A Cloaking Device for Transiting Planets

TL;DR

This paper proposes that advanced civilizations could cloak or broadcast their presence by manipulating transit light curves using laser emissions, serving as a form of communication or concealment detectable by current surveys.

Contribution

It introduces the concept of cloaking and signaling via transit light curve distortions using laser arrays, offering a new method for SETI detection and planetary concealment.

Findings

A civilization could cloak Earth from Kepler-like surveys with a 30 MW laser array for 10 hours annually.

A chromatic cloak requires a 250 MW laser array, making it more challenging.

Cloaking biological signatures like oxygen could be achieved with around 160 kW laser power.

Abstract

The transit method is presently the most successful planet discovery and characterization tool at our disposal. Other advanced civilizations would surely be aware of this technique and appreciate that their home planet's existence and habitability is essentially broadcast to all stars lying along their ecliptic plane. We suggest that advanced civilizations could cloak their presence, or deliberately broadcast it, through controlled laser emission. Such emission could distort the apparent shape of their transit light curves with relatively little energy, due to the collimated beam and relatively infrequent nature of transits. We estimate that humanity could cloak the Earth from Kepler-like broadband surveys using an optical monochromatic laser array emitting a peak power of about 30 MW for roughly 10 hours per year. A chromatic cloak, effective at all wavelengths, is more challenging requiring a large array of tunable lasers with a total power of approximately 250 MW. Alternatively, a civilization could cloak only the atmospheric signatures associated with biological activity on their world, such as oxygen, which is achievable with a peak laser power of just around 160 kW per transit. Finally, we suggest that the time of transit for optical SETI is analogous to the water-hole in radio SETI, providing a clear window in which observers may expect to communicate. Accordingly, we propose that a civilization may deliberately broadcast their technological capabilities by distorting their transit to an artificial shape, which serves as both a SETI beacon and a medium for data transmission. Such signatures could be readily searched in the archival data of transit surveys.