The search for mysterious "fast radio bursts" - very short but intense pulses of radio waves from space - continues. Scientists do not know what caused these powerful outbursts, but some of them suggest that signals may be transmitted to us by distant extraterrestrial civilizations. Astronomers are baffled by the phenomenon that has become another secret of radio astronomy.
Unusual radio burst
Not long ago, an international team of astronomers recorded the brightest fast radio burst ever detected. The outbreak of FRB 150807 lasted less than half a millisecond, that is, 0.1% of the time it takes a person to blink.
The study, published in Science, comes closest to answering the question of what is the source of these surges. It appeared a few days after other scientists reported that they saw a burst of radio waves along with gamma rays (extremely intense electromagnetic radiation).
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Where to find the source?
Despite the intensity of fast radio bursts, their nature and origin are still controversial. Some astronomers speculate that such short, intense flares are signals generated in the atmospheres of certain stars in our own galaxy, the Milky Way. This is a process similar to solar flares.
Other scientists argue that these flares may be caused by cosmic collisions, for example, of a neutron star (the collapsed core of a large star) with a black hole in some distant galaxy. But along with this, there are suggestions that fast radio flares may turn out to be alien signals.
Lorimer's impulse
The first fast radio burst, the Lorimer pulse, was discovered by a fluke by radio astronomers with the Australian Parkes telescope, which is used to search for pulsed radio emissions from rotating neutron stars called pulsars. The Lorimer pulse remained a mystery until other fast radio bursts were detected using devices such as the giant Arecibo radio telescope in Puerto Rico and the 100-meter Greenbank in the United States.
Learning problems
Even scientists have difficulty in understanding this mysterious phenomenon. This is partly due to the short duration of the flares, the limited resolution of telescopes, and the uncertainty of the position of the bursts in space. Trying to detect a surge and at the same time pinpoint where it will occur is difficult.
If the radio signal can be detected by telescopes looking for other forms of electromagnetic radiation (such as X-rays or "optical light"), it will help measure the distance and understand the physics behind the event. Perhaps the processes responsible for these bursts are similar to those that cause other cosmic rays, such as gamma-ray bursts. Astronomers suspect these same events are causing other wavelengths to be emitted. But it turned out that this signal is very difficult to catch.
Signal source distance
Indirect distance estimates were made by measuring how the radio signal is scattered. This can help determine the amount of material that light has passed through. Based on this, the distance to the source of the fast radio burst from the Earth can be estimated using various assumptions, such as the amount of matter between us. Such measurements have shown that the sources of fast radio bursts most likely lie outside our galaxy.
FRB 150807 is distinguished by its short duration, radio brightness and a high degree of linear "polarization". It is a property that describes the plane of the vibrations that make up the waves. Given the combination of these properties, new research suggests that the explosion occurred in a galaxy more than a billion light-years from Earth. These measurements were taken with the VISTA telescope. They are the most accurate ever done.
Analysis of magnetic properties
The polarization of light depends on the magnetic fields that surround it. Thus, with this data, the researchers were able to assess the magnetic properties of the plasma through which the radio waves passed. Their analysis shows that there is only a negligible amount of magnetized plasma near the radiation site. If this data is confirmed, scientists will be able to exclude highly magnetized objects, such as young neutron stars, magnetars or other objects from the number of radiation sources.
Prospects for future research
This study shows that the number of detected fast radio bursts is increasing, and their properties are becoming better known. This opens up a tempting prospect for scientists to finally understand what actually produces them. Fast radio bursts can also be used to map out magnetic fields in the universe because we know very little about them. The next breakout can occur after the first detection of a visible analogue of flares or optical persistence, which will help measure the exact distance.
This could happen even earlier than scientists expect, given other recent research and the tantalizing report of the first detection of gamma rays, the burst of which coincided with a fast radio burst. If these two outbreaks are indeed from the same source, which would be very interesting, it could mean that it is much more intense than we expected.
Analysis of FRB 150807 suggests that these events should not be rare. Future objects, such as the Large Synoptic Observation Telescope, which will survey the sky all night every few days, will no doubt revolutionize our minds and understanding of these mysterious bursts and the turbulent, ever-changing universe in which they appear.