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Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Astronomers see strontium in the remains of Kilonova, evidence that neutron star collisions produce heavy elements in the universe

Astronomers see strontium in the remains of Kilonova, evidence that neutron star collisions produce heavy elements in the universe



Astronomers have noticed strontium as a result of a collision between two neutron stars. This is the first time a heavy element has ever been found in a kilo, the explosive consequence of these types of collisions. The discovery plugs a hole in our understanding of how heavy elements form.

In 2017, the Laser Interferometer Gravity Wave Observatory (LIGO) and the European VIRGO Observatory detected gravitational waves coming from the confluence of two neutron stars. The merger event was named GW170817 and was approximately 130 million light-years away in galaxy NGC 4993. The resulting kilo-ray is called AT2017gfo, and the European Southern Observatory (ESO) has directed several of its telescopes to monitor it. at different wavelengths. In particular, they pointed to the very large telescope (VLT) and its X-Shooter tool to kilonova.

  This chart shows the scattered constellation Hydra (the female sea serpent), the largest and longest constellation in the sky. Most stars visible to the naked eye on a clear dark night are shown. The red circle marks the position of the galaxy NGC 4993, which became known in August 2017 as the site of the first source of gravitational wave, which was also identified by visible light as the kilo GW170817. NGC 4993 can be seen as a very weak patch with a larger amateur telescope. Image Credit: ESO, IAU and Sky & Telescope
This chart shows the scattered constellation Hydra (Female Serpent Serpent), the largest and longest constellation in the sky. Most stars visible to the naked eye on a clear dark night are shown. The red circle marks the position of the galaxy NGC 4993, which became known in August 2017 as the site of the first source of gravitational wave, which was also identified by visible light as the kilo GW170817. NGC 4993 can be seen as a very weak patch with a larger amateur telescope. Image Credit: ESO, IAU, and Sky & Telescope

The X-Shooter is a multi-wave spectrograph that observes ultraviolet B (UVB,) visible light and near-infrared (NIR.) Initially, the X-Shooter data suggests that there were heavier elements. But so far they have not been able to identify individual elements.

"This is the last phase of a decade of pursuit to determine the origin of the elements."

Darah Watson, lead author, University of Copenhagen.

These new results are presented in a new study entitled "Identification of strontium at the confluence of two neutron stars." Lead author is Darach Watson of the University of Copenhagen in Denmark. The document was published in the journal Nature on October 24, 2019.

"By reanalyzing the 2017 merger data, we have now identified the signature of one heavy element in this fireball, strontium, proving that the collision of neutron stars creates this element in the universe, "Watson said in a press release.

The impression of this artist shows two small but very dense neutron stars that merge and explode like a kilo. Such objects are the main source of very heavy chemical elements, such as gold and platinum, in the universe. The discovery of one element, strontium (Sr), has already been confirmed using data from the X-Shooter tool of the very large ESO telescope.

Forging chemical elements is called nucleosynthesis. Scientists have known about this for decades. We know that elements are formed in supernovae, outer layers of aging stars, and ordinary stars. But there is a difference in our understanding when it comes to capturing neutrons and how heavier elements are formed. According to Watson, this finding fills the gap.

"This is the last phase of decades of pursuit to determine the origin of the elements," Watson says. "We already know that the processes that create the elements happen mostly in ordinary stars, in supernatural explosions, or in the outer layers of old stars. But until now, we didn't know the location of the final, undetected process known as fast neutron capture, which created the heavier elements in the periodic table.

There are two types of neutron capture: fast and slow. Each type of neutron capture is responsible for creating about half the elements heavier than iron. Rapid neutron capture allows the atomic nucleus to capture neutrons faster than it can decay, creating heavy elements. The process was developed decades ago, and circumstantial evidence suggests that cinema is a likely place for rapid neutron capture. But so far it has not been observed on an astrophysical object.

This animation is based on a series of kilo spectra in NGC 4993 observed by the X-Shooter instrument of the very large ESO telescope in Chile. They cover a period of 12 days after the initial explosion on August 17, 2017. Kilonova is very blue initially, but then turns red and fades.
Credit: ESO / E. Pian et al ./S. Smartt & ePESSTO / L. Calçada

Stars are hot enough to produce many elements. But only the most extreme hot environments can create heavier elements like Strontium. Only these media, such as this kilo, have enough free neutrons around. In kilo atoms, they are constantly bombarded by huge numbers of neutrons, which allows the fast neutron capture process to create heavier elements.

"This is the first time we can directly relate newly created neutron capture material to a neutron star fusion, confirming that neutron stars are made of neutrons and binding the long-discussed fast neutron capture process to such mergers, "says Camilla Yul Hansen of the Max Planck Institute for Astronomy in Heidelberg, which played a major role in the study.

Although the X-Shooter data has been around for several years, astronomers were not sure they could see strontium in the kilowatt. They thought they saw him, but couldn't be sure right away. Our understanding of mergers of kilo and neutron stars is far from complete. There are complexities in the kilonova spectrum of the X-Shooter that needed to be addressed, especially as regards the identification of spectra of heavier elements.

<img src = "https://www.universetoday.com/wp-content/uploads/2019/10/Hubble_observes_first_kilonova-959×1024.jpg" alt = "On August 17, 2017, the Laser Gravity Wave Interferometer (LIGO) and the Virgo interferometer detect gravitational waves from a collision between two neutron stars, and within 12 hours, the observatories identified the event source in the NGC 4993 lenticular galaxy shown in this image, collected by NASA's NASA / NASA star telescope. kilo, is clearly visible in Hubble's observations, this is the first time it has been observed van the optical analogue of a gravitational-wave event Hubble observed that cinematic fading gradually over a period of six days, as shown in these observations made between August 22 and 28 (insertions) From ESA / Hubble, CC BY 4.0, https: //commons.wikimedia.org/w/index.php?curid=63442000 seconds19659021 seconds on August 17, 2017, Laser Interferometer Gravity Wave Observatory (LIGO) and Virgo interferometer and the two detected gravitational waves of collisions between stars. Within 12 hours, the observatories identified the event source in the NGC 4993 lenticular galaxy shown in this image, collected with the NASA / ESA Hubble Space Telescope. The associated star flash, a kilo, is clearly visible in Hubble's observations. This is the first time an optical analogue of a gravity wave event has been observed. Hubble observed that cinematic fading gradually over a period of six days, as shown in these observations made between 22 and 28 August (insertions). From ESA / Hubble, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=63442000 filmed19659006 troubled actually came the idea that we could see strontium pretty soon after the event, however, showing that this is demonstrative, the case turned out to be very difficult. This difficulty is due to our largely incomplete knowledge of the spectral appearance of the heavier elements in the periodic table, "said Copenhagen University researcher Jonathan Selsing, who was the key author of the article.

Until now, rapid neutron capture has been much debated but never observed. This work fills one of the holes in our understanding of nucleosynthesis. But it goes further than that. It confirms the nature of neutron stars.

After the neutron was discovered by James Chadwick in 1932, scientists have suggested the existence of a neutron star. In an article in 1934, astronomers Fritz Zwicke and Walter Baade argue that "the super-new represents the transition of an ordinary star to a neutron star consisting mainly of neutrons. Such a star can have a very small radius and extremely high density. ”

Three decades later, neutron stars are linked and identified by pulsars. But there is no way to prove that neutron stars are made of neutrons because astronomers cannot obtain spectroscopic confirmation.

But this discovery, by identifying strontium, which could only be synthesized by extreme neutron flux, proves that the neutron stars are indeed made of neutrons. As the authors say in their paper, "Identifying here an element that could be synthesized so quickly by extreme neutron flux provides the first direct spectroscopic evidence that neutron stars contain neutron-rich matter."

This is important work. The discovery closed two holes in our understanding of the origin of the elements. This confirms to observation what scientists knew theoretically. And that's always good.

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