[nb 1] Kowal also began to search for Type Ia supernovae in other galaxies, in an effort led by Zwicky to calibrate the magnitudes of these exploding stars so that they could be used as standard candles, reliable measures of the distance of their host galaxies (work which in the present has led to accurate measurements of the expansion of the universe).

In 1973, Caltech astronomers Eleanor Helin and Gene Shoemaker began an observing program to search out and track previously unknown near-Earth asteroids, the Planet-Crossing Asteroid Survey (PCAS), a photographic plate survey that began on the Palomar 18" Schmidt telescope.

Between December 1976 and February 1985, Kowal searched 6400 square degrees of sky in the ecliptic plane for distant, slow-moving Solar System objects.

[8] Only one object was found beyond Jupiter: 2060 Chiron, discovered in 1977, which had the unusual characteristic of features both like an asteroid and a comet.

In 1980, Kowal's research in astronomical history found a 1613 drawing by Galileo Galilei showing Neptune near Jupiter, predating the discovery of Neptune in 1846;[9] Kowal was awarded the inaugural R. R. Newton Award for Scientific History for this "shockingly outré" finding.