HD 33142
A retired A star with three planets in tightly packed orbits.
Last updated
HD 33142 is an 8th-magnitude red giant star roughly 394 light-years away in the constellation Lepus. It hosts three confirmed exoplanets: two Jupiter-sized worlds and a Saturn-like planet in a closer orbit.
Quick Facts
- Constellation
- Lepus
- Distance
- 394 ly
- Apparent magnitude
- 7.96
- Spectral type
- K0 III
- Mass
- 1.52 M☉
- Radius
- 4.17 R☉
- Effective temperature
- 5025 K
- Metallicity (iron abundance)
- 15% higher than the Sun
Facts from the source article.
Stellar characteristics
HD 33142 is a retired A star that has evolved off the main sequence and is now entering the red-giant branch. It has a spectral type of K0 III, a radius of 4.17 solar radii, and a mass of 1.52 solar masses. Its effective temperature of about 5025 K gives it an orange hue. The star is ten times more luminous than the Sun, but its apparent magnitude of 7.96 makes it invisible to the naked eye under typical conditions, though binoculars suffice.
Its metallicity is solar-like, with an iron abundance 15 percent higher than the Sun's. The star is roughly 2.72 billion years old, about three-fifths the age of the Solar System. The rotation period is estimated at 106 days from rotational broadening, but this value is highly uncertain because only an upper limit on rotation velocity is known and the axial tilt is undetermined. TESS light curves show no transit signals and indicate the star is photometrically quiet; Hipparcos data likewise show no variability.
Planetary system
The innermost planet, HD 33142 d, was confirmed in 2022 and has a mass about two-thirds that of Saturn, or 64 Earth masses. It orbits every 89.9 days with an eccentricity of 0.191 and a semi-major axis of 0.452 AU, an orbit resembling Mercury's. The first discovered planet, HD 33142 b, reported in 2011, is a Jovian world with a minimum mass of 1.26 Jupiter masses and a nearly circular orbit (eccentricity 0.049) lasting 330 days. The outermost planet, c, was initially described in 2016 as a super-Jupiter of at least 5.97 Jupiter masses with an 834-day period.
Later studies in 2019 and 2022 revised this downward: the 2022 study confirmed a planet with an 810-day period and a minimum mass of 0.89 Jupiter masses, with a low eccentricity and a semi-major axis of 1.955 AU. The system's massive planets in closely packed orbits make it prone to instability. While currently stable, one-third of 1,000 simulations with random initial conditions led to orbital destabilization within a million years; for unstable runs, the median survival time was only 8,500 years.
More in Planetary Systems with Three Confirmed Planets
Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: HD 33142 (CC BY-SA 4.0).
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