A neutron star called Swift J1822.3-1606 has become the subject of intense scientific investigation by scientists around the world. In fact, in recent months it’s been studied with space telescopes NASA’s RXTE (Rossi X-ray Timing Explorer) and Chandra X-ray Observatory, ESA’s XMM-Newton and Japanese Suzaku but also with ground-based telescopes Gran Canarias Telescope and Green Bank Telescope. What’s so special to deserve such attention?

Neutron stars are what remains when a star reaches the end of its life cycle, explodes in a supernova and the mass that remains is enough to make it collapse into an object smaller than a white dwarf. The minimum mass is estimated around 1.4 solar masses and it may reach about 3 solar masses: beyond that point a black hole would originate. In a neutron star, that mass is compacted in a sphere which may have a diameter of about 10-20 km (6-12 miles).

Neutron stars have a magnetic field a hundred billion times stronger than Earth’s. It causes the emission of electromagnetic radiation in regular pulses and for this reason these stars are called pulsars (PULSating stAR).

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However, there are neutron stars that have a magnetic field particularly intense even by the standards of that kind of stars that may be trillions of times stronger than Earth’s. For this reason, those stars have been called magnetars (MAGNETic StAR). They’re rare because it’s believed that their immense magnetic fields decay after a few thousands years and at that point they cease their typical X-ray emissions.

Swift J1822.3-1606 is a peculiar neutron star because it features the typical X-ray emission of a magnetar but its magnetic field appears to be that of a pulsar. A couple of years ago, another neutron star called SGR 0418+5729 was discovered with these hybrid characteristics and obviously it raised the curiosity of scientists.

The intense investigation of Swift J1822.3-1606 aims to try to understand where the energy that powers its X-ray emission comes from. It’s possible that these stars’ internal magnetic field is much more intense than on their surface but it’s not possible to measure it directly. It has a complex structure with twisted lines that form rings and because of its activity it may cause the X-ray emissions.

It’s possible that those hybrid neutron stars are more common than previously thought. Obviously, the investigation of Swift J1822.3-1606 and SGR 0418+5729 will continue, as well as the search for other magnetar of that type in order to understand neutron stars’ magnetic fields evolve.