Gamma ray burst GRB 140419A, the light from the explosion of a star more than 12 billion years ago, not long after the Big Bang, was recently detected and observed by ROTSE-IIIB, an astronomer’s team telescope from Southern Methodist University (SMU), Dallas, at the McDonald Observatory in the Davis Mountains of West Texas.
Scientists think that gamma-ray bursts, hot stars measuring as much as 50 solar masses that run out of fuel and implode, forming black holes, are the catastrophic collapse of a star at the end of its life.
ROTSE -IIIB was the first to observe the GRB 140419A burst and to capture an image. Robert Kehoe, physics professor and leader of the SMU astronomy team, said that GRB 140419A’s brightness, which is measured by its visibility by someone on Earth, was of the 12th magnitude, hinting it was only 10 times dimmer than what is visible through binoculars, and only 200 times dimmer than what is perceived by the human eye.”The difference in brightness is about the same as between the brightest star you can see in the sky, and the dimmest you can see with the naked eye on a clear, dark night,” Kehoe explained. “Considering this thing was at the edge of the visible universe, that’s an extreme explosion. That was something big. Really big.”
Another member of SMU astronomy team notes that “as NASA points out, gamma-ray bursts are the most powerful explosions in the universe since the Big Bang. These bursts release more energy in 10 seconds than our Earth’s sun during its entire expected lifespan of 10 billion years.”
Stressing the importance of the observation, Robert Kehoe explains that “gamma-ray bursts may be particularly massive cousins to supernovae, or may correspond to cases in which the explosion ejecta are more beamed in our direction. By studying them, we learn about supernovae.”
The spotting of GRB 140419A was particularly important because not until the late 1990s, when telescope technology improved, had scientists been able to detect optical light from gamma-ray bursts, since these flows of energy have the shortest wavelengths in the electromagnetic spectrum and are visible only through specific detectors.
The optical light of the gamma-ray bursts is provoked by the detonation of the outer layers of the star that shoot out material along the rotation axis in a powerful, high-energy gamma radiation. With the decline of the gamma radiation, the explosion produces an afterglow of visible optical light, which, in turn, fades. “The optical light is visible for anywhere from a few seconds to a few hours,” Kehoe says. “Sometimes optical telescopes can capture the spectra. This allows us to calculate the redshift of the light, which tells us how fast the light is moving away from us. This is an indirect indication of the distance from us.”
The images of the GRB 140419A’s burst, all of which can be seen here, will enable astronomers to analyze the observational data in order to draw further conclusions about the structure of the early universe. For Kehoe, “at the time of this gamma-ray burst’s explosion, the universe looked vastly different than it does now. It was an early stage of galaxy formation. There weren’t heavy elements to make Earth-like planets. So this is a glimpse at the early universe, and observing gamma-ray bursts is important for gaining information about the early universe.”
SMU’s Robotic Optical Transient Search Experiment (ROTSE) IIIb is a robotic telescope that forms part of a network of ground telescopes responsive to a NASA satellite, central to the space agency’s Swift Gamma-Ray Burst Mission. When the Swift satellite detects a gamma-ray burst, it instantly relays the location to telescopes around the world, such as SMU’s ROTSE-IIIb, which swing into action to observe the burst’s afterglow and capture images, said Govinda Dhungana, an SMU graduate student who participated in the gamma-ray burst research.