Issue No. 39

The Orbital Index

Issue No. 39 | Nov 19, 2019

🚀 🌍 🛰

Is the Universe flat or closed? Rather than being flat, in which two parallel lines will never cross, as modern cosmology predicts, a controversial new paper in Nature Astronomy re-analyzes data from the Planck space telescope and suggests instead that the Universe is closed—that it curves in on itself like an ellipsoid, in which parallel lines on the surface will eventually cross and return to where they started. The shape of the Universe is dependent on whether or not the density of matter and dark matter is enough to gravitationally balance outward expansion (likely from dark energy). The theory of Inflation predicts a very large and flat Universe close to this critical energy density. This new paper’s reanalysis of gravitational lensing in Cosmic Microwave Background data from the Planck satellite suggests that the Universe may be 5% over the critical density. While the original Planck team also noticed the lensing, they attribute the observation to a statistical fluke. Other current methods of calculating curvature still indicate flatness. Quanta Magazine has a good analysis and discussion, and notes that the majority of researchers feel “that the weight of evidence points to the Universe being flat.” Interestingly, the shape of a universe determines the value of Pi that will be measured in it. In a flat universe (with no other matter to mess up measurements), one gets the precise mathematical value of Pi, but in a closed universe, a measured circumference will be smaller than predicted by 2πr, and all the angles of a galaxy-spanning triangle will add up to more than 180°.

It's not my fault I haven't had a chance to measure the curvature of this particular universe.

Hayabusa 2 is headed home. After spending 16 months interrogating the near-earth asteroid Ryugu in every way a robotic clown car of experiments can imagine, the spacecraft is headed back to Earth to return multiple samples collected from the Cg-type asteroid. Ryugu’s orbit ranges from .96 AU to 1.41 AU with a period of 474 days, coming within just 95,400 km of Earth at its closest (just 1/4 LD), but is currently 1.7 AU away. Hayabusa will spend the next year closing that distance to Earth and will eject its sample capsule into the atmosphere in December 2020. The Hayabusa 2 mission follows in the footsteps of the groundbreaking Hayabusa mission which, despite being plagued with multiple technical difficulties, managed to return 1,500 grains of extra-terrestrial material from the asteroid Itokawa. The current six-year mission has gone much more smoothly than its predecessor and continues JAXA’s (likely very prescient) focus on robotic NEO exploration and mining.

Another unattributed Martian gaseous emission. Even as seasonal variations in Martian atmospheric methane remain a mystery (cf. Issue #18), odd variations have been detected in another atmospheric constituent: oxygen. Over the last three Martian years (~5 Earth years), Curiosity’s Sample Analysis at Mars (SAM) portable chemistry lab has detected “significant seasonal and interannual variability [in oxygen levels], suggesting an unknown atmospheric or surface process at work” (paper). “[W]e think it has to be something in the surface soil that changes seasonally because there aren’t enough available oxygen atoms in the atmosphere to create the behavior we see.NASA’s press release goes into more detail. It’s presumed to be an abiotic process, but, look, we’re not saying it’s aliens… but it’s aliens.

News in brief. A report from the OIG called to light the 60% difference in NASA’s funding of Starliner vs Crew Dragon (unsurprisingly Boeing defended, while Musk condemned it), this puts a Starliner seat cost at $90m—more than a ride on Soyuz; following in the footsteps of Made in Space, FOMS has manufactured ZBLAN fiber on the ISS (cf. Issue #30 for more about ZBLAN); Kepler demonstrated 100Mbps space-based Internet connectivity with the Arctic, providing data uplink to a climate change research vessel; China performed a hover test of their upcoming Mars lander (while also performing two orbital launches within 3 hours of each other); ISRO has started work on Chandrayaan-3—including a lander and rover with upgrades from those that failed in Chandrayaan-2—and is targeting a November 2020 launch; WFIRST passes preliminary design review; Ultima Thule has been renamed to Arrokoth, the Powhatan word for ‘sky’; the US Air Force is enthusiastic about SpaceX’s Starlink after demonstrating download speeds of 610 megabits/s into an airplane cockpit; and, Crew Dragon successfully completed a static fire of its SuperDraco engines (TLDR; no rapid unplanned disassembly this time around).

The last full shot of Ryugu by Hayabusa 2, taken November 18, as it departs for its year-long journey home.

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