HH 111
A prototype of highly collimated optical jet sources in Orion.
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HH 111 is a Herbig-Haro object found within the L1617 dark cloud, part of the larger Orion B molecular cloud in the constellation Orion. It serves as a key example of a highly focused optical jet, featuring multiple bow shocks and stretching roughly 2.6 light-years (0.8 parsecs) in length.
Located about 1,300 light-years (400 parsecs) from Earth, its central engine is the protostar IRAS 05491+0247, also known as VLA 1. This class I protostar, which drives the jets, has a luminosity of about 25 solar luminosities and is embedded within a 30 solar mass cloud core. The entire complex has a dynamical age of just 800 years. Near the central source lies an ammonia feature called NH3-S, a starless core whose interior has been stirred up by the jets from HH 111.
The jets themselves travel at speeds between 300 and 600 km/s. One component, blueshifted and bright in optical light, is accompanied by a fainter, redshifted counterjet. A second set of bipolar jets, designated HH 121, was detected in the near-infrared, angled 61° away from the HH 111 jets, suggesting the system contains multiple protostars.
Lore & Background
HH 111 lies within the L1617 dark cloud of the Orion B molecular cloud, about 1300 light-years from Earth. Its central source, IRAS 05491+0247 (also known as VLA 1), is a class I protostar with a luminosity of about 25 solar luminosities, embedded in a 30 solar mass cloud core. The jets from this source move at speeds of 300–600 km/s and consist of a blueshifted component bright in optical wavelengths and a faint redshifted counterjet.
The dynamical age of the complex is only 800 years. Near the central source, an ammonia feature called NH3-S was found, a starless core with a turbulent interior induced by HH 111. A second pair of bipolar jets, HH 121, was discovered in the near-infrared at an angle of 61° relative to the HH 111 pair, taken as evidence for a system with multiple protostars.
Reader's Guide
HH 111 serves as a key example of a highly collimated optical jet, demonstrating the early stages of protostellar outflow. Its multiple bow shocks and well-defined jet structure have made it a reference object for studying jet dynamics and shock physics. The discovery of a second bipolar jet pair (HH 121) at a different angle suggests the presence of multiple protostars within the system, offering insight into binary or multiple star formation. The nearby NH3-S core, with its turbulent interior induced by the HH 111 outflow, illustrates how protostellar jets can affect their surrounding environment.
With a dynamical age of only 800 years, HH 111 represents a very young outflow, providing a snapshot of early stellar evolution. Its blueshifted optical jet and faint redshifted counterjet highlight asymmetries common in such systems. The object remains a benchmark for models of jet collimation and propagation.
Frequently Asked Questions
What is HH 111?
HH 111 is a Herbig-Haro object—a bright knot of shocked gas produced by a protostellar jet—located inside the L1617 dark cloud within the Orion B molecular cloud in the constellation Orion. It is best known as a textbook example of an extremely well-collimated optical jet that displays several distinct bow shocks along its length.
How long is HH 111 and how fast do its jets travel?
The jet complex spans approximately 2.6 light-years (0.8 parsecs) from its driving protostar to the outermost shocks. Material within the jet is moving at speeds in the range of 300 to 600 kilometres per second, which is typical for high-velocity protostellar outflows.
Why do astronomers consider HH 111 important?
Sitting about 1,300 light-years away, HH 111 is widely treated as the prototype among highly collimated optical jet sources in the Orion region. Its clean, narrow jet geometry and multiple bow shocks make it a key reference point when studying how protostars launch and focus their outflows.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: HH 111 (CC BY-SA 4.0).
- Word definitions: the Codexery glossary, each quoted from its Wikipedia article.
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