Final answer:
We study galaxy formation by observing the light from distant galaxies, which provides a look back in time at their stages of development. Additionally, the oldest stars in our galaxy offer insights into early galactic history. This combined data helps reconstruct the evolutionary timeline of galaxies since the dawn of the universe.
Step-by-step explanation:
To study galaxy formation when it happened so long ago, astronomers observe and analyze the light from distant galaxies. This light acts as a cosmic time machine, providing information about the galaxy as it was when the light left it. By observing very distant 'baby' galaxies from different periods in the universe's history, we can see galaxies at various stages of development. This helps us to reconstruct the life story of galaxies, tracing back their evolution and origins. For instance, by studying galaxies as they were over 10 billion years ago, we learn about their size, shape, and star formation rates at different times, comparing them to the mature galaxies we see in the nearby universe today.
In addition to distant observations, astronomers also examine the oldest stars within our own galaxy, which serve as a sort of fossil record. These studies reveal that nearly all galaxies contain some very old stars, suggesting they formed early in the universe's history. This comprehensive approach, combining observations of distant galaxies and study of local stellar populations, allows us to piece together a coherent narrative of galactic evolution across the cosmos.