NASA’s Hubble, Webb Find Far-out Solar System Objects ‘Remember’ Past - UNIVERSE

 

This artist’s concept depicts a Trans-Neptunian Object, a small, faint, icy body orbiting the Sun beyond the orbit of Neptune. These objects are so small that even with NASA’s Hubble and Webb space telescopes, they appear only as tiny points of light.

Artwork: NASA, ESA, Leah Hustak (STScI)

For the first time, scientists used the joint power of NASA’s Hubble and James Webb Space Telescopes to study some of the most far-flung bodies in our solar system, Trans-Neptunian Objects (TNOs). Some of these are the smallest and faintest ever directly seen. The researchers unexpectedly found fewer small TNOs than they expected, and that the colors of these bodies followed the same relationships as their larger family members.

These objects are typically small, faint, icy bodies orbiting the Sun beyond the orbit of Neptune. Most are more than 100 million times dimmer than objects visible to the unaided eye. In two complementary papers published Tuesday in The Astronomical Journal, teams analyzed the color, composition, and size distribution of 27 newly discovered tiny, dim TNOs. 

This class of small bodies offers the best view into an early stage of planet-building, when a disk of dust and pebbles in orbit around the Sun coalesced into city-sized “planetesimals” — the solid building blocks that clump together to form planets — but had not yet merged into full-sized worlds.  Beyond Neptune, this second stage never happened, leaving behind a frozen population of planetesimals.

In the deepest TNO survey to date, teams led by PhD candidates from the University of Victoria in Canada, under the guidance of the National Research Council of Canada, and Northern Arizona University in Flagstaff examined a patch of sky simultaneously with Hubble, observing the TNOs’ visible light, and Webb, observing their infrared light. The team of researchers measured the objects' colors, which are like a fingerprint of the surface composition, as well as their sizes and determined their orbits. 

In the coordinated observations, the teams studied two different types of TNOs. The first, dynamically “cold” TNOs, are on their original, relatively circular orbits around the Sun in the plane of the solar system. The second type, dynamically “hot” TNOs, formed between the current locations of Uranus and Neptune but were pushed outward where they are today when the outer gas giants migrated early in the solar system’s history. Today they reside in highly elliptical orbits and move in and out of the plane of our solar system.

NASA's Goddard Space Flight Center; Lead Producer: Paul Morris

Prior to these observations, astronomers thought that small TNOs from both hot and cold populations would have undergone many collisions, changing their surfaces compared to larger TNOs. But that's not what the observations showed. Instead, the small bodies look like their larger counterparts. This implies that collisions are not changing the surfaces significantly—perhaps because there are fewer collisions than expected, or because the TNOs somehow retain their primordial, pre-collision compositions. The teams are still trying to unravel this mystery.

“You could imagine a scenario where getting knocked around and fragmented would change the surface composition, and then you would see a different surface color for tiny TNOs compared to their larger siblings. So it's really fascinating to see that the smallest objects are somehow 'remembering' and preserving the history of how they were made,” said Northern Arizona University PhD candidate Anastasia Morgan, who led the study of color and composition. 

“These dynamically ‘hot’ TNOs retain a signature of where they were born, even though they’ve been orbitally scrambled since then,” said co-author David Trilling of Northern Arizona University.

Both the “hot” and “cold” populations seem to keep the same colors as when they were formed, with little change since the birth of the solar system. 

The Webb data also allowed researchers to measure the number of objects of each size. They found that the overall size distributions for both populations were surprisingly similar.

“It's very interesting that the process of planetesimal formation ends up producing the same distribution of sizes for both cold and hot populations, despite forming in different regions of the early solar system. The process seems to be insensitive to disk conditions, producing similar planetesimal sizes whether the disk is hot or cold, and dense or fluffy,” said University of Victoria PhD candidate Marielle Eduardo, who led the study on size distribution. 

Researchers also found fewer of these very small bodies than they expected based on some planet formation models. Webb discovered 27 new, remarkably dim TNOs, one so faint it is equivalent to standing on Earth and seeing a small swarm of fireflies on the Moon. The smallest one they observed has a diameter of about 3 miles (5 kilometers), which is about five times smaller than what is possible to detect with the most sensitive ground-based telescopes.

This project would not have been possible without Hubble and Webb working together to detect and characterize these TNOs. With Hubble’s sensitivity in visible light and Webb’s in infrared, the space telescopes provide more insights than either can on its own.

The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.

Source: NASA’s Hubble, Webb Find Far-out Solar System Objects ‘Remember’ Past - NASA Science

One Species, Many Lives: How Evolution Splits Gut Bacteria Into Hidden Populations

Your gut isn’t home to a few hundred bacterial species living peacefully side by side, it’s more like a sprawling city where, within a single species, different “neighborhoods” of bacteria have quietly evolved to specialize in very different lifestyles. A new study led by researchers at the University of Vienna and published in Nature shows that many familiar gut bacterial species are actually made up of several genetically distinct populations, each adapted to different conditions inside the human body, and some of these hidden populations show up more often in older age, inflammatory bowel disease, colorectal cancer, and type 2 diabetes.

The Problem With Counting Species

Microbiome research usually sorts bacteria into species or broad genetic clusters. That’s convenient, but it can blur the picture: a species linked to a disease in one study might be harmless or even protective in another. The reason may be that we’ve been lumping together bacteria that look similar on paper but have actually gone their separate evolutionary ways inside the gut.

To get a sharper view, the team used a bioinformatic approach rooted in “reverse ecology”, inferring how organisms have adapted to their environment by reading the genetic traces left behind, rather than observing them directly. They combed through thousands of bacterial isolates from the human gut plus large-scale metagenomic data spanning multiple countries, ages, and health states.

Selective Sweeps: Evolution’s Fingerprints

What they were hunting for were signs of genome-wide selective sweeps, events where one bacterium picks up a beneficial mutation and, over time, out-competes and displaces its close relatives. A sweep like this narrows genetic diversity in the short term, but it also leaves behind a population that’s unusually uniform, both in ancestry and in function, and therefore easy to spot as a distinct cluster in genomic data.

Applying this lens to the data, the researchers found that many well-known gut bacterial species actually split into several such lineages, each apparently thriving under different conditions. As lead author Xiaoqian Annie Yu (Centre for Microbiology and Environmental Systems Science, University of Vienna) put it, accounting for evolutionary adaptation, rather than just counting species, reveals the biologically meaningful units in the microbiome far more precisely. Some of these sub-populations turn out to be disproportionately common in specific diseases, a pattern that gets washed out when a species is treated as one single entity.

Gut Bacteria Can Go Global, Fast

Perhaps the most striking finding: some of these highly successful bacterial populations spread across continents within just a few decades. That kind of rapid, global dispersal has mostly been documented in pathogens before, seeing it in ordinary gut commensals suggests person-to-person transmission may shape the microbiome as much as diet, medication, or lifestyle do. As study leader Martin F. Polz notes, well-adapted strains appear able to travel internationally and colonize new ecological niches, making the gut microbiome considerably more dynamic than previously assumed.

Why It Matters

If disease risk tracks with specific evolutionary populations rather than entire species, future diagnostics could get much more precise, flagging the exact bacterial lineage that matters instead of an entire, mixed-bag species. Longer term, this could open the door to therapies that selectively boost beneficial populations or suppress problematic ones, rather than broadly targeting a species that includes both. The next step for the team is figuring out which genes actually distinguish these populations, and what those genes do.

·         Many gut bacterial species contain several evolutionarily distinct sub-populations, not just one uniform group.

·         Some of these populations are linked to ageing, colorectal cancer, inflammatory bowel disease, and type 2 diabetes.

·         Successful lineages can spread worldwide within a matter of decades, a pattern once thought unique to pathogens.

·         The approach could sharpen future microbiome diagnostics and enable more targeted therapies.

Original publication: Xiaoqian et al. (2026), “Genome-wide sweeps create ecological units in the human gut microbiome,” Nature. DOI: 10.1038/s41586-026-10476-w 

Source: One Species, Many Lives: How Evolution Splits Gut Bacteria Into Hidden Populations