Authors: Mark Kalina
Appendix
5:
Luhman-16 and Arcadia:
The
Luhman-16 system is a brown dwarf system, approximately 6.65 light years from
Sol, in the constellation Vela. Prior to 2028, brown dwarf stars of its type
were assumed to be impossible as candidates for habitable exo-planets and the
Luhman-16 system was not regarded with much interest.
The
Luhman-16 system consists of two "brown dwarf" stars orbiting each
other slowly at a distance of approximately five hundred million kilometers.
Both are of the sort designated as "failed" stars, meaning that their
heat comes from gravitational compression rather than from actual nuclear
fusion. The larger of the two, Luhman-16A, is about 5 times colder and 20 times
smaller than Earth's sun, while the smaller, Luhman-16B, is approximately half
the size of, and even cooler than, its larger twin.
There
is one super-Jovian exo-planet orbiting Luhman-16B, and a second, terrestrial
exo-planet (Arcadia) closely orbiting Luhman-16A.
Luhman-16A
has been named "Ravi" after one of the names of Surya, the
chief
solar deity
in
Hinduism
.
Luhman-16B has been named "
Ragyi,"
after one of the wives of Surya. The super-Jovian planet orbiting Luhman-16B
has been named "Prabha," after another one of Surya's mythological
wives. The terrestrial planet orbiting Luhman-16A was originally given the
name
"Saranyu," after yet another one of Surya's wives, but was renamed
"
Arcadia" when it was discovered to be
habitable.
Arcadia
was first discovered by long distance observation, by the staff of Dr.
Taran
Bhatnagar
of the Indian
Institute of Astrophysics in
Bangalore
in 2028. The complex gravitational interactions of the Luhman-16 system had the
effect of hiding the presence of a terrestrial-mass planet closely orbiting
Luhman-16A from earlier Earth based observers, but Dr. Bhatnagar staff had the
advantage of more sensitive instruments than had been previously available.
Once
Arcadia was discovered, it quickly became a candidate for further exploration
by means of the then newly developed Morris–Thorne wormhole technology,
colloquially called "Tannhauser gate" technology.
The
first Tannhauser gate to explore the newly discovered world was initiated in
2032 and the first gate transit to the orbit of Arcadia occurred in 2039.
Initial surveys found an oxygen-nitrogen atmosphere and liquid water and the
planet, which had been tentatively designated "Saranyu," was renamed
"Arcadia" by Dr. Benjamin Tromp, the head of the expedition's
scientific team.
The
exploration of Arcadia proceeded, first with probes and orbital surveys, then
with manned landers. Work on a surface gate was initiated that same year, and
the surface gate was first opened in 2047.
Arcadia
has a diameter 12,102 km, a mass equal to .979 of Earth mass, an atmosphere
with a surface pressure of .991 atm. Surface gravity is 1.012 G. Oxygen makes
up 22% of the atmosphere by weight with nitrogen at 76% and 2% trace
atmospheric gasses, including argon, neon and carbon dioxide.
Arcadia's
surface is over 99% water. There is one major landmass, though this is quite
small by Earth standard (by which the Arcadian landmass would be categorized as
a large island.) The combined surface area of the main Arcadian landmass is
approximately 390,000 square kilometers.
Arcadia's
rotation gives it a 27.2 hour day. Arcadia orbits Luhman-16A at a distance of
only 9.55 million kilometers, which places it inside the very narrow "life
zone" of the relatively cool dwarf star. (For comparison, Earth's orbital
distance from the Sun is approximately 150 million kilometers.) Arcadia's
orbital period is approximately 37 Earth-days, or 32 Arcadian days, (a period
of time which colloquially serves as an "Arcadian month.") Arcadia
has an orbital eccentricity even lower than that of Earth (and thus a very
circular orbit.) This, along with Arcadia's axial tilt of just over 9 degrees,
leads to relatively undifferentiated seasons. There are three very small moons,
(three small, captured asteroids, the largest only 18 kilometers across) that,
from the surface, appear as bright, fast-moving stars.
Arcadia's
landmass is roughly equatorial. Mean daytime temperatures range from an average
low of 22 degrees C. (
about 72 degrees F.
)
to an average high of 45 degrees C. (
about
113 degrees F.
), but particularly hot days can exceed 50 degrees C. (
about 122 degrees F.
) and particularly
cold nights can drop into the high single digits (
somewhat below 50 degrees F.
)
Ravi, Arcadia's sun, has an
overall luminosity is less than 1% that of Earth's Sun, but actual light levels
on Arcadia are comparable to those of Earth due to Ravi's extreme proximity.
Arcadia's seas harbor extensive
single-cellular microscopic alien life, much of which is oxygen-producing. To
date, this native life has proven to be utterly biologically incompatible with
any Earth life; Arcadian microorganisms cannot survive inside Earth creatures
and cannot derive nourishment from or give nourishment to Earth life. To date,
no native macroscopic or multi-cellular life has discovered on Arcadia.
Arcadia's landmass has so far
been found to be utterly barren of native life. It is speculated that Arcadia's
biosphere is fairly young and that it has not yet colonized Arcadia's land.
Arcadian sea water has a mineral
content which is toxic to Earth life. Even when this water enters the water
cycle and descends as precipitation (which is rare on the Arcadian landmass) it
remains mildly toxic to Earth life. Thus, all water on Arcadia must be
desalinated and/or filtered before being used by humans, Earth animals, or for
Earth plants.
Arcadia has, to date, proven to
be
relatively
mineral poor. There are
no fossil fuels of any sort and no radioactive elements such as thorium or uranium
(that could be used for nuclear power) have been discovered. Arcadia has,
however, proven rich in iron and copper bearing ores, and some gold and silver
has been mined on a successful commercial basis from copper-dominated silver
and gold bearing ores.
Colonization
of Arcadia commenced in 2047. Initial optimism about a "third habitable exo-planet"
was quickly dimmed by Arcadia's harsh climate, but despite this (or perhaps
because of it) Arcadia became a popular colonization destination for an
assortment of political refugees from around the world, many seeking a place to
escape from nations where their status had become marginal at best.
Arcadian
population has since grown steadily by immigration and natural increase since
the first colonization efforts in 2047. As of 2077, the planetary population
stood at 6.7 million people. Of these, just under 500,000 are UEN-designated
Economic and Political Refugees housed in UEN-constructed Safe Relocation
Camps.
The
largest single settlement is Redstone City, with a population of approximately
490,000.