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  Night Sky

Enjoy the starry night skies
Be a considerate neighbor. Reduce nighttime glare.
Shield your outside lights downward.
Let the stars light up the night.

May 2015 night sky

—Charlie Christmann

Mysteries from afar?

The mystery began in 2007, when Duncan Lorimer was looking through old data, searching for the repetitive signatures of pulsars, fast rotating neutron stars that emit strong beams of radio waves as they rotate. Pulsars produce a short burst of static in radio telescopes as the radio beam sweeps past Earth. The rotational rate of many pulsars are so precise, they rival our best atomic clocks at time keeping. There are some ideas on using pulsars as a type of galactic GPS to locate spacecrafts in deep space. Each pulsar is identified by its characteristic pulse rate, ranging from hundredths of seconds to multiple seconds.

In the midst of their search, Dr. Lorimar and his team found a singular, strange event now dubbed the “Lorimar Burst.” What he found was a solitary radio burst lasting about one two hundredths of a second. If this pulse is coming from a pulsar, it should repeat regularly. Yet, after looking for ninety hours, no repeating pulse was found.

As a radio wave passes through space, the tenuous intervening matter tends to slow down lower frequencies, delaying their arrival at the radio telescope relative to the higher frequencies. This is called dispersion. The dispersion values measure the delay giving an indication of how much space is between the source and receiver. Looking at the Lorimar Burst, it was estimated that the pulse originated less than 3.3 billion light-years away, likely well outside our galaxy. However, in radio astronomy, one event is always suspect; it could be the result of some terrestrial or orbiting satellite radio source.

The Parks Radio Observatory (Australia) seems to be the hot spot for finding radio bursts. Not only was this the telescope that recorded the Lorimar Burst, but it also has found several examples of similar bursts called “Perytons.” However, Perytons seem to come from everywhere, while this Lorimar Burst seemed to originate just south of the Small Magellanic Cloud. So where do Perytons originate? After a thorough search, what they found came not from space, but from the cafeteria. Every time the microwave oven door was opened before the timer stopped, microwaves leaking from the open door resulted in a brief burst registered at the telescope. So, was the mysterious Lorimar Burst caused by something similar? The only way to tell is to find more examples.

A search of the Parks Radio data turned up more single event radio bursts, the first seen in 2011. All of the dispersion values seem to be mathematically related, each an integer multiple of 187.5. It seems highly unlikely that space would serve up such a specific relationship. Could this be a result of “LGM” (little green men)? After all, any intelligent life trying to communicate with us is expected to send some simple mathematical formula or relationship to start the conversation. The dispersion’s simple linear equation fits that expectation very well.

Most astronomers say LGM are not the likely source, but there are few other explanations.

Seven more Lorimar Bursts, now renamed to Fast Radio Bursts (FRB), were found by the Parks telescope through 2012, all in previously recorded data. In 2012, the Arecibo telescope in Puerto Rico found an FRB in recorded data, lending credence to the source being far from Earth. Then, in 2014, Parks found a FRB as it was happening, allowing other telescopes looking at wavelengths from radio to x-ray, to take a look at the location in the sky. None of the telescopes saw any afterglow at all, ruling out several possible causes of an FRB. “It could have given off as much energy in a few milliseconds as the Sun does in a day,” said paper co-author Dr. Daniele Malesani from the University of Copenhagen’s Dark Cosmology Centre, referring to the real-time observation. Dispersion measurements placed this event at 5.5 billion light-years away.

To date, only fourteen FRBs are known. Until more are found as they happen, and provide astronomers more clues, no one really wants to speculate on their cause. Perhaps the LGM will stop by soon and tell us what they are trying to say in their FRBs.


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