Two years after its launch, Astrosat — India’s first multi-wavelength space-based astronomical observatory — has confirmed the presence of younger stars hidden in globular clusters, which were believed to have housed only old stars. Launched on September 28, 2015, the satellite began performing full-scale scientific operations in April 2016. The first six months were devoted to performance verification and calibration of all payloads — Cadmium Zinc Telluride Imager (CZTI), Ultraviolet Imaging Telescope (UVIT), Scanning Sky Monitor (SSM), Large Area X-Ray Proportional Counters (LAXPC) Soft X-ray Telescope (SXT), along with Charged Particle Monitor (CPM).
A unique finding, which astronomers working with Astrosat data suggest, is the presence of much younger stars in globular clusters.
Dipankar Bhattacharya, senior scientist at Inter-University Centre for Astronomy and Astrophysics (IUCAA), whose work primary involves analysing data from CZTI, said, “Though some globular clusters have previously shown this anomalous behaviour, we could confirm the presence of an additional population of much younger stars in several clusters which were observed from the images which we studied. It could mean that these globular clusters, either have an inherent capability supporting formation of multiple generations of stars or could have been formed due to mergers of multiple star clusters.”
During a special review meeting in Bengaluru between September 26 and 27, all associated scientists from partnering institutions discussed major findings and results obtained using Astrosat. The meeting was presided by K Kasturirangan, former ISRO chairman, and A S Kiran Kumar, current ISRO chairman.
One of the strong points of this satellite has been its power to detect Gamma Ray Bursts (GRB). Experts highlighted confirmed detections of 110 GRBs, a significantly higher number in a period of 24 months. GRBs are important as they signify the birth of black holes.
Somak Raychaudhury, director, IUCAA, said, “CZTI is turning out to be one of the world’s best instruments in detecting GRBs and its wide field of view has provided an added advantage in getting results beyond our expectations.”
In the past decade, the astronomers had the knowledge of polarisation of not more than six GRBs, but after the launch of Astrosat, these figures have shown marked improvements.
Bhattacharya said, “We have managed to calculate polarisation of seven GRBs of the 11 brightest events, all of which were detected in the maiden year. The remaining four incidents were concluded to be in the non-polarised category.”
Performance of UVIT was also considered to be of high standards, with image resolutions being compared to those gathered by NASA’s Hubble Space Telescope and Galex missions.
Raychaudhury said, “The images’ resolution was commendable, and it was possible to see some of the galaxies and other celestial objects like never before.”
With all the on-board instruments functioning fine, the team has, so far, obtained data sets from 400 varied sources upon completing about 700 pointings into the space. Of these, a few sources were repeatedly observed to have better understanding of their changing behaviour.
Astronomical Society of India (ASI), which is responsible for reaching out to and educating students with activities pertaining to Astrosat, is planning to make all the results and developments available in multiple languages.
Niruj Mohan Ramanujam, ASI member, said, “The aim is to reach out to maximum number of school and college students and make it available for them in as many languages as possible for consumption. Most of our results are updated online.”
With Astrosat expected to operate for over five years since its launch, scientists have already held informal talks about the next generation satellite to conduct astronomy researchers.
Raychaudhury added, “ISRO has extended all its support to astronomy community to develop larger instruments or telescopes, as the space agency is now equipped to lift heavier payloads.”