Arella's Home

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Introduction

Arella's planet is fictitious, but her star isn't. Her world circles HD 172051 (also called HIP 91438) about 43 light years from here.

Mass 1.72×10³⁰ kg (0.865 Sol)

Mean radius 626753 km (0.90 Sol)

Temperature 5638K

Life span 1.62x10¹⁰ years

Age 4.3x10⁹ years

Spectral type G5V

Apparent mag 5.85

Metallicity [Fe/H] –0.21 dex

Constellation Sagittarius

Right ascension 18h 38m 53.4005s

Declination -21^o 03^' 06.7368^"

Local Brightness 121291 lux (0.95 Sol)

Mass	1.72×10³⁰ kg (0.865 Sol)
Mean radius	626753 km (0.90 Sol)
Temperature	5638K
Life span	1.62x10¹⁰ years
Age	4.3x10⁹ years
Spectral type	G5V
Apparent mag	5.85
Metallicity [Fe/H]	–0.21 dex
Constellation	Sagittarius
Right ascension	18h 38m 53.4005s
Declination	-21^o 03^' 06.7368^"
Local Brightness	121291 lux (0.95 Sol)

Arella lives on a large moon called Amphitrite. It orbits a gas giant called Serel. Amphitrite is just large enough to hold an atmosphere and has a gravity around 2/3 of Earth's. It orbits close enough to Serel to be tidally locked, so Arella always sees Serel looming large in her sky.

Amphitrite

Mean radius 4332 km (0.68 Earth)

Surface area 2.358×10⁸ km² (0.462 Earth)

Volume 3.405×10¹¹ km³ (0.314 Earth)

Mass 1.737×10²⁴ kg (0.29 Earth)

Mean density 5.1 g/cm³

Surface gravity 6.176 m/s² (0.63 g)

Day Length 33.6 Earth hours

Orbit radius 478720 km

Orbital period 33.6 Earth hours

Escape velocity 7.315 km/s

Albedo 0.26

Atmos. Press 0.93 earth

Land % 0.2%

Max elevation 97m

Obliquity 0.11 deg

Mean radius	4332 km (0.68 Earth)
Surface area	2.358×10⁸ km² (0.462 Earth)
Volume	3.405×10¹¹ km³ (0.314 Earth)
Mass	1.737×10²⁴ kg (0.29 Earth)
Mean density	5.1 g/cm³
Surface gravity	6.176 m/s² (0.63 g)
Day Length	33.6 Earth hours
Orbit radius	478720 km
Orbital period	33.6 Earth hours
Escape velocity	7.315 km/s
Albedo	0.26
Atmos. Press	0.93 earth
Land %	0.2%
Max elevation	97m
Obliquity	0.11 deg

Serel

Mean radius 94380 km (1.35 Jupiter)

Surface area 1.12×10¹¹ km² (1.82 Jupiter)

Volume 3.52×10¹⁵ km³ (2.45 Jupiter)

Mass 4.437×10²⁷ kg (2.34 Jupiter)

Mean density 1.26 g/cm³

Surface gravity 33.245 m/s² (3.39 g)

Day Length 11.63 earth hours

Orbit radius 1.30152x10⁸ km (0.87au)

Orbital period 318.7 Earth days, 227.6 Amphitrite days

Escape velocity 79.217 km/s

Albedo 0.49

Angle in sky 22.3 deg (44.6 Earth Moon widths)

Mean radius	94380 km (1.35 Jupiter)
Surface area	1.12×10¹¹ km² (1.82 Jupiter)
Volume	3.52×10¹⁵ km³ (2.45 Jupiter)
Mass	4.437×10²⁷ kg (2.34 Jupiter)
Mean density	1.26 g/cm³
Surface gravity	33.245 m/s² (3.39 g)
Day Length	11.63 earth hours
Orbit radius	1.30152x10⁸ km (0.87au)
Orbital period	318.7 Earth days, 227.6 Amphitrite days
Escape velocity	79.217 km/s
Albedo	0.49
Angle in sky	22.3 deg (44.6 Earth Moon widths)

Eclipses

Amphitrite is tidally locked so Serel stays put in the sky. The side of Amphitrite that faces Serel experiences a daily 2.08 hr eclipse. The following two plots show a typical eclipse, here at 20deg longitude. The second is a log plot that show a typical visual response to light levels. As Serel's phase approaches full at night, light levels increase. A full Serel casts over 2000 lux on Amphitrite's surface.

The side of facing Serel recieves less total illumination as shown in the following two plots.

History

Amphitrite started out with 12% land cover. Land species evolved. Plate tectonics ended. Later, hominid species evolved. Land erosion reduced land coverage and continents sank below the sea. Some land species, including the hominids, successfully made the transition back to water before their land completely disappeared beneath the sea.

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This page last updated 24-Jan-2018