Our Sky now and then $-$ searches for lost stars and impossible effects as probes of advanced extra-terrestrial civilisations

TL;DR

This paper explores the possibility of detecting advanced extraterrestrial civilizations by searching for physically impossible effects, such as disappearing stars or galaxies, in large astronomical survey datasets.

Contribution

It introduces a novel method of searching for signs of advanced alien technology through the identification of disappearing celestial objects in existing survey data.

Findings

Identified one candidate object for further follow-up, though with high uncertainty.

Estimated the probability of observing such disappearing events as less than one in a million.

Proposed a citizen science project to expand the search using the full USNO-B1.0 dataset.

Abstract

Searches for extra-terrestrial intelligence (SETI) using large survey data often look for possible signatures of astroengineering. We propose to search for physically impossible effects caused by highly advanced technology, by carrying out a search for disappearing galaxies and Milky Way stars. We select $\sim$ 10 million objects from USNO-B1.0 with low proper motion ($\mu$ $<$ 20 milli arcseconds / year) imaged on the sky in two epochs. We search for objects not found at the expected positions in the Sloan Digital Sky Survey (SDSS) by visually examining images of $\sim$ 290 000 USNO-B1.0 objects with no counterpart in the SDSS. We identify some spurious targets in the USNO-B1.0. We find one candidate of interest for follow-up photometry, although it is very uncertain. If the candidate eventually is found, it defines the probability of observing a disappearing-object event the last decade to less than one in one million in the given samples. Nevertheless, since the complete USNO-B1.0 dataset is 100 times larger than any of our samples, we propose an easily accessible citizen science project in search of USNO-B1.0 objects which have disappeared from the SDSS.