New Hubble Videos Show Star Jets in Action—A First

Ghostly Motion

Image and video courtesy ESA/NASA

Bright veils of dense gas seem to drift through space in a Hubble video of HH 1, a jet of material from a young star in the Orion nebula.

Astronomers aren't entirely sure how newborn stars create such jets. Current theory states that, in general, stars form from collapsing clouds of cold hydrogen gas. As a star grows, it gravitationally attracts more material, until the star is surrounded by a large, spinning disk of gas and dust.

Some of this material can spawn planets, but it's also possible material in the disk gradually spirals toward the star and escapes in the form of high-velocity polar jets. (Related: "Star Caught Eating Another Star, X-Ray Flare Shows.")

The jets vanish when the disk of material runs out, the theory goes, and the outflows usually last only about a hundred thousand years—a blink of an eye in the life of a star.

Published August 31, 2011

Cosmic Traffic Jam

Image and video courtesy ESA/NASA

Herbig-Haro object HH 47 pushes bright bow shocks through space in one of the new Hubble videos. This jet—which extends about ten times the width of our solar system—is being created by a young star in the southern constellation Vela.

The outflows may seem to glide gently in the videos. But in reality they're shooting out at more than 440,000 miles (700,000 kilometers) an hour.

The time-lapse movies show that clumps of gas in the jets are moving at different speeds, like traffic on a freeway. When fast-moving blobs "rear end" slower ones, they heat up the jet's material and generate new bow shocks. (See a picture of a bow shock made by a speeding star.)

Published August 31, 2011

Clumpy Evolution

Image and video courtesy ESA/NASA

Revealed by one of the new Hubble time-lapse videos, clumps of gas brighten and fade as bow shocks interact in the jet HH 34, which is being spewed by a star in the constellation Orion.

The new movies suggest that the characteristic clumps in these jets start to form relatively near the newborn stars. In HH 34, for example, Hartigan and colleagues traced one glowing knot to within about nine billion miles (14.5 billion kilometers) of the star.

(See an infrared picture of a baby star's twin jets.)

Published August 31, 2011

Reworking the Models

Image and video courtesy ESA/NASA

Based on the new Hubble videos, the team created this computer animation of a Herbig-Haro object and how it might evolve over several centuries.

"Taken together, our results paint a picture of jets as remarkably diverse objects that undergo highly structured interactions between material within the outflow and between the jet and the surrounding gas," team leader Hartigan said.

"This contrasts with the bulk of the existing simulations, which depict jets as smooth systems."

The team's results appear in the July 20 issue of the Astrophysical Journal.

Published August 31, 2011