In the early 1950s, astronomers George Herbig and Guillermo Haro independently catalogued several enigmatic clumps of nebulosity close to stars near the Orlon Nebula. These have since been called Herbig-Haro objects or 'HH' objects. Careful study later showed that many of the Herbig-Haro objects are portions of high-speed jets speeding away from newly-forming stars.
HH-47 in the top image is about half a light year long and 1,500 light years away. It lies at the edge of the Gum Nebula, possibly an ancient supernova remnant, in the southern constellations Vela and Puppis. The star responsible for the jet is hidden inside a dust cloud near the left edge of the image. The very complicated pattern in the jet suggests that the star might be wobbling, possibly because of the presence of a companion star. The jet has burrowed a cavity through the dense gas cloud. Shock waves form when it collides with interstellar gas causing the jet to glow. The white filaments on the left are reflecting light from the hidden star.
Underneath, the two images are HH-30 (left), which
is 450 light years away in the constellation Taurus, and HH-34 (right),
1,500 light years distant in the vicinity of the Orion Nebula. The view
of HH-30 reveals an edge-on disk of dust encircling a newly forming star.
Light from the star illuminates the top and bottom of the disk while the
star itself is hidden inside the densest part of the disk. The jet expands
for several billion kilometers from the star, but then stays confined to
a narrow beam. HH-34 shows a remarkable beaded structure, produced when
blobs of dense gas are ejected from the star like bullets from a machine
gun.
The bottom frame shows HH-1 and HH-2, the jets
from a young star 1,500 light years away in the constellation Orion. The
star is located midway between the blobs but is hidden from view behind
a dark cloud of dust. Tip-to-tip they span slightly more than a light year.
The pair of images above the bottom frame are close-ups of parts of it.
Camera: WFPC2
Credits: J. Morse/STScl, and NASA (HH-47);
C. Burrows (STSel & ESA), the WFPC2 Investigation Definition Team,
and NASA (HH-30); J. Hester (Arizona State University), the WFPC2 investigation
Definition Team, and NASA (HH-34 and HH-1/HH-2)
