Inspired by Warringer's post on Wolf 359, and by the fact that I'm never going to finish Into The Great Wide Open, I present for comment the worlds discovered by the Soviet Air Force 2013-14 Delta Pavonis Expedition. Enjoy!
The Delta Pavonis system
The D.Pavonis system consists of ten planets (under the current IAU criteria for such things), a partially-disrupted asteroid belt between planets five and six, as well as numerous dwarf planets, comets and other assorted debris. Navigation in the inner system is as clear of small debris as Sol. The star's Cochrane line lies at roughly 43 AU from the primary, though depending on vector this may be temporarily disrupted by the outermost planet.
The system was first surveyed by the Sozvezdie Soviet Deep Space Exploration Force in 2013.
Helheim
The innermost planet is a lump of nickel-iron similar in composition to Mercury and on a similar star-grazing orbit.
Alfheim
Orbiting too close to Delta Pavonis to retain much water, Alfheim is a 'hot Mars' world. Unlike Mars, Alfheim still possesses a substantial nitrogen-carbon dioxide atmosphere, which keeps the surface temperature a toasty 150C. Alfheim has one (as yet unnamed) moon, a chunk of rock 160 km across that probably started life as a near-solar asteroid.
Midgard
Despite being named for the mortal world, Midgard is nothing particularly exciting or hospitable. A rocky world with no substantial atmosphere, Midgard is only exciting when put up against Helheim or Alfheim.
Yggdrasil
The only inhabitable world in the Delta Pavonis system, Yggdrasil is a temperate world with a greater axial tilt than Earth, leading to stronger and more pronounced seasonal variation. Climate is a bit cooler and drier than Earth's, with much of the planet's water locked up in polar glacier fields. The interiors of the major continental landmasses are largely scrub desert, while the coastal areas and areas near rivers are dominated by fields of grass-analogues.
Evidence obtained by the Soviet expedition indicates that Yggdrasil was much wetter and more pleasant within the last few thousand years, until the planet experienced a series of impact events (how many is unknown, but at least one K-T Event-scale impact, and possibly more) within a very short timeframe. These impacts caused a massive dieback of Yggdrasil's preexisting biosphere, and apparently also triggered the global cooling event that locked the planet into its current state. Based on the Soviet survey, experts believe the biosphere entered a recovery state within the last 1,000 years and is recolonizing areas left barren by the impacts.
Yggdrasil has three moons: Urthur, Verthandi and Skuld. All three are small, metal-poor worlds similar to Luna in composition and size. Skuld is the innermost moon, roughly the same diameter as Ceres, and only interesting because of what is orbiting at its Lagrange-1 point.
Tannhauser Gate
An artifact of unknown origin, Tannhauser Gate has been orbiting at the Yggdrasil-Skuld L1 point for at least the last five thousand years.Either shortly before or shortly after the last bombardment of Yggdrasil. The object is a hexagonal ring with an inner diameter of twelve kilometers and a cross-section of 150m. It is composed of a mixture of basic light metals (mostly titanium and nickel), two transuranic elements previously unknown outside of high-energy particle accelerators, and an alien and seemingly inert strain of handwavium.
The discovery of Tannhauser Gate effectively aborted much of the Soviet expedition in order to focus on both the Gate and Yggdrasil. The Soviets initially believed that the artifact was produced by inhabitants of Yggdrasil, but a survey of the world revealed no signs of native intelligent life or civilization capable of building something that large.
Tannhauser's purpose was discovered by scientists aboard the Soviet ship Xenu Express, who noticed the artifact responded when probed with radio pulses sent at the right frequency. The Xenu Express managed to establish communication with the artifact's control system and succeeded in activating it. Once active, the artifact generated an immense gravitational force within the inner diameter which stabilized after several minutes into the terminal point of a wormhole.
Tachikoma-19028 volunteered to transit the wormhole's event horizon and see where, exactly, it led. Armed with everything the Xenu Express crew could find about the Gate's activation and deactivation protocols, Tachi-19028 launched from the GCU Yuri Gagarin on October 15, 2013 and entered the wormholeThis act earned Tachi-19028 the Order of Lenin by unanimous acclimation upon the expedition's return to Sol.. Six hours later, Tachi returned through the event horizon with star sightings and other measurements that allowed the expedition to locate the other end of the wormhole in the Zeta 1 Reticuli system.
![[Image: tannhausergate.png]](http://img688.imageshack.us/img688/69/tannhausergate.png)
Tannhauser Gate, photographed prior to activation. In the background is the planet Yggdrasil.
Asgard
A gas giant in the Jupiter size range, Asgard is largely unremarkable save for its orbit. Asgard's orbit is slightly more eccentric than most known gas giants, and by virtue of that is remarkably close when it comes into conjunction with Yggdrasil. It's believed that this proximity destabilizes moons and other debris in orbit around Asgard and eventually causes bombardment events on Yggdrasil.
Vanaheim
A smaller gas giant than Asgard, Vanaheim is an otherwise unremarkable butterscotch-colored world with an extensive system of small, icy moons.
Svartalfheim
Svartalfheim is an ice dwarf of no particular interest on a highly inclined orbit that suggests that it may once have been a moon of Asgard or Vanaheim that was ejected during the early formation of the Delta Pavonis system. It may once have had a subsurface ocean like Europa, Ganymede or Callisto, but the lack of tidal or solar heating has likely frozen Svartalfheim down to the core.
Nidavellir
A world of rock orbiting beyond Delta Pavonis' snow line, Nidavellir is an interesting puzzle. The planet has a light 'dusting' of ices and ammonia snow common to most snow line objects, but core samples taken by the Soviet expedition suggest that the interior is largely dry and free of volatiles.
Jotunheim
The third gas giant in the Delta Pavonis system, Jotunheim again is not especially remarkable. It's position well past the snow line gives it a deep blue color punctuated by thin clouds of methane. Larger than Asgard and Vanaheim, it has a collection of moons. One Jotun moon, Utgard-Loki, is a Mars-sized ice planet with a deep nitrogen atmosphere similar to Titan.
Niflheim
The largest gas giant in the system, Niflheim lies beyond the star's Cochrane line, deep in the local Kupier belt. Believed to be a wandering rogue captured by Delta Pavonis' gravity in the distant past, Niflheim wanders on a long eccentric orbit around Pavonis. Interestingly enough, it has no large moons, only a few small asteroid-sized stragglers apparently pulled from the local Kuiper and Oort during its wanderings.
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The Delta Pavonis system
The D.Pavonis system consists of ten planets (under the current IAU criteria for such things), a partially-disrupted asteroid belt between planets five and six, as well as numerous dwarf planets, comets and other assorted debris. Navigation in the inner system is as clear of small debris as Sol. The star's Cochrane line lies at roughly 43 AU from the primary, though depending on vector this may be temporarily disrupted by the outermost planet.
The system was first surveyed by the Sozvezdie Soviet Deep Space Exploration Force in 2013.
Helheim
The innermost planet is a lump of nickel-iron similar in composition to Mercury and on a similar star-grazing orbit.
Alfheim
Orbiting too close to Delta Pavonis to retain much water, Alfheim is a 'hot Mars' world. Unlike Mars, Alfheim still possesses a substantial nitrogen-carbon dioxide atmosphere, which keeps the surface temperature a toasty 150C. Alfheim has one (as yet unnamed) moon, a chunk of rock 160 km across that probably started life as a near-solar asteroid.
Midgard
Despite being named for the mortal world, Midgard is nothing particularly exciting or hospitable. A rocky world with no substantial atmosphere, Midgard is only exciting when put up against Helheim or Alfheim.
Yggdrasil
The only inhabitable world in the Delta Pavonis system, Yggdrasil is a temperate world with a greater axial tilt than Earth, leading to stronger and more pronounced seasonal variation. Climate is a bit cooler and drier than Earth's, with much of the planet's water locked up in polar glacier fields. The interiors of the major continental landmasses are largely scrub desert, while the coastal areas and areas near rivers are dominated by fields of grass-analogues.
Evidence obtained by the Soviet expedition indicates that Yggdrasil was much wetter and more pleasant within the last few thousand years, until the planet experienced a series of impact events (how many is unknown, but at least one K-T Event-scale impact, and possibly more) within a very short timeframe. These impacts caused a massive dieback of Yggdrasil's preexisting biosphere, and apparently also triggered the global cooling event that locked the planet into its current state. Based on the Soviet survey, experts believe the biosphere entered a recovery state within the last 1,000 years and is recolonizing areas left barren by the impacts.
Yggdrasil has three moons: Urthur, Verthandi and Skuld. All three are small, metal-poor worlds similar to Luna in composition and size. Skuld is the innermost moon, roughly the same diameter as Ceres, and only interesting because of what is orbiting at its Lagrange-1 point.
Tannhauser Gate
An artifact of unknown origin, Tannhauser Gate has been orbiting at the Yggdrasil-Skuld L1 point for at least the last five thousand years.Either shortly before or shortly after the last bombardment of Yggdrasil. The object is a hexagonal ring with an inner diameter of twelve kilometers and a cross-section of 150m. It is composed of a mixture of basic light metals (mostly titanium and nickel), two transuranic elements previously unknown outside of high-energy particle accelerators, and an alien and seemingly inert strain of handwavium.
The discovery of Tannhauser Gate effectively aborted much of the Soviet expedition in order to focus on both the Gate and Yggdrasil. The Soviets initially believed that the artifact was produced by inhabitants of Yggdrasil, but a survey of the world revealed no signs of native intelligent life or civilization capable of building something that large.
Tannhauser's purpose was discovered by scientists aboard the Soviet ship Xenu Express, who noticed the artifact responded when probed with radio pulses sent at the right frequency. The Xenu Express managed to establish communication with the artifact's control system and succeeded in activating it. Once active, the artifact generated an immense gravitational force within the inner diameter which stabilized after several minutes into the terminal point of a wormhole.
Tachikoma-19028 volunteered to transit the wormhole's event horizon and see where, exactly, it led. Armed with everything the Xenu Express crew could find about the Gate's activation and deactivation protocols, Tachi-19028 launched from the GCU Yuri Gagarin on October 15, 2013 and entered the wormholeThis act earned Tachi-19028 the Order of Lenin by unanimous acclimation upon the expedition's return to Sol.. Six hours later, Tachi returned through the event horizon with star sightings and other measurements that allowed the expedition to locate the other end of the wormhole in the Zeta 1 Reticuli system.
Tannhauser Gate, photographed prior to activation. In the background is the planet Yggdrasil.
Asgard
A gas giant in the Jupiter size range, Asgard is largely unremarkable save for its orbit. Asgard's orbit is slightly more eccentric than most known gas giants, and by virtue of that is remarkably close when it comes into conjunction with Yggdrasil. It's believed that this proximity destabilizes moons and other debris in orbit around Asgard and eventually causes bombardment events on Yggdrasil.
Vanaheim
A smaller gas giant than Asgard, Vanaheim is an otherwise unremarkable butterscotch-colored world with an extensive system of small, icy moons.
Svartalfheim
Svartalfheim is an ice dwarf of no particular interest on a highly inclined orbit that suggests that it may once have been a moon of Asgard or Vanaheim that was ejected during the early formation of the Delta Pavonis system. It may once have had a subsurface ocean like Europa, Ganymede or Callisto, but the lack of tidal or solar heating has likely frozen Svartalfheim down to the core.
Nidavellir
A world of rock orbiting beyond Delta Pavonis' snow line, Nidavellir is an interesting puzzle. The planet has a light 'dusting' of ices and ammonia snow common to most snow line objects, but core samples taken by the Soviet expedition suggest that the interior is largely dry and free of volatiles.
Jotunheim
The third gas giant in the Delta Pavonis system, Jotunheim again is not especially remarkable. It's position well past the snow line gives it a deep blue color punctuated by thin clouds of methane. Larger than Asgard and Vanaheim, it has a collection of moons. One Jotun moon, Utgard-Loki, is a Mars-sized ice planet with a deep nitrogen atmosphere similar to Titan.
Niflheim
The largest gas giant in the system, Niflheim lies beyond the star's Cochrane line, deep in the local Kupier belt. Believed to be a wandering rogue captured by Delta Pavonis' gravity in the distant past, Niflheim wanders on a long eccentric orbit around Pavonis. Interestingly enough, it has no large moons, only a few small asteroid-sized stragglers apparently pulled from the local Kuiper and Oort during its wanderings.
Next post: The worlds of Zeta 1 Reticulli!
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