The new source, dubbed GRB 221009A for its discovery date, turned out to be the brightest gamma-ray burst (GRB) ever recorded.

In a new study that appears today in the Astrophysical Journal Letters, observations of GRB 221009A spanning from radio waves to gamma-rays, including critical millimeter-wave observations with the Center for Astrophysics | Harvard & Smithsonian’s Submillimeter Array (SMA) in Hawaii, shed new light on the decades-long quest to understand the origin of these extreme cosmic explosions.

The gamma-ray emission from GRB 221009A lasted over 300 seconds. Astronomers think that such “long-duration” GRBs are the birth cry of a black hole, formed as the core of a massive and rapidly spinning star collapses under its own weight. The newborn black hole launches powerful jets of plasma at near the speed of light, which pierce through the collapsing star and shine in gamma-rays.

With GRB 221009A being the brightest burst ever recorded, a real mystery lay in what would come after the initial burst of gamma-rays. “As the jets slam into gas surrounding the dying star, they produce a bright `afterglow’ of light across the entire spectrum,” says Tanmoy Laskar, assistant professor of physics and astronomy at the University of Utah, and lead author of the study. “The afterglow fades quite rapidly, which means we have to be quick and nimble in capturing the light before it disappears, taking its secrets with it.”

As part of a campaign to use the world’s best radio and millimeter telescopes to study the afterglow of GRB 221009A, astronomers Edo Berger and Yvette Cendes of the Center for Astrophysics (CfA) rapidly gathered data with the SMA.

“This burst, being so bright, provided a unique opportunity to explore the detailed behavior and evolution of an afterglow with unprecedented detail — we did not want to miss it!” says Edo Berger, professor of astronomy at Harvard University and the CfA. “I have been studying these events for more than twenty years, and this one was as exciting as the first GRB I ever observed.”

“Thanks to its rapid-response capability, we were able to quickly turn the SMA to the location of GRB 221009A,” says SMA project scientist and CfA researcher Garrett Keating. “The team was excited to see just how bright the afterglow of this GRB was, which we were able to continue to monitor for more than 10 days as it faded.”

After analyzing and combining the data from the SMA and other telescopes all over the world, the astronomers were flummoxed: the millimeter and radio wave measurements were much brighter than expected based on the visible and X-ray light.

“This is one of the most detailed datasets we have ever collected, and it is clear that the millimeter and radio data just don’t behave as expected,” says CfA research associate Yvette Cendes. “A few GRBs in the past have shown a brief excess of millimeter and radio emission that is thought to be the signature of a shockwave in the jet itself, but in GRB 221009A the excess emission behaves quite differently than in these past cases.”

She adds, “It is likely that we have discovered a completely new mechanism to produce excess millimeter and radio waves.”

One possibility, says Cendes, is that the powerful jet produced by GRB 221009A is more complex than in most GRBs. “It is possible that the visible and X-ray light are produced by one portion of the jet, while the early millimeter and radio waves are produced by a different component.”

“Luckily, this afterglow is so bright that we will continue to study its radio emission for months and maybe years to come,” adds Berger. “With this much longer time span we hope to decipher the mysterious origin of the early excess emission.”

Independent of the exact details of this particular GRB, the ability to respond rapidly to GRBs and similar events with millimeter-wave telescopes is an essential new capability for astronomers.

“A key lesson from this GRB is that without fast-acting radio and millimeter telescopes, such as the SMA, we would miss out on potential discoveries about the most extreme explosions in the universe,” says Berger. “We never know in advance when such events will occur, so we have to be as responsive as possible if we’re going to take advantage of these gifts from the cosmos.”

“In the past, industries have promptly shifted away from the usage of toxic chemicals only to produce an equally toxic chemical, so this is something we are actively trying to avoid repeating,” said Kyle Sease, a graduate student at Central Washington University in Ellensburg, Washington. “Our study suggests that ATBC, but not other non-phthalate alternatives, could interfere with cells that maintain brain health. We think this finding warrants further testing of ATBC at different doses, in different settings and in whole organism models.”

Sease will present the new research at Discover BMB, the annual meeting of the American Society for Biochemistry and Molecular Biology, March 25-28 in Seattle.

Phthalates are used in hundreds of products, often to enhance durability or allow materials to bend and stretch. Studies have shown that phthalate exposure can affect the reproductive system and early development in a range of animals, although the health impacts in humans are not clear. ATBC has emerged as a leading phthalate alternative as companies seek to shift away from phthalates and is currently used in a variety of materials and products, including food and food packaging.

For the study, researchers grew cultures of neuroblastoma cells, which, in terms of growth and division, behave similarly to the glial cells that support and protect neurons in the brain. They then used molecular methods to study how ATBC and other chemicals affect genes and processes involved in cellular division. They found that neuroblastoma cells exposed to ATBC increased their expression of two genes associated with cellular stress (known as Nrf2 and p53) and also increased their production of an enzyme associated with cellular senescence (B-galactosidase), which can cause cells to stop growing and dividing.

The findings suggest that ATBC could interfere with the ability for glial cells to regenerate, which can reduce their ability to protect neural cells and lead to neurodegeneration and accelerated aging. It is also possible that ATBC exposure during early development — when neurons are actively growing and dividing — could affect neurons directly and interfere with brain development, the researchers said. Since neurons do not typically regrow once damaged, any effects on the brain likely would be permanent.

Two other phthalate alternatives, bis (2-ethylhexyl)-1, 4-benzenedicarboxylate (GPO) and dioctyl adipate (DOA), did not show the same effects as ATBC. “We found that two other plasticizers did not appear to affect cell division in these cells, so further understanding the different effects of different plasticizers will allow us to understand better how to make safe ones,” Sease said.

Kyle Sease will present this research from 4:30-6:30 p.m. PDT on Monday, March 27, in Exhibit Hall 4AB of the Seattle Convention Center (Poster Board No. 141) (abstract).

Research in recent years has shown that postponing the start time of high schools improves the amount of sleep that students get and reduces their sleepiness during school hours. But findings are mixed about whether this has a positive impact on grades.

To determine the impact specifically on university students, Associate Professor Joshua Gooley, from Duke-NUS’ Neuroscience & Behavioural Disorders Programme and colleagues used student Wi-Fi connection data, log-ins to university digital learning platforms, and activity data from special sensing watches to conduct large-scale monitoring of class attendance and sleep behaviour of tens of thousands of university students.

“We implemented new methods that allow large-scale monitoring of class attendance and sleep behaviour by analysing students’ classroom Wi-Fi connection data and their interactions with digital learning platforms,” said Dr Yeo Sing Chen, first author of the study and a Duke-NUS PhD graduate.

From the data, the researchers found that early class start times were associated with lower attendance, with many students regularly sleeping past the start of such classes. When students did attend an early class, they lost about an hour of sleep. Morning classes on more days of the week were also associated with a lower grade point average.

“If the goal of formal education is to position our students to succeed in the classroom and workforce, why are we forcing many university students into the bad decision of either skipping morning class to sleep more or attending class while sleep-deprived?” asked Assoc Prof Gooley. “The take-home message from our study is that universities should reconsider mandatory early morning classes.”

The researchers drew insights using the Wi-Fi connection logs of 23,391 students to find out if early morning classes were associated with lower attendance. They then compared the data with six weeks of watch-derived activity data from a subset of 181 students to determine if the students were sleeping instead of attending early morning classes.

They also analysed activity data with the day and night patterns of digital learning platform logins of 39,458 students to determine if early morning classes were associated with waking up earlier and getting less sleep. Finally, they studied the grades of 33,818 students and the number of morning classes these students were taking to determine if it impacted their grade point average.

The team is now investigating differences between class attendance, sleep, wellbeing and academic performance between early birds and night owls. “We expect to find that evening-type students will be at a learning disadvantage in early morning classes and have lower class attendance, shorter sleep, poorer mental health and lower grades compared with their peers,” said Assoc Prof Gooley.