Breakthrough Listen initiative detects 15 high-energy radio bursts from distant galaxy

Updated 2017-09-01 11:01:24 Xinhua

Breakthrough Listen, an initiative to find signs of intelligent life in the universe, has detected 15 brief but powerful radio pulses emanating from a mysterious and repeating source known as FRB 121102.

While fast radio bursts, or FRBs are brief pulses of radio emission from largely unknown sources, FRB 121102 is the only one known to repeat: more than 150 high-energy bursts have been observed coming from the object so far since it was identified last year as a dwarf galaxy about 3 billion light years from Earth.

"As well as confirming that the source is in a newly active state, the high resolution of the data obtained by the Listen instrument will allow measurement of the properties of these mysterious bursts at a higher precision than ever possible before," said Breakthrough Listen postdoctoral researcher Vishal Gajjar, who discovered the increased activity.

"Bursts from this source have never been seen at this high a frequency," Andrew Siemion, director of the Berkeley SETI Research Center and of the Breakthrough Listen program, was quoted as saying in a news release from the University California, Berkeley.

Siemion and his team alerted the astronomical community to the high-frequency activity via an Astronomer's Telegram on Aug. 28.

SETI stands for search for extraterrestrial intelligence, a collective term for scientific searches for intelligent extraterrestrial life.

First detected with the Parkes Telescope in Australia, fast radio bursts have now been seen by several radio telescopes around the world.

FRB 121102 was discovered on Nov. 2, 2012, and in 2015 it was the first fast radio burst seen to repeat, ruling out theories of bursts' origins that involved the catastrophic destruction of the progenitor, at least in this instance.

Regardless of FRB 121102's ultimate source, when the recently detected pulses left their host galaxy, our solar system was less than 2 billion years old, noted Steve Croft, a Breakthrough Listen astronomer at UC Berkeley.

Life on Earth consisted only of single-celled organisms and it would be another billion years before even the simplest multi-cellular life began to evolve.

As part of Breakthrough Listen's program to observe nearby stars and galaxies for signatures of extraterrestrial technology, the project science team at UC Berkeley added FRB 121102 to its list of targets.

In the early hours of Aug. 26, Gajjar observed that area of the sky using the Breakthrough Listen backend instrument at the Green Bank Telescope in West Virginia.

The instrument accumulated 400 terabytes of data over a five-hour period, observing across the entire 4 to 8 GHz frequency band.

This large dataset was searched for signatures of short pulses from the source over a broad range of frequencies, with a characteristic dispersion, or delay as a function of frequency, caused by the presence of gas in space between Earth and the source.

The distinctive shape that the dispersion imposes on the initial pulse is an indicator of the amount of material between us and the source, and hence an indicator of the distance to the host galaxy.

Analysis by Gajjar and the Breakthrough Listen team revealed 15 new pulses from FRB 121102.

The observations show for the first time that fast radio bursts emit at higher frequencies than previously observed, with the brightest emission occurring at around 7 GHz.

Possible explanations for the repeating bursts range from outbursts from rotating neutron stars with extremely strong magnetic fields -- so-called magnetars -- to a more speculative idea: They are directed energy sources, powerful laser bursts used by extraterrestrial civilizations to power spacecraft.

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