This is an image of the FS Tau multi-star system taken by the Hubble Space Telescope. The bright object at the nebula's heart is FS Tau A, a newly ignited T Tauri star, but its companion on the right side, FS Tau B, hasn't ignited yet. It's still in the process of collapsing and heating up, releasing heat from the gravitational collapse. The Harbig-Haro protostar releases jets of fast-moving energized material, visible as the blue material stretching across the nebula.

Blue supergiants are a rare type of star that is vastly larger and more luminous than the Sun. They can have 16-40 times the mass of the Sun and put out 10,000 times more radiation. Only a tiny fraction of the most massive stars should become blue supergiants, yet they're more common in the Universe than they should be. A new study has shown that merging stars can account for the discrepancy, turning two smaller stars into a single blue supergiant.