[Paper Review] `Oumuamua is not Artificial

J. I. Katz|arXiv (Cornell University)|Feb 15, 2021

Agriculture and Rural Development Research4 references4 citations

TL;DR

Katz argues that 'Oumuamua is not of artificial origin, rejecting the hypothesis of an alien probe due to implausible mission timing, inefficiency of a flyby, tumbling dynamics inconsistent with flexible sails, and lack of detectable signals. The paper further demonstrates that the Breakthrough Starshot laser-sail concept is physically infeasible due to structural stress, material limits, and energy constraints.

ABSTRACT

I summarize evidence against the hypothesis that `Oumuamua is the artificial creation of an advanced civilization. An appendix discusses the flaws and inconsistencies of the "Breakthrough" proposal for laser acceleration of spacecraft to semi-relativistic speeds. Reality is much more challenging, and interesting.

Motivation & Objective

• To challenge the hypothesis that 'Oumuamua is an artificial interstellar probe launched by an advanced civilization.
• To analyze the physical and engineering infeasibilities of the Breakthrough Starshot laser-sail concept for interstellar travel.
• To evaluate the plausibility of interstellar probes being launched with sufficient precision to target the Solar System.
• To assess whether the observed non-gravitational acceleration of 'Oumuamua can be explained by natural processes.

Proposed method

• Analyzes the ballistic coefficient required to produce 'Oumuamua’s observed non-gravitational acceleration, finding it inconsistent with known sail materials.
• Evaluates the time required for a civilization to predict Earth’s technological development and launch a probe, concluding it would require >10⁵ years and thus implausible timing.
• Assesses the structural stress on a laser-sail during acceleration, using the force equation F = Mₚa and sail stress F/(Ch) to show aluminum sails would fail under required loads.
• Derives the minimum sail thickness h(r) = F/(2πrσ) and calculates mass increase due to thickening, showing that 10 m² sails would require ~14 g mass to survive, exceeding the 1 g payload mass budget.
• Evaluates signal transmission feasibility from interstellar probes, calculating received power levels at Earth and showing they are far below detectable thresholds.
• Considers relay systems for interstellar communication, concluding that nuclear-powered relays would be too massive and slow to deploy in time.

Experimental results

Research questions

• RQ1 Could an advanced civilization have launched a probe toward the Solar System with sufficient foresight to intercept 'Oumuamua’s trajectory?
• RQ2 Is the observed non-gravitational acceleration of 'Oumuamua consistent with a low-ballistic-coefficient artificial sail?
• RQ3 Can the Breakthrough Starshot laser-sail design achieve 0.2c acceleration without structural failure under the required forces?
• RQ4 What are the detectable signatures of an artificial interstellar probe, and are they consistent with the observed data on 'Oumuamua'?
• RQ5 Is interstellar communication via laser transmission from a 1 g probe feasible over 1 pc, given signal strength and background noise?

Key findings

• The required ballistic coefficient of ~0.1 g/cm² for 'Oumuamua’s acceleration is orders of magnitude higher than that of known solar sails or laser-sail concepts.
• A civilization would need to have launched a probe ~10⁵ years ago to reach the Solar System in time, making the timing of such a mission implausible.
• The structural stress on an aluminum sail with 300 Å thickness exceeds 2000 kbar, over 600 times the yield strength of aluminum, making it physically impossible.
• To achieve the required force, the sail mass would need to be ~14 g for a 10 m² sail, exceeding the 1 g payload mass budget and invalidating the original design.
• The minimum sail area consistent with the 1 g mass budget is only 0.06 m², requiring laser intensity 170 times higher than assumed, exceeding thermal tolerance.
• Signal transmission from a 1 g probe at 1 pc would yield only ~3 photons per second at a 10 m telescope, far below detectable levels against the 3 K cosmic background.