Elliptical view of galaxies past

摘要

How and when galaxies assembled their mass to become the structures seen today are among astronomy's big outstanding questions. A comprehensive study of nearby galaxies provides a new angle on the issue. Compared with other scientists, astronomers are at a disadvantage: they cannot perform laboratory experiments on stars and galaxies. But they can exploit a unique advantage: thanks to the finite speed of light, they can observe objects as they were in the past. Current telescopes allow galaxies to be observed as they were back to about 13 billion years ago. What a palaeontologist wouldn't give for a similar time machine for taking pictures of dinosaurs when they were alive!