Observing the most energetic events in the universe is not an easy task. They are so energetic that they are excellent at penetrating matter, so the traditional approach of telescopes – mirrors and detectors – has to be adapted to catch the powerful light of X-rays and gamma rays. Now, astronomers have revealed the most accurate of a neutron star's gamma ray beam – the most accurate gamma ray image ever taken.
This breakthrough image is of the Vela Pulsar, a well-known gamma-ray source. A pulsar is a degenerate stellar object not much bigger than a city, and we are seeing it from 800 light-years away. The resolution is 40 times better than the previous best image, and it is quite incredible.
The observations were taken by a new telescope designed for gamma rays. A stack of photographic film can trace gamma rays with high precision. The films are not stopping the powerful gamma rays but being stacked one over the other, they can record the direction of the gamma rays.
To remove the interference of the atmosphere, the stack was attached to a balloon that lifted it to an altitude of 35 to 45 kilometers (22 to 28 miles). The wind was moving the balloon and the telescope around, so cameras were used to understand the motion of the system. But there was a final issue.
The pancake stack is like a long-exposure but the film itself doesn’t record the time, so the team made sure that the bottom layers of the pancake would move at a precise speed. This allowed precise measurements between the camera-recorded motions and the tracing in the pancake. The result speaks for itself: the highest-resolution gamma-ray image.
"We captured a total of several trillion tracks with an accuracy of 1/10,000 millimeters. By adding time information and combining it with attitude monitoring information, we were able to determine ‘when’ and ‘where’ the events originated with such precision that the resulting resolution was more than 40 times higher than that of conventional gamma-ray telescopes," Shigeki Aoki from Kobe University said in a statement.
The new approach can allow different and complementary approaches to gamma-ray observations, both on the ground and in space. Although it's early days, it has great potential.
"By means of scientific balloon-borne experiments, we can attempt to contribute to many areas of astrophysics, and in particular to open up gamma-ray telescopy to 'multi-messenger astronomy' where simultaneous measurements of the same event captured through different techniques are required," Aoki added.
"Based on the success of the 2018 balloon experiment these data were generated with, we will expand the observation area and time in upcoming balloon flights and are looking forward to scientific breakthroughs in the field of gamma-ray astronomy."
The study is published in The Astrophysical Journal.