October 7, 1999
Photo No. H99-35
Hubble Heritage Projects First Anniversary
HH 32 is an example of a "Herbig-Haro object," which is formed when
young stars eject jets of material back into interstellar space. This
object, about 1,000 light-years from Earth, is somewhat older than
Hubble's variable nebula, and radiation from the bright central star has
already cleared much of the dust out of the central region, thus
exposing the star to direct view.
Many young stars, like the central
object in HH 32, are surrounded by disks of gas and dust that form as
additional material is attracted gravitationally from the surrounding
nebula. Material in the disk gradually spirals in toward the star and
eventually some of it accretes onto the star, increasing its mass. A
fraction of the gas, however, is ejected perpendicularly to the disk at
speeds near 200 miles per second, and forms two oppositely directed
jets. These jets plow into the surrounding nebula, producing strong
shock waves that heat the gas and cause it to glow in the light of
hydrogen atoms (red) and sulfur ions (blue); this glow is called a
Herbig-Haro object, in honor of astronomers George Herbig and Guillermo
Haro, who did much of the early work in this area in the 1950's.
The jet on the top side, whose furthest extent is about 0.2 light-year from the
star, is pointed more nearly in our direction, while the opposite jet on
the bottom lies on the far side of the star and is fainter because it is
partially obscured by dust surrounding the star.
The Hubble Heritage team made this image from observations of HH 32
acquired by Salvador Curiel (UNAM) and collaborators.
Image Credit: NASA/The Hubble Heritage Team (AURA/STScI).