Two years ago, Archisman Ghosh, 32, was a string theory physicist, just like Sheldon Cooper of the popular sitcom The Big Bang Theory. Then, around the same time Cooper left string theory to study dark matter, Ghosh decided to move on to astrophysics at the International Centre for Theoretical Sciences (ICTS), Bengaluru. "String theory was, well, all theory. I wanted to work in a field where I would be able to see some experimental results,'' he says.
On September 14 last year, a 0.2-second chirp was recorded at the Laser Interferometer Gravitational-wave Observatory (LIGO) in the United States. Within three minutes, the 990 scientists working on the project across the globe were alerted of the "event''. Ghosh was among the young ones who did not consider it so significant initially. He thought it was a "blind'', a false message that the centre sends to everyone in the consortium periodically to check their responses. The email came at 3.21pm, and by night, he got another email from LIGO, this time asking him to use the "statistical parameter estimation'' to figure out the mass and spin of the final remnant of the body, which turned out to be a black hole. "At that moment, I knew we were onto something really big. I had just written a paper explaining that the first discovery would most likely be a binary star. We had not dreamt that we would begin by discovering a black hole. I have been on a high since that moment.''
His colleague and teammate Abhirup Ghosh is even more ecstatic. "Most people in the LIGO consortium were working on testing the gravitational ray hypothesis on binary neutron stars. I had been focusing on the possibility of two black holes; it was even the topic of my summer project as an undergraduate. I didn't know then that I would be a part of LIGO someday and that this very hypothesis would be proved.'' Abhirup, 27, was later asked to figure out whether the event and the readings were in agreement with Einstein's general theory of relativity. "Archisman's and my analyses were among the first after the event. We began working the very next day and by September 18, both of us had uploaded pages on LIGO's site for the entire collaboration to see the results,'' says the postdoctoral scholar.
THE INDIAN HAND in this project is a significant one, with 61 scientists from nine institutes working on some aspect of the experiment or other. Add to that the people of Indian origin in foreign universities. "That could easily be another 20 to 30,'' says Tarun Souradeep, professor at the Inter University Centre for Astronomy and Astrophysics, Pune. "Initially, there was just Sanjeev Dhurandhar [now professor emeritus, IUCAA]. But after India's tie-up with LIGO in 2011, opportunities opened up. Many researchers in their 40s, who were working abroad, returned. But, more importantly, it gave opportunities for beginners in India to get associated with a prestigious international project,'' says Souradeep, who is a founding member of IndIGO (Indian Initiative in Gravitational-wave Observations).
Anuradha Samajdar is perhaps the youngest Indian in the LIGO consortium. The 25-year-old is doing an integrated PhD at the Indian Institute of Science and Education Research, Kolkata. "My role in the project is a minuscule one, it is embarrassing to get so much attention all of a sudden,'' she says. Samajdar, along with her professor Rajesh Nayak, was part of a team that analysed the signal (of the gravitational wave) to check whether it matches with Einstein's theory of general relativity. She's overwhelmed. She grew up in Kolkata, where she barely got to gaze at stars, though she is named after a constellation. "You had to go to the terrace for that, my parents wouldn't allow me,'' she says. She drifted into astrophysics because she liked coding and this particular research had lots of that work. "I never thought that so early in my career, I would be part of something so big. I don't think anything in future will be as momentous as this event.''
Others don't agree, however. “The LIGO observatory is only working at a third of its designed sensitivity, and we have already had this discovery. Imagine what all we can find when it works at full sensitivity, by 2019,” says Abhirup. And with the VIRGO observatory, Italy, to join in the search and a proposed one in India to join in the next few years, observations will get triangulated and data collection more sophisticated. "As it is, only a third of the data that LIGO gathered has been analysed,'' says Souradeep.
ANIRBAN AIN, 26, grew up near Visva-Bharati University in West Bengal, in a semi-urban environment where stars shone bright at night. His interest in cosmology began early and when he was in class ten, he took instructions from a science magazine and built his first telescope. "I looked up at the moon and saw the mountains on its surface. It was marvellous.” A PhD student in IUCAA, Ain works on making maps using gravitational waves. "We have just recorded an event, but now gravitational waves can be used to observe stars just as we use light. We can make gravitational wave maps of the cosmos, just as we do with X-rays, or light waves. The future is fantastic,'' he says.
Recently, the Indian Space Research Organisation (ISRO) launched a stellar observatory, Astrosat, into space. ISRO has an agreement with LIGO for research collaboration. "When there are future observations, all devices will crane towards that bit of the universe, and Astrosat, which is a multi-spectrum observatory, will certainly be part of it,'' says Nayak, adding that the announcement that India will build a gravitational-wave observatory is another magnet for young talent. While researchers do tend to go to various universities globally, being part of the founding team of a new venture is certainly an attractive option. Nayak, 45, who grew up in Kasaragod, Kerala, recalls the sky being an important aspect of village life. "But it was watching Halley’s comet in 1986 that spurred me towards this field,'' he says.
After the announcement, life has certainly changed for the young researchers. Samajdar is learning to accept that she is a star, "though a small one'', while Archisman realises that all other personal and professional work that has been piling up since September has to be tackled. Abhirup, who has been sleepless with excitement, hopes to get some much-needed rest. But with doctors' appointments and rehearsal for a play, it may not be happening anytime soon.
