NGC 346, one of the most dynamic star-forming regions in nearby galaxies, is full of mystery. Now that’s less of a mystery with new results from NASA’s James Webb Space Telescope.
NCG 346 is located in the Small Magellanic Cloud (SMC), a dwarf galaxy close to our Milky Way. The SMC contains lower concentrations of elements heavier than hydrogen or helium, which astronomers call metals, compared to the Milky Way. Since dust grains in space consist mainly of metals, the researchers expected that there would be low amounts of dust and that it would be difficult to detect. New data from Webb reveals otherwise.
Astronomers studied this region because the conditions and abundance of metals in the SMC are similar to those seen in galaxies billions of years ago, at a time in the universe known as “cosmic noon.” , where star formation was at its peak. About 2 to 3 billion years after the big bang, galaxies formed stars at a breakneck pace. The fireworks of star formation that took place then are still shaping the galaxies we see around us today.
“A galaxy during cosmic noon wouldn’t have NGC 346 like the Small Magellanic Cloud; it would have thousands” of star-forming regions like this, said Margaret Meixner, an astronomer at the Universities Space Research Association and principal investigator of the research team. “However, although NGC 346 is now the only furiously star-forming massive cluster in its galaxy, it provides us with an excellent opportunity to probe the conditions that were in place at cosmic noon.”
By observing protostars that are still forming, researchers can determine whether the process of star formation in the SMC is different from the one we observe in our own Milky Way. Previous infrared studies of NGC 346 have focused on protostars heavier than about 5 to 8 times the mass of our Sun. “With Webb, we can probe lighter protostars, as small as a tenth of our Sun, to see if their formation process is affected by low metal content,” says Olivia Jones of the United Kingdom Astronomy Technology Centre, Royal Observatory Edinburgh, program co. -investigator.
As stars form, they collect gas and dust, which can look like ribbons in Webb images, from the surrounding molecular cloud. The material accumulates in an accretion disc that gives birth to the central protostar. Astronomers have detected gas around protostars in NGC 346, but Webb’s near-infrared observations mark the first time they have also detected dust in these disks.
“We see the building blocks, not only of stars, but also potentially of planets,” said Guido De Marchi of the European Space Agency, co-scientist of the research team. “And since the Small Magellanic Cloud has a galaxy-like environment during cosmic noon, it’s possible that rocky planets formed earlier in the universe than we might have thought.” »
The team also has spectroscopic observations from Webb’s NIRSpec instrument, which they continue to analyze. These data should provide new insights into the material that accumulates on individual protostars, as well as the environment immediately surrounding the protostar.
These results will be presented on January 11 at a press conference at the 241st meeting of the American Astronomical Society. The observations were obtained during the 1227 program.