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Stars are born all across the universe. This process is often hidden behind thick clouds of gas and dust. The James Webb Space Telescope (JWST) is built to see through that dust. It looks at infrared light, which can pass through the cosmic dust that blocks other kinds of light.
A team led by University of Florida student Taehwa Yoo used JWST to study a huge star-forming region in our galaxy. This region is called Westerhout 51, or W51. It is about 17,000 light-years away from Earth. The telescope showed many new details of the star-making activity happening there. Adam Ginsburg, a professor of astronomy at the University of Florida, explained, “With older telescopes, we can’t see through the dust to see the young stars. Now we can.”
Even JWST cannot see through the very densest clouds. The team compared JWST’s pictures to older ones from another powerful telescope called ALMA. They found that each telescope saw different parts of the star-forming process. However, what JWST could see was full of new detail. Yoo said, "Because of James Webb, we can see those hidden, young massive stars forming. By looking at them, we can study how they form."
The W51 region is divided into several areas where stars are forming. JWST focused on a part called W51A. It is the youngest star-forming area in the region. The telescope found clouds of hot, ionized gas and warm dust. Some of this dust is shaped into long, thin filaments. The science team saw a clear cavity, or empty space, around one of the newborn stars. This suggests the star is "eating away" at the material around it. They also saw giant gas bubbles, dark dust filaments, and jets of gas shooting away from baby stars.
The team looked closely at two massive groups of baby stars, called W51-E and W51-IRS2. They used two of JWST’s main cameras. Most of the stars they saw are still growing. They pull in more material and have not yet reached their final size. Some of these stars are very young. They may have formed only in the last million years.
Yoo's group estimates that the stars in W51A have a combined mass equal to about 10,000 stars like our Sun. Many are young and very massive. Astronomers do not know a lot about their earliest stages of life. In some spots, these young stars are still hidden by thick clouds. Luckily, the ALMA telescope has already found over 200 compact spots in W51A. These spots are called "Pre/Protostellar Objects" or PPOs. Stars are actively forming or will soon start to form there.
Astronomers understand the basic steps of star birth. First, a large cloud of gas and dust slowly comes together under gravity. It forms a hot, dense core. This core is where the future star will be. After pulling in more material for a long time, the core gets hot and dense enough for nuclear fusion to start. In this process, hydrogen atoms in the star's center fuse into helium. This releases huge amounts of energy. This moment marks the official birth of the star. Before that, the baby star often blows material away in a powerful jet.
High-mass stars born this way affect everything around them. They interact with nearby gas clouds. This can change how other stars form in the same region. The strong radiation from these massive stars can even tear apart the gas clouds. This can stop new stars from forming by removing the material they need. From the JWST images, it is clear that all of these steps are happening right now in W51A.
In a recent paper, Yoo’s team wrote that W51A contains several hot cores linked to massive baby stars. These areas are rich in complex chemistry. They are likely the source of something called maser emissions. Masers are like lasers, but they come from specific molecules in space. In W51A, masers come from molecules like hydroxide, methanol, and ammonia. These masers act as tracers. They point to the dense molecular clouds where stars are expected to form.
Besides these early-stage hot cores, the team also saw at least one bright "knot" of light from a baby star. This light comes from ionized iron and hydrogen within the cloud. They think it is caused by a jet shooting out from a hot young star. The jet heats up and changes the nearby space, called the interstellar medium.
This new study of W51 with JWST gives astronomers a much clearer picture of the different stages of star birth. These are stages normally hidden from view. The quality of the JWST data revealed more information and new structures. This helps astronomers explain star formation more fully. “They are not the first photos of this region, but they are the best,” said Ginsburg. “They’re so much better that they are essentially brand new photos. Every time we look, we learn something new.”