The protostar, as astronomers call it, is ejecting a complex jet of material
riddled with knots and bow shocks, much like the waves pushed out by a boat.
Stripped of its normally opaque surroundings by the intense ultraviolet radiation
produced by nearby massive stars, this young stellar object is likely one of
the last of its generation in this region of space, astronomers said.
Its apparently fragile state of existence exposes the limitations that young
stars face in attempting to form in such a violent environment.
"Most young stars are embedded in very dense molecular clouds, which makes
our view of the early stages of star formation normally impossible with optical
telescopes," says Travis Rector of the University of Alaska Anchorage,
co-author of a paper on the young stellar object (YSO) in the December issue
of Astrophysical Journal Letters. "This is one of only a few cases
where a protostar is visible, making it a valuable discovery that will be studied
in detail."
Optical images of the jet taken at the WIYN 0.9-meter telescope at the National
Science Foundation’s Kitt Peak National Observatory in Arizona show a highly-collimated
jet, now known as Rosette HH1, stretching for more than 8,000 astronomical units
(1 AU = 150 million kilometers). It contains a prominent knot and hints of others,
which can be interpreted as "bullets" of material being ejected from
the rapidly rotating YSO at faster than the speed of sound. Bow shocks on the
other side of the YSO suggest the existence of a degenerated counterjet extending
in the opposite direction.
Other observations by co-author Jin Zeng Li of the Chinese Academy of Sciences
in Beijing confirm the interpretation.
"If it is indeed a counterjet, it may be the only existing observational
evidence of how bipolar jets evolve into monopoles, or at least highly asymmetric
jets," according to Jin Zeng Li. "This suggests that this infant star
has been starved of material as its accretion disk is evaporated, leaving a
very low-mass star. In some cases, this process might result in an isolated
brown dwarf or planetary mass object, offering a potential evolutionary solution
for such lone objects that have been spotted in the Orion Nebula and other nearby
hotspots in the Milky Way."
An accretion disk is the material that swirls around a star after its birth.
Planets sometimes form out of this material.
Located 1,500 light-years from Earth in the constellation Monoceros, the Rosette
Nebula contains ionized hydrogen that is excavated by the strong stellar winds
from hot stars.
Credit: T. Rector/University of Alaska Anchorage,
WIYN and NOAO/AURA/NSF
