For many years, scientists have been trying to figure out why stars are forming at an unusually fast rate in the Phoenix galaxy cluster. This cluster, located 5.8 billion light-years away from Earth, is an extraordinary and puzzling part of the universe. However, thanks to NASA’s James Webb Space Telescope, scientists now have the missing piece of the puzzle. This discovery builds on over a decade of research using NASA’s Chandra X-ray Observatory, Hubble Space Telescope, and several powerful ground-based observatories.

The mystery of the phoenix cluster

A galaxy cluster is a large group of galaxies that are held together by gravity. Most of these clusters have a supermassive black hole at the center. Normally, this black hole stops the gas in the cluster from cooling down enough to form stars because it releases a lot of energy and radiation. But the Phoenix cluster is different. Even though it has a supermassive black hole that is 10 billion times heavier than our Sun, it is still creating stars at an unusually fast rate. Scientists have been trying to figure out why this is happening.

“We can compare our previous studies of the Phoenix cluster, which found differing cooling rates at different temperatures, to a ski slope," explained Michael McDonald from the Massachusetts Institute of Technology (MIT). He is the principal investigator of the study. "The Phoenix cluster has the largest reservoir of hot, cooling gas of any galaxy cluster—analogous to having the busiest chair lift, bringing the most skiers to the top of the mountain. However, not all of those skiers were making it down the mountain, meaning not all the gas was cooling to low temperatures. If you had a ski slope where there were significantly more people getting off the ski lift at the top than were arriving at the bottom, that would be a problem!"

For a long time, scientists were unsure about what was happening. They suspected there was some missing gas playing a key role in the process, but they couldn’t see it. That is, until now.

Webb telescope unlocks the puzzle

Thanks to NASA's James Webb Space Telescope, scientists have found the missing piece of the puzzle. The Webb Telescope helped them find a special type of gas that exists between two extreme temperatures. One is super-hot gas at 18 million degrees Fahrenheit, and the other is cooler gas at 18,000 degrees Fahrenheit. The gas they discovered is warm, about 540,000 degrees Fahrenheit. This warm gas helps explain why stars are forming so quickly in the Phoenix cluster.

To study this, scientists used Webb’s Mid-Infrared Instrument (MIRI), which allowed them to capture detailed two-dimensional spectroscopic data from the core of the Phoenix cluster. “Previous studies only measured gas at the extreme cold and hot ends of the temperature distribution throughout the centre of the cluster. We were limited—it was not possible to detect the ‘warm’ gas that we were looking for. With Webb, we could do this for the first time,” McDonald explained.

This discovery of the warm gas happened because of both Webb’s advanced instruments and nature’s help. The scientists were able to find two different types of atoms—neon and oxygen. These atoms form under similar conditions but act differently in different types of light. Oxygen usually gives off light in ultraviolet, which is hard to detect. But neon gives off light in infrared, which is much easier for Webb’s instruments to pick up.

“In the mid-infrared wavelengths detected by Webb, the neon VI signature was absolutely booming. Even though this emission is usually more difficult to detect, Webb’s sensitivity in the mid-infrared cuts through all of the noise," said Michael Reefe, also from MIT and the lead author of the paper published in Nature.

What does this mean for studying other galaxy clusters?

Now that scientists have solved the mystery of the Phoenix cluster, they are excited about the possibility of using the same techniques to study other galaxy clusters. While Phoenix is an extreme case, this breakthrough could provide valuable insights into how stars form in other parts of the universe.

This discovery is a big step toward understanding the complex processes behind star formation. Scientists hope to apply this method to other galaxy clusters, which could provide answers to some of the biggest questions in astronomy.

The importance of the James Webb Space Telescope

The James Webb Space Telescope is the most advanced space telescope ever built. It helps scientists study things like our solar system, distant planets, and even the beginnings of the universe. Webb is a project led by NASA, with support from the European Space Agency (ESA) and the Canadian Space Agency (CSA).

The Webb Telescope’s ability to find the warm gas in the Phoenix cluster is just one example of how it is changing the way we understand space. Thanks to Webb, scientists now have the tools to explore the universe’s biggest mysteries. The discovery in the Phoenix cluster shows how Webb is helping to solve long-standing questions about the cosmos.

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