NASA’s James Webb Space Telescope will be looking for cosmic reservoirs of water as well as other key building blocks of habitable planets, researchers have revealed.
Molecular clouds in space hold most of the water in the universe and scientists have postulated that these clouds serve as nurseries for newborn stars and their planets. Within these clouds, on the surfaces of tiny dust grains, hydrogen atoms link with oxygen to form water. Carbon joins with hydrogen to make methane. Nitrogen bonds with hydrogen to create ammonia. All of these molecules stick to the surface of dust specks, accumulating icy layers over millions of years. The result is a vast collection of “snowflakes” that are swept up by infant planets, delivering materials needed for life as we know it.
“If we can understand the chemical complexity of these ices in the molecular cloud, and how they evolve during the formation of a star and its planets, then we can assess whether the building blocks of life should exist in every star system,” said Melissa McClure of the Universiteit van Amsterdam, the principal investigator on a research project to investigate cosmic ices.
In order to understand these processes, one of Webb’s Director’s Discretionary Early Release Science projects will examine a nearby star-forming region to determine which ices are present where.
“We plan to use a variety of Webb’s instrument modes and capabilities, not only to investigate this one region, but also to learn how best to study cosmic ices with Webb,” said Klaus Pontoppidan of the Space Telescope Science Institute (STScI), an investigator on McClure’s project.
This project will take advantage of Webb’s high-resolution spectrographs to get the most sensitive and precise observations at wavelengths that specifically measure ices. Webb’s spectrographs, NIRSpec and MIRI, will provide up to five times better precision that any previous space telescope at near- and mid-infrared wavelengths.
The team will use Webb’s sensitive infrared detectors to observe stars behind the molecular cloud. As light from those faint, background stars passes through the cloud, ices in the cloud will absorb some of the light. By observing many background stars spread across the sky, astronomers can map ices within the cloud’s entire expanse and locate where different ices form. They will also target individual protostars within the cloud itself to learn how ultraviolet light from these nascent stars promotes the creation of more complex molecules.
Astronomers also will examine the birthplaces of planets, rotating disks of gas and dust known as protoplanetary disks that surround newly formed stars. They will be able to measure the amounts and relative abundances of ices as close as 5 billion miles from the infant star, which is about the orbital distance of Pluto in our solar system.
In order to understand Webb’s observations, scientists will need to conduct experiments on Earth. Webb’s spectrographs will spread incoming infrared light into a rainbow spectrum. Different molecules absorb light at certain wavelengths, or colors, resulting in dark spectral lines. Laboratories can measure a variety of substances to create a database of molecular “fingerprints.”
When astronomers see those fingerprints in a spectrum from Webb, they can then identify the molecule or family of molecules that created the absorption lines.