Hubble time! 🌌 The spiral galaxy NGC 3596 is situated 90 million light-years from Earth in the constellation Leo. The galaxy was discovered in 1784 by astronomer William Herschel, the namesake of our Herschel Space Observatory. NGC 3596 appears almost perfectly face-on when viewed from Earth, showcasing the galaxy’s neatly wound spiral arms. The bright arms mark where the galaxy’s stars, gas and dust are concentrated. Star formation is also most active in a galaxy’s spiral arms, as shown by the brilliant pink star-forming regions and young blue stars tracing NGC 3596’s arms in this image. What causes these spiral arms to form? It’s a surprisingly difficult question to answer, partly because of the remarkable diversity of spiral galaxies. Some have clear spiral arms, while others have patchy, feathery arms. Some have prominent bars across their centres, while others have compact, circular nuclei. Some have close neighbours, while others are isolated. Early ideas of how spiral arms...