1 00:00:01,000 --> 00:00:07,800 The NASA/ESA Hubble Space Telescope is named after the famous astronomer Edwin Hubble. 2 00:00:08,000 --> 00:00:15,000 He discovered that there are galaxies outside of our own and that the Universe is expanding. 3 00:00:15,320 --> 00:00:23,000 However, these remarkable discoveries wouldn’t have been possible without one exceptional astronomer before him — 4 00:00:23,000 --> 00:00:26,000 Henrietta Swan Leavitt. 5 00:00:35,000 --> 00:00:39,000 Henrietta Leavitt — the woman who measured the Universe 6 00:00:40,340 --> 00:00:46,800 Henrietta Leavitt was born in Lancaster, Massachusetts in 1868. 7 00:00:47,000 --> 00:00:55,500 She studied at Oberlin College, Ohio, and then Harvard University's Society for the Collegiate Instruction of Women. 8 00:00:57,000 --> 00:01:03,000 It wasn’t until her final year at university that she began to study astronomy — 9 00:01:03,000 --> 00:01:09,000 but this sparked a keen interest that she would pursue for the rest of her life. 10 00:01:10,500 --> 00:01:14,400 She began to work at Harvard Observatory as a “computer” 11 00:01:14,400 --> 00:01:20,000 — one of several skilled women hired to process astronomical data. 12 00:01:21,060 --> 00:01:26,000 She helped with cataloguing the brightness of every measurable star 13 00:01:26,000 --> 00:01:32,000 and was quickly promoted to be head of the photographic stellar photometry department. 14 00:01:34,500 --> 00:01:38,800 Supplied with photographic plates of the stars in the southern sky, 15 00:01:38,800 --> 00:01:45,500 Leavitt was tasked with classifying variable stars — ones that fluctuate in brightness. 16 00:01:47,000 --> 00:01:51,000 While studying these changing stars she noticed a pattern: 17 00:01:51,000 --> 00:01:56,000 the brighter the star, the longer the period of the fluctuations. 18 00:01:56,000 --> 00:02:02,000 The easily measured length of the star’s fluctuations directly leads to its brightness 19 00:02:02,000 --> 00:02:04,000 — and to its distance. 20 00:02:05,000 --> 00:02:08,880 The observation of these Cepheid variables turned out to be the key 21 00:02:08,880 --> 00:02:13,500 to a fundamental change in our understanding of the Universe. 22 00:02:16,000 --> 00:02:20,500 Edwin Hubble used this “measuring tape” to determine the distance 23 00:02:20,500 --> 00:02:25,000 to what was then known as the Andromeda nebula. 24 00:02:25,500 --> 00:02:31,000 The result showed that Andromeda was actually not part of the Milky Way 25 00:02:31,000 --> 00:02:35,000 but a galaxy on its own, millions of light-years away. 26 00:02:36,000 --> 00:02:44,000 Edwin Hubble discovered that our Universe contains many more galaxies than just the Milky Way. 27 00:02:46,500 --> 00:02:51,500 Hubble measured the distances to more and more galaxies using Leavitt’s Law. 28 00:02:52,000 --> 00:03:00,000 These measurements led him to another astounding deduction: the entire Universe is expanding. 29 00:03:00,000 --> 00:03:06,000 He gathered the first observational evidence for the big bang. 30 00:03:09,500 --> 00:03:14,500 Henrietta Swan Leavitt never knew the impact of her discovery. 31 00:03:14,500 --> 00:03:21,000 She died three years before Hubble announced his revelation about the Andromeda Galaxy. 32 00:03:21,000 --> 00:03:29,000 However, even today Leavitt’s discovery remains a vital foundation of modern cosmology 33 00:03:29,000 --> 00:03:34,000 and it is still used to determine the distances to galaxies. 34 00:03:40,000 --> 00:03:44,000 Hubblecast is produced by ESA/Hubble at the European Southern Observatory in Germany 35 00:03:44,000 --> 00:03:48,740 The Hubble mission is a project of international cooperation between NASA and the European Space Agency. 36 00:03:49,000 --> 00:03:54,000 Subtitles by ESA/Hubble. Translation by ---