What is it?
- A magnetar is a rare compact type of neutron star teeming with high energy and magnetism. They experience violent eruptions or intense bursts in the form of transient X-ray pulses which are several orders higher than that of the Sun.
- Magnetars are relatively rare objects, with only about thirty having been spotted within the Milky Way so far.
Why in News:
- An international group of researchers has succeeded in measuring for the first time the characteristics of a flare on a distant magnetar.
- The team includes astronomers from Norway, Spain and the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital.
- The magnetar they have studied is about 13 million light years away, in the direction of the NGC 253, a prominent galaxy in the Sculptor group of galaxies.
- Scientists involved in the research say that the single event released energy equivalent to what the Sun would radiate in one lakh years.
How magnetars form
- During the course of their evolution, massive stars – with masses around 10-25 times the mass of the Sun – eventually collapse and shrink to form very compact objects called neutron stars. A subset of these neutron stars are the so-called magnetars which possess intense magnetic fields. These are highly dense and have breathtakingly high rotation speeds – they have rotational periods that can be just 0.3 to 12.0 seconds.
- Magnetars have high magnetic fields in the range of 1015 gauss and they emit energy in the range given by luminosities of 1037 – 1040 joules per second. Compare this to the luminosity of the sun which is in the order of 1026 joules per second.
Significance of the discovery
- Eruptions in magnetars are believed to be due to instabilities in their magnetosphere, or “starquakes” produced in their crust – a rigid, elastic layer about one kilometre thick. This causes waves in the magnetosphere, and interaction between these waves causes dissipation of energy.
- This instability triggers Alfven waves that are also common in the Sun. The interactions between multiple Alfven waves ultimately release massive energies, appearing as giant flares lasting for a few milliseconds.
- Magnetars are very difficult to observe when they are silent. It is only during a flare that they can be observed, and these flares are so short-lived that it presents a formidable problem.
- This is the first extragalactic magnetar that has been thoroughly researched.
- Comprehension of these eruptions can give information on the structure of these enigmatic things.
- The finding might open the path for future research into how magnetic stresses are generated around neutron stars.