Webb Discovers Star Formation in Dusty Ribbons of a star cluster NGC 346

The active star cluster NGC 346 is located within a nebula 200,000 light years away and is visible in this image from NASA's James Webb Space Telescope's Near-Infrared Camera (NIRCam). Webb shows that there are more more building blocks for planets and stars than previously thought, in the form of clouds that are dense with dust and hydrogen. Two different forms of hydrogen may be seen in the gas arcs and plumes in this photograph. The more orange gas represents dense, molecular hydrogen, which is significantly colder at around -200 °C or less (roughly -300 °F), and associated dust, whereas the pink gas represents energetic hydrogen, which is typically as hot as around 10,000 °C (nearly 18,000 °F) or higher.

Credits: NASA, ESA, CSA, O. Jones (UK ATC), G. De Marchi (ESTEC), and M. Meixner (USRA). Image processing: A. Pagan (STScI), N. Habel (USRA), L. Lenkic (USRA) and L. Chu (NASA/Ames)

January 11, 2023

One of the most active star-forming areas in nearby galaxies, NGC 346, is shrouded in mystery. With the help of recent discoveries made by NASA's James Webb Space Telescope, it is now less enigmatic. 

The Small Magellanic Cloud (SMC), a dwarf galaxy near to the Milky Way, is where NCG 346 is situated. Compared to the Milky Way, the SMC has lower amounts of metals, which are substances heavier than hydrogen or helium. Scientists anticipated that there would be little dust and that it would be challenging to identify because the majority of dust grains in space are made of metals. Webb's most recent data shows the reverse.

The reason why astronomers investigated this area is that the SMC's circumstances and metal content are similar to those that were present in galaxies billions of years ago, at the height of star production known as "cosmic noon." Galaxies began generating stars at a rapid rate about 2 to 3 billion years after the big bang. The galaxies we see around us today are still shaped by the star formation fireworks that occurred then.

Researchers can determine whether the star formation process in the SMC differs from what we see in our own Milky Way by looking at protostars that are still forming. Protostars with masses greater than around 5 to 8 times that of the Sun were the main subject of earlier infrared observations of NGC 346. The United Kingdom Astronomy Technology Centre, Royal Observatory Edinburgh's Olivia Jones is a co-investigator on the project. "With Webb, we can probe down to lighter-weight protostars, as small as one tenth of our Sun, to see if their formation process is affected by the lower metal content," she said.

As stars develop, they absorb gas and dust from the surrounding molecular cloud, which can appear as ribbons in Webb images. A disk of accretion receives the material and nourishes the core protostar. Within NGC 346, astronomers have discovered gas around protostars, but Webb's near-infrared studies are the first to reveal dust in these disks.

According to Guido De Marchi of the European Space Agency, a co-investigator on the study team, "We're witnessing the building blocks, not just of stars, but also potentially of planets." The Small Magellanic Cloud's environment is similar to that of galaxies at cosmic noon, therefore it's likely that rocky planets developed earlier in the universe than previously believed.

Additionally, the team is still processing spectroscopic data from Webb's NIRSpec sensor. These findings should offer fresh perspectives on the matter accreting onto particular protostars as well as the surroundings right around the protostar. 

On January 11, 2023 these findings will be announced at a press conference during the 241st meeting of the American Astronomical Society.

Source - NASA