What's a nebula?
Nebula is a cloud of gas and dust in space. Nebulae come in different shapes and colors, and probably represent the most beautiful creations in space. They represent God's artwork on a canvas of unimaginable size.1
Some nebulae were formed as a result of star explosion. As the star exploded, the material from it was sent outward, resulting in gas and dust flying outward at incredible speeds. These clouds continue to grow in size every minute, and become trillions of miles in diameter. One such explosion resulting in a supernova remnant, as they are called, was actually observed by astronomer Johannes Kepler, in 1604, and it's called Kepler's Supernova.
It has been hypothesized for quite some time that nebulae are star forming regions; but nobody has ever observed a star form out of a nebula, just because of a simple fact that it would take much longer for a star to form, than the entire age of modern science movement. The only thing we can see is a bunch of dust, clearing in some areas, condensing in other areas. It's kind of like watching an object behind a smoke curtain. Once the smoke clears, we either see an object behind it, or we see an empty space. So it is with a nebula. As we look at a cloud of dust, we may wonder if an object might appear once the smoke clears. It's pretty difficult for a cloud of gas to condense enough to form a star, though. So, just because it looks like a star is forming inside a cloud, we can't conclude that a star is actually forming there, until the smoke clears.
Image of Kepler's Supernova
Lisle, Jason. Taking Back Astronomy. Green Forest, AR: Master, 2006. Print.
"Kepler's Supernova." Wikipedia. N.p., n.d. Web. .
Image courtesy of NASA