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SETI Institute Employs SETI Ellipsoid Technique:
In a paper published in the Astronomical Journal, a team of researchers from the SETI Institute, Berkeley SETI Research Center and the University of Washington reported an exciting development for the field of astrophysics and the search for extraterrestrial intelligence (SETI), using observations from the Transiting Exoplanet Survey Satellite (TESS) mission to monitor the SETI Ellipsoid, a method for identifying potential signals from advanced civilizations in the cosmos. The SETI Ellipsoid is a strategic approach for selecting potential technosignature candidates based on the hypothesis that extraterrestrial civilizations, upon observing significant galactic events such as supernova 1987A, might use these occurrences as a focal point to emit synchronized signals to announce their presence.
In this work, researchers show that the SETI Ellipsoid method can leverage continuous, wide-field sky surveys, significantly enhancing our ability to detect these potential signals. By compensating for the uncertainties in the estimated time-of-arrival of such signals using observations that span up to a year, the team implements the SETI Ellipsoid strategy in an innovative way using state-of-the-arc technology.
[...] In examining data from the TESS continuous viewing zone, covering 5% of all TESS data from the first three years of its mission, researchers utilized the advanced 3D location data from Gaia Early Data Release 3. This analysis identified 32 prime targets within the SETI Ellipsoid in the southern TESS continuous viewing zone, all with uncertainties refined to better than 0.5 light-years. While the initial examination of TESS light curves during the Ellipsoid crossing event revealed no anomalies, the groundwork laid by this initiative paves the way for expanding the search to other surveys, a broader array of targets, and exploring diverse potential signal types.
[...] The SETI Ellipsoid method, combined with Gaia's distance measurements, offers a robust and adaptable framework for future SETI searches. Researchers can retrospectively apply it to sift through archival data for potential signals, proactively select targets, and schedule future monitoring campaigns.
"As Dr. Jill Tarter often points out, SETI searches are like looking for a needle in a 9-D haystack," said co-author Dr. Sofia Sheikh. "Any technique that can help us prioritize where to look, such as the SETI Ellipsoid, could potentially give us a shortcut to the most promising parts of the haystack. This work is the first step in searching those newly-highlighted parts of parameter space, and is an exciting precedent for upcoming large survey projects like LSST."
Journal Reference:
Bárbara Cabrales et al 2024 AJ 167 101 DOI 10.3847/1538-3881/ad2064
(Score: 3, Interesting) by Immerman on Thursday February 22 2024, @02:45AM
I don't think it can be used to amplify a signal - I'm pretty sure it's more a matter of it being an incredibly powerful natural beacon that will draw scrutiny so they could to try to catch our attention with a much, much weaker artificial signal.
On further examination, it seems like ellipsoid bit is based on the idea that they send out a signal when they see a supernova, and when we see the supernova we can then use a 3-D starmap to determine when other stars saw it, and thus when the soonest "follow up signal" that could be sent from any other star would reach us. With those stars forming an ellipsoid shell that starts as nearly a line, and then grows as more time elapses: Basically, one year after we see the nova the shell will include all stars where the distance from nova->sender->us is one light-year longer than the straight nova->us path, after ten years it includes all stars where the crooked path is 10ly longer, etc.
The ellipsoid comes as a result of the fact that all points where the crooked path is N units longer than the straight path will lie on the surface of the same ellipsoid. Basically the same reason you can draw a 2-D ellipse using two pins and a loop of string.
It doesn't seem terribly useful though, since we don't listen to signals based on their 3D origin, but rather their 2D position in our skydome. And there will always be a bunch of stars near the surface of the ellipsoid in every direction.
It also seems like a rather flawed idea, since since there's only a few supernovas per century in our galaxy, rendering them practically useless as a beacon. Who is going to have the equipment just sitting around to broadcast an incredibly powerful omnidirectional signal a few times a century, in response to an event that's incredibly difficult to predict?
And if you include supernovas from other galaxies, then the ellipsoid becomes degenerate for senders in this galaxy, since the spherical supernova wavefront is effectively just a flat plane passing though our galaxy. While senders in other galaxies would be all but impossible to detect unless they were broadcasting with enough power to rival thousands of suns. Plus it would likely be fairly pointless to send such a signal, since any response would come at least many millions of years later, long after the original signal was probably forgotten.