{"id":78709,"date":"2026-09-08T08:28:27","date_gmt":"2026-09-08T15:28:27","guid":{"rendered":"https:\/\/in.nau.edu\/news\/?p=78709"},"modified":"2026-09-08T08:28:27","modified_gmt":"2026-09-08T15:28:27","slug":"trans-neptunian-objects","status":"publish","type":"post","link":"https:\/\/in.nau.edu\/news\/trans-neptunian-objects\/","title":{"rendered":"Study finds that far-out solar system objects \u2018remember\u2019 their past"},"content":{"rendered":"

What can distant, tiny objects in space tell us about how our solar system formed? As it turns out, quite a lot.<\/span>\u00a0<\/span><\/p>\n

A pair of new studies, one of which was led by NAU Ph.D. candidate\u00a0<\/span>Anastasia Morgan<\/span><\/b>, examined Trans-Neptunian Objects (TNOs)\u2014some of the most far-flung bodies in the solar system\u2014in an effort to\u00a0better understand how the system formed and how it has evolved. The studies were the first in history to harness the joint power of NASA\u2019s\u00a0<\/span>Hubble<\/span><\/a>\u00a0and\u00a0<\/span>Webb<\/span><\/a>\u00a0telescopes.<\/span>\u00a0<\/span><\/p>\n

Morgan and her colleagues expected to find lots of variation in the TNOs\u2019 colors, shapes and materials, evidence that the objects have been traveling and colliding with each other for eons. What they found instead was\u00a0very little\u00a0variation, suggesting much less movement than they imagined.<\/span>\u00a0<\/span><\/p>\n

\u201cFor these objects to have a lot of the same color and shape, it\u2019s telling us that they have probably sat there and not been very\u00a0collisionally\u00a0active,\u201d Morgan said.\u00a0<\/span>\u201cThe models say they should have been altered by collisions, but that’s just not what we’re seeing.\u201d<\/span>\u00a0<\/span><\/p>\n

Morgan\u2019s study, along with a complementary study led by University of Victoria Ph.D. candidate Marielle Eduardo, was published\u00a0<\/a><\/span>Sept. 8<\/span>\u00a0in The Astronomical Journal.<\/span>\u00a0<\/span><\/p>\n

Crash\u00a0course on TNOs<\/span><\/b>\u00a0<\/span><\/h3>\n

TNOs are typically small, faint, icy bodies orbiting the Sun beyond the orbit of Neptune. Most TNOs are more than 100 million times dimmer than objects visible to the unaided eye. The TNOs Morgan studied are some of the smallest and faintest that have ever been\u00a0directly\u00a0seen; to get an idea of just how small and faint, imagine, she said, standing on Earth and trying to measure a swarm of fireflies on the Moon without magnification.\u202f<\/span>\u00a0<\/span><\/p>\n

Morgan said TNOs offer 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 \u201cplanetesimals,\u201d but had not yet merged into full-sized planets. Beyond Neptune, this second stage never happened, leaving behind a frozen population of planetesimals.<\/span>\u00a0<\/span><\/p>\n

\u201cTNOs hold some of the history of the formation and evolution of the outer solar system,\u201d Morgan said. \u201cThey tell us what was here at the beginning, and more broadly, they give us clues into how other planetary systems are formed.\u201d<\/span>\u202f<\/span>\u00a0<\/span><\/p>\n

In the two coordinated studies, Morgan and Eduardo\u2019s teams studied TNOs in one tiny patch of sky using Hubble, which\u00a0observes\u00a0the objects\u2019 visible light, and Webb, which\u00a0observes\u00a0their infrared light. Using those telescopes, Morgan measured their colors\u2014which are like a fingerprint of the surface composition\u2014and Eduardo measured their size distribution.<\/span>\u00a0<\/span><\/p>\n

Before this study, astronomers thought small TNOs would have undergone many collisions, changing their surfaces.\u00a0But\u00a0that’s\u00a0not what the observations showed. Instead, the small TNOs looked a lot like their larger family members. This implies that collisions are not changing the surfaces significantly\u2014perhaps because there are fewer collisions than expected, or perhaps because the TNOs somehow\u00a0retain\u00a0their primordial, pre-collision compositions. The teams are still trying to unravel this mystery.<\/span>\u00a0<\/span><\/p>\n

\u201cYou 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,\u201d Morgan said. \u201cSo,\u00a0it’s\u00a0really fascinating to see that the smallest objects are somehow \u2018remembering\u2019 and preserving the history of how they were made.\u201d<\/span>\u00a0<\/span><\/p>\n

David Trilling<\/span><\/b>, a co-author of the study and a professor of physics and astronomy at NAU, said even TNOs that had moved to a different orbit since being formed seemed\u00a0relatively unchanged.<\/span>\u00a0<\/span><\/p>\n

\u201cThey retain a signature of where they were born, even though their orbits have been scrambled since then,\u201d Trilling said.<\/span>\u00a0<\/span><\/p>\n

Eduardo found fewer\u00a0very small\u00a0TNOs than the research expected based on\u00a0previous\u00a0planet formation models. The Webb telescope discovered 27 new, remarkably dim TNOs, the smallest among them about 5 to\u00a010 kilometers, or six miles, in diameter which is about five times smaller than what is possible to detect with ground-based telescopes.<\/span>\u00a0<\/span><\/p>\n

Unraveling the universe\u2019s mysteries<\/span><\/b>\u00a0<\/span><\/h3>\n

When it comes to our understanding of the outer solar system, what do these findings mean? Trilling said they could\u00a0demonstrate\u00a0that we\u00a0don\u2019t\u00a0know space as well as we thought.<\/span>\u00a0<\/span><\/p>\n

\u201cWe thought we\u2019d see lots of variation in the color and size of these TNOs, and we didn\u2019t,\u201d Trilling said. \u201cThat means\u00a0there\u2019s\u00a0something\u00a0not quite right\u00a0about our understanding of how the solar system got to where it is now. Is it an evolutionary misunderstanding? Did we not get the\u00a0upheaval\u00a0right? The\u00a0previous\u00a0science\u00a0doesn\u2019t\u00a0seem to capture how we got where we are today.\u201d<\/span>\u00a0<\/span><\/p>\n

This pair of studies could have big implications for future studies on the formation of the solar system, Morgan added.\u202f<\/span>\u00a0<\/span><\/p>\n

\u201cThe models tell us TNOs collided with other bodies a lot, but our observations tell us the history of the outer solar system may have been less collisional,\u201d she said. \u201cWhen the data are inconsistent with the existing models, it means we need to refine and re-test the models. It also means we need to analyze more data, and we will; there\u2019s terabytes and terabytes of it out there.\u201d<\/span>\u00a0<\/span><\/p>\n

\"Northern<\/span><\/p>\n


\nJill Kimball | NAU Communications
\n(928) 523-2282 | jill.kimball@nau.edu<\/a><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

What can distant, tiny objects in space tell us about how our solar system formed? As it turns out, quite a lot.\u00a0 A pair of new studies, one of which was led by NAU Ph.D. candidate\u00a0Anastasia Morgan, examined Trans-Neptunian Objects (TNOs)\u2014some of the most far-flung bodies in the solar system\u2014in an effort to\u00a0better understand how…<\/a><\/p>\n","protected":false},"author":2880,"featured_media":78713,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-78709","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-faculty-staff"],"acf":[],"_links":{"self":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts\/78709","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/users\/2880"}],"replies":[{"embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/comments?post=78709"}],"version-history":[{"count":3,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts\/78709\/revisions"}],"predecessor-version":[{"id":78714,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts\/78709\/revisions\/78714"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/media\/78713"}],"wp:attachment":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/media?parent=78709"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/categories?post=78709"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/tags?post=78709"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}