Astronomers witnessed the boat, the brightest cosmic event ever recorded, demonstrating the power of time domain and multi-messenger astronomy. This event and others like it provide insight into the dynamic processes of the universe and the role of cooperation in scientific discovery.
Stephen LeSage's phone started vibrating after halftime on Oct. 9, 2022, while he was watching a soccer game in Atlanta with a friend. When Lesage saw the incoming messages, the match no longer seemed important. There had been a rare cosmic event, and he needed to access his computer immediately.
NASA's Fermi Gamma Ray satellite and Neil Gehrels-Swift Observatory have detected an unusually bright signal in space and sent automatic alerts to scientists. Lesage's team's Fermi chat channel lit up with messages as the scientists coordinated their follow-up strategy.
“Everyone in that group was like, ‘This thing is crazy! “Who's in charge of analyzing this? This is what we've been waiting for,” recalls Lesage, a graduate student at the University of Alabama, Huntsville. “Go time!”
This unusual event turned out to be a cosmic explosion that was perhaps the brightest in x-ray and gamma-ray energies since the beginning of civilization. Astronomers called it “the boat”, “the brightest of all.” Lesage led an analysis of Fermi data that showed how bright the boat really was. More than 150 telescopes in space and on Earth followed to obtain more details about the event including NASAIXPE (X-ray Polarimetry Explorer), the Hubble Space Telescope, the James Webb Space Telescope, as well as the European Space Agency's XMM-Newton telescope.
The universe is changing
The boat is an example of what astronomers call time-domain and multi-message astronomy. The “time domain” part refers to events occurring in the universe that telescopes can observe as they occur, such as a supernova or the merger of two neutron stars. “Multi-messenger astronomy” refers to a variety of “messengers” that transmit information from the universe, including all forms of light, high-energy particles, and ripples in space-time called Gravitational waves.
While the universe may appear to change very slowly, over millions or even billions of years, its celestial occupants sometimes produce dramatic changes in a matter of days or even fractions of seconds. Galaxy centers shine when their central black holes eat matter. Siphon black holes plasma From nearby stars. The stars explode. Neutron stars collide with black holes, neutron stars collide with neutron stars, and black holes merge with black holes. Even distant collisions of celestial bodies can send out powerful ripples that can be detected by space-based and ground-based telescopes and instruments. Many of these phenomena are unpredictable in terms of where and when they will occur next.
NASA has two “observer” satellites with wide fields of view that send out alerts when they detect sudden gamma-ray brightening: Fermi and Swift. Fermi's Gamma-ray Burst Observer, the Large Area Telescope, and the Swift Burst Alert Telescope are key instruments that may be the first to detect these events.
“When something impulsive happens, when something explodes and explodes, or something gets crushed and collapses, that happens,” said Valerie Connaughton, who leads the High-Energy Astrophysics portfolio and the Time-Domain and Multimessaging Astronomy Initiative within NASA's Astrophysics Division. Headquarters in Washington.
Once scientists receive an alert on their computers and phones, they may be able to team up with other telescopes to follow the event. By using a variety of different observatories and space instruments to study these highly unpredictable flashes, scientists can piece together what, where, when and why they observed a “blip” in the usual quiet of space.
After comparing observations of the boat from several telescopes, scientists determined that this unusually bright explosion came from a supernova, specifically, from the core collapse of a rapidly rotating massive star. And later, with data from NASA Nustar During the mission, scientists found that the flow of material released from the exploding star had a more complex shape than they originally thought.
““A giant star has just exploded, and we have to study it and find out what happened, reverse engineer the parts and put them back together again,” Lesage said.
“Time-domain astronomy allows us to obtain fundamental answers about the properties of the universe, fundamental physics itself, and the origin of the elements.”
— Eric Burns, astrophysicist, Louisiana State University
New bright signals
Just five months after the boat, scientists received an alert from Fermi about the second brightest gamma-ray burst seen in the past 50 years. This newer signal is GRB 230307A, which occurred in March 2023, joined the boat in the category of “long” gamma-ray bursts, lasting for 200 seconds, compared to 600 for the boat. Thanks to infrared data from NASA James Webb Space TelescopeScientists have determined that GRB 230307A probably had a very different origin: the merger of two neutron stars about a billion light-years away from Earth. Furthermore, Webb discovered the rare element tellurium, which indicates this Neutron star Mergers create heavy items like this.
This result still puzzles astronomers like Eric Burns, co-author of paper GRB 230307A and a member of the Fermi team at Louisiana State University. Neutron star mergers should not produce such long gamma-ray bursts, and current models of atomic physics do not fully explain the mid-infrared wavelengths discovered by Webb. He hopes Webb will help us learn more about these types of events in the next few years.
“Time-domain astronomy allows us to obtain fundamental answers about the properties of the universe, fundamental physics itself, and the origin of elements,” Burns said.
Cosmic “messengers” associated with transient cosmic flashes also help scientists reconstruct their origins. Initial detection of gravitational waves in 2015 by LegoThe Laser Interferometer Gravitational-Wave Observatory showed that the universe could be observed in a completely new way, and opened a new era in which multiple messengers could be used to study sudden fluctuations in the universe.
In 2017, scientists demonstrated this possibility by combining gravitational wave observations with data from several different ground-based and space-based observatories to study a kilonova, or neutron star merger, named GW170817. Among the insights from extensive study of these kilonovas, Burns and his colleagues used them to make the first precise measurement of gravitational velocity, “the last major confirmation of Einstein's prediction,” he said.
Today, the LIGO network, supported by the US National Science Foundation, the European VIRGO, and Japan's KAGRA, searches for gravitational wave events.
Doomed neutron stars spin toward their demise in this illustration. Gravitational waves drain orbital energy, causing stars to move closer together and merge. As they collide, some of the debris is blown away in particle jets moving at nearly the speed of light, producing a brief gamma-ray burst. Image source: NASA Goddard Space Flight Center/Conceptual Image Laboratory
Light is the only type of “messenger” from the universe that has been detected for both the boat and the gamma-ray burst that appears to have produced tellurium. A near Antarctica experiment called IceCube, supported by NSF, looked for high-energy neutrinos coming from the same region of the sky as each event, but found none. However, the lack of observed neutrinos helps scientists constrain the possibilities of how these events occur.
“This multiple messaging approach is important, even when you don't have detection,” said Michela Nigro, an astrophysicist and assistant professor at Louisiana State University. “It really helps rule out some scenarios, as well as telling us something new when we have discoveries.”
For Lesage, who is writing his thesis on the boat, time-domain astronomy and multiple correspondences are an exciting area of study. The same boat is still occupied by him and other astronomers as they look at all the processes revealed by the exceptionally bright light from this intense event. But more transient events are sure to come, and they will keep scientists on their toes as they chase them with a wide array of telescopes and instruments.
“It's just passing events, look now or you'll miss it,” Lesage said. “See as fast as you can.”
Further reading: Telescopes in the case
In the next few years, NASA will launch new “observing” satellites to help search for sudden transient events like this. It includes several CubeSatsa class of miniature spacecraft built in standardized cube modules measuring 4 inches (10 cm) on each side:
- BurstCubeIt will be launched in March 2024 to monitor gamma ray signals
- BlackCat, to be launched in 2025, to detect X-ray light
- StarburstIt will be launched in 2027 to monitor gamma ray signals
International partnerships also include this type of science:
- Terraces (The Transient Ultraviolet Astronomy Satellite), a small satellite of the Israel Space Agency and the Weizmann Institute of Science, with a wide field of view specializing in ultraviolet light, has contributions from NASA. It is expected to be launched in 2026.
In addition, NASA telescopes with other primary objectives can help search for these unusual events:
- spiriton its way to the metal-rich asteroid Psyche, has a gamma-ray spectrometer that astronomers can use to detect gamma-ray bursts as the spacecraft journeys toward its destination over the next several years.
- wise, which mapped the sky at infrared wavelengths, found many new distant objects and cosmic phenomena. the Newways The mission, which reuses the WISE telescope, scans near-Earth space for potentially dangerous asteroids.
- NASA's Nancy Grace Roman Space Telescope, an infrared observatory that will shed light on the mysteries of ancient dark energy and discover thousands of exoplanets, is designed to have a wide-sky view and will undoubtedly pick up fleeting infrared signals. The observatory will conduct several surveys to search for these phenomena, and the mission will support several teams to study related topics ranging from variable stars to the birth of black holes and active galaxies. Roman is scheduled to launch by May 2027, and will also provide alerts about changes in the sky it detects.
- Near Earth Object Surveyor (NEO Surveyor) mission. Infrared detectors will be used to expand the search for asteroids and comets that may pose a threat to Earth. The images to be taken by NEO Surveyor are also expected to capture many distant background objects.
“Infuriatingly humble alcohol fanatic. Unapologetic beer practitioner. Analyst.”