SPACE — Astronomers are one step closer to answering what causes mysterious bursts of radio waves from outer space. Two NASA X-ray telescopes recently observed one of these events known as fast radio bursts (FRB).
The observations were made only a few minutes before and after the event occurred. That set scientists on the path to better understanding these extreme radio events.
Although they only last a fraction of a second, fast radio bursts can release as much energy as the sun produces in a year. The light also forms a laser-like beam, which differentiates it from more chaotic cosmic explosions such as gamma-ray bursts.
Because the bursts are so brief, it is often difficult to determine where they come from. Prior to 2020, a number of explosions were traced to sources outside our galaxy. It was too far away for astronomers to see what created it.
Also Read: What is a Gamma Ray Burst?
In 2020, a fast radio burst occurred in our home galaxy, the Milky Way. It originates from extremely dense objects called magnetars, the collapsed remains of exploding stars.
In October 2022, the same magnetar called SGR 1935+2154 produced another fast radio burst. The explosion was immediately studied in detail by two NASA space telescopes; The Neutron Star Interior Composition Explorer (NICER) on the International Space Station and the Nuclear Spectroscopic Telescope Array (NuSTAR) in low earth orbit.
The telescope observed the magnetar for hours, seeing what happened to the surface of the source object and its surrounding environment before and after the fast radio burst. The results have been described in a new study published in the journal Nature.
The explosion occurs between two ‘disturbances’ when the magnetar suddenly starts to spin faster or slows down. SGR 1935+2154 is estimated to be about 20 kilometers across and rotating about 3.2 times per second. This means the surface is moving at about 7,000 mph.
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Disturbances that slow or speed up its movement will require a large amount of energy. Researchers were surprised to see the slowing magnetar return to its pre-disturbance speed in just nine hours. That’s about 100 times faster than anything ever observed in a magnetar before.
“Usually, when disturbances occur, magnetars take weeks or months to return to their normal speed. “That may be related to how fast the radio burst is produced,” said Chin-Ping Hu, an astrophysicist at the National Changhua University of Education in Taiwan and lead author of the new research.
When trying to deduce how magnetars produce fast radio bursts, scientists have many variables to consider. For example, magnetars, which are a type of neutron star, are so dense that a teaspoon of their material would weigh about a billion tons on Earth.
That high density also means a strong gravitational pull. Meanwhile, the strong gravity means the magnetar’s surface is a volatile place, which regularly releases bursts of X-rays and higher energy light.
2024-02-14 21:37:00
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