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Spirals in Dust Around Young Stars May Betray Presence of Massive Planets
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By NASA
NASA/JPL-Caltech This Oct. 4, 2017, illustration shows a hypothetical uneven ring of dust orbiting KIC 8462852, also known as Boyajian’s Star or Tabby’s Star. The star has experienced unusual dips in brightness over a matter of days, as well as much subtler but longer-term dimming trends. Scientists proposed several explanations for this unexpected behavior, ranging from Tabby’s Star swallowing a planet to alien “megastructures” harvesting the star’s energy. However, a study using NASA’s Spitzer and Swift missions as well as the Belgian AstroLAB IRIS observatory suggests that the cause of the dimming over long periods is likely an uneven dust cloud moving around the star.
Learn more about this enigmatic star, named after Tabetha Boyajian, the Yale University postdoc who discovered it with the help of citizen scientists.
Image credit: NASA/JPL-Caltech
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By NASA
Hubble Space Telescope Home NASA’s Hubble Finds… Hubble Space Telescope Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts News Hubble News Hubble News Archive Social Media Media Resources Multimedia Multimedia Images Videos Sonifications Podcasts E-books Lithographs Fact Sheets Glossary Posters Hubble on the NASA App More Online Activities 5 Min Read NASA’s Hubble Finds Sizzling Details About Young Star FU Orionis
An artist’s concept of the early stages of the young star FU Orionis (FU Ori) outburst, surrounded by a disk of material. Credits:
NASA-JPL, Caltech In 1936, astronomers saw a puzzling event in the constellation Orion: the young star FU Orionis (FU Ori) became a hundred times brighter in a matter of months. At its peak, FU Ori was intrinsically 100 times brighter than our Sun. Unlike an exploding star though, it has declined in luminosity only languidly since then.
Now, a team of astronomers has wielded NASA’s Hubble Space Telescope‘s ultraviolet capabilities to learn more about the interaction between FU Ori’s stellar surface and the accretion disk that has been dumping gas onto the growing star for nearly 90 years. They find that the inner disk touching the star is extraordinarily hot — which challenges conventional wisdom.
The observations were made with the telescope’s COS (Cosmic Origins Spectrograph) and STIS (Space Telescope Imaging Spectrograph) instruments. The data includes the first far-ultraviolet and new near-ultraviolet spectra of FU Ori.
“We were hoping to validate the hottest part of the accretion disk model, to determine its maximum temperature, by measuring closer to the inner edge of the accretion disk than ever before,” said Lynne Hillenbrand of Caltech in Pasadena, California, and a co-author of the paper. “I think there was some hope that we would see something extra, like the interface between the star and its disk, but we were certainly not expecting it. The fact we saw so much extra — it was much brighter in the ultraviolet than we predicted — that was the big surprise.”
A Better Understanding of Stellar Accretion
Originally deemed to be a unique case among stars, FU Ori exemplifies a class of young, eruptive stars that undergo dramatic changes in brightness. These objects are a subset of classical T Tauri stars, which are newly forming stars that are building up by accreting material from their disk and the surrounding nebula. In classical T Tauri stars, the disk does not touch the star directly because it is restricted by the outward pressure of the star’s magnetic field.
The accretion disks around FU Ori objects, however, are susceptible to instabilities due to their enormous mass relative to the central star, interactions with a binary companion, or infalling material. Such instability means the mass accretion rate can change dramatically. The increased pace disrupts the delicate balance between the stellar magnetic field and the inner edge of the disk, leading to material moving closer in and eventually touching the star’s surface.
This is an artist’s concept of the early stages of the young star FU Orionis (FU Ori) outburst, surrounded by a disk of material. A team of astronomers has used the Hubble Space Telescope’s ultraviolet capabilities to learn more about the interaction between FU Ori’s stellar surface and the accretion disk that has been dumping gas onto the growing star for nearly 90 years. They found that the inner disk, touching the star, is much hotter than expected—16,000 kelvins—nearly three times our Sun’s surface temperature. That sizzling temperature is nearly twice as hot as previously believed. NASA-JPL, Caltech
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The enhanced infall rate and proximity of the accretion disk to the star make FU Ori objects much brighter than a typical T Tauri star. In fact, during an outburst, the star itself is outshined by the disk. Furthermore, the disk material is orbiting rapidly as it approaches the star, much faster than the rotation rate of the stellar surface. This means that there should be a region where the disk impacts the star and the material slows down and heats up significantly.
“The Hubble data indicates a much hotter impact region than models have previously predicted,” said Adolfo Carvalho of Caltech and lead author of the study. “In FU Ori, the temperature is 16,000 kelvins [nearly three times our Sun’s surface temperature]. That sizzling temperature is almost twice the amount prior models have calculated. It challenges and encourages us to think of how such a jump in temperature can be explained.”
To address the significant difference in temperature between past models and the recent Hubble observations, the team offers a revised interpretation of the geometry within FU Ori’s inner region: The accretion disk’s material approaches the star and once it reaches the stellar surface, a hot shock is produced, which emits a lot of ultraviolet light.
Planet Survival Around FU Ori
Understanding the mechanisms of FU Ori’s rapid accretion process relates more broadly to ideas of planet formation and survival.
“Our revised model based on the Hubble data is not strictly bad news for planet evolution, it’s sort of a mixed bag,” explained Carvalho. “If the planet is far out in the disk as it’s forming, outbursts from an FU Ori object should influence what kind of chemicals the planet will ultimately inherit. But if a forming planet is very close to the star, then it’s a slightly different story. Within a couple outbursts, any planets that are forming very close to the star can rapidly move inward and eventually merge with it. You could lose, or at least completely fry, rocky planets forming close to such a star.”
Additional work with the Hubble UV observations is in progress. The team is carefully analyzing the various spectral emission lines from multiple elements present in the COS spectrum. This should provide further clues on FU Ori’s environment, such as the kinematics of inflowing and outflowing gas within the inner region.
“A lot of these young stars are spectroscopically very rich at far ultraviolet wavelengths,” reflected Hillenbrand. “A combination of Hubble, its size and wavelength coverage, as well as FU Ori’s fortunate circumstances, let us see further down into the engine of this fascinating star-type than ever before.”
These findings have been published in The Astrophysical Journal Letters.
The observations were taken as part of General Observer program 17176.
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.
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contacts:
Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
Abigail Major, Ray Villard
Space Telescope Science Institute, Baltimore, MD
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Last Updated Nov 21, 2024 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
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Lunar dust may seem unimposing, but it presents a significant challenge for space missions. Its abrasive and jagged particles can damage equipment, clog devices, and even pose health risks to astronauts. This project addresses such issues by developing advanced coatings composed of crumpled nano-balls made from atomically thin 2D materials such as MoS₂, graphene, and MXenes. By crumpling these nanosheets—much like crumpling a piece of paper—we create compression and aggregation resistant particles that can be dispersed in sprayable solutions. As a thin film coating, these crumpled nano-balls form corrugated structures that passively reduce dust adhesion and surface wear. The deformable crumpled nano-ball (DCN) coating works by minimizing the contact area between lunar dust and surfaces, thanks to its unique nano-engineered design. The 2D materials exhibit exceptional durability, withstanding extreme thermal and vacuum environments, as well as resisting radiation damage. Additionally, the flexoelectric and electrostatically dissipative properties of MoS₂, graphene, and MXenes allow the coating to neutralize and dissipate electrical charges, making them highly responsive to the charged lunar dust environment. The project will be executed in three phases, each designed to bring the technology closer to real-world space applications. First, we will synthesize the crumpled nano-balls and investigate their adhesion properties using advanced microscopy techniques. The second phase will focus on fundamental testing in simulated lunar environments, where the coating will be exposed to extreme temperatures, vacuum, radiation, and abrasion. Finally, the third phase will involve applying the coating to space-heritage materials and conducting comprehensive testing in a simulated lunar environment, targeting up to 90% dust clearance and verifying durability over repeated cycles of dust exposure. This research aligns with NASA’s goals for safer, more sustainable lunar missions by reducing maintenance requirements and extending equipment lifespan. Moreover, the potential applications extend beyond space exploration, with the technology offering promising advances in terrestrial industries such as aerospace and electronics by providing ultra-durable, wear-resistant surfaces. Ultimately, the project contributes to advancing materials science and paving the way for NASA’s long-term vision of sustainable space exploration.
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Establishing a permanent base on the moon is a critical step in the exploration of deep space. One significant challenge observed during the Apollo missions was the adhesion of lunar dust, which can build up on vehicle, equipment, and space suit. Highly fine and abrasive, the dust particles can have adverse mechanical, electrical, and health effects. The proposed research aims to develop a new class of hierarchical, heterogenous nanostructured coating that can passively mitigate adhesion of lunar particles. Using scalable nanolithography and surface modification processes, the geometry and material composition of the nanostructured surface will be precisely engineered to mitigate dust adhesion. This goal will be accomplished by: (1) construct multi-physical models to predict the contributions of various particle adhesion mechanisms, (2) develop scalable nanofabrication processes to enable precise control of hierarchical structures, and (3) develop nanoscale single-probe characterization protocols to characterize adhesion forces in relevant space environments. The proposed approach is compatible with roll-to-roll processing and the dust-mitigation coating can be transfer printed on arbitrary metal, ceramic, and polymer surfaces such as space suits, windows, mechanical machinery, solar panels, and sensor systems that are vital for long-term space exploration.
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Lunar dust, with its chemical reactivity, electrostatic charge, and potential magnetism, poses a serious threat to astronauts and equipment on the Moon’s surface. To address this, the project proposes developing structured coatings with anisotropic surface features and electrostatic dissipative properties to passively mitigate lunar dust. By analyzing lunar dust-surface interactions at multiple scales, the team aims to optimize the coatings’ surface structures and physical properties, such as Young’s modulus, electrical conductivity, and polarity. The project will examine tribocharging, external electric fields, and the effects of particle shapes and sizes. Numerical sensitivity analyses will complement simulations to better understand lunar dust dynamics. Once fabricated, the coatings will be tested under simulated lunar conditions. The team will employ a state-of-the-art nanoscale force spectroscopy system, using atomic force microsope (AFM) microcantilevers functionalized with regolith to measure dust-surface interactions. Additional experiments will assess particle adhesion and removal, with scanning electron microscopy used to analyze remaining dust. This project aims to provide insights into surface structure effects on dust adhesion, guiding the creation of lightweight, durable coatings for effective dust mitigation. The findings will foster collaborations with NASA and the aerospace industry, while offering training opportunities for students entering the field.
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