Stars don’t appear out of nowhere. They form inside vast clouds of gas and dust called nebulae. A nebula is essentially a stellar nursery: a giant region of mostly hydrogen, often hundreds of light-years across, slowly collapsing under its own gravity.
As parts of the cloud clump together, they get denser and hotter. When the center of a clump gets hot enough - about 10 million degrees C - hydrogen atoms start fusing together into helium, releasing enormous energy. That’s when a star “switches on” and starts to shine.
The Orion Nebula is one of the closest stellar nurseries to us, only 1,300 light-years away, and you can see it with the naked eye as a faint patch in Orion’s sword. Other famous nurseries include the Eagle Nebula (home of the iconic Hubble image known as the “Pillars of Creation”) and the Carina Nebula, where the James Webb Telescope has photographed the gentle, sparkling beginning of brand-new stars.
