News in Science

Hubble movies show baby stars in the making

Stellar jets US astronomers have used images taken by NASA's Hubble Space Telescope, to capture massive supersonic jets streaming from newly formed stars.

The jets are travelling at an amazing 700,000 kilometres an hour, creating powerful bow shocks that light up the molecular gas and dust clouds in which the stars form.

Astronomers first noticed these fast moving stellar jets about 50 years ago. They believe the Sun produced similar jets when it formed about 4.5 billion years ago.

The work compiled by scientists including Professor Patrick Hartigan from Rice University in Houston Texas and published in The Astrophysical Journal, offers astronomers their first glimpse of the dynamic behaviour of stellar jets, forcing a rethink of some theories about the processes occurring during star birth.

Hartigan began using Hubble to collect still images of stellar jets from three new born stars in 1994.

All three are about 1350 light-years away, two near the Orion Nebula, and the third in the constellation Vela.

He then revisited the same stars in 1998 and 2008.

"The images are frozen snapshots in time, but we would need to watch for hundreds of thousands of years to see how things actually play out," says Hartigan.

By lacing the Hubble images together and using a computer to fill in what occurred between, Hartigan and colleagues created a video showing clouds of dust and gas within the jets moving at different speeds - something which wasn't obvious in the still images.

"The spectacular Hubble images show beautiful filaments and detailed structure in the nebulae where stars are born", says Hartigan.

"The interesting stuff happens when things are jumbling around, blowing past one another or slamming into slower moving parts, causing shockwaves."

Insights from fluid dynamics

Hartigan and colleagues hadn't seen these huge collisions before and showed them to scientists familiar with the physics of nuclear explosions.

Hartigan says, "The fluid dynamicists immediately picked up on familiar patterns in the shockwaves, an aspect of the physics, astronomers overlook, and that led to a different interpretation for some of the features we were seeing".

Theoretical astrophysicist Dr Geoff Bicknell from the Australian National University says a picture may be worth a thousand words, but these movies are worth a million.

Bicknell says, "It's going to help us focus on the dynamics of jet outflows from young stars, what causes the structures we see, and how they form from processes that occur very close to the young star".

"One interesting feature are the knots being ejected in a quasi-periodic manner, which is telling us something about the eccreation process which we don't understand yet", says Bicknell.