Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Mensa |
Right ascension | 06h 06m 29.84725s [1] |
Declination | −72° 30′ 45.5674″ [1] |
Apparent magnitude (V) | 9.10 [2] |
Characteristics | |
HD 42936A | |
Evolutionary stage | main sequence star |
Spectral type | K0 IV/V [3] |
B−V color index | +0.91 [4] |
HD 42936B | |
Evolutionary stage | main sequence star |
Spectral type | L [5] |
Astrometry | |
Radial velocity (Rv) | 35.64±0.49 [1] km/s |
Proper motion (μ) | RA: −0.716 mas/yr [1] Dec.: −382.755 mas/yr [1] |
Parallax (π) | 21.2496±0.1143 mas [1] |
Distance | 153.5 ± 0.8 ly (47.1 ± 0.3 pc) |
Absolute magnitude (MV) | 5.78 [2] |
Orbit [6] | |
Primary | HD 42936A |
Companion | HD 42936B |
Period (P) | 506.89±0.01 d |
Semi-major axis (a) | 1.139±0.004 AU |
Eccentricity (e) | 0.596±0.001 |
Inclination (i) | 63.89±0.78° |
Argument of periastron (ω) (secondary) | 158.88+0.03 −0.01° |
Semi-amplitude (K1) (primary) | 2.65731+0.00033 −0.00002 km/s |
Details [6] | |
HD 42936A | |
Mass | 0.900±0.009 M☉ |
Radius | 0.861±0.005 R☉ |
Luminosity | 0.510±0.003 [7] L☉ |
Surface gravity (log g) | 4.266±0.045 cgs |
Temperature | 5,201±20 K |
Metallicity [Fe/H] | 0.147±0.013 dex |
Rotation | 21.8+0.5 −16.5 d [8] |
Rotational velocity (v sin i) | 3.17±0.1 km/s |
Age | 9.6±0.8 Gyr |
HD 42936B | |
Mass | 91.90±0.85 MJup |
Other designations | |
DMPP-3, CD−72°312, CPD−72°451, GC 7845, HD 42936, HIP 28941, SAO 256269 [9] | |
Database references | |
SIMBAD | data |
Exoplanet Archive | data |
HD 42936, also known as DMPP-3, is a star located in the southern circumpolar constellation Mensa. With an apparent magnitude of 9.1, [2] it is too faint to be detected with the naked eye but can be seen with a telescope. The star is relatively close at a distance of about 153 light-years (47 parsecs ) but is receding with a heliocentric radial velocity of 35.6 km/s . [1]
HD 42936 is an early K-type star with the blended luminosity class of a main sequence star and a subgiant. [3] At present it has 87% the mass of the Sun and 91% the radius of the Sun. [8] The object shines at 51% the luminosity of the Sun [7] from its photosphere at an effective temperature of 5,138 K, [8] which gives it an orangish yellow glow. HD 42936 has iron abundance 151% that of the Sun, meaning it is metal enriched [10] despite an age of 10.9 billion years. [8]
HD 42936 has a very low mass companion star in a close orbit, [8] approaching to 0.498 AU at periastron. [6]
In 2019, a radial velocity analysis carried out by a team of astronomers led by astronomer John R. Barnes of the Dispersed Matter Planet Project (DMPP) confirmed the existence of a super-Earth in orbit around DMPP-3 A. Planets in close binary star systems such as this are rare. [8]
A follow-up study in 2023 refined the parameters of the planet and companion star, and detected two additional radial velocity signals. One of these could be caused by a second, Earth-mass planet closer to the star, but the other, 800-day signal cannot be caused by an orbiting body because the companion star would make its orbit unstable. The study concludes that the 800-day signal must be caused by stellar activity, but if not for the companion star it could have been considered a likely planet, which has implications for other radial velocity planet detections. [6]
Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
c(unconfirmed) | ≥1.065+0.173 −0.259 M🜨 | 0.033+0.002 −0.0001 | 2.26+0.20 −0.10 | 0 | — | — |
b | ≥2.22+0.50 −0.28 M🜨 | 0.0670+0.0003 −0.0002 | 6.6732+0.0011 −0.0003 [8] | 0.174+0.032 −0.084 | — | — |