Stargazers meet, make plans for multimessenger astronomy

Dr Ajith revealed that the researchers had drawn up a list of big questions, evolved over work done in the last five years.

The first international conference on the subject of gravitational wave (GW) astronomy after the discovery of gravitational waves was announced, in February, was held recently at International Centre for Theoretical Sciences (ICTS), Bengaluru. Preceded by a discussion meeting which was exclusively for experts in the field, the conference entitled "Future of Gravitational Wave Astronomy," aimed at setting down future paths for gravitational wave researchers.

Speaking to this correspondent along the sidelines of the conference, Dr P Ajith of ICTS, the organiser of the conference said, “The big discovery [of gravitational waves], made last year and announced in February, essentially marks the end of an era — the quest for the detection of gravitational waves. It has also opened out a new branch of astronomy. Now, the idea is to make detection of gravitational waves a tool of gravitational wave astronomy. This can test our understanding of fundamental physics, astronomy, cosmology etc. It marks the beginning of a new era.”

One could appreciate the conviction shared by the group, as the speakers included people who had started their careers working on the gravitational waves and carried the baton over the decades until the detection of the gravitational wave GW150914, as it is called.

Marking frontiers

It is apparent from talking to Dr Ajith that the next big revolution in the field of gravitational wave research could be around the corner — simultaneous observations of gravitational waves and electromagnetic waves, the so-called multimessenger astronomy. “For example, by looking at the gravitational waves, we can get make fairly accurate information on the masses of the neutron stars, of their spin etc. On the other hand, the electromagnetic signals will tell you the chemical composition of the ejected material, the red shift, etc. By combining these we can learn a lot more about the stars,” he explained.

Examples of sources that can emit both gravitational waves and electromagnetic waves are the merger of two neutron stars, or that of a black hole and a neutron star. It is fascinating that ASTROSAT, with its capacity to detect x-rays can come in useful to detect and help LIGO in its study of x-ray binaries, a pair made up of a neutron star and a normal star that emits electromagnetic radiation at the x-ray wavelengths, for example, Scorpius X1.

The discussion meeting itself was strictly for the experts only; however, when asked, Dr Ajith revealed that the researchers had drawn up a list of big questions, evolved over work done in the last five years, which upcoming, future versions of the gravitational wave detectors will allow them to grapple with. “We started writing down some fifteen big questions in science and discussed whether any of these could be addressed by a future GW observatory. Of course, we don’t have any concrete answers yet, but the discussion has started and participants of the workshop who are from India and different parts of the world, will take it forward.”

What is the nature of black holes? Would Einstein’s theory break down at some scale? Can we see some signs of extra dimensions? The questions continue — to fascinate and to prod evolution.

The opening talk of the conference, by Stan Whitcomb, Caltech, who is the chief scientist of the LIGO laboratory (the detectors which detected the gravitational wave on September 14, 2015) was on “Advanced LIGO in the dawn of gravitational wave astronomy.” This set the tone of the ensuing talks which probed various possibilities in the area. “The idea of this conference was to bring together people from all over India, mainly gravitational wave physicists and also people from neighbouring areas, namely, astrophysics, cosmology and theoretical and experimental physics, also,” said Dr Ajith.