Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Libra |
Right ascension | 14h 34m 16.81166s[2] |
Declination | −12° 31′ 10.4145″[2] |
Apparent magnitude (V) | 11.32[3] |
Characteristics | |
Spectral type | M4.0V[4] |
B−V color index | 1.633±0.052[3] |
Variable type | BY Dra |
Astrometry | |
Radial velocity (Rv) | −1.36±0.20[2] km/s |
Proper motion (μ) | RA: −355.138 mas/yr[2] Dec.: 593.040 mas/yr[2] |
Parallax (π) | 159.9225 ± 0.0546 mas[2] |
Distance | 20.395 ± 0.007 ly (6.253 ± 0.002 pc) |
Absolute magnitude (MV) | 12.41[3] |
Details[4] | |
Mass | 0.291±0.013 M☉ |
Radius | 0.299±0.009 R☉ |
Luminosity (bolometric) | 0.010106±0.000069 L☉ |
Surface gravity (log g) | 4.76±0.13 cgs |
Temperature | 3347±50 K |
Metallicity [Fe/H] | −0.18±0.15 dex |
Rotation | 96±2 d |
Rotational velocity (v sin i) | <2.0 km/s |
Age | 0.8–8.0 Gyr |
Other designations | |
Database references | |
SIMBAD | data |
Location of HN Librae in the constellation Libra |
HN Librae, also known as Gliese 555, is a small star with one or more orbiting exoplanets in the constellation Libra. With an apparent visual magnitude of 11.32,[3] it can only be viewed through a telescope. The system is located at a distance of 20.4 light years based on parallax measurements, but is drifting closer to the Sun with a radial velocity of −1.4 km/s.[2] It does not appear to belong to any known stellar moving group or association.[4]
This is an M-type main-sequence star, a red dwarf, with a stellar classification of M4.0V. The chromosphere of this star is weakly active, causing starspots that vary the stellar luminosity as it rotates.[4] It has 29% of the mass of the Sun and 30% of the Sun's girth. On average, the star is radiating just 1% of the luminosity of the Sun from its photosphere at an effective temperature of 3,347 K. The star is spinning slowly with a rotation period of around 96 days.[4]
Planetary system
[edit]In 2019, one planet candidate detected by radial velocity was reported in a preprint (never accepted for publication as of 2024), among 118 planets around M dwarf stars. This would have a minimum mass about 30 times that of Earth and orbit with a period of about 450 days.[6]
However, later radial velocity observations by the CARMENES survey published in 2023 did not confirm a planet at this period, but instead found a different planet.[7] This is a super-Earth or mini-Neptune (the discovery paper uses the term "sub-Neptune") with a minimum mass of 5.5 Earths and a period of 36 days, placing it within the habitable zone. A second planet candidate was also found, with a minimum mass of 9.7 Earths and a period of 113 days, but this signal could not be confirmed as having a planetary origin due to its similarity to the rotation period of the star.[4]
Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | ≥5.46±0.75 M🜨 | 0.1417±0.0023 | 36.116+0.027 −0.029 |
0.079+0.090 −0.055 |
— | — |
c (unconfirmed) | ≥9.7±1.9 M🜨 | 0.3040+0.0048 −0.0051 |
113.46+0.19 −0.20 |
— | — | — |
References
[edit]- ^ Weis, Edward W. (March 1994). "Long Term Variability in Dwarf M Stars". The Astronomical Journal. 107: 1135–1140. Bibcode:1994AJ....107.1135W. doi:10.1086/116925. Archived from the original on 1 March 2022. Retrieved 20 January 2022.
- ^ a b c d e f 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.
- ^ a b c d Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
- ^ a b c d e f g González-Álvarez, E.; Kemmer, J.; et al. (July 2023). "The CARMENES search for exoplanets around M dwarfs. A sub-Neptunian mass planet in the habitable zone of HN Lib". Astronomy & Astrophysics. 675: A141. arXiv:2305.19677. Bibcode:2023A&A...675A.141G. doi:10.1051/0004-6361/202346276.
- ^ "BD-11 3759". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-12-09.
- ^ Barnes, J. R.; et al. (2019-06-11). "Frequency of planets orbiting M dwarfs in the Solar neighbourhood". arXiv:1906.04644 [astro-ph.EP].
- ^ Ribas, I.; Reiners, A.; et al. (February 2023). "The CARMENES search for exoplanets around M dwarfs. Guaranteed time observations Data Release 1 (2016-2020)". Astronomy & Astrophysics. 670: A139. arXiv:2302.10528. Bibcode:2023A&A...670A.139R. doi:10.1051/0004-6361/202244879.
Well, that’s interesting to know that Psilotum nudum are known as whisk ferns. Psilotum nudum is the commoner species of the two. While the P. flaccidum is a rare species and is found in the tropical islands. Both the species are usually epiphytic in habit and grow upon tree ferns. These species may also be terrestrial and grow in humus or in the crevices of the rocks.
View the detailed Guide of Psilotum nudum: Detailed Study Of Psilotum Nudum (Whisk Fern), Classification, Anatomy, Reproduction