Astronomers
have observed for the first time a jet of matter spiraling outward from an
infant star, as if a lengthy strand of curly pasta.
The
enormous jet, which shoots out in two directions, is rocketing material away
from the so-called protostar and into interstellar space at more than
"supersonic speeds." From end to end, the bipolar jet extends 16,000 astronomical
units (AU), where 1 AU is the average distance between the Earth and sun.
Called Herbig-Haro
(HH) 211, the protostar is located about 1,000 light-years away in the
constellation Perseus. Scientists have estimated HH 211 started gathering
stellar material about 20,000 or so years ago.
"It's
like an infant compared to the sun," said astronomer Qizhou Zhang of the
Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "Ultimately
this object we observed will grow into a star like the sun, but right now it's
only 6 percent of the mass of the sun."
The finding,
detailed in the Dec. 1 issue of the Astrophysical Journal, confirms a
key step of star
formation, one that astronomers have suspected since the 1980s.
Stellar
birth
Stars are
thought to form at the center of rotating disks of hydrogen gas and dust. Over
time, protostars
pack on material from spinning disks, meanwhile getting hotter and hotter,
until they begin nuclear fusion. This hydrogen-burning process keeps full-blown
stars aglow.
However,
there's a stellar glitch of sorts. Similar to dizzying rides that rotate so
swiftly riders stick to the outer walls, as a disk rotates faster and faster,
the swirling matter sticks to the disk's outer edge. The gas can't fall inward
toward the star
until it sheds excess spin power called angular momentum.
"It
has to get rid of the spin energy otherwise the matter will just keep swirling
around in this disk around the star without actually going into the star,"
Zhang told SPACE.com.
Reverse
whirlpool
Theory
suggests nascent stars could shed excess angular momentum in the form of gas
spiraling outward around shooting jets. Zhang and his colleagues glimpsed such
spiraling gas using the Submillimeter Array (SMA), which consists of eight radio
telescopes located atop Mauna Kea in Hawaii.
Measurements
showed matter rotating around the jet's axis in a sort of "reverse
whirlpool." The results suggest the bipolar jet moves outward at a speed
greater than 200,000 mph (322,000 kph), while matter swirls around the jet's
major axis at more than 3,000 mph (4,828 kph).
"HH
211 essentially is a 'reverse whirlpool,'" Zhang explained. "Instead
of water swirling around and down into a drain, we see gas swirling around and
outward."
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