The NASA/ESA/CSA James Webb Space Telescope has captured a very detailed image of the Herbig-Haro object 797 (HH 797), which is located in the northern constellation of Perseus.
This Webb image shows a Herbig-Haro object called HH 797. Image credit: NASA / ESA / CSA / Webb / T. Ray, Dublin Institute for Advanced Studies.
Herbig-Haro objects are small bright patches of nebulosity associated with protostars.
These objects were first observed in the 19th century by the American astronomer Sherburne Wesley Burnham, but were not recognized as being a distinct type of emission nebula until the 1940s.
The first astronomers to study them in detail were George Herbig and Guillermo Haro, after whom they have been named.
Herbig-Haro objects are formed when hot gas ejected by a newborn star collides with the gas and dust around it at speeds of up to 250,000 kmh (155,000 mph), creating bright shock waves.
They come in a wide array of shapes, the basic configuration is usually the same: twin jets of heated gas, ejected in opposite directions from a forming star, stream through interstellar space.
Herbig-Haro objects are transient phenomena — they disappear into nothingness within a few tens of thousands of years.
“HH 797, which dominates the lower half of this image, is very close to the young open star cluster IC 348, which is located near the eastern edge of the Perseus dark cloud complex,” Webb astronomers said.
“The bright infrared objects in the upper portion of the image are thought to host two further protostars.”
The new image of HH 797 was captured with the Near-InfraRed Camera (NIRCam) onboard Webb.
“Infrared imaging is powerful in studying newborn stars and their outflows, because the youngest stars are invariably still embedded within the gas and dust from which they are formed,” the astronomers explained.
“The infrared emission of the star’s outflows penetrates the obscuring gas and dust, making Herbig-Haro objects ideal for observation with Webb’s sensitive infrared instruments.”
“Molecules excited by the turbulent conditions, including molecular hydrogen and carbon monoxide, emit infrared light that Webb can collect to visualize the structure of the outflows.”
“NIRCam is particularly good at observing the hot (thousands of degrees Celsius) molecules that are excited as a result of shocks.”
In an earlier study, astronomers found that for cold molecular gas associated with HH 797, most of the red-shifted gas (moving away from us) is found to the south (bottom right), while the blue-shifted gas (moving towards us) is to the north (bottom left).
A gradient was also found across the outflow, such that at a given distance from the central protostar, the velocity of the gas near the eastern edge of the jet is more red-shifted than that of the gas on the western edge.
“Astronomers in the past thought this was due to the outflow’s rotation,” the researchers said.
“In this higher resolution Webb image, however, we can see that what was thought to be one outflow is in fact made up of two almost parallel outflows with their own separate series of shocks (which explains the velocity asymmetries).”
“The source, located in the small dark region (bottom right of center), and already known from previous observations, is therefore not a single but a double star. Each star is producing its own dramatic outflow.”
“Other outflows are also seen in this image, including one from the protostar in the top right of center along with its illuminated cavity walls.”
