Source of powerful cosmic ray signals found beyond our Milky Way

Andrew Fazekas
Weather and Science writer
Geekquinox
An artist's concept of the shower of particles produced when Earth's atmosphere is struck by ultra-high-energy cosmic rays.

Astronomers for the first time have managed to hunt down the source of three high-energy ray signals being emitted beyond our Milky Way. The hope is that this discovery might help us better understand the mysterious origins of deadly cosmic rays that flood the universe and bombard our solar system.

Cosmic rays are believed to be produced by some of the most violent events in the cosmos – like supernova explosions – and are a billion times more powerful than anything created in our supercolliders here on Earth. They constantly flood our solar system and appear to come from every direction in the universe.

So not surprisingly, finding their sources has been near impossible because these charged particles get bounced around in all directions in space by the magnetic fields they encounter as they fly across interstellar space. However, a team of astronomers has now found a way to help us in our hunt. It turns out cosmic rays do also produce a convenient tracer particle called gamma-rays, which don’t get deflected along their travels, and so by tracing back their journey, their origins can be be found much more easily.

In this new research, the newfound gamma-ray signals appear to be produced at prodigious rates by three different types of objects located within a single satellite galaxy of the Milky Way some 180,000 light years away from Earth known as the Large Magellanic Cloud.

In the newly-published study this week in the journal Science, researchers used the High Energy Stereoscopic System (HESS) – a collection of four 13-meter telescopes located in the deserts of Namibia, Africa – to observe a region of our companion galaxy that is actively forming stars. 

For 210 hours, researchers took high-resolution snapshots that revealed the telltale blue light indicating a source of gamma-rays from three distinct sources in our companion galaxy. These super-bright sources include the most powerful pulsar wind nebula, the most powerful supernova remnant, and a gaseous shell blown by multiple stars and supernovae dubbed a superbubble.

This weird superbubble, dubbed 30 For C, is the most interesting to the team as it now represents an unexpected new source type for these high-energy rays and is the first observational evidence like it.  Carved out by multiple stellar blasts events within a star cluster and associated intense stellar winds, the cosmic cavity stretches some 280 light years across.

Our study of these mysterious particles goes beyond just pushing the frontiers of astrophysics research – it has a practical side. Cosmic rays are expected to be a clear and present danger for future crews of deep space travel. While our planet’s atmosphere offers protection, any future human missions venturing out into the solar system will have to deal with the cosmic rays issue. 

A recent study coming out of University of New Hampshire looking into health risks for missions to Mars suggests that a crew would be exposed to significantly increased medical dangers from cosmic rays.

Our sun’s own activity does act as a natural buffer against many of those nasty cosmic rays. However, solar activity is predicted to continue to decrease in the coming decades, which means that astronauts on long-term, deep space voyages will be exposed to growing levels of radiation. 

In fact, researchers estimate that if current solar activity trends continue, 30-year-old male astronauts will only be able to safely spend 320 days in space, while females will just get to spend 240 days. While this limitation might not cause a problem with close-by targets like the moon or asteroids, this would be problematic for a mission to Mars – the closest planet to Earth – since it can take between six to nine months just to get there with current technology.

Also, there have been surprising studies that have suggested that over time, Earth has gone through periods of intense bombardment by cosmic radiation that may have triggered climate change, genetic mutations, and even extinction events.

Hopes now are that all this new detective work using gamma-rays as tracers of mammoth cosmic blasts will shed light on the elusive cosmic rays seen across the universe.