A new era opens in astrophysics. The precision that Earth’s powerful space observatories allow us to enjoy is changing the way humans observe the universe, allowing us to witness phenomena millions of light years away; or, what is the same, that happened millions of years ago.
A team of scientists from the Carnegie Institution has provided the first image of two neutron stars colliding in the galaxy NGC 4993, about 130 million light years distant from Earth, in the constellation Hydra.
A phenomenon that has important implications. It has caused two historical events: the fifth detection of gravitational waves, for the first time, produced by the merger of two neutron stars and, in addition, the origin of heavy elements as a result of this merger, such as gold, platinum and uranium.
In collaboration with scientists at the University of California, Santa Cruz, the team used the Swope telescope at Las Campanas Observatory to discover the light produced by the merger, pinpointing the origin of a gravitational wave signal.
Not only is it a milestone for physics to observe the collision of two neutron stars , but so are these two historic detections; on the one hand, gravitational waves (that is, ripples in the space-time fabric, which prove its existence, as Einstein predicted); and, on the other, the answer to the question that astrophysicists had been asking for decades: when were heavy elements created?
What are neutron stars?
Neutron stars are incredibly dense debris left behind from supernova explosions. Theoretical astrophysicists have speculated for years about what happens when two of them merge, but until now, this phenomenon has never been observed.
Black hole mergers do not emit light and are therefore invisible to telescopes. However, they had long calculated that neutron star mergers produce light and gravitational waves , so the detection of these events was eagerly awaited. And finally, this detection has occurred.
To give us an idea of its density: “Only one teaspoon of a neutron star weighs as much as all the people on Earth,” according to Carnegie team leader Tony Piro.
“The ability to study the same event with gravitational waves and light is a true revolution in astronomy,” according to Piro. “Now we can study the universe with two completely different probes, which teach us things that we could never know with just one or the other.”
How are heavy elements detected?
Scientists separate the light from a celestial object into its wavelengths, just as a prism spreads sunlight to the colors of the rainbow. Analyzing light in this way helps astronomers measure the speed and chemical composition of cosmic sources.
As scientists followed the afterglow of the explosion, they discovered some key features of the radioactive decay of heavy elements. This suggests that these elements were synthesized after the merger, solving a mystery that had been hidden for 70 years.
In February 2016, the LIGO project announced the first detection of gravitational waves caused by the merger of two black holes, a discovery that received the Nobel Prize in Physics in 2017.
References: ‘Swope Supernova Survey 2017a (SSS17a), the optical counterpart to a gravitational wave source’. Science 16 Oct 2017. DOI: 10.1126 / science.aap9811
Image: NASA Goddard Space Flight Center / CI Lab
