Decoding mysterious celestial signals

For years, scientists have noticed seemingly random radio signals emanating from the heavens. Now, thanks in part to enterprising scientists and an antenna made of cake pans, they might have an answer.

Discovered in 2007 by an American astronomer, so-called fast radio bursts are rare and faint. They last only thousandths of a second and are barely strong enough to stand out against the natural static of the universe.

That made an April 2020 burst extraordinary. Two different antennae caught it, allowing American and Canadian scientists to surmise the energy originated from a rare magnetar star somewhere in this galaxy. They published a Nov. 4 study in Nature that helped finally unravel this fleeting mystery.

Space- and ground-based telescopes typically pick up fast radio bursts for only a few milliseconds. West Virginia University astronomer Duncan Lorimer first noticed the strange signals in 2007 as he and a student combed through telescope survey data.

Based on the angle at which the waves hit the Earth, most researchers believed they came from outside the Milky Way galaxy. Earlier in 2020, physicist Avi Loeb of Harvard University wrote that the level of decay found in the observed signals required a length of travel greater than our galaxy could account for. He reasoned the heat needed to produce a fast radio burst would be hotter than any known object. “One followed by 35 zeros, or a hundred decillion degrees Kelvin,” he wrote in a June issue of Scientific American. “I have argued that if an FRB occurred in the Milky Way, we could detect it with a cellphone.”

But what about a cake pan?

While Canadian researchers observed the April 2020 burst via a $20 million radio telescope in British Columbia, California Institute of Technology astronomy graduate student Christopher Bochenek caught the same event on his three homemade antennae, which cost about $15,000. Two are in the California desert. The third is stationed near Delta, Utah. The doctoral student said the instrument was “the size of a large bucket. It’s a piece of 6-inch metal pipe with two literal cake pans around it.”

Bochanek and the Canadian team confirmed the burst came from within the Milky Way galaxy. Scientists at McGill University monitoring the CHIME array were able to pinpoint the source of the April burst to a magnetar star in the Vulpecula constellation.

That discovery lends credence to one of the prevailing theories about the origins of fast radio bursts. Scientists believe when large stars die, they collapse into hyperdense neutron stars. A star many times the size of the Sun could shrink to the size of Manhattan at the end of its life. The resulting celestial body would be so dense that a teaspoon of neutron star would weigh more than 1 billion tons.

Some physicists have speculated magnetars are rare types of neutron stars that begin spinning at rates measured in the hundreds or even thousands of revolutions per minute, generating extreme magnetism.

Scientists are starting to understand that fast radio bursts probably come in different varieties. Bochanek and the Canadian team observed an isolated burst from within our galaxy. But the Canadian team from McGill has tracked a consistently repeating signal they observe every 16 days. Danielle Michilli of McGill said that burst is “tens of thousands to millions of times more powerful than anything we have detected in our galaxy.”