M.K. Vainu Bappu Co-Discovered a Comet in 1949, Co-Authored the 1957 Wilson-Bappu Paper and Planned the 2.34-Metre Telescope at Kavalur That Now Bears His Name

The Indian Institute of Astrophysics (IIA) opened the centenary year of its founder-director on 10 August 2026, at its 55th Founder’s Day, a year before the date on which Manali Kallat Vainu Bappu would have turned 100. Bappu (1927 to 1982) took the photographic plate on which Comet Bappu-Bok-Newkirk was found, put his name to a 1957 paper whose result astronomers still use to estimate how bright a star really is, and pressed for the 2.34-metre telescope at Kavalur that now carries his name. The International Astronomical Union (IAU) lists him as its president for 1979 to 1982.

An hour-long plate at Oak Ridge

The plate was exposed in the early hours of 2 July 1949 with the 24-inch and 33-inch Jewett Schmidt telescope at the Oak Ridge station of Harvard College Observatory. R. C. Kapoor’s 2013 historical note in Current Science says the exposure ran 55 minutes (a 1950 report he quotes says sixty), that Bappu took it under the direction of Bart Bok, and that it was Bappu’s first long exposure with that instrument. Gordon Newkirk, an undergraduate who happened to pass by while Bok and Bappu checked the plate’s quality, noticed a trail on it. Bok identified the trail as a comet, not an asteroid. Harlow Shapley announced the object on Harvard’s announcement cards that July as Comet Bappu-Bok-Newkirk, now catalogued as C/1949 N1. Kapoor’s note, titled as the only comet with an Indian’s name to it, gives its revised orbital period as about 60,000 years.

The Donohoe Comet-Medal committee of the Astronomical Society of the Pacific faced a question of whom to credit. Kapoor reproduces its report, which said the only fair solution was “a triple award”, and lists medals 242, 243 and 244 for Bappu, Bok and Newkirk.

Bappu was at Harvard on a Government of Hyderabad scholarship to work on photoelectric photometry of eclipsing variable stars. On 13 July 1949 the education department of the Indian embassy in Washington relayed a cable from Hyderabad asking him to keep to that topic. Fred Whipple, chairman of Harvard’s astronomy department, replied on 26 July that missing the object on his plates would have been “a sin of scientific omission”. The Hyderabad side answered on 3 August that it had written to Shapley and was glad to hear Bappu’s work was satisfactory, according to the letters Kapoor prints from the IIA archives.

One calcium line, 185 stars

The next result carrying Bappu’s name is a paper by O. C. Wilson and Bappu in the Astrophysical Journal of 1957. They measured the H and K emission lines of ionised calcium in 185 stars of spectral types G, K and M, on spectra recorded at 10 angstroms per millimetre with the 32-inch camera at Mount Wilson or the 36-inch at Palomar. Plotting the logarithm of the emission width against the stars’ absolute magnitude (a measure of true brightness, the brightness a star would show at a standard distance) gave a straight line over a range of 15 magnitudes. The authors read it as the width varying with the one-sixth power of luminosity.

Their conclusion was that the width could serve as a luminosity indicator: one good spectrogram, they estimated, should fix a late-type star’s absolute magnitude to within about half a magnitude. A check against stars with measured parallaxes gave a mean error of 0.6 magnitude for the method. Set against a star’s apparent brightness, an absolute magnitude gives its distance.

The paper records how the work was divided. The investigation began with a first set of spectra in 1938 and 1939, a second set followed in 1951 and 1952, and the paper says all the plate measuring was done by Wilson, who finished before any data were plotted to avoid bias. A footnote gives Bappu’s address as the Uttar Pradesh State Observatory at Naini Tal. The authors added that they had no theory to account for the relation.

Later work has kept the relation in use. Pace, Pasquini and Ortolani recalibrated it in 2003 using 119 nearby stars with Hipparcos magnitudes and found a root-mean-square scatter of 0.6 magnitude; they judged it unsuitable for accurate distances to single stars but useful for clusters, and for the open cluster M67 it gave a distance modulus of 9.65, in good agreement with main-sequence fitting. In 2022 Rosas-Portilla, Schröder and Jack measured 32 stars with Gaia parallaxes and reported that the result supports a physical reading of the effect, the theory the 1957 authors lacked: line saturation and photon redistribution in the calcium of the star’s chromosphere, the thin layer above its visible surface.

Naini Tal, then Kodaikanal

Ram Sagar’s history of ARIES, the Nainital institute, records that the Uttar Pradesh State Observatory was formed on 20 April 1954 and that Bappu, then about 27, joined it at Varanasi on 1 November 1954 as chief astronomer. He persuaded the state government to move the observatory from a dusty, hazy city to a better site: first to a cottage at Nainital in November 1955, and in November 1961, after Bappu had left, to Manora Peak. IIA’s archive profile credits Bappu with choosing Manora Peak in 1955. Sagar adds that a photoelectric photometer Bappu designed gave the first photoelectric astronomical observations in Asia.

In 1960 Bappu became director of the Kodaikanal Observatory, the solar observatory in the Palani hills described in our piece on its century of sun records. Madras Musings and IIA’s archive profile both describe him modernising it. The account by J. C. Bhattacharyya and K. T. Rajan adds the workshop: A. P. Jayarajan built up an optical shop at Kodaikanal, whose first instrument was a small Schmidt camera made in late 1964. The shop later ground and figured a 24-inch mirror, which in 1968 projected an image of a hanging key so lifelike, the authors write, that the Union Minister Karan Singh tried to pick it up.

In 1971 the Kodaikanal observatory became the autonomous Indian Institute of Astrophysics, financed by the Government of India, with Bappu as its founder-director.

Choosing Kavalur

At a meeting of the Standing Advisory Board for Astronomy soon after he took over at Kodaikanal, Bhattacharyya and Rajan write, Bappu proposed searching the extreme south of India for a site, since a location close to the equator gives access to almost the whole sky. The first expedition set out in 1962 and covered hill sites from Kanyakumari to the Tirupati and Tirumalai hills, carrying a portable telescope and judging the steadiness of the image at each stop. It settled on the Javadi hills in Tamil Nadu, in a sandalwood reserve near the small village of Kavalur. The authors report seeing better than one arc second on several nights, and say Bok described the seeing there as excellent. Bappu’s own history says the site was chosen after fifteen months of seeing tests and that the field observatory was started in 1968.

The first research telescope at Kavalur was a 38-centimetre Cassegrain reflector. Bappu had also pursued a one-metre telescope from Carl Zeiss of Jena: ordered in 1965, delivered in March 1969, and installed by German engineers by May 1972. Bhattacharyya and Rajan write that within a short time of the one-metre going into service, a discovery was made during an occultation (a star passing behind a body in the solar system): Kavalur data from 7 June 1972 showed a thin atmosphere on Jupiter’s moon Ganymede.

Kavalur’s 40-inch telescope, the one-metre Zeiss, followed the occultation of the star SAO 158687 by Uranus on the night of 10 to 11 March 1977. Bhattacharyya’s account says the team, working with a photoelectric record, saw the star vanish for 9 seconds and found further dips, and cabled the IAU’s Central Bureau. A team from Cornell University observing from NASA’s airborne observatory had the longest record, and its leader, Elliot, worked out that the dips came from narrow rings. Bhattacharyya and Bappu then published the Kavalur record in Nature in 1977, describing new features of the ring system.

Thirty-one years from committee to green signal

Bhattacharyya and Rajan trace the large telescope to the committee headed by M. N. Saha, appointed by the Government of India in 1945, which recommended a central observatory with at least one large telescope. (Saha’s other work is in our article on the ionisation equation.) The Kodaikanal director of the day, A. K. Das, proposed a telescope of the 100-inch class, but it was pruned from the first five-year plan, and Bappu kept pressing for funds from the late 1960s. He put a proposal to IIA’s Governing Council in September 1971, naming the spiral structure of the Galaxy in the southern sky, stellar chromospheres, and the shapes and chemical makeup of external galaxies as principal themes, and the Council decided the telescope would be a national facility open to all Indian astronomers.

In 1972 the institute asked for quotes on mirror blanks. Corning Glass Works of the United States quoted 200,000 US dollars for a 2.5-metre blank of a low-expansion ceramic, about 17 lakh rupees at the exchange rate of the time, the authors write. Schott of West Germany offered a slightly smaller blank of similar material for 100,000 Deutsche Marks, about 5 lakh rupees, a price possible because two other buyers were sharing the casting costs. IIA accepted. The blank, 93 inches (2.36 metres) across, arrived in May 1974.

For the mount IIA engaged Tata Consulting Engineers of Bombay in December 1974. In 1975 Bappu toured American observatories with the firm’s engineer D. P. Panchal, and Harlan Smith of the University of Texas at Austin, a friend of Bappu, supplied a duplicate set of drawings for the 107-inch telescope at McDonald Observatory. Tata Consulting Engineers submitted the concept report in November 1976, and the Council approved Kavalur as the site that month after comparison seasons at two alternatives, one in the Baba Budan hills and one in the Horsley hills. A Project Management Board with Bappu as chair took charge.

Built in India, finished without him

The country had no machine that could grind a mirror of that size, so Laxmi Vijay Brass and Iron Works of Ahmedabad built one, and the blank was loaded onto it in the IIA optical shop in Bangalore on 19 December 1979. Rough grinding finished in about three months, smoothing in December 1980, and the long work of figuring began in September 1981. The mount went to Walchandnagar Industries, which received the order in September 1979 and handed over the finished mount in mid-1984. Control panels were built with the Bhabha Atomic Research Centre, and the authors give the rotating dome’s weight as 250 tons. Bhattacharyya and Rajan put the total cost, including buildings and the VAX computer, at around 6 crore rupees.

Bappu did not see it finished. He went abroad for a short assignment, underwent a cardiac bypass operation in Munich in August 1982 and died there. The authors write that the two scientists leading the figuring and testing, Jayarajan and A. K. Saxena, took the work forward themselves, with one visit in late 1984 from the optical expert Don Loomis, and produced the primary mirror to better accuracy than first aimed at. The last figuring ran to May 1985 and the mirror was aluminised on 26 July 1985.

First light, and the name

Jayarajan, who had spent five years on the mirror, was chosen for the first look through it on the night of 31 October 1985, according to Bhattacharyya and Rajan. Bhattacharyya took the first photograph on 2 November 1985, of the Pleiades. On 6 January 1986 the Prime Minister, Rajiv Gandhi, who had come to Kavalur to watch Halley’s comet according to Kapoor, named the telescope the Vainu Bappu Telescope and the whole site the Vainu Bappu Observatory. IIA’s Council dedicated it as a national facility a few months later.

The authors, writing in 1992, called it the largest optical telescope in Asia and said that, apart from the Anglo-Australian Telescope and the Mauna Kea reflectors, no other observatory in the Asia-Pacific region had telescopes of its size. Sagar’s ARIES history states it was India’s largest optical telescope until the 3.6-metre telescope at Devasthal began operating in 2016. IIA now lists a fibre-fed echelle spectrograph on the telescope that has reached a resolution of 70,000, and says better than 100,000 is possible with a narrower slit.

What the record leaves open

The telescope’s size is quoted three ways. Bhattacharyya and Rajan explain that the Schott blank measured 2,360 millimetres, that 2,340 millimetres was the planned aperture, and that the clear aperture measured after installation was 2,322 millimetres; “90-inch” is the common name. Dates in popular accounts also vary. Madras Musings gives 1983 for commissioning, while the IIA authors give first light in October 1985 and the naming in January 1986. Some accounts credit the 2.34-metre telescope with the 1972 Ganymede and 1977 Uranus observations; IIA’s own accounts place both at Kavalur years before the large mirror existed, with the Uranus night on the 40-inch telescope.

Bappu received the Padma Bhushan in 1981, according to Kapoor and IIA’s archive profile. The IAU’s list of past executive committees gives his presidency as 1979 to 1982, and he had been a vice-president from 1967 to 1973; Madras Musings calls him the only Indian astronomer to reach that office. IIA’s Vainu Bappu Observatory page, last updated on 6 February 2026, says visitor programmes are suspended during maintenance on the 2.3-metre telescope, while a 15-centimetre telescope is used for public sky viewing on Saturday evenings in clear weather.

The Minor Planet Center’s citation for asteroid 2596 Vainu Bappu, discovered by R. M. West at La Silla on 19 May 1979, calls him the initiator and driving force of many projects, among them “the 2.3-m Kavalur telescope, entirely designed and built in India”.