NASA Webb Finds Early-Universe Analog’s Surprising Expertise for Making Dust

Newswise — Using NASA’s James Webb Space Telescope, astronomers have noticed two uncommon sorts of mud within the dwarf galaxy Sextans A, one of the vital chemically primitive galaxies close to the Milky Way. The discovering of metallic iron mud and silicon carbide (SiC) produced by ageing stars, together with tiny clumps of carbon-based molecules, exhibits that even when the universe had solely a fraction of in the present day’s heavy components, stars and the interstellar medium might nonetheless forge strong mud grains. This analysis with Webb is reshaping concepts about how early galaxies advanced and developed the constructing blocks for planets, as NASA explores the secrets and techniques of the universe and our place in it.

Sextans A lies about 4 million light-years away and incorporates solely 3 to 7 p.c of the Sun’s metallic content material, or metallicity, the astrophysical time period for components heavier than hydrogen and helium. Because the galaxy is so small, in contrast to different close by galaxies, its gravitational pull is just too weak to retain the heavy components like iron and oxygen created by supernovae and ageing stars.

Galaxies prefer it resemble those who crammed the early universe simply after the large bang, when the universe was made from largely hydrogen and helium, earlier than stars had time to counterpoint house with ‘metals.’ Because it’s comparatively shut, Sextans A provides astronomers a uncommon probability to check particular person stars and interstellar clouds below circumstances just like these shortly after the large bang.

“Sextans A is giving us a blueprint for the first dusty galaxies,” mentioned Elizabeth Tarantino, postdoctoral researcher on the Space Telescope Science Institute and lead creator of the ends in one of many two research introduced at a press convention on the 247th assembly of the American Astronomical Society in Phoenix. “These results help us interpret the most distant galaxies imaged by Webb and understand what the universe was building with its earliest ingredients.”

Forging mud with out common elements

One of these research, published in the Astrophysical Journal, honed in on a half a dozen stars with the low-resolution spectrometer aboard Webb’s MIRI (Mid-Infrared Instrument). The knowledge collected exhibits the chemical fingerprints of the bloated stars very late of their evolution, referred to as asymptotic large department (AGB) stars. Stars with plenty between one and eight occasions that of the Sun go via this section.

“One of these stars is on the high-mass end of the AGB range, and stars like this usually produce silicate dust. However, at such low metallicity, we expect these stars to be nearly dust-free,” mentioned Martha Boyer, affiliate astronomer on the Space Telescope Science Institute and lead creator in that second companion research. “Instead, Webb revealed a star forging dust grains made almost entirely of iron. This is something we’ve never seen in stars that are analogs of stars in the early universe.”

Silicates, the same old mud shaped by oxygen-rich stars, require components like silicon and magnesium which are nearly nonexistent in Sextans A. It could be like attempting to bake cookies in a kitchen with out flour, sugar, and butter. 

A traditional cosmic kitchen, just like the Milky Way, has these essential elements within the type of silicon, carbon, and iron. In a primitive kitchen, like Sextans A, the place nearly all of these elements are lacking, you barely have any proverbial flour or sugar. Therefore, astronomers anticipated that with out these key elements, stars in Sextans A couldn’t “bake” a lot mud in any respect. 

However, not solely did they discover mud, however Webb confirmed that one in all these stars used a completely totally different recipe than common to make that mud. 

The iron-only mud, in addition to silicon carbide produced by the much less huge AGB stars regardless of the galaxy’s low silicon abundance, proves that advanced stars can nonetheless construct strong materials even when the standard elements are lacking. 

“Dust in the early universe may have looked very different from the silicate grains we see today,” Boyer mentioned. “These iron grains absorb light efficiently but leave no sharp spectral fingerprints and can contribute to the large dust reservoirs seen in far-away galaxies detected by Webb.”

Tiny clumps of natural molecules

In the companion study, presently below peer evaluation, Webb imaged Sextans A’s interstellar medium and found polycyclic fragrant hydrocarbons (PAHs), that are advanced, carbon-based molecules and the smallest mud grains that glow in infrared mild. The discovery means Sextans A is now the lowest-metallicity galaxy ever discovered to comprise PAHs.

But, in contrast to the broad, sweeping PAH emission seen in metal-rich galaxies, Webb revealed PAHs in tiny, dense pockets just a few light-years throughout.

“Webb shows that PAHs can form and survive even in the most metal-starved galaxies, but only in small, protected islands of dense gas,” mentioned Tarantino. 

The clumps possible signify areas the place mud shielding and fuel density attain simply excessive sufficient to permit PAHs to kind and develop, fixing a decades-long thriller about why PAHs appear to fade in metal-poor galaxies.

The crew has an approved Webb Cycle 4 program to make use of high-resolution spectroscopy to check the detailed chemistry of Sextans A’s PAH clumps additional. 

Connecting two discoveries

Together, the outcomes present that the early universe had extra numerous mud manufacturing pathways than the extra established and confirmed strategies, like supernova explosions. Additionally, researchers now know there’s extra mud than predicted at extraordinarily low metallicities. 

“Every discovery in Sextans A reminds us that the early universe was more inventive than we imagined,” mentioned Boyer. “Clearly stars found a way to make the building blocks of planets long before galaxies like our own existed.”

The James Webb Space Telescope is the world’s premier house science observatory. Webb is fixing mysteries in our photo voltaic system, trying past to distant worlds round different stars, and probing the mysterious constructions and origins of our universe and our place in it. Webb is a global program led by NASA with its companions, ESA (European Space Agency) and CSA (Canadian Space Agency).

For extra info and high-resolution photos, please go to https://science.nasa.gov/missions/webb/nasa-webb-finds-early-universe-analogs-unexpected-talent-for-making-dust.

Media Contacts:
Hannah Braun
Space Telescope Science Institute, Baltimore, Md.
[email protected]