HD 45364

HD 45364 is a star in the southern constellation of Canis Major. It is too faint to be visible to the naked eye, having an apparent visual magnitude of 8.08.^[1] The distance to this system is 112 light years based on parallax.^[2] It is drifting further away from the Sun with a radial velocity of +16.4 km/s,^[2] having come within 49 light-years some 1.5 million years ago.^[1]

HD 45364

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Canis Major[1]
Right ascension	06h 25m 38.47436s[2]
Declination	−31° 28′ 51.4307″[2]
Apparent magnitude (V)	8.08[1]
Characteristics
Evolutionary stage	main sequence[2]
Spectral type	G8V[3]
B−V color index	0.719±0.015[1]
V−R color index	0.01
Astrometry
Radial velocity (Rv)	+16.40±0.14[2] km/s
Proper motion (μ)	RA: +52.242[2] mas/yr Dec.: −11.771[2] mas/yr
Parallax (π)	29.1339±0.0172 mas[2]
Distance	111.95 ± 0.07 ly (34.32 ± 0.02 pc)
Absolute magnitude (MV)	+5.51[1]
Details[4]
Mass	0.88±0.02 M☉
Radius	0.82±0.01 R☉
Luminosity	0.562±0.004 L☉
Surface gravity (log g)	4.55±0.03 cgs
Temperature	5,540±31 K
Metallicity [Fe/H]	−0.14±0.03[1] dex
Rotational velocity (v sin i)	1.672±0.665[5] km/s
Age	3.4±2.7 Gyr
Other designations
CD−31°3286, HD 30579, HIP 30579, SAO 196806[6]
Database references
SIMBAD	data
Exoplanet Archive	data

This object is an ordinary G-type main-sequence star with a stellar classification of G8V,^[3] which indicates it is generating energy through core hydrogen fusion. It is around 3.4 billion years old and is spinning with a projected rotational velocity of 1.7 km/s.^[5] The star has 88% of the mass of the Sun and 82% of the Sun's radius. It is radiating 56% of the luminosity of the Sun from its photosphere at an effective temperature of 5,540 K. As of August 2008 there are two confirmed extrasolar planets (or exoplanets) orbiting around it.^[7]

Planetary system

HD 45364 is one of only a relative few systems that have had more than one exoplanet discovered in its orbit. The two planets, HD 45364 b and HD 45364 c respectively, were both discovered in August 2008 using the radial velocity method. The pair was initially believed to be orbiting the host star with a 3:2 mean motion resonance,^[7] which means the inner planet is completing three orbits for every two orbits of the outer planet.

Hydrodynamic formation scenario of HD45364

It was difficult to explain how such resonant configuration of planetary orbits could evolve,^[8] mainly due to the planets orbital eccentricities being about 4-5 times too high, although planetary system formation models involving hydrodynamic effects have been proposed.^[9]

As in 2022, refined radial-velocity data shows the planetary orbits are more circular and widely spaced, therefore planets are slightly out of mean motion resonance state.^[10]

The HD 45364 planetary system^[10]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥0.1893+0.0062 −0.006 MJ	0.6793+0.0016 −0.0015	225.79+0.81 −0.76	0.067±0.016	—	—
c	≥0.5490+0.0075 −0.0074 MJ	0.9020±0.0010	345.43+0.54 −0.57	0.019+0.011 −0.010	—	—