American astronomer Hubble was born in Marshfield, Missouri. 19 10 graduated from the university of Chicago. Hubble mainly studies modern extragalactic astronomy. From 1923 to 1924, when he was at Wilson Observatory, he took photos of the Andromeda spiral nebula with a telescope of 100 inch, and found that there were 36 variable stars in the constellation, of which 12 was Cepheid. According to these variables, the distance to the nebula is 900,000 light years (the current data is 2 million light years), which proves that the spiral nebula belongs to a galaxy far away from the Milky Way. 1925, Hubble further studied the structure of the Milky Way, and found some new stars, Cepheid variables, globular clusters, gas nebulae, red giant stars, Supergiant star and other stars, and determined the distance to these stars and the scale of the distance beyond the river.

Photographs of Saturn taken by modern spacecraft

1929, Hubble compared the apparent velocity of the Milky Way measured by shriver with the distance to the Milky Way, obtained the linear relationship between them, namely Hubble's law, and determined the coefficient value of this relationship, namely Hubble's constant. This discovery is the observational basis for expanding the concept of the universe. Hubble has two books on extragalactic astronomy, Nebula World published in 1936 and Cosmic Observation Law published in 1937.