Scientists for the first time detected both gravitational waves and light created by the merging of two neutron stars. This sensational event has opened doorways to understanding various facets of the universe.
About 130 million years ago, two neutron stars collided into each other setting off immense amounts of energy and gravitational waves. The reverberations of this event reached us a few weeks back, taking the entire scientific world by storm.
On the 16th of October, 2017, the European Southern Observatory (ESO) announced an unprecedented discovery stemming from the discovery of both gravitational waves and light from the same event. The earlier discovery of gravitational waves last year had groundbreaking effects – and this observation has taken us a step ahead in understanding these waves.
The first observations of this event happened on 17 August, 2017 at around 8.41 AM, ET. The LIGO and Virgo interferometers detected gravitational waves passing through the earth. Moments later, NASA’s Fermi Gamma-ray Space Telescope and ESA’s International Gamma Ray Astrophysics Laboratory detected a short-lasting gamma ray burst in similar regions of the sky. This lead to the undoubted conclusion that the gravitational waves and the burst arose from a single event. A more explicit solidification of the discovery occurred 11 hours after the initial observation, when scientists detected a bright spot in the galaxy NGC4993.
This particular discovery occurred not in one or two observatories, but in 70 observatories which made observations in multiple wavelengths of light.
“I had never seen anything like it,” said Stephen Smartt, who led the observations with the ESO. “Our data, along with data from other groups, proved to everyone that this was not a supernova or a foreground variable star, but was something quite remarkable.”
Scientists have long known that a merger of inspiraling neutron stars would consequently form a kilonova. A kilonova is an explosive event that is multifold times brighter than a supernova. Although the kilonova was an established idea, this is the first ever time one has been observed.
A hundred years ago, Albert Einstein had accurately predicted the existence of ripples in the fabric of spacetime, known as gravitational waves. These wiggles had been at the cutting-edge of science in 2016, and their discovery was lauded recently with the Nobel Prize in Physics this year. The Laser Interferometer Gravitational-Wave Observatory (LIGO) had detected them for the very first time last year. These waves are set off by the most violent happenings in the universe – exploding stars, colliding black holes and neutron stars. These waves travel at the speed of light away from the source, which is why the gravitational waves and the gamma ray burst of the recent neutron star collision were observed at around the same time. These waves are encoded with the information of the merger of the systems of black holes or neutron stars, taking us a long way in understanding the working of the universe.
WHAT IS A NEUTRON STAR?
As the name suggests, neutron stars are composed of neutrons that are packed in an extremely dense form. When a star exhausts its fuel and explodes, a supernova occurs, which causes the core of the star to collapse inward on itself. If the star is 2 to 3 times more massive than our sun, the mass of the core keeps compressing under the effect of gravity to become a black hole eventually. However, if the star is a little less massive, the compression of the core will make protons and electrons to combine to give neutrons which form an immensely dense mass – a neutron star.
When two neutron stars orbit each other, they expend energy in the form of gravitational waves. So, as they lose energy, they spiral in closer to each other finally colliding to create a kilonova. This phenomenon emits incredible amounts of energy and a large amount of debris. It is in this debris that heavy elements in the periodic table like gold, lead and platinum are found. Building these elements require an excess of neutrons that are well provided in neutron stars. With intense study, scientists say that this particular collision puffed out debris that contained more than ten thousand earths worth of precious metals.
Evidently, this discovery of the neutron star merger will open up new avenues in understanding where these heavy elements come from and the process of their forging from these stars.
SUMMING IT ALL UP
This detection of the collision of two neutron stars has probably commenced a new era in science. With multiple observatories working independently and yet cooperatively, we have been able to put together seemingly unrelated events into a single, groundbreaking discovery.
With scientific facilities improving day by day, we are sure to have more and more questions of the universe answered.