HD 43197
A dim star with two Jovian planets, named for a thunder god.
HD 43197, also known by the proper name Amadioha, is a star located in the southern constellation Canis Major. The name Amadioha, chosen by Nigeria during the NameExoWorlds campaign marking the IAU's centennial, comes from the Igbo god of thunder. With an apparent visual magnitude of 8.98, this ninth-magnitude star is too faint to be seen without a telescope. Parallax measurements place the system about 204 light-years from the Sun, and it is moving away at a radial velocity of +72 km/s. Its closest approach to Earth occurred roughly 583,000 years ago, when it came within 26.76 parsecs.
The star's stellar classification is G8/K0 IV/V, indicating a spectrum between G8 and K0 types and a luminosity class that blends main-sequence (V) and subgiant (IV) characteristics. It is a weakly active star with high metallicity—about 2.5 times that of the Sun. HD 43197 has roughly the same mass and size as the Sun, though its luminosity is only 74% of solar. Its age is estimated at a minimum of three billion years, and models suggest it is at the very end of its main-sequence lifetime.
Planetary system In 2009, the HARPS planet search program detected a Jovian planet in a highly eccentric orbit around the star. This planet spends about 78% of its orbital period within the habitable zone of the host star, though temperatures can become extreme during periastron passage. A second super-Jovian planet was discovered in 2022 using a combination of radial velocity and astrometry. If the inner planet shares the same orbital inclination as the outer one, its true mass would be approximately that value.
Quick Facts
- Apparent visual magnitude
- 8.98
- Distance
- 204 light-years
- Radial velocity
- +72 km/s
- Stellar classification
- G8/K0 IV/V
- Metallicity
- 5 halves that of the Sun
- Luminosity
- 74% solar
- Age
- at least 3 billion years
Facts from the source article.
Lore & Background
HD 43197 is a ninth-magnitude star too dim to be seen with the naked eye. Its spectrum is intermediate between G8 and K0, and its luminosity class blends main sequence (V) and subgiant (IV) characteristics. The star is weakly active, has high metallicity, and is about the same mass and size as the Sun, though only 74% as luminous. Its age is estimated at least three billion years, and it is modeled to be at the very end of its main sequence life. The system is drifting away from the Sun with a radial velocity of +72 km/s; its closest approach occurred some 583,000 years ago when it came within 26.76 pc.
Reader's Guide
HD 43197's significance lies in its planetary system, which includes two Jovian planets. The first, announced in 2009 by the HARPS planet search program, is a Jovian planet in a highly eccentric orbit. It spends about 78% of its orbital period in the habitable zone of the host star, though temperatures can reach extreme levels during periastron passage. In 2022, a second super-Jovian planet was discovered using a combination of radial velocity and astrometry. Assuming the inner planet shares the outer planet's orbital inclination, its true mass would be about a certain value. The star's proper name, Amadioha, connects it to Igbo mythology and the international NameExoWorlds campaign, highlighting cultural recognition in astronomy. The system's high metallicity and the star's end-of-main-sequence status provide context for the formation and evolution of its planets.
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