As with most children, a picture of these youngsters taken today won't look the same as one snapped a few months from now. The movies show jets of gas plowing into space at hundreds of thousands of miles per hour and moving shadows billions of miles in size. Both systems are probably less than a million years old, making them relative newborns, given that stars typically live for billions of years. Hubble's Wide Field and Planetary Camera 2 first observed them in 1995. The pictures were then combined into movies that document startling activity in the early stages of a star's life.
Stars form in clouds of gas and dust that collect into a swirling disk.
Outflows of gas, like the bubbles and jets seen in these images, occur when some of the material feeding the infant star from the surrounding disk is diverted away by the star's magnetic field and accelerated out its magnetic poles. These outflows are often squeezed into narrow jets that can extend many light-years away from the star. Such outflows are a common and natural result of stellar birth. KB XZ Tauri is a young system with two stars orbiting each other. The bubble appears much broader than the narrow jets seen in other young stars, but it is caused by the same process - the ejection of gas from a star.