Astronomy:LTT 3780
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Hydra[1] |
| Right ascension | 10h 18m 35.137s[2] |
| Declination | −11° 43′ 00.24″[2] |
| Apparent magnitude (V) | 13.07±0.015[3] |
| Characteristics | |
| Spectral type | M3.5 V + M5.0 V[4] |
| Apparent magnitude (B) | 14.678 |
| Apparent magnitude (G) | 11.8465±0.0005[3] |
| Apparent magnitude (J) | 9.007±0.030[3] |
| Astrometry | |
| Radial velocity (Rv) | 0.27±0.34[2] km/s |
| Proper motion (μ) | RA: −341.537[2] mas/yr Dec.: −247.747[2] mas/yr |
| Parallax (π) | 45.3972 ± 0.0301[2] mas |
| Distance | 71.85 ± 0.05 ly (22.03 ± 0.01 pc) |
| Absolute magnitude (MV) | 11.36±0.02[3] |
| Position (relative to LTT 3780)[4] | |
| Component | LP 729-55 |
| Epoch of observation | J2015.5 |
| Angular distance | 15.81±0.150″ |
| Position angle | 96.9±0.2° |
| Observed separation (projected) | 348±3 AU {{{projsepref}}} |
| Details | |
| LTT 3780 | |
| Mass | 0.363±0.008[5] M☉ |
| Radius | 0.375±0.011[5] R☉ |
| Luminosity | 0.0165±0.0021[6] L☉ |
| Surface gravity (log g) | 4.85±0.03[5] cgs |
| Temperature | 3,358±92[6] K |
| Metallicity [Fe/H] | 0.06±0.14[5] dex |
| Rotation | 104±15[3] |
| Rotational velocity (v sin i) | < 1.3[3] km/s |
| Age | 3.10+6.20 −0.98[6] Gyr |
| LP 729-55 | |
| Mass | 0.136±0.004[3] M☉ |
| Radius | 0.173±0.005[3] R☉ |
| Other designations | |
| 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 star system in the constellation Hydra. This star is host to a pair of orbiting exoplanets. Based on parallax measurements, it is located at a distance of 72 light years from the Sun. LTT 3780 has an apparent visual magnitude of 13.07,[3] requiring a telescope to view.
The 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.[3] The abundance of iron, an indicator of the star's metallicity, appears higher than in the Sun.[4] The star is inactive, showing a negligible level of magnetic activity in its chromosphere.[3] 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.[3]
Collectively designated LDS 3977, the two stars in this system share a common proper motion and have an angular separation of 15.8″, which corresponds to a (physical) projected separation of 348 astronomical unit|AU.[4] At this separation, the orbital period would be ~9,100 years.[3] The fainter member is a red dwarf with a class of M5.0 V.[4] It has 14% of the mass of the Sun and 17% of the Sun's radius.[3]
Planetary system
In 2020, an analysis carried out by a team of astronomers led by astronomer Ryan Cloutier of the TESS project confirmed the existence of two planets on mildly eccentric orbits, the inner being a super-Earth and the outer a small gas planet about half the mass of Uranus.
LTT 3780 b
The inner planet, LTT 3780 b, is an 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; CO2 atmospheres with a surface pressure of at least 0.01 bar can be ruled out.[8]
LTT 3780 c
Astronomers utilizing the Gemini South 8.1-meter telescope performed an atmospheric survey of LTT 3780 c through high-resolution transmission spectroscopy. From observations during a single 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.[9] A later study with JWST found stronger evidence for methane along with moderate to strong signs of either heavier hydrocarbons or sulfur-bearing molecules. This study also put constraints on the atmospheric abundance of water vapor, CO and CO2.[10]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 2.34±0.10[5] M⊕ | 0.01195+0.00028 −0.00029 |
0.7683793(4) | 0 | 86.10+0.92 −0.68° |
1.31±0.05[5] R⊕ |
| c | 7.89±0.26[5] 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
- List of multiplanetary systems
References
- ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R Constellation record for this object at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 Cloutier, Ryan et al. (2020). "A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780". The Astronomical Journal 160 (1): 3. doi:10.3847/1538-3881/ab91c2. Bibcode: 2020AJ....160....3C.
- ↑ 4.0 4.1 4.2 4.3 4.4 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. doi:10.1051/0004-6361/202037867. Bibcode: 2020A&A...642A.173N.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Weisserman, Drew; Gromek, Nicole; Cloutier, Ryan; Bali, Komal; Cadieux, Charles; Plotnykov, Mykhaylo; L'Heureux, Alexandrine; Srivastava, Avidaan et al. (2026-04-08). "Super-Earth masses and stellar abundances from NIRPS reveal tentative evidence for water-rich formation around M dwarfs". Astronomy & Astrophysics.
- ↑ 6.0 6.1 6.2 6.3 Bonfanti, A. et al. (2024). "Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley". Astronomy & Astrophysics 682. doi:10.1051/0004-6361/202348180. Bibcode: 2024A&A...682A..66B.
- ↑ "LTT 3780". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=LTT+3780.
- ↑ Allen, Natalie H. et al. (August 2025). "Hot Rocks Survey IV: Emission from LTT 3780 b is consistent with a bare rock". The Astronomical Journal 170 (4): 240. doi:10.3847/1538-3881/adfc51. Bibcode: 2025AJ....170..240A.
- ↑ Cabot, Samuel H. C. et al. (2024-05-01). "High-resolution Spectroscopic Reconnaissance of a Temperate Sub-Neptune". The Astrophysical Journal Letters 966 (1). doi:10.3847/2041-8213/ad3828. Bibcode: 2024ApJ...966L..10C.
- ↑ 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:2512.15844 [astro-ph.EP].
Coordinates: 
10h 18m 35.137s, −11° 43′ 0.242″
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