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Starts With A Bang

Five reasons why the signals from Stephen Hawking’s Breakthrough Initiative aren’t aliens

I’m not saying it wasn’t aliens… but… it wasn’t aliens.

“Just the fact that you so desperately attempt to dismantle our theory proves that we are on the right track. Otherwise you would not feel so threatened by our theories!” –Giogrio Tsoukalos (in a letter to Jason Colavito)

On Saturday, August 26th, astronomers reinvestigated a source that emitted a little-understood event: a fast radio burst (FRB).

A small section of the Karl Jansky Very Large Array, one of the world’s largest and most powerful arrays of radio telescopes. Image credit: John Fowler.

In 2012, a series of nine bursts were observed by both the Very Large Array and Arecibo, four of which were seen simultaneously.

The Arecibo radio telescope as viewed from above. The 1000 foot (305 m) diameter was the largest single-dish telescope from 1963 until 2016. Arecibo helped pinpoint the location of the first known repeating FRB source. Image credit: H. Schweiker/WIYN and NOAO/AURA/NSF.

For the first time, this allowed us to pinpoint the location of a FRB’s source: a dwarf galaxy 3 billion light years away.

The host galaxy of these fast radio bursts is a dwarf galaxy with an active galactic nucleus. The stars within it, on average, have far fewer heavy elements (and hence, rocky, potentially habitable planets) than the ones in our Milky Way. Image credit: Gemini Observatory/AURA/NSF/NRC.

Last month’s reinvestigation discovered a series of 15 repeating FRBs from the same source, each lasting under 300 microseconds.

A sequence of 14 of the 15 detected bursts illustrate their dispersed spectrum and extreme variability. The streaks across the colored energy plot are the bursts appearing at different times and different energies because of dispersion caused by 3 billion years of travel through intergalactic space. Image credit: UC Berkeley.

Is it advanced, powerful aliens? There are five reasons why that’s likely untrue.

The positions of the known fast radio bursts as of 2013, including four that were discovered that help prove the extragalactic origins of these objects. Image credit: MPIfR/C. Ng; Science/D. Thornton et al.

1.) They’re too common. Based on the bursts we’ve seen, there are over 10,000 unique FRBs, every day, over the entire sky.

While FRBs are powerful, the pulses are also irregular in time, variable in energy, and otherwise indicative of a natural, not intelligent, origin. Image credit: Astronomer’s Telegram #10675; Gajjar, Vishal et al. (29 August, 2017).

2.) The FRB signal is variable. The energy density, signal strength, and time intervals are all irregular, evidence of a natural phenomenon.

Waterfall plot of the fast radio burst FRB 110220 discovered by Dan Thornton (University of Manchester). The image shows the power as a function of time (x axis) for more than 800 radio frequency channels (y axis) and shows the characteristic sweep one expects for sources of galactic and extragalactic origin. Image credit: Matthew Bailes / Swinburne University of Technology / The Conversation.

3.) Active galaxies have produced similar radio signals. Flickering, feeding, supermassive black holes can cause them. The galaxy housing these FRBs possesses exactly this.

The Roumoules transmitter is the main broadcasting facility for long-wave and medium-wave broadcasting of Radio Monte Carlo near Roumoules, France. The medium-wave towers, shown here, are the most powerful in the world, and are nineteen orders of magnitude weaker than the signals we’re seeing in FRBs. Image credit: David Gestalder.

4.) FRBs are 1019 times stronger than humanity’s strongest transmissions. They’re all at least that powerful, with no micro-FRBs.

There are many cases in the Universe, such as imploding stars or neutron star collisions, that are strongly suspected of creating high-energy bursts of electromagnetic energy. Magnetars, which should be a particular part of the life-cycle of many neutron stars/pulsars, may be the natural explanation for FRBs. Image credit: NASA / SkyWorks Digital.

5.) Many astrophysical explanations exist for FRBs. AGNs and magnetars are common; no aliens are necessary.

The under-construction CHIME radio telescope may be the ultimate testing ground for a new technique to chart large objects in the universe using fast radio bursts; it should detect hundreds of them every day. Image credit: Keith Vanderlinde.

Mostly Mute Monday tells the astronomical story of a phenomenon, event, or object in pictures, visuals, and no more than 200 words.

Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.


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