Astronomers can detect powerful bursts of energy from the deep, deep cosmos.
Sometimes, the source of these bursts is mysterious.
Scientists recently observed a giant blast some 130 million light-years from Earth. Previously, they detected a colossal collision here from a well-known merger between two neutron stars — collapsed stars that are perhaps the densest objects in the universe. But that dramatic event, which produced a potent stream of energy, began to fade. Around three and a half years later, something else, something new, created another curious blast or release of energy.
"There's something else happening now," Edo Berger, a professor of astronomy at Harvard University and one of the scientists who detected this new cosmic event, told Mashable.
The burst of energy, picked up by NASA's Chandra X-ray Observatory (which detects emissions from extremely hot places in the universe), was intense. Astronomers liken it to the sonic boom made when a speeding plane breaks the sound barrier.
In new research published in The Astrophysical Journal Letters, astronomers propose two possible scenarios that might explain the event, neither of which has ever been observed before, explained Aprajita Hajela, an astronomer who led the research. Hajela is a PhD student in the Department of Physics and Astronomy at Northwestern University.
A "kilonova glow": A what? In this leading explanation, when two neutron stars (bodies so incredibly dense that a teaspoon of neutron star weighs around a whopping 1 billion tons) collided, they created an extremely bright blast, called a kilonova. Kilonovas may be of great importance to the universe, and our lives: Astronomers suspect important elements and metals are forged in these blasts, like gold and platinum. "It is one of the proposed predominant sites for the heavier elements in the universe," explained Hajela.
But after this immense kilonova explosion, astronomers propose that debris expanded out into space, generating a shock wave, or blast. The blast heated up anything around like gases or stardust. This is the kilonova glow or afterglow we can detect from millions of light-years away.
Black hole: Another possibility is the dramatic neutron star merger created a black hole — an "object with a gravitational pull so strong that nothing, not even light, can escape it," explains NASA — and now matter from the collision is falling into the black hole. When debris falls in, it releases bounties of energy as it spirals around the powerful, dark object. This could be the source of this newly detected energy from distant space.
It's not surprising that two neutron stars collided in space. In fact, it's common for stars to orbit near other stars in the same solar system. Many stars aren't loners, like the sun. "Most stars are actually found in systems with one or more companions," explained Hajela. Eventually, the stars run out of fuel and collapse. Then, as profoundly dense neutron stars, they can lose momentum and collide, resulting in great mergers and bursts of energy.
Now, the looming question is how astronomers will determine if they're detecting a kilonova afterglow, or matter falling into a black hole. They'll continue watching the type of light, or radiation, coming from this deep space location. That will reveal the source. (If it's an afterglow, they'd expect more radio emissions; but black holes give off X-ray emissions.)
Who knows what else these next observations will reveal about the ongoing events in the deep cosmos?
"This is still not the end of the story," Berger said.
