A new snapshot of a busy star cluster from the Hubble Space Telescope proves the legendary observatory’s still got it, even in the golden age of the James Webb Space Telescope.
The image shows the most detailed view of NGC 346 yet, a stellar nursery within the Small Magellanic Cloud, a dwarf galaxy that orbits the Milky Way some 210,000 light-years away in the constellation Tucana. Though the cluster has been observed in the past, this is the first time data from all three light wavelengths — infrared, visible, and ultraviolet — have been combined in one picture. The result is a spectacular portrait of how stars form and influence their surroundings in space.
But this glowing cradle of newborn stars also gives astronomers clues about what our universe may have looked like when it was a young whippersnapper.
“The Small Magellanic Cloud is less rich in elements heavier than helium,” according to the European Space Agency, which owns and operates Hubble with NASA. “This makes conditions in the galaxy similar to what existed in the early universe.”
The Hubble Space Telescope, a partnership of NASA and the European Space Agency, studies the universe in mostly visible light from low-Earth orbit.
Credit: NASA
The cluster, full of more than 2,500 newborn stars that blaze blue in the Hubble image, is in a galaxy with far fewer heavy chemical substances than the Milky Way. It’s mostly made of hydrogen and helium. Because of this, scientists have used it as a case study for what star formation might have looked like billions of years ago.
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The cores of stars are considered element factories: They make carbon, for instance, the same chemical on which humans and much of life on Earth are based. Then, through supernova explosions, they spread these heavier elements, like calcium found in bones and iron in blood, across interstellar space. This dispersal seeds new generations of stars and planets.
Given that most of the chemicals in the universe are thought to have come from exploded stars, scientists have rationalized that the firstborn must have been composed almost entirely of hydrogen and helium, the primitive material that emerged from the Big Bang. Over time, as stars died and scattered heavier elements, subsequent generations of stars formed with more diverse and complex ingredients.
Surrounding the cluster in the Hubble image is a glowing pink cloud called a nebula, where hot, young stars give off ultraviolet light that illuminates the surrounding hydrogen gas. These bright areas are short-lived — only shining as long as the gigundo stars that power them. Astronomers say the big stars only last a few million years, a mere blip in the 13.8 billion years of the universe.
Snakelike dark clouds of thick dust are what’s left of the original star-making material that hasn’t been pushed away yet by growing stars. The massive stars, many times larger than the sun, are able to do this with intense radiation and powerful stellar winds — streams of charged particles — that clear empty bubbles of space.
Scientists recently used Webb, Hubble’s powerful infrared counterpart, to survey 10 stars in the same cluster. They discovered that, even at the stars’ relatively old ages, they still maintained substantial disks, the clouds of gas and dust surrounding them that can eventually coalesce to form baby worlds.
Previous thinking was that these primitive stars would have lost their lightweight disks pretty quickly, said study leader Guido De Marchi, after just two or three million years.
“This also implies that planets have more time to form and grow around these stars,” De Marchi said.
