Radio Waves Pin Down Star Heavier Than Sun

The powerful Giant Metrewave Radio Telescope (GMRT) located in India on the hills of Narayangaon on the Pune-Nashik highway has spotted its first pulsar—a rare spinning star that is heavier than the sun. Discovered by a team from Pune’s National Centre of Radio Astrophysics (NCRA), the Arecibo Observatory in Puerto Rico and the McGill University, Canada, it has unique features found among only a few dozen pulsars until now. ‘‘This was not a blind search,’’ NCRA-TIFR centre director Nityanand Rajaram said. ‘‘It required supercomputing power.’’ Over 1,000 pulsars are known to astrophysicists since the first was detected in 1967. But it remains an unusual discovery because a pulsar is a small, dense, rotating star emitting radio waves, elusive and hard to pin down in astro searches. Since 2001, astrophysicists from India and abroad have kept a celestial vigil at the GMRT campus. Spread over 20 km near Khodad village in rural Pune with 30 giant parabolic antennae— each about 45 m in diameter or the size of a small swimming pool, this one is the world’s most powerful radio telescope in metre wavelength. Twenty per cent of GMRT’s observation time goes into the study of pulsars, and one-third of this time is used by foreign observers, who apply for sanction every six months to GMRT’s time allocation committee. ‘‘We’ve found a binary millisecond pulsar,’’ says Nityanand. It means this pulsar—10 kms in size—rotates a dizzying 200 times every second in an unusually elongated orbit instead of a circular orbit. Its width is about half its length. ‘‘We were searching among particular star clusters,’’ says Nityanand. The pulsar was spotted near the centre of a star cluster called NGC1851. The location was pinned down using GMRT’s capability of making a ‘‘picture’’ with radio waves, by combining signals from the 30 antennae. For now, until an international paper is published on the subject, NCRA cautiously terms the find ‘‘interesting and a sign of things to come.’’