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October 30, 2021 Archives

Saturday, October 30, 2021

THE HAPPENING WORLD: Breakthrough Listen Candidate Signal Evaluated to be Terrestrial Interference

On 2019-04-29, the Parkes radio telescope in Australia was observing the closest star, Proxima Centauri, to study its flare behaviour. The Breakthrough Listen project was conducting a piggy-back analysis of the signals, filtering for narrow-band emissions which might indicate transmissions from a technological civilisation. A signal was received, persisting for two and a half hours, which passed all of the tests for such a signal:

  1. It is a ~Hz-wide narrowband signal, which cannot be created by any known or foreseeable astrophysical system, only by technology.
  2. It exhibits a non-zero drift rate, as expected for a transmitter that was not on the surface of the Earth.
  3. Its drift rate appears approximately linear in each 30 min ‘panel’ (one single-target observation from a cadence of observations that makes up a waterfall plot), but the drift rate changes smoothly over time, as expected for a transmitter in a rotational/orbital environment.
  4. It is absent in the off-source observations (see ‘Initial investigation and parametrization of blc1’), as expected for a signal that is localized on the sky.
  5. It persists over several hours, making it unlike other interferers from artificial satellites or aircraft that we have observed before.

The signal was declared a “candidate” by Breakthrough Listen and given the name “blc1” for Breakthrough Listen Candidate 1”. Two papers published in the 2021-10-25 issue of Nature Astronomy:

have now concluded that the signal was likely terrestrial interference. From the abstract of the second paper:

… [W]e find that blc1 is not an extraterrestrial technosignature, but rather an electronically drifting intermodulation product of local, time-varying interferers aligned with the observing cadence. We find dozens of instances of radio interference with similar morphologies to blc1 at frequencies harmonically related to common clock oscillators.

A popular “front of book” article in the same issue with the somewhat sensational title “Mysterious ‘alien beacon’ was false alarm” summarises the results. The actual source of the signal has not been identified, and the signal has never been observed since.

Here is an interview with Shane Smith, the Hillsdale College undergraduate intern at the Berkeley SETI project, who discovered the signal in the Parkes data.

Posted at 13:43 Permalink

CONTEXT: From 1970—IBM System/370 Product Announcements

The IBM System/370 was announced in June 1970 as the replacement for its extremely successful System/360 range of mainframes. It was 100% upward compatible with System/360, running the same operating systems and application programs and supporting the same peripherals, and thus provided an easy migration path for System/360 customers. It replaced the “solid logic” circuitry used in the 360 with monolithic integrated circuits, and the 370/145 and all subsequent models replaced core memory with semiconductor main memory.

When the System/370 was announced, many observers were surprised it did not include virtual memory, which was all the rage in computer architecture at the time, and which IBM had previously introduced in the System/360 model 67 in 1965. In 1972, the original System/370 models 155 and 165 were replaced by the 158 and 168 which did support virtual memory, as did all subsequent models in the series. The System/370 would continue to be marketed for twenty years until replaced by the System/390, with numerous evolutionary changes in the architecture over time.

The IBM 3211 printer shown in the final film was stunning. Nobody made printers like IBM—this beast would crank out 2000 lines per minute, day and night, box after box of paper, without a hiccup.

Posted at 13:00 Permalink

TRACKING WITH CLOSEUPS: Exploring Ant Nest Architecture with Molten Metal

Prof. Walter Tschinkel's book, Ant Architecture: The Wonder, Beauty, and Science of Underground Nests, published in June 2021, describes the techniques he has developed for casting ant nests and what he has learned about the various ways ants structure their subterranean habitats.

Posted at 12:21 Permalink

CONTINUITY: KIC 8462852 (Boyajian's Star): Possible Periodicity?

The mystery star KIC 8462852, “Tabby's Star”, which the Kepler spacecraft observed to exhibit stunning (up to 22%) and irregular dimming events, continues to defy explanation. In 2017, Gary Sacco and two co-authors reported “A 1574-day periodicity of transits orbiting KIC 8462852”. The period has come around again, and current observations indicate the dips have returned, but not as deep as observed by Kepler. Images of the star have been found on archival plates exposed in 1978 and 1935 showing dimming consistent with the periodicity. In this interview, Gary Sacco provides an update on the current observing season, the archive discoveries, and speculations on the cause of the dimming events.

Posted at 11:41 Permalink