HD 221287 b

HD 221287 b, also known as Pipitea, is an exoplanet that orbits HD 221287, approximately 173 light years away in the constellation of Tucana. This planet has mass >3.12 M_J (>992 M_🜨) and orbits in a habitable zone at 1.25 AUs (6.06 μpc) from the star, taking 1.25 years to orbit at 29.9 km/s around the star. Dominique Naef [fr] discovered this planet in early 2007 by using HARPS spectrograph located in Chile.^[1]

HD 221287 b / Pipitea

Discovery
Discovered by	Dominique Naef [fr] et al.[1]
Discovery site	Chile
Discovery date	March 5, 2007
Detection method	HARPS
Orbital characteristics
Apastron	1.35 AU (202,000,000 km)
Periastron	1.15 AU (172,000,000 km)
Semi-major axis	1.25 ± 0.04 AU (187,000,000 ± 6,000,000 km)
Eccentricity	0.08 ± 0.11
Orbital period (sidereal)	456.1 ± 6.5 d 1.2487 y
Time of periastron	2,453,263 ± 100
Argument of periastron	98 ± 72
Semi-amplitude	71 ± 13
Star	HD 221287
Physical characteristics
Mass	>3.12 ± 0.78 MJ (992 M🜨)

Based on a probable 10⁻⁴ fraction of the planet mass as a satellite,^[2] the planet can have a Mars-sized moon with habitable surface.^[3] On the other hand, this mass can be distributed into many small satellites as well.

It was named "Pipitea" by representatives of the Cook Islands in the IAU's 2019 NameExoWorlds contest, with the comment "Pipitea is a small, white and gold pearl found in Penrhyn lagoon in the northern group of the Cook Islands."^[4]

Insolation data for HD 221287 b

Further information: Luminosity and Climate model § Zero-dimensional models

From Luminosity and distance irridance can be calculated: ^{[note 1]}

Planet Distance	Insolation (W/m2)	% of Earth's
Earth's Aphelion Flux	1321.544	96.74%
HD 221287 b Apastron flux	1,351.050	98.90%
Earth's Average Flux [note 2]	1366.079	100.00%
Earth's Perihelion Flux	1412.903	103.43%
HD 221287 b Average flux [note 3]	1,575.865	115.36%
HD 221287 b Periastron flux	1,861.844	136.29%
Venus' Aphelion Flux	2585.411	188.72%
Venus' Average Flux	2620.693	191.30%
Venus' Perihelion Flux	2656.70	193.93%

See also

• HD 100777 b
• HD 190647 b

Notes

1. From ${\displaystyle {\begin{smallmatrix}L=4\pi R^{2}\sigma T_{\rm {eff}}^{4}\end{smallmatrix}}}$, where ${\displaystyle {\begin{smallmatrix}L\end{smallmatrix}}}$ is the luminosity, ${\displaystyle {\begin{smallmatrix}R\end{smallmatrix}}}$ is the radius, ${\displaystyle {\begin{smallmatrix}T_{\rm {eff}}\end{smallmatrix}}}$ is the effective surface temperature and ${\displaystyle {\begin{smallmatrix}\sigma \end{smallmatrix}}}$ is the Stefan–Boltzmann constant.
2. Earth's Solar Constant.
3. ${\displaystyle f_{p}={\frac {(1.80245\times 3.0572\times 10^{25})}{((1.25-(1.25\times 0.08))\times 149597870700)^{2}}}}$