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Tenebris is the second closest planet to Alpha Centauri A and also the biggest planet in the solar system around Alpha Centauri A. The planet is the type astronomers would call a gas giant. Tenebris' outer layers are mainly made of gas such as hydrogen and helium - though it differs a bit from the gas giants we know from our own solar system: Jupiter and Saturn.   Like Neptune and Uranus, Tenebris is classified at times as an ice giant as its atmosphere contains "ice" made of Water, Ammonia and Methane.  

The surface

  Tenebris has a complex structured atmosphere made of thick clouds that to the naked eye looks icy blue. It is believed to have clouds made of mostly water close to the surface - as it is heavier than some of the other gasses found in its atmosphere. The uppermost layers contain clouds of methane which gives the planet its blue colour. The centre around the core of the planet is compressed ices and rocks and is extremely compact.   Giant storms form in the thick clouds because of the fast rotation the planet has - some storms might even have been there for decades - as the inner core of the planet rotates the outer light layers tries to keep up. Intricate swirls and patterns form on the surface, and storms can be seen from afar. Lightning in the uppermost layers has also been spotted frequently, which suggest variations in electrical charges in the air. At times, white streaks can be seen at the equator as some of the ice from lower layers gets up to the outer layers.    


    A full rotation on Tenebris is quite short at 14.56 hours which makes surface conditions something spectacular as described above.
by CatRobi
by CatRobi


109.782 km  

Surface Gravity

0.886 g (0.886 times the gravity felt on Earth)  

Average surface temperature

The outer layers: -12.4 Celsius (260.75 kelvin)   The inner layers -57.1 Celsius (216.05 kelvin)  

Days (Lenght)

One day on Tenebris is 14.56 hours on Earth.  


168.12 Earth days 277.12 Tenebris days  

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Even though the orbit of Tenebris is quite close to Alpha Centauri A, surface conditions is no where near identical to Ignis, as the two almost couldn't be any more eachothers opppsites.   The orbit itself is quite circular and seasons on Tenebris is hardly anything to write home about. The distance at it's furthest (aphelion) from Alpha Centauri A is 110.297.100 km (0.735 AU) and the closest (perihelion) is 108.592.300 km (0.723 AU).    


Tenebris is Domus's neighbor and is relatively close. Satellites have made several flybys, and some even orbit the planet at all times. Because of the rather stable orbit, satellites around Tenebris are at lower risks of damaging solar winds. Though we know enough to be sure what the atmosphere is made of, we can't say much about the core. The strong winds and storms surrounding the planet at all times, almost makes it impossible to land anything on the hard surface.   What little we know of the core, we can't exactly explain as much as we would like. Tenebris' core is dormant, to the extent that the heat signal is smaller than the amount of radiation it gets from Alpha Centauri A   This same phenomenon is seen in our own solar system but has never been understood, only theories of giant impacts long ago stealing the liquid cores energy is thrown around.      


As many known planets, Tenebris has its own children surrounding it in smaller orbits. Humans observed the first moon when they started to observe the planet, and after that, many more have been added to the collection.   It has 9 known moons, some a lot smaller than our own moon, and some much larger. One of the larger ones is speculated to be an old relic of something that once hit Tenebris. The largest moon has gotten the name Shadow as it at times really look like Tenebris shadow.   Data from Shadow is also shown to say, that many of the same elements are found on one of the sides of the moon, which further indicates contact between Tenebris and Shadow in early times.
by CatRobi

Cover image: by CatRobi


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