Helliconia Summer - Brian W. Aldiss [640]
In other words, pre-capture conditions were better than might be expected, while post-capture conditions are more severe.
Orbital Motions
Helliconia’s ‘Small Year’, that is to say its annual orbit about its parent Star B, is equal to 1.42 Earth years.
The motions of stars A and B are such that B orbits A in the equivalent of 2592 Earth years. Star B, in accordance with Kepler’s laws, moves in its orbit at a varying speed, slowing as it reaches the most distant point (apastron) from Star A, speeding up when it nears Star A (at periastron). In consequence, its planets, Helliconia included, spend less time enjoying maximum energy than they do receiving minimum energy.
Fig. 2 shows the ‘Great Year’ of Helliconia about the giant primary, where t = time in Earth years from apastron.
It is the Great Year which has predominant influence over Helliconia’s climate, and Star A which provides most of Helliconia’s heat and energy.
Figure 2. Orbit.
The x to x sector marks the 500 E years of deepest winter on either side of apastron.
The y to y sector marks the period at periastron when Star A appears brighter than Star B in Helliconia’s skies.
Points V, V, and V indicate approximately the periods in which the three books of the volume are set.
The time from 311 to 633 E years marks a period of fairly rapid improvement in climatic conditions. After that, a slow warming process sets in towards periastron. From 1929 E years, a fairly rapid decline takes place. On either side of apastron is a period of over five E centuries when the climate is either severe or unsettled; a minor ice age is either building up or else in slow decline. This contrasts with a more brief 238 E years of high summer, over periastron.
The orbits of the four Star B planets are at the following (E) distances from their primary:
Copaise 0.31AU Aganip 0.82AU
Helliconia 1.26AU Ipocrene 1.53AU
An Avernian shrine stands on Aganip (Bk.2x), it marks the spot where the 512 future occupants of the Avernus satellite were housed during the construction of the Earth Observation Station.
HELLICONIA’S MOON
The Helliconian satellite lost during the period of capture was known to the phagors as T’Sehn-Hrr. It holds the key to one of the discomfiting secrets of human life on Helliconia. (The truth is uncovered by SartoriIrvrash in Vol.2, xxi, to his detriment.)
Helliconian humans divide their small year of 480 days into weeks and tenners. One week is eight days. One tenner is 6 weeks (i.e. 48 days). So the year is divided into ten equal parts.
AVERNUS AS SATELLITE
Avernus is a satellite placed in orbit about Helliconia by the terrestrial expedition. It is designated Earth Observation Station. Its function is to relay data on all facets of Helliconia back to Earth. To the inhabitants of Helliconia, the OES is known as Kaidaw, because of its perceived rapid motion against the stars.
Avernus has an almost circular circumpolar orbit, its mean distance above planetary surface being:
Orbital radius measured from centre of planet 5731 miles
Orbital period 2hrs 9mins 30 secs
Shape: spherical Diameter 0.62 miles
Mass 18,000,000 tonnes
(1.8 × 1010 Kg)
Depending on the latitude of an observer, Avernus takes about 20-24 minutes to cross the sky, from rising to setting. From the ground, its maximum angular diameter when overhead presents 137.5 seconds of arc. Inhabitants can observe Avernus undergoing rather complex phases when it is passing overhead.
Some Avernus History
When the starship from earth was closing into orbit about Star B, 512 colonists were hatched, almost full-grown (i.e. as late adolescents). The DNA of fertilised human egg cells was computer-stored in nanowombs. The colonists were reared in six ‘families’ or clans, each destined for specific duties.
Once they had been landed at a base on Aganip, automated construction units began the building of the EOS, using local stellar material. Owing to difficulties and set-backs, construction took