What is the fine-grained topic of the following text: Using the Hubble Space Telescope to measure the distance to Type 1a supernovas and Cepheid stars, a team at the Space Telescope Science Institute was able to improve the accuracy of earlier measurements, which increase that expansion rate between five and nine percent. Only return the topic.
Improving accuracy of distance measurements to supernovas and Cepheid stars using the Hubble Space Telescope.