What’s small, irregularly shaped and recently underwent a spurt of star formation? The dwarf galaxy NGC 1705, an oddball starburst galaxy about 17 million light years from Earth. Such irregular dwarf galaxies tend to contain little raw material beyond hydrogen and helium and are thought to be similar to the first galaxies forming in the wake of the Big Bang. This Hubble Space Telescope image was collected in a project to better understand the interplay between stars, clusters and ionised gas in nearby star-forming galaxies. Looking at NGC 1705 in H-alpha light using Hubble’s Wide Field Camera 3, researchers were able to discern thousands of emission nebulae caused by ultraviolet light from hot, young stars making surrounding gas clouds glow. Hubble studied NGC 1705 in 1999 using an older camera, but the Wide Field Camera 3 provides a much more detailed view.
It is known today that merging galaxies play a large role in their evolution, and the formation of elliptical galaxies in particular. However, there are only a few merging systems close enough to be observed in depth. The pair of interacting galaxies seen here — known as NGC 3921 — is one of these systems. But ‘close’ is a relative term: NGC 3921 lies 270 million light-years away.
This NASA/ESA Hubble Space Telescope image reveals NGC 1222, a galaxy with a rather eventful story to tell. NGC 1222 has been described as a peculiar example of a so-called lenticular galaxy, but one that exhibits very recent star formation on a huge scale — an event known as a starburst — due to having recently consumed two dwarf galaxies.