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Image of the NGC 346 Nebula taken by Webb.
New images taken by the Webb telescope reveal how stars formed during "cosmic noon" more than 10 billion years ago.
The Small Magellanic Cloud, about 200,000 light-years from Earth, is a satellite galaxy of the Milky Way and one of its closest neighbors, known for its lack of metallic elements heavier than hydrogen and helium. In astronomy, heavier elements than hydrogen and helium are called metallic elements.)
The levels of metallic elements in the Small Magellanic Cloud reflect its unique environment, similar to the early universe, and can therefore be used to study what galaxies looked like in the early universe, when the universe was just about two or three billion years old and at the peak of star formation. Although various telescope missions have studied the Small Magellanic Cloud in the past, much remains to be learned.
Now, with Webb's high-resolution imaging, astronomers have discovered more than 33,000 young stars embedded in the NGC 346 nebula, the brightest and largest star-forming region in the Small Magellanic Cloud.
At the 241st American Astronomical Society meeting in Seattle, Jan. 11, Meixner shared early imaging results using the Webb telescope to photograph NGC 346.
"Gas and dust belts"
Cosmic dust is produced when stars and planets form, and when their formation stops, the dust hovers in the interstellar medium. As a derivative of the process of star and planet formation, dust has a heavy metal composition similar to that of stars and planets. Until now, astronomers thought heavy elements such as carbon, oxygen and iron were necessary to form the dust that terrestrial planets eventually achieved, all of which were present in relatively low concentrations in the Small Magellanic Cloud.
So when astronomers used Webb's powerful Near-Infrared Camera (NIRCam) instrument to study NGC 347, they were surprised to find "gas and dust belts" in the interstellar medium. The discovery is early evidence that NGC 347 is "dusty" despite its low metal content and has the raw materials needed to form rocky planetary systems.
Using Webb's six NIRCam filters, the team found more than 33,000 sources they called "infrared ultrasound." In low-mass stars, dust in the surrounding disk of debris absorbs starlight and re-emits it at infrared wavelengths. So when astronomers detect infrared radiation, it usually means they've detected dust.
"We are happy to see the dust around these celestial bodies," Meixner told reporters at a news conference.
NGC 346 has been studied by telescope missions in the past, but this is the first time astronomers have imaged dust. For example, the now-retired Spitzer telescope found 87 massive young stars in the same region, but it wasn't powerful enough to identify smaller stars. The Hubble Space Telescope also found thousands of pre-main-sequence stars scattered throughout the nebula and connected to each other by filaments of gas and dust. However, many of these stars remain undiscovered because Hubble is insensitive to dust around such stars.
Now, Webb is helping astronomers uncover these dust-encased stars, and the Webb telescope can detect young stars 10 magnitudes lower than Spitzer and pre-main sequence stars 2 magnitude lower than Hubble. Searching for star-forming regions in infrared wavelengths allows astronomers to spot many stars that are invisible or misidentified at optical wavelengths.
In the coming months, astronomers hope to find out if the process of star formation in the Small Magellanic Cloud is similar to what we observe from our own galaxy. They also plan to continue observing the region's primordial stars. These stars become larger and richer by absorbing the dust around them, so it remains to be seen how much of the dust that has been discovered by Webb can survive the formation of the star, and whether the dust left will eventually be enough to form rocky planets.
The Webb telescope has already unveiled a large number of young new stars, and astronomers say this is just the beginning.
"We're just scratching the surface of the data now, and we're going to roll back the data to almost the limit of brown dwarfs and see what we can find." Meixner said.
Article Source:
https://www.space.com/james-webb-space-telescope-dusty-ribbons-young-stars-neighbor-galaxy
Astronomical cake
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