| HUBBLE | Edwin, US astronomer noted for his investigations of nebulae (6) |
| STRUVE | Otto -; Russian-born US astronomer noted for his studies in stellar spectroscopy and discovery of ionised interstellar hydrogen (6) |
| MESSIER | Charles, French astronomer noted for his catalogue of nebulae and star clusters (7) |
| MOSES | Edwin, US 400m hurdler unbeaten in 122 consecutive races (5) |
| DEIMOS | Smaller and outermost of the two moons of Mars, discovered by US astronomer Asaph Hall in 1877 (6) |
| PHOEBE | Satellite of Saturn, discovered by US astronomer William Henry Pickering in 1899 (6) |
| HOYLE | Fred, English astronomer noted for his steady-state theory of the universe (5) |
| MASSES | Nebulae |
| CLOUDS | Nebulae |
| COSMIC | Like galaxies and nebulae |
| HERBAL | The woman's put up a place for scientific investigation of plants (6) |
| REPORT | Investigation of lariat rope-running heading to the West (6) |
| REASON | Work by Thomas Paine subtitled Being an Investigation of True and Fabulous Theology (3,3,2,6) |
| OMARKHAYYAM | Persian poet, mathematician, and astronomer, noted for the Rubaiyat, a collection of quatrains, popularised in the West by Edward FitzGerald |
| SURVEYS | Investigations of opinions of a group of people (7) |
| MCCARTHY | Joseph - - -, US Republican senator who led investigations of alleged Communist infiltration into the US government in the 1950s (8) |
| INQUESTS | Investigations of tricky questions, nothing less (8) |
| IDIOTIC | Senseless to get beginners in immunology doing investigations of the ear |
| EDWINHUBBLE | US astronomer whose eponymous law states that the velocity of a galaxy is proportional to its distance from the observer (5,6) |
| LYSITHEA | Moon of Jupiter discovered by US astronomer Seth Barnes Nicholson in 1938, later named after an Oceanid and lover of Zeus (8) |
