Scitech | Pulsars: the cosmic lighthouses

Discovering our galactic backyard

Correction appended on November 16

Carl Sagan wrote in his best-selling science book Cosmos that “the surface of the Earth is the shore of the cosmic ocean.” Generations of emboldened astrophysicists have expanded our knowledge of the universe up to this decade. Today, we can follow the Curiosity Rover as it cruises over Mars, and the Voyager 1 spacecraft, launched in 1977, after it finally penetrated the interstellar space beyond our solar system in September. The Kaspi lab at McGill focuses their gaze on the pulsars that sprinkle our own Milky Way like lighthouses on the cosmic shore.

Vicky Kaspi, a Canada Research Chair in Observational Astrophysics and the head of the McGill Pulsar Group, has spent over 20 years examining one such phenomenon in our universe. Neutron stars are the remnants of stars four to eight times bigger than our sun. These stars end their lives with a bang – blowing out their outer layers in a spectacular supernova explosion. The gravitational pull from the explosion causes the centre of the star to collapse, creating a neutron star. Pulsars, a subset of neutron stars, span 20 kilometres across, and spin hundreds of times each second, emitting lighthouse-like beams of radio waves from their poles. A teaspoon of these celestial objects weighs several thousand tons, and occasionally, unexpectedly, they explode – “particularly when we go on vacation,” Kaspi jokes.

Kaspi’s lab uses orbiting NASA satellites and large, ground based telescopes in Arecibo, Puerto Rico and West Virginia to capture X-ray and radio waves to study the pulsar emissions. The light from their rotations is detected from Earth at periodic intervals. These ‘pulses’ come so regularly that their accuracy is comparable to the highest atomic clock standards.

Pulsars act like ships sailing through the cosmic ocean producing gravitational ripples in the fabric of space and time.

Pulsars act like ships sailing through the cosmic ocean producing gravitational ripples in the fabric of space and time. Albert Einstein’s theory of special relativity suggests that space and time exist on a continuum, with time as the fourth dimension. In this space-time continuum, faster moving objects will experience time at a slower rate. Large masses will cause this space-time fabric to warp and this warpage – known to us as gravity – shapes the orbits of celestial bodies. In rare instances, two pulsars may exist in a binary orbit around each other, creating perfect conditions for the examination of Einstein’s theory of relativity.

Robert Archibald, a graduate student in the Pulsar Group, studies a highly magnetized kind of pulsar called a magnetar. Magnetars, at only a few thousand years old, are some of the youngest stars in the galaxy, and are among the most magnetic objects in the known universe. If the moon were a magnetar, it would wipe out all the electronics on our planet. Archibald first heard of Kaspi’s work in 2008, when Kaspi appeared on an episode of CBC Radio One’s science program “Quirks and Quarks.” He recently published the first firm piece of evidence of a decrease in the rotation period of a magnetar, an important discovery in the study of these objects. “These are conditions we can’t create in a laboratory on Earth,” he says. “They are the only places where you have matter behaving at these extreme conditions.”

A major concern for radio astronomers is the increasing saturation of Earth’s atmosphere with radio signals. “Radio quiet zones” such as the one surrounding the Green Bank Telescope in West Virginia, are increasingly hard to come by in the age of laptops and iPhones. Still, scientists are harnessing new technologies to improve detection methods beyond anything we have ever imagined; for example, extrasolar planets, or ‘exoplanets,’ are emerging from cosmic obscurity to teach us more about planets that reside outside of our galaxy, and give us renewed hope in the search for extraterrestrial life. For Kaspi, however, our galaxy is fascinating enough – as she says, “I’m busy in my backyard.”

The article previously stated that the pulsars were found within our solar system. In fact, pulsars only exist outside our solar system. The Daily regrets the error.


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