Motion of Jets from an Embryonic Star (HH-30)

This NASA Hubble Space Telescope image reveals unprecedented detail in a newly forming star called HH-30. Exposures taken a year apart show the motion of high speed blobs of gas (arrows) that are being ejected from the star at a half-million miles per hour.

The jets emanate from the center of a dark disk of dust which encircles the star and hides it from view. Presumably the disk feeds material onto the star, and some of it is superheated and squirts out along the star's spin axis. The presence of the blobs suggests that the star formation process is fitful and episodic, as chunks of material fall onto the newborn star.

For the first time, Hubble Space Telescope shows the accretion disk which is about the size of our solar system, around a forming star. The top and bottom surfaces of the disk can be seen directly in this view, which visually confirms the conventional accretion disk theory for star formation. When the star becomes hot enough it will stop accreting material and blow away much of the disk - but perhaps not before planets have formed around the star. The generally accepted theory for the creation of our solar system is that it formed from a disk, and that the orbits of the planet are the "skeletal" remnant of the disk. It also explains why the planets all orbit the Sun in the same direction and roughly the same plane. The disk can be seen to "flare" away from the star. (It is thicker at larger distances from the star.) This behavior can be understood because it takes material farther out in the disk longer to settle to the disk midplane. The flaring has been conjectured in order to explain details of the spectra of such objects, but never directly observed before on these scales.

The picture was taken with the Wide Field Planetary Camera 2. HH-30 lies 450 light-years away in the constellation Taurus.