Multiple views of the galaxy NGC 4303 as seen with the VLT and ALMA (with annotations)

This video shows images of NGC 4303, a spiral galaxy with a bar of stars and gas at its centre located approximately 55 million light-years from Earth in the constellation Virgo, taken at many different wavelengths of light. The observations were conducted with the Multi-Unit Spectroscopic Explorer (MUSE) instrument on ESO’s Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. 

The first two images are from the MUSE data. Initially the green, red and infrared (g, r, i) emission is shown, which is used to reveal the distribution of young stars. This fades to a combination of g, r, i emission with radiation from warm gas clouds of hydrogen (Hα), doubly ionised oxygen — [OIII] — and singly ionised sulphur — [SII] —, elements that signal the presence of newly born stars.

The next image shows the ALMA data only. ALMA was used to map cold clouds of molecular gas, which provide the raw material from which stars form. Thousands of stars can form in just one of these molecular clouds, yet these stellar nurseries are invisible to the human eye — they can only be observed via the radio waves emitted by carbon monoxide (CO).

The following image is a combination of all the MUSE and ALMA data, forming a colourful cosmic firework, which is helping astronomers to unlock the secrets of star formation.

The images were taken as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) project, which is making high resolution observations of nearby galaxies with telescopes operating across the electromagnetic spectrum.