Think of the Hubble Space Telescope as the latest movie-star agent. This week NASA has released new movies of two stellar youngsters, each of which, say Hubble astronomers, is destined for greatness.

The objects, which lie about 450 light-years from Earth, were spotted quite by surprise spewing out large jets of gases and charged particles at hundreds of thousands of miles per hour so fast that changes in the objects shapes were soon detected as well.

"Serendipity is often key in observational sciences like astronomy," said Alan Watson, an astronomer at the Instituto de Astronomía in Morelia, Mexico. "We were stunned to find such interesting things going on. We were originally using Hubble to look at a star which is near both [objects]. However, once we found these we were determined to go back and look at them again in more detail."

Both of the objects are extremely young each is no more than one million years old. One of the stars, known to astronomers as HH 30, can be seen spitting out a very narrow stream of gas. The other object, XZ Tauri, is actually a pair of stars blowing out gas in the form of a huge bubble.

After observing both HH 30 and XZ Tauri between 1995 and 2000, Hubble astronomers noticed that the objects had changed so much, they were able to combine successive snapshots of them to create a time-lapse movie for each. The fact that these objects have changed so much over a relatively short period provides astronomers with a great deal of information about the formation of such stellar newborns.

The bulbous ejection blowing out from the twin star-system XZ Tauri extends almost 60 billion miles (96 billion kilometers) from the young stars, which are visible at the lower left of Hubbles images. The two stars orbit each other at a distance of 4 billion miles (6 billion kilometers) about the space from our sun to the planet Pluto.

Astronomers believe that this hot gas bubble, which pops the thermometer at 17,500 degrees Fahrenheit (9,700 degrees Celcius), is being ejected by one of the stars in XZ Tauri, though they still do not know which.

The bubble appears to be only about 30 years old a mere blip in the cosmological timescale of stellar lifetimes, which can last into the billions of years.

Astronomers observing XZ Tauri say that the most interesting aspect of the objects grand bubble is the fact that it changed dramatically in appearance between 1995 and 1998. In 1995, the interior and edge of the bulb appeared about the same brightness, indicating that they were roughly the same temperature. But by 1998, the outside edge of the bubble was much brighter than before. Experts believe this brightening was caused by a recombination of local free electrons (negatively charged particles) with other atoms in the area. This recombination apparently cooled the bubbles edge while causing it to emit light.

The most intriguing aspect of Hubbles HH 30 images, say astronomers, is the gas jet flowing from the systems central star. The jet, which flows between 200,000 and 600,000 miles (320,000 and 960,000 kilometers) per hour, is similar to those that flow out of black holes, though they are much less energetic. This is because HH 30s central star is only about the size of our sun much, much less massive than black holes, which can weigh in at up to several billion times the mass of our sun.

Astronomers say that the streaming jets in HH 30 are formed as material is ejected along the magnetic field lines surrounding the disk of gas and dust surrounding the local central star. This material is ejected as large clumps of gas and energy, which later dissipate into interstellar space.

In the Hubble image of HH 30, astronomers cant actually see the central star from which a large gas jet is streaming because it is obscured by its edge-on disk. Such disks are quite common in the universe, said Alan Watson, but they have been very difficult to observe directly because the light from the central star usually drowns out the light of the disk. HH 30, in contrast, is great to observe because the position of the disk relative to the Hubble telescope blocks the central stars bright light.

Astronomers are also interested in HH 30 because they believe it resembles what the sun and our solar system may have looked like long, long ago. "We think that our own sun went through a similar phase 5 billion years ago, with disks and jets and the whole nine yards," said Watson. "So we can use HH 30 as a time machine to go back 5 billion years to study the origins of our own sun."

Future Hubble Space Telescope observations of both XZ Tauri and HH 30 will continue at least through the next few years. Astronomers hope that new studies of these intriguing objects will add a great deal to their current understanding of stellar and solar-system formation.