Webb Probes Most Massive Star-Forming Region of Small Magellanic Cloud

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Astronomers using the NASA/ESA/CSA James Webb Space Telescope have revealed many new pockets of star formation in NCG 346, an open star cluster in the Small Magellanic Cloud, a dwarf galaxy close to our Milky Way.

This image, taken by the Near-Infrared Camera (NIRCam) onboard the NASA/ESA/CSA James Webb Space Telescope, shows the star cluster NGC 346. Webb reveals the presence of many more building blocks than previously expected, not only for stars, but also planets, in the form of clouds packed with dust and hydrogen. The plumes and arcs of gas in this image contains two types of hydrogen. The pink gas represents energized hydrogen, which is typically as hot as around 10,000 degrees Celsius (approximately 18,000 degrees Fahrenheit) or more, while the more orange gas represents dense, molecular hydrogen, which is much colder at around minus 200 degrees Celsius or less (approximately minus 300 degrees Fahrenheit), and associated dust. The colder gas provides an excellent environment for stars to form, and, as they do, they change the environment around them. The effect of this is seen in the various ridges throughout, which are created as the light of these young stars breaks down the dense clouds. The many pillars of glowing gas show the effects of this stellar erosion throughout the region. In this image blue was assigned to the wavelength of 2.0 microns (F200W), green was assigned to 2.77 microns (F277W), orange was assigned to 3.35 microns (F335M), and red was assigned to 4.44 microns (F444W). Image credit: NASA / ESA / CSA / O. Jones, UK ATC / G. De Marchi, ESTEC / M. Meixner, USRA / A. Pagan, STScI / N. Habel, USRA / L. Lenkic, USRA / L. Chu, NASA’s Ames Research Center.

This image, taken by the Near-Infrared Camera (NIRCam) onboard the NASA/ESA/CSA James Webb Space Telescope, shows the star cluster NGC 346. Webb reveals the presence of many more building blocks than previously expected, not only for stars, but also planets, in the form of clouds packed with dust and hydrogen. The plumes and arcs of gas in this image contains two types of hydrogen. The pink gas represents energized hydrogen, which is typically as hot as around 10,000 degrees Celsius (approximately 18,000 degrees Fahrenheit) or more, while the more orange gas represents dense, molecular hydrogen, which is much colder at around minus 200 degrees Celsius or less (approximately minus 300 degrees Fahrenheit), and associated dust. The colder gas provides an excellent environment for stars to form, and, as they do, they change the environment around them. The effect of this is seen in the various ridges throughout, which are created as the light of these young stars breaks down the dense clouds. The many pillars of glowing gas show the effects of this stellar erosion throughout the region. In this image blue was assigned to the wavelength of 2.0 microns (F200W), green was assigned to 2.77 microns (F277W), orange was assigned to 3.35 microns (F335M), and red was assigned to 4.44 microns (F444W). Image credit: NASA / ESA / CSA / O. Jones, UK ATC / G. De Marchi, ESTEC / M. Meixner, USRA / A. Pagan, STScI / N. Habel, USRA / L. Lenkic, USRA / L. Chu, NASA’s Ames Research Center.

NGC 346 is located about 210,000 light-years away in the constellation of Tucana.

This massive star-forming region resides in the Small Magellanic Cloud, a dwarf galaxy that is a satellite of our Milky Way Galaxy.

Also known as ESO 51-10, Kron 39 or Lindsay 60, it was discovered on August 1, 1826 by the Scottish astronomer James Dunlop.

NGC 346 has a diameter of 150 light-years and a mass of 50,000 solar masses.

Webb probed this region because the conditions and amount of metals within the Small Magellanic Cloud resemble those seen in galaxies billions of years ago, during an era in the Universe known as Cosmic Noon, when star formation was at its peak.

Some 2 to 3 billion years after the Big Bang, galaxies were forming stars at a furious rate. The fireworks of star formation happening then still shape the galaxies we see around us today.

“A galaxy during Cosmic Noon wouldn’t have one NGC 346 like the Small Magellanic Cloud does; it would have thousands of star-forming regions like this one,” said Dr. Margaret Meixner, an astronomer at the Universities Space Research Association.

“But even if NGC 346 is now the one and only massive cluster furiously forming stars in its galaxy, it offers us a great opportunity to probe conditions that were in place at Cosmic Noon.”

By observing protostars still in the process of forming, astronomers can learn if the star formation process in the Small Magellanic Cloud is different from what they observe in the 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 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,” said Dr. Olivia Jones, an astronomer with the United Kingdom Astronomy Technology Centre at Royal Observatory Edinburgh.

As stars form, they gather gas and dust, which can look like ribbons in Webb imagery, from the surrounding molecular cloud. The material collects into an accretion disk that feeds the central protostar.

Astronomers have detected gas around protostars within NGC 346, but Webb’s near-infrared observations mark the first time they have also detected dust in these disks.

“We’re seeing the building blocks, not only of stars, but also potentially of planets,” said Dr. Guido De Marchi, a researcher at ESA.

“And since the Small Magellanic Cloud has a similar environment to galaxies during Cosmic Noon, it’s possible that rocky planets could have formed earlier in the Universe than we might have thought.”

The researchers presented their findings this week at the 241st meeting of the American Astronomical Society (AAS 241) in Seattle, Washington.

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M. Meixner et al. 2023. Early Imaging Results with JWST/NIRCam: Young Star Formation in NGC 346. AAS 241, program number: 444.09

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