LTT 3780
| Observation data Epoch J2000 Equinox 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 mas/yr[2] Dec.: −247.747 mas/yr[2] |
| Parallax (π) | 45.3972±0.0301 mas[2] |
| 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° |
| Projected separation | 348±3 AU |
| 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 | |
| G 162-44, LP 729-54, LTT 3780, NLTT 23974, 2MASS J10183516-1142599[7] | |
| 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 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
[edit]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
[edit]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
[edit]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
[edit]References
[edit]- ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
- 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 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. arXiv:2003.01136. Bibcode:2020AJ....160....3C. doi:10.3847/1538-3881/ab91c2. S2CID 211817805.
- 1 2 3 4 5 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:2003.01140. Bibcode:2020A&A...642A.173N. doi:10.1051/0004-6361/202037867. S2CID 211818198.
- 1 2 3 4 5 6 7 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:2604.07447.
- 1 2 3 4 Bonfanti, A.; et al. (2024). "Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley". Astronomy & Astrophysics. 682 A66. arXiv:2311.12577. Bibcode:2024A&A...682A..66B. doi:10.1051/0004-6361/202348180.
- ↑ "LTT 3780". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-03-06.
- ↑ Allen, Natalie H.; Espinoza, Néstor; 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. arXiv:2508.14210. Bibcode:2025AJ....170..240A. doi:10.3847/1538-3881/adfc51.
- ↑ Cabot, Samuel H. C.; et al. (2024-05-01). "High-resolution Spectroscopic Reconnaissance of a Temperate Sub-Neptune". The Astrophysical Journal Letters. 966 (1) L10. arXiv:2403.18891. Bibcode:2024ApJ...966L..10C. doi:10.3847/2041-8213/ad3828.
- ↑ 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].
