In 1920, astronomers Harlow Shapley and Heber Curtis held a Great Debate. Shapley argued that the spiral nebulae were small ...

At a meeting of the American Astronomical Society in January 1925, a paper read by one of his colleagues on his ... of fuzzy objects that might be mistaken for comets. He intended for comet hunters to ...

Two Grand Canyon-size features on the far side of the moon were likely formed in about 10 minutes after an unknown object slammed into the moon 3.8 billion years ago.

At a meeting of the American Astronomical Society in January 1925, a paper read by one of his colleagues ... He intended for comet hunters to avoid them since they did not move across the sky.

“It was destroyed by erosion, plate tectonics, and other geologic processes ... “Nearly four billion years ago, an asteroid or comet flew over the lunar south pole, brushed by the mountain ...