For the first time, astronomers may have noticed the afterglow of an epic cosmic event known as the “kilo”.
Kilons are huge explosions caused by neutron stars that collide with each other, sending an intense jet of high-energy particles through space.
They produce luminous radioactive light, which produces large amounts of important elements such as silver, gold, platinum and uranium.
Researchers believe they have discovered a “follow-up” from a 2017 kilonian event in the form of X-rays captured by NASAChandra X-ray Observatory.
In this artist’s performance, the fusion of two neutron stars to form a black hole (hidden in a bright bulge in the center of the image) generates opposite, high-energy jets of material (blue) that heat the material around the stars, causing it to emit X – rays (reddish clouds). X-rays can also be produced during violent collisions when the material falls into a black hole (golden yellow disk around the central bulge)
KILONOVA: A HUGE COSMIC EVENT
Kilons are huge explosions caused by neutron stars that collide with each other, sending an intense jet of high-energy particles through space.
They produce luminous radioactive light, which produces large amounts of important elements such as silver, gold, platinum and uranium.
The merger between the two neutron stars – some of the densest objects in the universe – creates an explosion 1,000 times brighter than a classic new one.
The new study was led by experts at the Northwestern Center for Interdisciplinary and Astrophysical Research (CIERA) in Evanston, Illinois.
“We entered unexplored territory here to study the effects of neutron star fusion,” said Arajata Hajala of Northwestern, who is leading the study.
“For the first time we are looking at something new and exceptional. This gives us the opportunity to study and understand new physical processes that have not been observed so far.
Neutron stars – the collapsed nuclei of giant stars – have very small radii (usually 18.6 miles or 30 km) and very high densities, made up mostly of tightly packed neutrons. They are among the densest objects in the universe.
When two neutron stars orbit close to each other, they gradually stop inward due to gravitational radiation, almost like two coins getting closer and closer as they reach the center of rotation of charity coins.
When the two neutron stars meet, their fusion results in the formation of either a more massive neutron star or a black hole, depending on the mass.
Kilonova is essentially the explosion that comes from the merger event, which is 1000 times brighter than the classic new one.
The artist’s impression of neutron stars merging, producing gravitational waves and leading to a kilo
CHANDRA X-RAY OBSERVATORY
Chandra is one of NASA’s four major observatories – large, powerful space astronomical telescopes that were launched between 1990 and 2003.
The amazing four – Spitzer, Chandra, Hubble and Compton – were created to specifically observe areas of the light spectrum.
Satellite light readings can allow scientists to distinguish the mass and size of stars in other galaxies and their planets.
The Great Observatories program demonstrates the power of using different wavelengths of light to create a more complete picture of the universe, NASA said.
Of the four, only Hubble and Chandra now remain active, as Compton was decommissioned in 2000 and Spitzer in 2020.
As early as 2017, scientists discovered the fusion of two neutron stars in a galaxy called NGC 4993, thanks to a gravitational wave signal called GW170817.
In this case, a narrow, off-axis jet of high-energy particles accompanies the merger event of GW170817.
Now, three and a half years after the merger, the jet has faded, revealing a new source of mysterious X-rays.
As a leading explanation for the new X-ray source, astrophysicists believe that the expanding debris from the merger generates a shock – similar to the sound boom of a supersonic plane.
This shock then heats up the surrounding materials, which generates X-ray emissions, known as kilone follows.
An alternative explanation is that materials falling into a black hole – formed as a result of the fusion of neutron stars – have caused X-rays. Both scenarios would be the first for the field.
To distinguish the two explanations, astronomers will continue to observe GW170817 in X-rays and radio waves.
If it’s a kilogram of radiance, X-rays and radio emissions are expected to become brighter in the next few months or years.
But if this involves matter falling on a newly formed black hole, then the X-ray output must remain stable or decrease rapidly, and no radio emission will be detected over time.
Artistic representation of the Chandra X-ray Observatory Space Telescope, with visible Uranus in the background
“Further study of GW170817 could have far-reaching implications,” said study co-author Kate Alexander, a postdoctoral fellow at CIERA in Northwestern.
“The discovery of the subsequent radiance of the kilo would mean that the merger did not immediately lead to a black hole.
“Alternatively, this object could offer astronomers a chance to study how matter falls on a black hole several years after its birth.”
The study was published in The Astrophysical Journal Letters.
WHAT ARE NEUTRON STARS?
Neutron stars are the collapsed, burned nuclei of dead stars.
When the big stars reach the end of their lives, their core will collapse, blowing away the outer layers of the star.
This leaves an extremely dense object known as a neutron star, which crushes more mass than is contained in the sun to the size of a city.
A neutron star usually has a mass that is perhaps half a million times the mass of Earth, but they are only about 20 kilometers (12 miles) in diameter.
A handful of material from this star would weigh as much as Mount Everest.
They are very hot, maybe a million degrees, highly radioactive and have incredibly intense magnetic fields.
This makes them probably the most hostile environment in the universe today, according to Professor Patrick Sutton, head of the Department of Gravitational Physics at Cardiff University.
Dense objects, especially their nuclei, are key to our understanding of the heavy elements of the universe.