Telescopes and Observatories of India: Sites and Facts

The correct answer is B, Pune in Maharashtra. The array stands at Khodad, near Narayangaon, about eighty kilometres north of Pune, on flat land chosen for its low level of man-made radio interference, and it is operated by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. A, Nainital, is the district that holds Devasthal, where the optical telescopes of ARIES are placed, so the two sites are often interchanged in options. C has no major radio array of this kind, although it hosts other scientific institutions. D is the home of the Vikram Sarabhai Space Centre, which builds launch vehicles and is not an observatory. Remember GMRT with metre wavelengths and with Maharashtra. The array works in the band of about 100 to 1,500 megahertz, where pulsars and hydrogen clouds are studied.

The correct answer is A, thirty dishes of forty-five metres each. Fourteen of them stand close together in a central square of about one kilometre, and the remaining sixteen are spread along three arms in a Y shape stretching some twenty-five kilometres, which gives the array both the sensitivity of a filled aperture and the resolution of a wide one. The dishes are built of a light wire mesh stretched over a frame of rope trusses, a design that made them cheap enough to build in India. B understates both numbers. C simply swaps the two figures, which is exactly the trap an examiner wants a hurried candidate to fall into. D matches no Indian facility at all. Fourteen dishes in the central square and sixteen on the three arms is the split worth carrying into the exam hall.

The correct answer is B, the Aryabhatta Research Institute of Observational Sciences, an autonomous institute of the Department of Science and Technology at Nainital that grew out of the old Uttar Pradesh State Observatory. The telescope was built in collaboration with Belgium and activated in 2016 on the Devasthal ridge at about 2,450 metres, and the same site carries a 1.3 metre fast optical telescope and the four metre liquid mirror telescope. A runs Kavalur, Hanle and Kodaikanal, not Devasthal. C of Ahmedabad runs the Udaipur Solar Observatory and the infrared telescopes on Mount Abu. D at Bengaluru runs the radioheliograph at Gauribidanur, so each option names a real institute with a different set of telescopes. The same institute ran the older telescopes at Manora Peak in Nainital before the Devasthal ridge was developed.

The correct answer is A, Hanle in Ladakh. The Indian Astronomical Observatory sits there at about 4,500 metres in a cold desert, one of the highest and driest observing sites in the world, where very little water vapour and almost no artificial light make the sky exceptionally clear and dark. The telescope is operated by remote command over a satellite link from the centre at Hosakote near Bengaluru, which saves observers the journey. B holds the infrared telescopes of the Physical Research Laboratory. C holds the 2.34 metre Vainu Bappu Telescope of the same institute that runs Hanle, which is why the two are confused. D is the site of the GMRT radio array and has no optical telescope. The same site also carries the high altitude gamma ray telescopes of the atomic energy establishment, which need equally clear air.

The correct answer is B, the Kodaikanal Solar Observatory in the Palani hills of Tamil Nadu, set up in 1899 when solar work was moved from the old Madras Observatory to a hill station with clearer air. It is now part of the Indian Institute of Astrophysics, and its digitised archive of daily photographs of the solar disc, sunspots and the chromosphere is among the longest continuous records of the Sun anywhere, which makes it valuable for the study of long solar cycles. A is a night-time optical observatory for stars and galaxies. C watches the Sun but at radio frequencies and was set up much later. D is an optical site of the twenty-first century with no solar programme of this kind. Its sunspot drawings and spectroheliograms are now used to reconstruct the solar activity of the past hundred years.

The correct answer is A, Kavalur in Tamil Nadu. In 1977 astronomers watched Uranus pass in front of a distant star from the observatory in the Javadi hills, and the dips in the star's light before and after the planet itself crossed showed that rings surround Uranus. The site later received the 2.34 metre telescope named after Vainu Bappu, who founded the observatory, and it belongs to the Indian Institute of Astrophysics. B is a solar observatory and could not have made such an observation. C was developed as an observing site only in the closing years of the twentieth century, two decades after the event. D hosts optical telescopes but had no part in this particular discovery. The method used, watching a star dim as a body passes in front of it, is called occultation.

The correct answer is C, 2015. AstroSat was launched on 28 September 2015 by PSLV-C30 from Sriharikota into a near equatorial low Earth orbit. It carries five payloads, including the Ultraviolet Imaging Telescope, the Soft X-ray Telescope, the Large Area X-ray Proportional Counter, the Cadmium Zinc Telluride Imager and a scanning sky monitor, so that the same source can be studied in the ultraviolet and in both soft and hard X-rays at once, which few observatories can do. A is the year of Chandrayaan-1, the first lunar mission, and B of the Mars Orbiter Mission, both of which candidates confuse with AstroSat because all three are firsts. D belongs to Chandrayaan-2. Its scanning sky monitor also looks for sources that brighten suddenly, such as X-ray binaries in outburst.

The correct answer is B, a halo orbit around the Lagrange point L1 of the Sun-Earth system, about 1.5 million kilometres from the Earth in the direction of the Sun. At that point the gravitational pulls of the Sun and the Earth combine with the orbital motion so that a spacecraft keeps station with the Earth, and from there the Sun can be watched continuously without any eclipse or occultation. The observatory was launched on 2 September 2023 and carries seven payloads, chief among them the Visible Emission Line Coronagraph for the solar corona. A is where remote sensing satellites go. C is the orbit of the Chandrayaan missions. D describes no Indian mission. Six other payloads measure the solar wind, energetic particles and the magnetic field around the spacecraft.

The correct answer is A, Sawai Jai Singh II of Amber and Jaipur, who built the five masonry observatories in the early eighteenth century to correct the astronomical tables then in use. Their instruments, such as the giant sundial called the Samrat Yantra and the hemispherical Jai Prakash Yantra, measured time, declination and the positions of the planets with shadow and sightline alone, and the Jaipur site was inscribed on the UNESCO World Heritage List in 2010. B was the revenue minister of Akbar and is remembered for the land settlement, not for astronomy. C was an earlier ruler of Amber in the Mughal service. D ruled the Sikh empire in the nineteenth century, long after these observatories were built. The observatory at Delhi, which stands near Connaught Place, is the one most often shown in textbook photographs.

The correct answer is A, Maharashtra, at a site in the Hingoli district. A gravitational wave detector is an L-shaped interferometer whose two arms, each four kilometres long, are watched for the minute change in length produced when a wave from colliding black holes or neutron stars passes through the Earth. Detectors must be far apart to fix the direction of a source, so the Indian observatory will work with the two in the United States and with the one in Italy. B, C and D are wrong on the site, although they hold other research facilities, and candidates often place the project in Karnataka because so many astronomy institutes have their offices at Bengaluru. Each arm will hold a vacuum pipe along which laser beams travel, and much of the hardware comes from the American project.