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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

See Explanation. Clicking on the picture will download the highest resolution version available.

Galileo Demonstrates the Telescope

Explanation: Galileo Galilei made a good discovery great. Upon hearing at age 40 that a Dutch optician had invented a glass that made distant objects appear larger, Galileo crafted his own telescope and turned it toward the sky . Galileo quickly discovered that our Moon had craters , that Jupiter had its own moons , that the Sun has spots , and that Venus has phases like our Moon . Galileo , who lived from 1564 to 1642, made many more discoveries. Galileo claimed that his observations only made sense if all the planets revolved around the Sun , as championed by Aristarchus and Copernicus , not the Earth , as was commonly believed then. The powerful Inquisition made Galileo publicly recant this conclusion , but today we know he was correct.

Date October 14, 2001
Credit Credit: Original portrait by Justus Sustermans painted in 1636.
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
A service of: ASD at NASA / GSFC,
NASA Science Activation & Michigan Tech. U.