Adrian Melott, a KU professor of physics and astronomy, is researching the effects supernovae have on earth.

Outer space can be a dangerous place.

Under the blue skies of earth, it can be easy to forget that we live in space. When we do think of the dangers from above, we typically focus on comets and asteroids — things that can smack us on the head or destroy entire cities on impact.

But also hurdling through space is energy from exploding stars that can, when close enough, have ruinous effects on earthlings.

A researcher at Kansas University wants to better understand those effects. After studying the large-scale structure of the universe for much of his career, Adrian Melott, a KU physics and astronomy professor, turned his attention to studying the relationship between catastrophic cosmic events and the evolution of terrestrial life.

This year Melott and colleagues from MidAmerica Nazarene University and Washburn University won a $500,000 grant from NASA for a three-year project to study the effects of a nearby supernova on the planet.

Cosmic explosions

The term “nearby” is relative here. An extremely close explosion would be in the neighborhood of 30 light years, or roughly 176 trillion miles, away from the Earth. The chances of one going off that close anytime in the near future are slim, Melott said.

A supernova can outshine an entire galaxy. They are most often caused by energy released by the collapse of a massive star, one many times the mass of the sun.

If close enough, energy from a supernova would pelt the Earth with radiation, scrambling its atmosphere and ripping away much of the ozone, leaving Earth more vulnerable to UV rays. The resulting surge of radiation on the planet could trigger cancers in many animals and kill plants and plankton, setting off a wave of death through the food chain.

It would be “a disaster,” Melott said.

Melott’s past work has linked an even larger cosmic phenomenon, a gamma ray burst, to a mass extinction event 440 million years ago. These events, caused by the collapse of a spinning massive star into a black hole, are the brightest events in the universe and can be seen in far away galaxies.

Gamma ray bursts are even more destructive and unpredictable than supernovas.

“A gamma ray burst could nail us by surprise,” Melott said.

But they are also far more rare than supernovas. Melott said the probability of either happening close enough to trigger disaster on earth in the foreseeable future is low, on the order of one in a million in the course of a decade.

His advice is to not lose sleep over the idea.

Creating and destroying

Although they might not be a threat in the near future, supernovas and gamma ray bursts could have had an important role in humanity’s past, if they did indeed cause extinctions and leave other imprints on evolution.

To study the possibility, Melott and colleagues have blended several fields together in their research, including astrophysics, geology, climate science, planet science, biology and paleontology.

“It’s this crazy mixture,” he said. It’s also exhausting. Melott said he reads between 1,000 and 2,000 journal abstracts from a numerous fields every week.

When they’re done, the team hopes to have a better idea of the probability of life existing in the galaxy, given the frequency of astronomical events such as supernovas.

The NASA-funded study will look at a supernova that occurred 2.5 million years ago. That event was near enough to Earth, possibly 150 light years away, to send a radioactive isotope of iron to Earth that could not have come from any other source.

It was not so close as to spark widespread disaster, but it might have had some impact on life, and Melott and colleagues are studying that impact in detail.

One intriguing possibility — and Melott hastens to that it hasn’t been proven one way or the other — is that the radiation could have affected the course of human evolution either through changing the climate or by directly altering human DNA through radiation.

“Humans underwent a burst of change at that time,” Melott said. If their study shows the radiation was high enough to change the climate or even the human genome, Melott said, “It might mean we owe our existence partially to that event.”

Supernovas destroy and create. Regardless of the outcome of Melott’s study, scientists are fairly certain that life on Earth would not be possible at all without supernovas. That is because most of the heavy elements in the universe were generated by supernovas.

Without them, Melott said, “the universe would basically just be hydrogen and helium.”