In December last year, the media reported an appealing signal we at the Breakthrough Listen task found in our radio telescope data. Called BLC1, the signal didnt seem the result of any identifiable astrophysical activity or any familiar Earth-based interference.
The problem was, we werent prepared to discuss it. You desire to be very cautious about getting it ideal before you make any announcements when youre browsing for signs of extraterrestrial life. In 2015 we had only just started secondary verification tests, and there were a lot of unanswered concerns.
Today we are all set to report that BLC1 is, regretfully, not a signal from smart life beyond Earth. Rather, it is radio interference that closely imitates the type of signal weve been trying to find. Our results are reported in two papers in Nature Astronomy.
Searching for solar flares and indications of life
The story of BLC1 starts in April 2019, when Andrew Zic, who at the time was a PhD student at the University of Sydney, started observing the nearby star Proxima Centauri with numerous telescopes to look for flare activity. At 4.22 light years away, Proxima Centauri is our nearby outstanding next-door neighbor, but it is too faint to see with the naked eye.
Flares from stars are bursts of energy and hot plasma that may impact (and likely damage) the atmosphere of any worlds in their course. Though the Sun produces flares, they are not strong or regular sufficient to interfere with life in the world. Understanding how and when a star flares teaches us a lot about whether those worlds might be suitable for life.
The Parkes radio telescope in Australia. Credit: CSIRO
Proxima Centauri hosts an Earth-sized exoplanet called Proxima Centauri b, and Andrews observations recommended the planet is buffeted by fierce “space weather condition.” While bad area weather condition doesnt rule out life existing in the Proxima Centauri system, it does suggest the worlds surface is likely to be unwelcoming.
Still, as our closest neighbor, Proxima Centauri b stays a compelling target for the look for extraterrestrial intelligence (or SETI). Proxima Centauri is one of the only stars we might potentially ever check out in our life time.
At the speed of light, a two-way trip would take 8.4 light years. We cant send a spaceship that quickly, however there is hope that a small electronic camera on a light sail might reach there in 50 years and beam back pictures.
Because of this, we signed up with forces with Andrew Zic and his collaborators, and utilized CSIROs Parkes telescope (also called Murriyang in the Wiradjuri language) to run SETI observations in parallel with the flare activity search.
An appealing summer job
The BLC1 signal. Each panel in the plot is an observation towards Proxima Centauri ( on source), or toward a recommendation source ( off source). BLC1 is the yellow drifting line, and is just present when the telescope is pointed at Proxima Centauri. Credit: Smith et al., Nature Astronomy
We thought searching these observations would be an outstanding task for a summer student. In 2020, Shane Smith, an undergraduate student from Hillsdale College in Michigan, United States, joined the Berkeley SETI Research Experience for Undergraduates program and began sifting through the information. Towards the end of his job, BLC1 popped out.
The Breakthrough Listen group rapidly ended up being intrigued by BLC1. The concern of proof to declare a detection of life beyond Earth is exceedingly high, so we dont let ourselves get too delighted up until weve applied every test we can think of. The analysis of BLC1 was led by Sofia Sheikh, at the time a PhD student at Penn State, who ran an extensive set of tests, a lot of which were new.
There was lots of proof pointing toward BLC1 being an authentic sign of extraterrestrial innovation (or “technosignature”). BLC1 has lots of qualities we anticipate from a technosignature:
Today we are all set to report that BLC1 is, sadly, not a signal from intelligent life beyond Earth. The BLC1 signal. BLC1 is the yellow drifting line, and is just present when the telescope is pointed at Proxima Centauri. The Breakthrough Listen group quickly ended up being captivated by BLC1. BLC1 is– maybe– simply an unpleasant distortion from a device with an overdriven radio frequency amplifier.
Sofias analysis led us to conclude BLC1 is most likely radio disturbance from right here on Earth. Sofia had the ability to reveal this by searching throughout the entire frequency series of the Parkes receiver and finding “lookalike” signals, whose attributes are mathematically connected to BLC1.
Unlike BLC1, the lookalikes do appear in off-source observations. As such, BLC1 is guilty by association of being radio interference.
Not the technosignature we were trying to find
We dont understand exactly where BLC1 was originating from, or why it wasnt spotted in off-source observations like the lookalike signals. Our finest guess is that BLC1 and the lookalikes are generated by a process called intermodulation, where 2 frequencies blend together to produce new disturbance.
If youve listened to blues or rock guitar, you are most likely knowledgeable about intermodulation. When a guitar amp is deliberately overdriven (when you turn it as much as 11), intermodulation includes a pleasant-sounding distortion to the tidy guitar signal. So BLC1 is– possibly– just an undesirable distortion from a gadget with an overdriven radio frequency amplifier.
Regardless of what triggered BLC1, it was not the technosignature we were looking for. It did, however, make for an exceptional case study, and showed that our detection pipelines are selecting and working up unusual signals.
Proxima Centauri is just one of lots of hundreds of billions of stars in the Milky Way. To search them all, we require to keep our momentum, to continue to enhance our tools and confirmation tests, and to train the next generation of astronomers, like Shane and Sofia, who can continue the search with the next generation of telescopes.
Written by Danny C Price, Senior research study fellow, Curtin University.
This short article was first published in The Conversation.
References:
” Analysis of the Breakthrough Listen signal of interest blc1 with a technosignature verification framework” by Sofia Z. Sheikh, Shane Smith, Danny C. Price, David DeBoer, Brian C. Lacki, Daniel J. Czech, Steve Croft, Vishal Gajjar, Howard Isaacson, Matt Lebofsky, David H. E. MacMahon, Cherry Ng, Karen I. Perez, Andrew P. V. Siemion, Claire Isabel Webb, Andrew Zic, Jamie Drew and S. Pete Worden, 25 October 2021, Nature Astronomy.DOI: 10.1038/ s41550-021-01508-8.
” A radio technosignature search towards Proxima Centauri resulting in a signal of interest” by Shane Smith, Danny C. Price, Sofia Z. Sheikh, Daniel J. Czech, Steve Croft, David DeBoer, Vishal Gajjar, Howard Isaacson, Brian C. Lacki, Matt Lebofsky, David H. E. MacMahon, Cherry Ng, Karen I. Perez, Andrew P. V. Siemion, Claire Isabel Webb, Jamie Drew, S. Pete Worden and Andrew Zic, 25 October 2021, Nature Astronomy.DOI: 10.1038/ s41550-021-01479-w.
we just saw BLC1 when we were looking towards Proxima Centauri, and didnt see it in when we looked in other places (in “off-source” observations). Interfering signals are commonly seen in all instructions, as they “leakage” into the telescope receiver
the signal just inhabits one narrow band of frequencies, whereas signals from stars or other astrophysical sources take place over a much broader variety
the signal gradually wandered in frequency over a 5-hour duration. A frequency drift is expected for any transmitter not fixed to Earths surface area, as its movement relative to us will trigger a Doppler result
the BLC1 signal persisted for several hours, making it unlike other disturbance from synthetic satellites or airplane that we have actually observed before.
