Giant Metrewave Radio Telescope detects two unidentified pulsars 

While combing through space news, have you ever come upon the term ‘pulsar?’ Well, if you have, you would know that it refers to a compact, heavily magnetised rotating neutron star that emits radio pulses (signals) periodically. In fact, the word ‘pulsar’ has been derived from the term ‘pulsating radio source’ meaning a source that generates radio signals. Are you now wondering what a neutron star is? It is nothing but a degenerate star that has been so collapsed by gravity that its electrons and protons (negatively and positively charged particles respectively) merge into neutrons due to intense pressure. Here is a brand-new information for you on pulsars.  

Recently, the highly distinguished Giant Metrewave Radio Telescope or GMRT (a radio telescope that operates in low-frequency bandwidth and has been studying the universe since 2000) has detected two previously unidentified pulsars, that are both slow and possess narrow widths. This discovery has been conducted by the Pune-based National Centre for Radio Astrophysics (NCRA) as part of their GMRT High Resolution Southern Sky (GHRSS) Survey.  

Interestingly, this new finding was done using earlier data from the GMRT, the only difference being that it is now upgraded with a superior and latest algorithm that is specifically designed to detect pulsars efficiently from all periods and widths. And guess what? This brand-new technique for effective pulsar-searching has also only been recently developed by a team of scientists from NCRA, University of Manchester, National Naval Laboratory of USA and West Virginia University of USA. In fact, it was mentioned in a scientific paper that was published in the Astrophysical Journal in July 2022. Its speciality is that it can look for periodical signals from pulsars with the help of instrumental variation and terrestrial interferences, something that was missing till date.  

By now, you already know what a pulsar is. But what about how they are born or how they evolve? That’s completely a different story altogether. As some of you might know, certain massive stars have a nature to blow up as part of violent explosions called supernova. Following their imminent collapse, most leave only debris, while only a few fade into invisibility and remain as neutron stars. Guess what happens next. These compact city-sized celestial objects often stay close to the centre of the explosion remnant. Why? Because they have high density which in turn force them to harbour strong magnetic fields. As a result, they also rotate rapidly (but for a short span) that allows them to extract energy and form beams of radiation. These beams when often caught by radio telescopes such as the GMRT give an appearance of a sequence of regular radio pulses or ‘pulsars.’  

Now, with time, the pulsar’s speed slows down as there is gradual loss of rotational energy, evidently making its rotational period longer. In fact, there are times when the rotational speed is so slow and its duration is so long that the pulsar loses almost all its power, can no longer radiate radio pulses and even shifts to something called a ‘pulsar graveyard.’ Before you start wondering which this place is, it refers to the place of retirement for pulsars that no longer possess the magnetic field strengths or sufficient rotational speeds to sustain the entire radiation process. However, long-period pulsar such as the J2144-3933 with rotation period of 8.5 seconds often stands as the exception as despite being in the pulsar graveyard, it continues emitting radio signals. While scientists are still not sure how this happens, they sure know how to keep looking for them using cutting-edge pulsar search methods, such as the upgraded algorithm on GMRT. Sources cite that these high-end methods can go beyond excess noise for longer periods, do not interfere with slow variations in telescope system and are even able to trace radio frequencies from extra-terrestrial radio sources, such as the long-period pulsars.  

So far, the scientists at NCRA had discovered 31 neutron stars as part of their GHRSS survey that has been on since 2014, but hadn’t found traces of long-period pulsars, until recently.