Signal Synchronization Strategies and Time Domain SETI with Gaia DR3

Brief

Nilipour et al. (2023) cross-reference Gaia Data Release 3's catalog of 10.5 million variable stars with two event-synchronized SETI frameworks using four supernovae (SN 1987A, 1604, 1572, 1054) as Schelling focal points. The SETI Ellipsoid method yields 465 targets and the Seto scheme yields 403 targets for a combined 868 candidates with crossing times inside Gaia's three-year photometric baseline. For each candidate, the authors propose splitting the stellar light curve at its crossing time and testing for statistically significant changes in variability parameters, amplitude, frequency, or phase, as a proxy for an artificial signal. A major constraint throughout is distance uncertainty: only 43,237 of the 9.3 million stars with Bailer-Jones distances have uncertainties below 1 light-year, limiting precision timing to the nearest stellar neighborhood.

Metadata

Category

Search

Venue

The Astronomical Journal

Type

Peer-reviewed

Year

2023

Authors

Andy Nilipour, James R. A. Davenport, Steve Croft, Andrew P. V. Siemion

DOI

10.3847/1538-3881/acde79

arXiv

2308.00066

Access

Open access

Length

14.5 M

Instruments

Gaia

Data sources

Gaia DR3, Gaia EDR3, Gaia Science Alerts, Bailer-Jones et al. 2021 photogeometric distances

Tags

SETI, technosignature, time-domain astronomy, signal synchronization, variable stars, supernovae

Key points

• Fewer than 0.01% of the 10.5-million-star Gaia DR3 variable catalog have SETI Ellipsoid or Seto crossing times falling within the 2014–2017 epoch photometry window.p.1
• The SETI Ellipsoid applied to four supernovae (SN 1987A, 1604, 1572, 1054) returns 465 targets: 217 keyed to SN 1987A, 121 to SN 1604, 119 to SN 1572, and 8 to SN 1054.p.8
• The Seto scheme, which requires only an angular position and a depth bound rather than a precise stellar distance, returns 403 targets across three supernovae (SN 1987A excluded because its geometry produces zero qualifying stars).p.11
• Only 43,237 of 9.3 million variable stars with photogeometric distances have uncertainty below 1 light-year; all lie within 2,000 light-years of Earth, roughly 0.5% of the catalog.p.3
• The SETI Ellipsoid's semi-major axis expands at half the speed of light, meaning older supernovae produce ellipsoids entirely outside the 100-pc solar neighborhood; Galactic SNe are necessary to probe the broader Gaia catalog.p.5
• The Seto scheme covers exactly half the sky centered on the source event before its search window closes; for SN 1054 that closure occurs around the year 3620 CE.p.10
• The majority of the 868 candidates are classified as solar-like variables (rotational modulation, flares, spots), complicating variability analysis but suggesting possible main-sequence habitability analogues.p.11
• The proposed technosignature test splits each star's light curve at its crossing time and compares variability parameters before and after, targeting long-duration modulations rather than transient pulses given Gaia's sparse per-star cadence.p.2

Verbatim

• “we find that less than 0.01% of stars in the sample have crossing times, the times at which we would expect to receive synchronized signals on Earth, within the date range of available Gaia observations.”

  p.1

• “Stars with a distance uncertainty less than 1 lyr are the most ideal; there are 43,237 such stars total, mostly at low distances.”

  p.3

• “So, the semi-major axis grows at half the speed of light.”

  p.5

• “We find a total of 868 candidates with SETI Ellipsoid or Seto crossing times falling in the time range of Gaia DR3 epoch photometry.”

  p.11

Most interesting

• SN 1987A is excluded from the Seto scheme entirely, its geometry produces zero qualifying stars in the 2014–2017 date range, despite being the most recently observed supernova in the sample.
• The Seto scheme avoids stellar distance errors by using only angular separations and a depth bound, making it robust to the large parallax uncertainties that cripple SETI Ellipsoid timing at distances beyond ~2,000 light-years.
• For source events older than roughly 650 years, the nearest point on the SETI Ellipsoid lies entirely outside the 100-pc solar neighborhood, ruling out nearby-star searches for all Galactic historical supernovae.
• Future Square Kilometre Array parallax measurements of the Crab Pulsar are specifically cited as the path to improving SN 1054 distance precision enough to make Seto timing uncertainties practical.
• Gaia's machine-learning variability classifier outputs a single most-likely type per star; the authors note that a genuine technosignature might be misclassified or fall outside all 24 predefined Gaia variability classes.
• The candidate table's crossing times are given in Barycentric Julian Date to sub-day precision, enabling direct scheduling of follow-up observations against a deterministic geometric prediction.