A maelstrom of matter and energy

This Picture of the Week from the NASA/ESA Hubble Space Telescope depicts the galaxy NGC 4951, a spiral galaxy that’s located 49 million light-years from Earth in the constellation Virgo.

The data used to make this image were captured by Hubble as part of a programme to examine how matter and energy travel in nearby galaxies. Galaxies continuously undergo a cycle of star formation whereby the gas in a galaxy forms molecular clouds, which collapse to create new stars, which then disperse the clouds they formed from with powerful radiation or stellar winds in a process called feedback. The remaining gas is left to form new clouds elsewhere. This cycle of moving matter and energy determines how fast a galaxy forms stars and how quickly it burns through its supplies of gas — that is, how it evolves over the course of its life. Understanding this evolution depends on the nebulae, stars and star clusters in the galaxy: when they formed and their past behaviour. Hubble has always excelled at measuring populations of stars, and the task of tracking gas and star formation in galaxies including NGC 4951 is no exception.

NGC 4951 is also a Seyfert galaxy, a type of galaxy that has a very bright and energetic nucleus called an active galactic nucleus. This image demonstrates well how energetic the galaxy is, and some of the dynamic galactic activity which transports matter and energy throughout it: a shining core surrounded by swirling arms, glowing pink star-forming regions, and thick dust.

[Image Description: A spiral galaxy, tilted diagonally. It has thick, cloudy spiral arms wrapping around the core. They are filled with pink patches marking new star formation, young blue stars, and dark wisps of dust that block light. The galaxy glows brightly from its core. It is on a dark background, with a few distant galaxies and unrelated stars around it.]