Recent observations of ice molecules by the James Webb Space Telescope will help scientists understand how habitable planets form.
Using the James Webb Space Telescope (JWST), astronomers have observed and measured the coldest-ever ice in the deepest parts of an interstellar molecular cloud. According to new research published in the journal Nature Astronomy, the frozen molecules have a temperature of minus 263 degrees Celsius.
Molecular clouds, made up of frozen molecules, gases and dust particles, are where stars and planets are born – including habitable planets like ours. In this latest study, the team of scientists used JWST’s infrared camera to study a molecular cloud called Chameleon I, about 500 light-years from Earth.
In the dark, cold cloud, the team identified frozen molecules such as carbonyl sulfur, ammonia, methane, methanol, and more. According to the researchers, these molecules will one day be part of the hot core of a growing star and possibly part of future exoplanets. They also contain the building blocks of habitable worlds: carbon, oxygen, hydrogen, nitrogen and sulfur – a molecular cocktail known as COHNS.
“The results give us insight into the initial, dark chemical stage of ice formation on the grains of interstellar dust that will become the centimeter-sized pebbles from which planets are formed,” lead study author Melissa McClure, an astronomer, said in a statement. at the observatory in Leiden, the Netherlands.
A dusty nursery
Stars and planets form in molecular clouds like Chameleon I. Over millions of years, gas, ice, and dust form into more massive structures. Some of these structures heat up and form as the cores of young stars. As stars grow, they absorb more and more material and become hotter. After the star forms, the remnants of gas and dust around it form a disk. This matter begins to collide again, clumping together and eventually forming larger bodies. One day these clusters may become planets. Even habitable ones like ours.
“These observations open a new window into the pathways for the formation of simple and complex molecules that are necessary to create the building blocks of life,” McClure said in a statement.
Inventory of ice molecules found deep in the Chameleon I molecular cloud
An inventory of ice molecules found deep in the Chameleon I molecular cloud. Graphs show spectral data from three of the instruments on the James Webb Space Telescope. In addition to simple ices such as water, the scientific team was able to identify frozen forms of a wide range of molecules, from carbon dioxide, ammonia and methane to the simplest complex organic molecule, methanol.
In addition to the molecules identified, the team found evidence for molecules more complex than methanol (listed in the bottom panel). Although they haven’t definitively pinpointed these signals to specific molecules, it proves for the first time that complex molecules form in the icy depths of molecular clouds before stars are born.
The top three panels show the brightness of the background star as a function of wavelength. The lower brightness indicates absorption by ice and other materials in the molecular cloud. The bottom panel shows the optical depth, which is essentially a logarithmic measure of how much light from the background star is absorbed by the cloud ices. It is used to emphasize the weaker spectral features of the less common varieties of ice. [Credit: NASA, ESA, CSA, and J. Olmsted (STScI), K. Pontoppidan (STScI), N. Crouzet (Leiden University), and Z. Smith (Open University)]
JWST will send its first pictures in July 2022, and scientists are currently using the $10 billion telescope’s instruments to demonstrate what kinds of measurements are possible. To identify the molecules in Chameleon I, the researchers used light from stars beyond the molecular cloud. When light is directed towards us, it is characteristically absorbed by the dust and molecules in the cloud. These absorption patterns can be compared to known patterns established under laboratory conditions.
The team also found more complex molecules that they could not specifically identify. But the discovery proves that complex molecules do form in molecular clouds before they are absorbed by growing stars.
“The identification of complex organic molecules, such as methanol and potentially ethanol, also suggests that many star and planetary systems developing in this particular cloud will inherit molecules in a fairly advanced chemical state,” study co-author Will Rocha noted in the statement. astronomer at the Leiden Observatory.
While the team found COHNS in the cold molecular soup, it did not find as high a concentration of the molecules as might be expected in a dense cloud like Chameleon I. How a habitable world like ours got the icy COHNS is still a major question among astronomers. One theory is that COHNS were delivered to Earth by collisions with icy comets and asteroids.
“This is just the first of a series of spectral pictures we will get to see how ice particles evolve from their initial synthesis to the comet-forming regions of protoplanetary disks,” McClure said. “This will tell us which mixture of icy particles—and therefore which elements—may eventually be delivered to the surface of terrestrial exoplanets or incorporated into the atmospheres of giant gas or ice planets.”
Reference: McClure, M.K., Rocha, W.R.M., Pontoppidan, K.M. et al. An Ice Age JWST inventory of dense molecular cloud ices. Nat Astron (2023). https://doi.org/10.1038/s41550-022-01875-w
Source: The James Webb Telescope detected the coldest ice in the known universe – and it contains the building blocks of life, Live Science
Photo: In this image from the James Webb Space Telescope, a bluish cloud of molecular gas shimmers in the light of distant stars Credit: NASA, ESA, CSA and M. Zamani (ESA/Webb)