ArXiv_(identifier)):[2003.01140](https://arxiv.org/abs/2003.01140). [Bibcode](/source/Bibcode_(identifier)):[2020A&A...642A.173N](https://ui.adsabs.harvard.edu/abs/2020A&A...642A.173N). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202037867](https://doi.org/10.1051%2F0004-6361%2F202037867). [S2CID](/source/S2CID_(identifier)) [211818198](https://api.semanticscholar.org/CorpusID:211818198).

1. ^ [***a***](#cite_ref-Weisserman2026_4-0) [***b***](#cite_ref-Weisserman2026_4-1) [***c***](#cite_ref-Weisserman2026_4-2) [***d***](#cite_ref-Weisserman2026_4-3) [***e***](#cite_ref-Weisserman2026_4-4) [***f***](#cite_ref-Weisserman2026_4-5) [***g***](#cite_ref-Weisserman2026_4-6) Weisserman, Drew; Gromek, Nicole; Cloutier, Ryan; Bali, Komal; Cadieux, Charles; Plotnykov, Mykhaylo; L'Heureux, Alexandrine; Srivastava, Avidaan; Carmona, Andres (2026-04-08). "Super-Earth masses and stellar abundances from NIRPS reveal tentative evidence for water-rich formation around M dwarfs". *Astronomy & Astrophysics*. [arXiv](/source/ArXiv_(identifier)):[2604.07447](https://arxiv.org/abs/2604.07447).

1. ^ [***a***](#cite_ref-Bonfanti2024_5-0) [***b***](#cite_ref-Bonfanti2024_5-1) [***c***](#cite_ref-Bonfanti2024_5-2) [***d***](#cite_ref-Bonfanti2024_5-3) Bonfanti, A.; et al. (2024). ["Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley"](https://doi.org/10.1051%2F0004-6361%2F202348180). *Astronomy & Astrophysics*. **682** A66. [arXiv](/source/ArXiv_(identifier)):[2311.12577](https://arxiv.org/abs/2311.12577). [Bibcode](/source/Bibcode_(identifier)):[2024A&A...682A..66B](https://ui.adsabs.harvard.edu/abs/2024A&A...682A..66B). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202348180](https://doi.org/10.1051%2F0004-6361%2F202348180).

1. **[^](#cite_ref-SIMBAD_6-0)** ["LTT 3780"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=LTT+3780). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2020-03-06.

1. **[^](#cite_ref-Allen2025_7-0)** Allen, Natalie H.; Espinoza, Néstor; et al. (August 2025). ["Hot Rocks Survey IV: Emission from LTT 3780 b is consistent with a bare rock"](https://doi.org/10.3847%2F1538-3881%2Fadfc51). *[The Astronomical Journal](/source/The_Astronomical_Journal)*. **170** (4): 240. [arXiv](/source/ArXiv_(identifier)):[2508.14210](https://arxiv.org/abs/2508.14210). [Bibcode](/source/Bibcode_(identifier)):[2025AJ....170..240A](https://ui.adsabs.harvard.edu/abs/2025AJ....170..240A). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/adfc51](https://doi.org/10.3847%2F1538-3881%2Fadfc51).

1. **[^](#cite_ref-Cabot2024_8-0)** Cabot, Samuel H. C.; et al. (2024-05-01). ["High-resolution Spectroscopic Reconnaissance of a Temperate Sub-Neptune"](https://doi.org/10.3847%2F2041-8213%2Fad3828). *The Astrophysical Journal Letters*. **966** (1) L10. [arXiv](/source/ArXiv_(identifier)):[2403.18891](https://arxiv.org/abs/2403.18891). [Bibcode](/source/Bibcode_(identifier)):[2024ApJ...966L..10C](https://ui.adsabs.harvard.edu/abs/2024ApJ...966L..10C). [doi](/source/Doi_(identifier)):[10.3847/2041-8213/ad3828](https://doi.org/10.3847%2F2041-8213%2Fad3828).

1. **[^](#cite_ref-9)** Rigby, Frances E.; Madhusudhan, Nikku; Sarkar, Subhajit; Pica-Ciamarra, Lorenzo; Holmberg, Måns; Moses, Julianne I. (2025). "A JWST Transmission Spectrum of the Temperate Sub-Neptune TOI-732 c". [arXiv](/source/ArXiv_(identifier)):[2512.15844](https://arxiv.org/abs/2512.15844) [[astro-ph.EP](https://arxiv.org/archive/astro-ph.EP)].

v t e Constellation of Hydra List of stars in Hydra Hydra in Chinese astronomy Stars Bayer α (Alphard) β γ (Naga) δ ε (Ashlesha) ζ η θ ι (Ukdah) κ λ μ ν ξ ο π ρ σ (Minchir) τ1 τ2 υ1 (Zhang) υ2 φ1 φ2 φ3 χ1 χ2 ψ ω b1 b3 C F Flamsteed 1 2 3 6 (a) 9 10 12 (D) 14 15 17 19 20 21 23 24 25 26 27 (P) 28 29 33 (A) 34 37 44 47 48 50 51 (k) 52 (l) 54 (m) 55 56 57 58 (Solitaire) 59 60 10 Crt 17 Crt 20 Crt 2 Sex Variable R U V W TW EX HS KU LQ V361 V419 V421 V478 V484 HR 3378 3538 3749 (G) 3750 3858 (I) 3862 3919 3923 (Felis) 4162 4328 4339 (β Ant) 4445 5265 HD 72659 74156 82943 86226 86264 90156 (γ Ant) Other 2MASS 1114−2618 ESO 439-26 Gliese 328 Gliese 357 Gliese 433 Gliese 453 GJ 3634 HAT-P-30 HE 1256−2738 HE 1327−2326 LHS 2065 LHS 3003 LTT 3780 SDSS J090745.0+024507 WASP-25 WASP-36 WASP-84 WASP-166 (Filetdor) WISE 0855−0714 WISEA J1141−3326 Exoplanets Gliese 357 d HD 72659 b HD 74156 b c HD 82943 b c HD 86226 b HD 86264 b TW Hydrae b (unconfirmed) WASP-193b Star clusters Messier 48 Messier 68 NGC 5694 Price-Whelan 1 Nebulae Abell 33 Abell 35 NGC 3242 Southern Owl Nebula Galaxies Messier 83 NGC 2617 2642 2697 2708 2758 2835 2848 2865 2890 2935 2936 2937 2960 2962 2986 2992 3030 3052 3054 3081 3109 3124 3200 3285 3285B 3290 3305 3307 3308 3309 3311 3312 3313 3314 3315 3316 3336 3369 3383 3393 3402 3463 3464 3585 3621 3673 3717 3904 3923 3936 4980 4993 5042 5061 5078 5085 5101 5135 5260 5264 5495 5626 Other 3C 196.1 AM 1316−241 Arp 7 CTQ 327 ESO 510-G13 GAMA202627 GLEAM J0917−0012 Hydra A IC 535 MRC 1138−262 Peekaboo Galaxy PKS 1151−348 RX J0911.4+0551 SDSS J0841+0101 TN J0924−2201 Tololo 1247−232 ZwCl 1693 BCG Galaxy clusters Abell 754 Abell 3411 Abell 3412 Bullet Group Hickson 40 Astronomical events GW170817 Category

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