Using technology similar to that found in smartphone cameras, NASA scientists are developing upgraded sensors to reveal more details about black hole outbursts and exploding stars — all while being less power hungry and easier to mass produce than detectors used today.
“When you think about black holes actively shredding stars, or neutron stars exploding and creating really high-energy bursts of light, you are looking at the most extreme events in the universe,” said research astrophysicist Dr. Regina Caputo. “To observe these events, you need to look at the highest-energy form of light: gamma rays.”
Gamma-ray bursts are the most luminous explosions in the cosmos. Astronomers think most occur when the core of a massive star runs out of nuclear fuel, collapses under its own weight, and forms a black hole, as illustrated in this animation. The black hole then drives jets of particles that drill all the way through the collapsing star at nearly the speed of light. These jets pierce through the star, emitting X-rays and gamma rays (magenta) as they stream into space. They then plow into material surrounding the doomed star and produce a multiwavelength afterglow that gradually fades away. The closer to head-on we view one of these jets, the brighter it appears. Credit: NASA's Goddard Space Flight Center
Download high-resolution video and images from NASA’s
Scientific Visualization Studio
Caputo leads an
instrument-development effort called AstroPix at NASA’s Goddard Space Flight
Center in Greenbelt, Maryland. The silicon pixel sensors in AstroPix — still in
development and testing — are reminiscent of the semiconductor sensors that
allow smartphone cameras to be so small.
“Gamma rays are notoriously tricky
to measure because of the way that the incoming particle interacts with your
detector,” said Dr. Amanda Steinhebel, a NASA Postdoctoral Program fellow
working with Caputo.
Gamma rays are wavelengths of light
more energetic than ultraviolet and X rays, and their photons act more like
particles than waves. “Instead of just being absorbed by a sensor like visible
light,” Steinhebel said, “gamma rays bounce all around.”
NASA’s Fermi Gamma-ray Space
Telescope, which has studied the gamma-ray sky since 2008, solved the “bounce”
problem in its main instrument by using towers of strip-shaped sensors. This table-sized
cube, Fermi’s Large Area Telescope, was itself groundbreaking technology when
the mission launched.
Each strip maps a gamma-ray strike
in a single-dimension, while layers of strips oriented perpendicular to each
other record the second dimension. Gamma rays generate a
cascade of energetic strikes through multiple layers, providing a map pointing back to
the source.
About the size of a golf bag, a
space telescope instrument using AstroPix sensors would
require half as many layers as the Fermi strip detector technology, Caputo
said.
In a practical application like this sounding rocket test instrument design, a gamma-ray observatory would use multiple layers of Astropix sensors, which could then track a 3-dimensional particle trajectory through a series of two-dimensional, pixelated detectors.Credits: Regina Caputo
“It’s easier to tell exactly where particles interact,” Steinhebel said, “because you just identify the point in the grid that it interacted with. Then you use multiple layers to literally trace back the paths that particles took through it.”
AstroPix could record lower-energy
gamma rays than current technology, Steinhebel explained, because these photons
tend to get lost filtering through the multiple layers of a strip detector.
Capturing them would provide more information about what happens during
short-lived, energetic events. “These low-energy gamma rays are most common
during peak burst brightness,” she explained.
The pixel detectors also consume
less electricity to operate, Caputo said, a major upside for future missions
planning out their power usage.
Pixelated silicon detectors have
been proven in particle accelerator experiments, she said, and their common use
and mass production for cell phones and digital cameras make them easier and
less expensive to obtain.
Developing different prototypes
over multiple years and seeing AstroPix create accurate plots of gamma-ray
light has been exhilarating and extremely satisfying, Steinhebel said.
While the team continues to work on
developing and improving their technology, Caputo said the next step would be
to launch the technology on a short sounding rocket flight for further testing
above Earth’s atmosphere.
They hope to benefit a future
gamma-ray mission intended to further the study of high-energy universe events.
“We can do such cool science with
this,” Caputo said. “I just want to see that happen.”
Banner image: All three versions of
AstroPix sensor chips are on display from the oldest on the left to version 3
on the right. Version three, which began testing in April 2023 has bigger
pixels and improved functionality. Goddard’s Astropix team includes members
around the world working together to develop and test a next generation
gamma-ray detector. (Image credit: Regina Caputo)
By Elizabeth Markham
NASA’s
Goddard Space Flight Center, Greenbelt, Md.
Source: New Detectors Could Improve Views of Gamma-Ray Events | NASA
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