Space photo of the week: James Webb telescope shocks scientists with image of ancient galaxy roaring back to life

An image of a galaxy — The James Webb Space Telescope's image of the Leo P dwarf galaxy.

(Image credit: NASA, ESA, CSA, Kristen McQuinn (STScI))

What it is: The Leo P dwarf galaxy

Where it is: 5.3 million light-years away in the constellation Leo

That's a big surprise to astronomers because small, isolated galaxies like Leo P were thought to have switched off their star-forming factories when the universe was about a billion years old, during a cosmic era known as "the Epoch of Reionization." It followed the cosmic dark ages, which refers to a period during the early universe when the dense fog of neutral hydrogen gas blocked light. When the first stars formed then exploded as supernovas, they spread energetic ultraviolet light capable of ionizing hydrogen atoms, or splitting them back into electrons and protons, according to NASA.

Using JWST's Near Infrared Camera (NIRCam) to determine the brightness and colors of thousands of stars within the dwarf galaxy, researchers found that Leo P formed stars early on in the universe but stopped doing so shortly after the Epoch of Reionization. That was expected. However, the researchers also discovered that the galaxy reignited after a few billion years and started forming new stars again. Astronomers have gathered similar measurements for three other isolated galaxies, but found that star production ceased within all of them and never resumed, so it's unclear why Leo P reignited.

TOPICS

Jamie Carter is a Cardiff, U.K.-based freelance science journalist and a regular contributor to Live Science. He is the author of A Stargazing Program For Beginners and co-author of The Eclipse Effect, and leads international stargazing and eclipse-chasing tours. His work appears regularly in Space.com, Forbes, New Scientist, BBC Sky at Night, Sky & Telescope, and other major science and astronomy publications. He is also the editor of WhenIsTheNextEclipse.com.