HD 33142 is a solitary 8th-magnitude red giant located about 394 light-years (121 pc) away in the southern constellation of Lepus. It is orbited by three confirmed exoplanets, namely the Jupiter-sized planets HD 33142 b and c, and a Saturn-like planet, d, located closer to the star.
  | |
| Observation data Epoch J2000.0[1] Equinox J2000.0[1] | |
|---|---|
| Constellation | Lepus |
| Right ascension | 05h 07m 35.54139s |
| Declination | −13° 59′ 11.3368″ |
| Apparent magnitude (V) | 7.96[2] |
| Characteristics | |
| Evolutionary stage | Red-giant branch star |
| Spectral type | K0III[3] |
| B−V color index | 0.935[3] |
| J−H color index | 0.442[2] |
| J−K color index | 0.553[2] |
| Astrometry | |
| Radial velocity (Rv) | 33.980499[4] km/s |
| Proper motion (μ) | RA: -7.488[1] mas/yr Dec.: 33.693[1] mas/yr |
| Parallax (π) | 8.2719 ± 0.0202 mas[1] |
| Distance | 394.3 ± 1.0 ly (120.9 ± 0.3 pc) |
| Absolute magnitude (MV) | 2.24[a] |
| Details[3] | |
| Mass | 1.52±0.03 M☉ |
| Radius | 4.17+0.03 −0.07 R☉ |
| Luminosity | 10.00+0.09 −0.23 L☉ |
| Surface gravity (log g) | 3.375+0.021 −0.002 cgs |
| Temperature | 5025.4+23.6 −15.5 K |
| Metallicity [Fe/H] | 0.06±0.01 dex |
| Rotational velocity (v sin i) | ≤2 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
Stellar characteristics
editHD 33142 belongs to a class of "retired A stars," meaning it was likely once an A-type main-sequence star but has since evolved past the main sequence.[5][6] Now, it is entering the red-giant branch with a spectral type of K0 III, a radius of 4.17 R☉, and a mass of 1.52 M☉.[3] The effective temperature of HD 33142 is estimated to be about 5,025 K (4,752 °C; 8,585 °F), giving it an orange color. The star is ten times as bright as the Sun, which, combined with its distance from Earth, places its apparent magnitude at 7.96,[2] making it too faint to be visible by the naked eye under most circumstances, but it can be observed using binoculars.[7] It has a solar-like metallicity of 0.06, which translates to an iron abundance 15% higher than the Sun. The star is aged approximately 2.72 billion years,[3] making it three-fifths as old as the Solar System (4.568 billion years old[8]).
The star's rotation period has been measured to be about 106 days from rotational broadening (i.e., Doppler broadening caused by the star's rotation), but this value is very uncertain as only the upper limit of the rotation velocity is known and the axial tilt is entirely undetermined. Light curves obtained by the TESS reveal no transit signals and suggest that the star is photometrically quiet. Archived data from Hipparcos photometry generally agree with this, with no indication of variability.[3]
Planetary system
editIn 2011, Johnson et al. reported the discovery of a Jovian planet, HD 33142 b, alongside 17 other planets orbiting retired A stars.[5] It revolves around the star in an Earth-like circular (eccentricity 0.049) orbit that lasts 330 days (0.90 years) each, and has an estimated minimum mass of 1.26 MJ.
The second planet, c, was discovered by Bryan et al. in 2016, and was initially described as a super-Jupiter with a minimum mass of 5.97 MJ and an orbital period of 834 ± 29 days (2.283 ± 0.079 years).[9] A 2019 follow-up study by Luhn et al., independently reported radial velocity signals that indicated the existence of a planet with a similar period of 809 ± 26 days (2.215 ± 0.071 years), but with a far smaller mass of 0.62 MJ.[6] A 2022 study by Trifonov et al. seems to agree more with the latter, confirming an 810-day period planet weighing at least 0.89 MJ. Its orbit has a low eccentricity and a semi-major axis of 1.955 AU, roughly twice that of planet b.[3]
In 2022, at the same time Trifonov et al. confirmed the previous two planets, they also reported another smaller object, d, with a mass of 64 ME, two-thirds that of Saturn (95 ME[10]). With a period of 89.9 days, an eccentricity of 0.191, and a semi-major axis of 0.452 AU, its orbit closely resembles that of Mercury, which has a period of 88.0 days, an eccentricity of 0.2056, and a semi-major axis of 0.3871 AU.[11]
Stability and future
editThe HD 33142 system features massive planets in closely packed orbits, which makes it prone to orbital instability due to gravitational perturbations. While the system is presently stable, out of the 1,000 simulations conducted by Trifonov et al. with randomly generated initial conditions, one-third of them resulted in orbital destabilization within the million-year simulation span. For the unstable runs, the planetary system's median survival time was a mere 8,500 years.[3]
Having left the main-sequence stage, HD 33142 is in the midst of developing into a red giant, and is expected to undergo two periods of rapid expansion in the next 300 million years: first during the red-giant branch, when it will reach a diameter of ~0.75 AU; and then in the asymptotic giant branch, ballooning to around 1.45 AU; all before ceasing nucleosynthesis and shriveling up into a white dwarf. In both phases, tidal forces from the bloated star cause orbital decay. According to simulations, the two inner planets, d and b, will be engulfed by the star before the tip of the red-giant branch as their orbits contract. The outermost planet, c, is predicted to survive the red-giant branch and migrate outward to ~2.5 AU, but will ultimately either succumb to the same fate during the asymptotic giant branch, or be ejected from the system entirely.[3]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| d | ≥0.20+0.02 −0.03 MJ |
0.452 ± 0.003 | 89.9 ± 0.1 | 0.191+0.140 −0.128 |
— | ~0.832[12] RJ |
| b | ≥1.26 ± 0.05 MJ | 1.074 ± 0.007 | 330.0 ± 0.4 | 0.049+0.032 −0.030 |
— | ~1.22[13] RJ |
| c | ≥0.89+0.06 −0.05 MJ |
1.955+0.016 −0.012 |
810.2+0.38 −0.42 |
0.081+0.055 −0.047 |
— | ~1.24[14] RJ |
Notes
edit- ^ Calculated from star's luminosity.
References
edit- ^ a b c d Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
- ^ a b c d e "HD 33142". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 12 October 2024.
- ^ a b c d e f g h i j Trifonov, Trifon; et al. (22 September 2022). "A New Third Planet and the Dynamical Architecture of the HD 33142 Planetary System*". The Astronomical Journal. 164 (4). American Astronomical Society: 156. arXiv:2206.03899. Bibcode:2022AJ....164..156T. doi:10.3847/1538-3881/ac7ce0. ISSN 0004-6256.
- ^ Jönsson, Henrik; et al. (17 August 2020). "APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South". The Astronomical Journal. 160 (3). American Astronomical Society: 120. arXiv:2007.05537. Bibcode:2020AJ....160..120J. doi:10.3847/1538-3881/aba592. ISSN 0004-6256.
- ^ a b Johnson, John Asher; et al. (29 November 2011). "Retired a Stars and Their Companions. Vii. 18 New Jovian Planets". The Astrophysical Journal Supplement Series. 197 (2). American Astronomical Society: 26. arXiv:1108.4205. Bibcode:2011ApJS..197...26J. doi:10.1088/0067-0049/197/2/26. ISSN 0067-0049.
- ^ a b Luhn, Jacob K.; et al. (20 March 2019). "Retired A Stars and Their Companions. VIII. 15 New Planetary Signals around Subgiants and Transit Parameters for California Planet Search Planets with Subgiant Hosts". The Astronomical Journal. 157 (4). American Astronomical Society: 149. arXiv:1811.03043. Bibcode:2019AJ....157..149L. doi:10.3847/1538-3881/aaf5d0. ISSN 0004-6256.
- ^ Zarenski, Ed (2004). "Limiting Magnitude in Binoculars" (PDF). Cloudy Nights. Archived (PDF) from the original on 21 July 2011. Retrieved 6 May 2011.
- ^ Bouvier, A.; Wadhwa, M. (2010). "The age of the Solar System redefined by the oldest Pb–Pb age of a meteoritic inclusion". Nature Geoscience. 3 (9): 637–641. Bibcode:2010NatGe...3..637B. doi:10.1038/NGEO941. S2CID 56092512.
- ^ Bryan, Marta L.; et al. (14 April 2016). "Statistics of Long Period Gas Giant Planets in Known Planetary Systems". The Astrophysical Journal. 821 (2). American Astronomical Society: 89. arXiv:1601.07595. Bibcode:2016ApJ...821...89B. doi:10.3847/0004-637x/821/2/89. ISSN 0004-637X.
- ^ Williams, David R. (23 December 2016). "Saturn Fact Sheet". NASA. Archived from the original on 17 July 2017. Retrieved 12 October 2017.
- ^ Williams, David R. (25 November 2020). "Mercury Fact Sheet". NASA. Archived from the original on 3 April 2019. Retrieved 19 April 2021.
- ^ "HD 33142 d - NASA Science". Retrieved 12 October 2024.
- ^ "HD 33142 b - NASA Science". Retrieved 12 October 2024.
- ^ "HD 33142 c - NASA Science". Retrieved 12 October 2024.