Less than a century ago, Edwin Hubble showed that certain "nebulae" are actually galaxies like our Milky Way, by using the so-called period-luminosity relationship of variable stars known as cepheids, that allowed him to estimate distances. Using cepheids located in the Andromeda "nebula", Hubble concluded in the 1920s that Andromeda is far outside our Galaxy. Later, Hubble found that the most distant galaxies have the largest velocities away from Earth. This means that the Universe is expanding, and that everything started in the Big Bang.
|Andromeda "nebula". (c) NASA.|
Thus, observations from the Peruvian Andes were key to set the standard ruler to measure large distances, leading to the birth of Extragalactic Astronomy and Cosmology. In another post I'll describe how observations gathered in Harvard's observatory in Arequipa led to the birth of Stellar Astrophysics.