Webb has detected the presence of a heavy element resulting from the merger of stars.

Webb’s study of the second-brightest gamma-ray burst ever observed unveils a remarkable discovery involving the element tellurium. A dedicated team of scientists harnessed the power of several space and ground-based telescopes, including NASA’s cutting-edge James Webb Space Telescope, along with the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. Together, they closely examined the exceptionally bright gamma-ray burst known as GRB 230307A and successfully pinpointed the source of the explosion—a merger of neutron stars.

What makes this finding even more fascinating is that the James Webb Space Telescope played a crucial role in identifying the presence of tellurium, a chemical element, in the aftermath of this extraordinary celestial event, shedding light on the composition and dynamics of the universe.

Gamma-ray burst (GRB) 230307A imaged by the NIRCam (Near-Infrared Camera) instrument.

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The image captured by NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) instrument provides a glimpse of Gamma-Ray Burst (GRB) 230307A and its associated kilonova, along with their neighboring galaxies and foreground stars. This particular GRB is believed to have been generated by the merger of two neutron stars. Interestingly, these neutron stars were ejected from their original galaxy and embarked on a journey spanning about 120,000 light-years, roughly equivalent to the diameter of our Milky Way galaxy, before finally merging hundreds of millions of years later.

The image and the data collected indicate that elements close to tellurium on the periodic table, including vital elements like iodine, which plays a crucial role in Earth’s biology, are likely to be present in the ejected material from the kilonova. A kilonova is an explosive event resulting from the merging of a neutron star with either a black hole or another neutron star.

Andrew Levan, the lead author of the study and affiliated with Radboud University in the Netherlands and the University of Warwick in the UK, highlighted the significance of this discovery, noting that it allows scientists to fill in the gaps in our understanding of the origins of elements, nearly 150 years after Dmitri Mendeleev formulated the periodic table.

For a long time, the idea of neutron star mergers as the “pressure cookers” for producing heavy elements beyond iron has been a theory, but obtaining substantial evidence had proven challenging for astronomers. Webb’s observations provide crucial insights into the creation of these elusive, heavier elements and confirm the role of neutron star mergers in this process.

Long gamma-ray bursts last for several minutes.

Kilonovae events are exceptionally rare in the cosmos, which makes their observation a challenging task. These events are often associated with short gamma-ray bursts (GRBs), which were traditionally considered to be bursts lasting less than two seconds. Short GRBs can be the result of infrequent mergers between astronomical objects, like neutron stars. In contrast, long gamma-ray bursts can persist for several minutes and are typically linked to the dramatic demise of massive stars.

A specific instance, GRB 230307A, is particularly noteworthy. It was initially detected by NASA’s Fermi Gamma-ray Space Telescope in March and stands out as the second-brightest GRB observed in over half a century of astronomical observations. It was approximately 1,000 times brighter than the typical gamma-ray bursts Fermi detects.

Additionally, GRB 230307A was unusual because it had a duration of 200 seconds, which would typically place it in the category of long-duration gamma-ray bursts. What makes it even more intriguing is that, despite its longer duration, it is believed to have originated from the merger of two neutron stars, indicating that not all long GRBs necessarily result from the explosive death of massive stars.

Collaboration of several telescopes on the ground and in space to detect gamma-ray bursts.

The collaborative efforts of numerous telescopes on both the ground and in space played a crucial role in unraveling the details of a significant astronomical event. This event serves as an excellent example of how satellites and telescopes can work in unison to witness and understand changes in the universe as they happen in real-time.
Upon the initial detection of the event, a rapid and comprehensive series of observations, conducted from both Earth-based and space telescopes, were set into motion. Instruments such as Swift were instrumental in locating the source in the sky and monitoring how its brightness evolved over time. These observations covered a wide range of the electromagnetic spectrum, including gamma-ray, X-ray, optical, infrared, and radio wavelengths. These multi-wavelength observations revealed several key characteristics of the event that are typical of a kilonova.
Kilonovae are known for their rapid nature. The material involved in the explosion expands swiftly. As this entire cloud of material expands, it cools off rapidly. Consequently, the peak of its emitted light becomes visible in the infrared part of the spectrum and gradually shifts to a redder hue over a period of days to weeks. This color shift, from the optical to the infrared and the redness of the light, are distinctive features that define kilonovae and helped astronomers classify this event as such.

GRB 230307A’s kilonova Emission Spectrum.

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This graphic presents a comparison between the spectral data of the kilonova associated with GRB 230307A, as observed by NASA’s James Webb Space Telescope, and a kilonova model. Both spectra exhibit a distinctive peak in the spectrum, specifically in the region linked to tellurium, marked in red. Notably, the detection of tellurium in this spectrum, an element even rarer than platinum on Earth, marks a significant milestone as it represents Webb’s first direct observation of a heavy element from a kilonova.

The conditions at the time of observation were optimal for the James Webb Space Telescope’s NIRCam (Near-Infrared Camera) and NIRSpec (Near-Infrared Spectrograph) instruments to investigate this dynamic environment. The spectrum shows broad lines, indicating the high-speed ejection of material. However, one feature stands out—the presence of tellurium, which emits light in the spectrum.

Webb’s sensitive infrared capabilities also allowed scientists to pinpoint the originating location of the two neutron stars that led to the formation of this kilonova. These neutron stars were part of a binary system in a spiral galaxy, located roughly 120,000 light-years away from the kilonova’s point of origin. Despite experiencing two separate supernova explosions, which transformed one of the stars into a neutron star, the binary system of neutron stars remained gravitationally bound and was eventually ejected from their home galaxy. These neutron stars traveled a vast distance, roughly equivalent to the diameter of the Milky Way galaxy, before merging several hundred million years later.

The prospects for discovering more kilonovae in the future are bright, thanks to the increasing collaboration between space and ground-based telescopes, enabling astronomers to study dynamic changes in the universe. Instruments like the James Webb Space Telescope can delve deeper into space, while upcoming telescopes, like the Nancy Grace Roman Space Telescope, with its remarkable field of view, will enhance our ability to track the occurrence and characteristics of such astronomical explosions.

In summary, the findings discussed in this study have been published in the journal Nature, and they highlight the transformative capabilities of Webb and its potential to further our understanding of the universe as we explore even heavier elements in space.

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