A Year After India's Space Odyssey
When India launched AstroSat, the country’s first dedicated space observatory, a little over a year ago, it was an occasion for celebration. With the launch, India became just the fifth territory to boast of an observatory among the stars after the United States, Russia, the European Union and Japan. In the context of the mission, however, the launch is a little bit like a wedding: it’s expensive (that said, the cost of the AstroSat is much lower than any other space observatory), there are lots of guests and you hope everything goes off without a hitch. The actual work of gathering data, transmitting it back to earth and then analysing it starts later, once the satellite is in orbit. The significance of AstroSat extends beyond being a first for India too. Among its five payloads is the Large Area X-Ray Proportional Counter (LAXPC), which is the only instrument of its kind in existence. Built by the Tata Institute for Fundamental Research in Mumbai, the LAXPC isn’t revolutionary technology, but it is unique and the only instrument currently in space that is capable of studying high energy X-rays emitted by a black hole or a neutron star. That made it all the more important that the device functioned as advertised, as the astronomy community around the world has been watching. “The instrument has achieved all the parameters we had proposed”, Professor J S Yadav, who heads the LAXPC instrument at TIFR, told Mirror earlier this week. “So we can study the innermost parts of the accretion discs close to the compact objects (like black holes). We can measure the temperature. We can also study the timing, which will record the high energy and low-energy X-Rays and also the delay between the two.” Accretion discs are formed by mass from companion regular stars in orbital motion around a massive central body, such as a black hole. Their temperatures run to millions of degrees, which causes them to emit X-Rays. Obviously, these are conditions that cannot be recreated in a lab and therefore the only way to study these phenomena is to do it in space. While low-energy X-Rays from accretion discs have been observed in the past, the LAXPC has a much wider range (from 3 to 80 kilo-electron volts) and has the ability to study high energy X-Rays (above 30 KeV). “It has a sensitivity which is not possible with any other instrument,” Yadav said. According to a statement issued by TIFR, by studying these X-Rays, scientists can decipher the “geometry and dynamic behaviour of the gas swirling around a spinning black hole”. Since the LAXPC is the only device providing this information, Yadav said there was keen interest from the international scientific community in the LAXPC and it has boosted the standing of Indian science. “This is Indian data. So far, we had data from other missions belonging to other countries. This is the other way around. It has created confidence in the international community that we can do it. We always believed we could do it but the international community may not have. But now, they see the data. It has definitely improved our image,” adds Yadav, who hopes that the data AstroSat gathers will help scientists understand energy efficiency better. Even a nuclear reactor has an energy efficiency of just 0.7 per cent, while accretion discs can have energy efficiency of anywhere from 10 to 50 per cent, he explains. The LAXPC team’s first set of findings will be published in the Astrophysical journal and Yadav expects many more research papers to come out of the project as AstroSat should remain in orbit for at least five years. On the first of October, the data was also thrown open to proposals from Indian astronomers outside the project to do their own research, with the team receiving five to six times more proposals than they can accommodate. “It will encourage, in a big way, the astronomic community. We expect many young people to come (into the field),” he said. Unsurprisingly, he is also a believer that India needs to do more missions of the kind. “This is a new thing, so you have to be 100 per cent sure that the new results are not an artifact of the instrument or the analysis software, and it is real. You are on the frontier and that is significant.”
