First ever detection of a heavy element created by the collision of neutron stars

Newly formed strontium, an element used in fireworks, has been discovered in space for the first time ever, following observations made by the ESO telescope

[Translation by Dr. Nachmani Moshe]

For the first time ever, a newly formed heavy element, strontium, has been detected in space, following the merger of two neutron stars. This finding was discovered thanks to the spectrograph on the VLT telescope and has just been published in the journal Nature.

This discovery confirms the hypothesis that heavy elements present in the universe were formed following the merger of neutron stars, a finding that is the missing piece of the aggregate in the field of the formation of chemical elements. In 2017, following the discovery of gravitational waves passing through Earth on the LIGO and VIRGO observatories, ESO (the European Southern Observatory in Chile) turned its telescopes in Chile towards the source of the discovery: a neutron star merger called GW170817. Astronomers believe that if indeed heavy elements were created following collisions of neutron stars, then it would be possible to discover signatures of these elements within a kilonova, that emission of a light beam resulting from the explosion created after such a merger. Indeed, this is exactly what a team of European researchers has now carried out, using data obtained from a telescope located at the ESO Observatory.

Following the merger of GW170817, the fleet of telescopes at this observatory began to monitor the explosion's signals over a wide range of wavelengths. Essentially, the telescopes monitored a series of spectra in the wavelength range between the ultraviolet and the near infrared. Initial analysis of these wavelengths hinted at the presence of heavy elements in the kilonova, but astronomers have not been able to identify specific elements, until now. "Thanks to a reanalysis of the 2017 data from the merger event, we have now identified the signature of one defined heavy element within this fireball, the element strontium, demonstrating that a neutron star collision caused the creation of this element in the universe," says the paper's lead author Darach Watson. from the University of Copenhagen in Denmark. On Earth, strontium occurs naturally in soil and is present in higher concentrations in several minerals. Its salts are used to create bright red fireworks.

Astronomers have been well aware of the physical processes leading to the creation of the chemical elements since the XNUMXs. Over the following decades, researchers uncovered the cosmic locations that are the origins of every one of these heavy element nuclei except one. "This is the last step in a decades-long pursuit aimed at determining the origin of the elements," says the lead researcher. "We now know that the processes that led to the creation of the elements took place mostly in normal stars, following supernova explosions or in the outer layers of ancient stars. However, until today we did not know the exact location of the final, hidden process, known as 'fast neutron capture', the process that caused the formation of the heavier elements in the periodic table." Fast neutron capture is a process in which atomic nuclei capture neutrons at a sufficiently high speed that allows the formation of very heavy elements. Although many elements are formed in the cores of stars, the formation of elements heavier than iron, such as strontium, requires an even hotter environment filled with large amounts of free neutrons. Fast neutron capture only occurs in extreme environments where atoms are bombarded by a significant amount of neutrons.

"This is the first time that we can directly link matter that has just been created through neutron capture to the merger of neutron stars, a finding that confirms the fact that neutron stars are composed of neutrons while linking the controversial process to mergers such as these," says the lead researcher. Researchers are only now beginning to better understand neutron star and kilonova mergers. Due to the limited understanding of this new phenomenon and other complexities contained in the data the telescopes provided following the explosion, astronomers have been unable to identify definite elements until now. "Actually, we thought we were probably observing strontium pretty soon after the event. However, proving that this is indeed the case was quite a challenge. This difficulty arose from our very incomplete knowledge of the spectrum of the heavier elements in the periodic table," explains the lead researcher.

More of the topic in Hayadan:

• Radio observations shed light on a neutron star collision event
• "With the LIGO upgrade we will be able to discover dozens of gravitational wave events per year"
• For the first time, gravitational waves and light waves were discovered from the same event - the merger of two neutron stars