High-mass stars, which are eight or more times the mass of our Sun, live hard and die young. They often end their short lives in violent explosions called supernovas, but their births are much more of a mystery. They form in very dense, cold clouds of gas and dust, but little is known about these regions. In 2021, shortly after the launch of NASA’s James Webb Space Telescope, scientists plan to study three of these clouds to understand their structure.
These cold clouds—which can have up to 100,000 times the mass of the Sun—are so dense that they appear as big, dark blobs on the sky. While they seem devoid of stars, the clouds are actually just obscuring the light from background stars. These dark patches are so thick with dust that they even block out some wavelengths of infrared light, a type of light that is invisible to human eyes and can usually can penetrate through dusty clouds. That’s why they are called “infrared-dark clouds.” However, the unprecedented sensitivity of Webb enables observations of background stars even through these very dense regions.
To understand how massive stars form, you have to understand the environment in which they form. But one of the things that makes studying massive star formation so difficult is that as soon as a star turns on, it radiates intense ultraviolet light and strong and powerful winds.
Battersby likens the process to baking cookies: As soon as you bake them, they’re totally different than the dough itself. If you’ve never seen dough before, you may not have a good idea of what that baking process would look like. The infrared-dark clouds are like the raw dough before you bake it. Studying these clouds is akin to getting a chance to look at the cookie dough, seeing what goes into it, and learning what its consistency is.
Understanding massive stars and their environments is important for a variety of reasons. First, in their explosive deaths, they release many elements that are essential for life. Elements heavier than hydrogen and helium—including the building blocks of life on Earth—come from inside massive stars. Massive stars have transformed a universe that was almost completely composed of hydrogen to the rich, complex environment that is able to produce planets and people.
Massive stars also produce enormous amounts of energy. As soon as they are born, they give off light, radiation and winds that can create bubbles in the interstellar medium, possibly sparking star formation in different locations. These expanding bubbles could also break up a region where new stars are forming. Finally, when a massive star dies in a spectacular explosion, it forever changes its surroundings.
Source: “Piercing the Dark Birthplaces of Massive Stars with Webb” NASA, 10 April 2020.<https://www.nasa.gov/feature/goddard/2020/piercing-the-dark-birthplaces-of-massive-stars-with-webb>