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Star Light, Star Bright, Its Explanation is Out of Sight
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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
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
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A 3D simulation showing the evolution of turbulent flows in the upper layers of the Sun. The more saturated and bright reds represent the most vigorous upward or downward twisting motions. Clear areas represent areas where there is only relatively slow up-flows, with very little twisting.NASA/Irina Kitiashvili and Timothy A. Sandstrom NASA supercomputers are shedding light on what causes some of the Sun’s most complex behaviors. Using data from the suite of active Sun-watching spacecraft currently observing the star at the heart of our solar system, researchers can explore solar dynamics like never before.
The animation shows the strength of the turbulent motions of the Sun’s inner layers as materials twist into its atmosphere, resembling a roiling pot of boiling water or a flurry of schooling fish sending material bubbling up to the surface or diving it further down below.
“Our simulations use what we call a realistic approach, which means we include as much as we know to-date about solar plasma to reproduce different phenomena observed with NASA space missions,” said Irina Kitiashvili, a scientist at NASA’s Ames Research Center in California’s Silicon Valley who helped lead the study.
Using modern computational capabilities, the team was able, for the first time to reproduce the fine structures of the subsurface layer observed with NASA’s Solar Dynamics Observatory.
“Right now, we don’t have the computational capabilities to create realistic global models of the entire Sun due to the complexity,” said Kitiashvili. “Therefore, we create models of smaller areas or layers, which can show us structures of the solar surface and atmosphere – like shock waves or tornado-like features measuring only a few miles in size; that’s much finer detail than any one spacecraft can resolve.”
Scientists seek to better understand the Sun and what phenomena drive the patterns of its activity. The connection and interactions between the Sun and Earth drive the seasons, ocean currents, weather, climate, radiation belts, auroras and many other phenomena. Space weather predictions are critical for exploration of space, supporting the spacecraft and astronauts of NASA’s Artemis campaign. Surveying this space environment is a vital part of understanding and mitigating astronaut exposure to space radiation and keeping our spacecraft and instruments safe.
This has been a big year for our special star, studded with events like the annular eclipse, a total eclipse, and the Sun reaching its solar maximum period. In December 2024, NASA’s Parker Solar Probe mission – which is helping researchers to understand space weather right at the source – will make its closest-ever approach to the Sun and beat its own record of being the closest human-made object to reach the Sun.
The Sun keeps surprising us. We are looking forward to seeing what kind of exciting events will be organized by the Sun."
Irina Kitiashvili
NASA Scientist
“The Sun keeps surprising us,” said Kitiashvili. “We are looking forward to seeing what kind of exciting events will be organized by the Sun.”
These simulations were run on the Pleaides supercomputer at the NASA Advanced Supercomputing facility at NASA Ames over several weeks of runtime, generating terabytes of data.
NASA is showcasing 29 of the agency’s computational achievements at SC24, the international supercomputing conference, Nov. 17-22, 2023, in Atlanta, Georgia. For more technical information, visit:
https://www.nas.nasa.gov/sc24
For news media: Members of the news media interested in covering this topic should reach out to the NASA Ames newsroom.
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Last Updated Nov 21, 2024 Related Terms
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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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Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
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This e-book highlights the mission’s recent discoveries and observations related to the birth, evolution, and death of stars.
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By NASA
5 Min Read Making Mars’ Moons: Supercomputers Offer ‘Disruptive’ New Explanation
A NASA study using a series of supercomputer simulations reveals a potential new solution to a longstanding Martian mystery: How did Mars get its moons? The first step, the findings say, may have involved the destruction of an asteroid.
The research team, led by Jacob Kegerreis, a postdoctoral research scientist at NASA’s Ames Research Center in California’s Silicon Valley, found that an asteroid passing near Mars could have been disrupted – a nice way of saying “ripped apart” – by the Red Planet’s strong gravitational pull.
The team’s simulations show the resulting rocky fragments being strewn into a variety of orbits around Mars. More than half the fragments would have escaped the Mars system, but others would’ve stayed in orbit. Tugged by the gravity of both Mars and the Sun, in the simulations some of the remaining asteroid pieces are set on paths to collide with one another, every encounter further grinding them down and spreading more debris.
Many collisions later, smaller chunks and debris from the former asteroid could have settled into a disk encircling the planet. Over time, some of this material is likely to have clumped together, possibly forming Mars’ two small moons, Phobos and Deimos.
To assess whether this was a realistic chain of events, the research team explored hundreds of different close encounter simulations, varying the asteroid’s size, spin, speed, and distance at its closest approach to the planet. The team used their high-performance, open-source computing code, called SWIFT, and the advanced computing systems at Durham University in the United Kingdom to study in detail both the initial disruption and, using another code, the subsequent orbits of the debris.
In a paper published Nov. 20 in the journal Icarus, the researchers report that, in many of the scenarios, enough asteroid fragments survive and collide in orbit to serve as raw material to form the moons.
“It’s exciting to explore a new option for the making of Phobos and Deimos – the only moons in our solar system that orbit a rocky planet besides Earth’s,” said Kegerreis. “Furthermore, this new model makes different predictions about the moons’ properties that can be tested against the standard ideas for this key event in Mars’ history.”
Two hypotheses for the formation of the Martian moons have led the pack. One proposes that passing asteroids were captured whole by Mars’ gravity, which could explain the moons’ somewhat asteroid-like appearance. The other says that a giant impact on the planet blasted out enough material – a mix of Mars and impactor debris – to form a disk and, ultimately, the moons. Scientists believe a similar process formed Earth’s Moon.
The latter explanation better accounts for the paths the moons travel today – in near-circular orbits that closely align with Mars’ equator. However, a giant impact ejects material into a disk that, mostly, stays close to the planet. And Mars’ moons, especially Deimos, sit quite far away from the planet and probably formed out there, too.
“Our idea allows for a more efficient distribution of moon-making material to the outer regions of the disk,” said Jack Lissauer, a research scientist at Ames and co-author on the paper. “That means a much smaller ‘parent’ asteroid could still deliver enough material to send the moons’ building blocks to the right place.”
It’s exciting to explore a new option for the making of Phobos and Deimos – the only moons in our solar system that orbit a rocky planet besides Earth’s.
Jacob Kegerreis
Postdoctoral research scientist at NASA’s Ames Research Center
Testing different ideas for the formation of Mars’ moons is the primary goal of the upcoming Martian Moons eXploration (MMX) sample return mission led by JAXA (Japan Aerospace Exploration Agency). The spacecraft will survey both moons to determine their origin and collect samples of Phobos to bring to Earth for study. A NASA instrument on board, called MEGANE – short for Mars-moon Exploration with GAmma rays and Neutrons – will identify the chemical elements Phobos is made of and help select sites for the sample collection. Some of the samples will be collected by a pneumatic sampler also provided by NASA as a technology demonstration contribution to the mission. Understanding what the moons are made of is one clue that could help distinguish between the moons having an asteroid origin or a planet-plus-impactor source.
Before scientists can get their hands on a piece of Phobos to analyze, Kegerreis and his team will pick up where they left off demonstrating the formation of a disk that has enough material to make Phobos and Deimos.
“Next, we hope to build on this proof-of-concept project to simulate and study in greater detail the full timeline of formation,” said Vincent Eke, associate professor at the Institute for Computational Cosmology at Durham University and a co-author on the paper. “This will allow us to examine the structure of the disk itself and make more detailed predictions for what the MMX mission could find.”
For Kegerreis, this work is exciting because it also expands our understanding of how moons might be born – even if it turns out that Mars’ own formed by a different route. The simulations offer a fascinating exploration, he says, of the possible outcomes of encounters between objects like asteroids and planets. These events were common in the early solar system, and simulations could help researchers reconstruct the story of how our cosmic backyard evolved.
This research is a collaborative effort between Ames and Durham University, supported by the Institute for Computational Cosmology’s Planetary Giant Impact Research group. The simulations used were run using the open-source SWIFT code, carried out on the DiRAC (Distributed Research Utilizing Advanced Computing) Memory Intensive service (“COSMA”), hosted by Durham University on behalf of the DiRAC High-Performance Computing facility.
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Members of the news media interested in covering this topic should reach out to the NASA Ames newsroom.
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Last Updated Nov 20, 2024 Related Terms
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s X-59 quiet supersonic research aircraft sits in its run stall at Lockheed Martin’s Skunk Works facility in Palmdale, California, firing up its engine for the first time. These engine-run tests start at low power and allow the X-59 team to verify the aircraft’s systems are working together while powered by its own engine. The X-59 is the centerpiece of NASA’s Quesst mission, which seeks to solve one of the major barriers to supersonic flight over land by making sonic booms quieter.NASA/Carla Thomas NASA’s Quesst mission marked a major milestone with the start of tests on the engine that will power the quiet supersonic X-59 experimental aircraft.
These engine-run tests, which began Oct. 30, allow the X-59 team to verify the aircraft’s systems are working together while powered by its own engine. In previous tests, the X-59 used external sources for power. The engine-run tests set the stage for the next phase of the experimental aircraft’s progress toward flight.
The X-59 team is conducting the engine-run tests in phases. In this first phase, the engine rotated at a relatively low speed without ignition to check for leaks and ensure all systems are communicating properly. The team then fueled the aircraft and began testing the engine at low power, with the goal of verifying that it and other aircraft systems operate without anomalies or leaks while on engine power.
Lockheed Martin test pilot Dan Canin sits in the cockpit of NASA’s X-59 quiet supersonic research aircraft in a run stall at Lockheed Martin’s Skunk Works facility in Palmdale, California prior to its first engine run. These engine-run tests featured the X-59 powered by its own engine, whereas in previous tests, the aircraft depended on external sources for power. The X-59 is the centerpiece of NASA’s Quesst mission, which seeks to solve one of the major barriers to supersonic flight over land by making sonic booms quieter.NASA/Carla Thomas “The first phase of the engine tests was really a warmup to make sure that everything looked good prior to running the engine,” said Jay Brandon, NASA’s X-59 chief engineer. “Then we moved to the actual first engine start. That took the engine out of the preservation mode that it had been in since installation on the aircraft. It was the first check to see that it was operating properly and that all the systems it impacted – hydraulics, electrical system, environmental control systems, etc. – seemed to be working.”
The X-59 will generate a quieter thump rather than a loud boom while flying faster than the speed of sound. The aircraft is the centerpiece of NASA’s Quesst mission, which will gather data on how people perceive these thumps, providing regulators with information that could help lift current bans on commercial supersonic flight over land.
The engine, a modified F414-GE-100, packs 22,000 pounds of thrust, which will enable the X-59 to achieve the desired cruising speed of Mach 1.4 (925 miles per hour) at an altitude of approximately 55,000 feet. It sits in a nontraditional spot – atop the aircraft — to aid in making the X-59 quieter.
Engine runs are part of a series of integrated ground tests needed to ensure safe flight and successful achievement of mission goals. Because of the challenges involved with reaching this critical phase of testing, the X-59’s first flight is now expected in early 2025. The team will continue progressing through critical ground tests and address any technical issues discovered with this one-of-a-kind, experimental aircraft. The X-59 team will have a more specific first flight date as these tests are successfully completed.
The testing is taking place at Lockheed Martin’s Skunk Works facility in Palmdale, California. During later phases, the team will test the aircraft at high power with rapid throttle changes, followed by simulating the conditions of an actual flight.
NASA’s X-59 quiet supersonic research aircraft sits in its run stall at Lockheed Martin’s Skunk Works facility in Palmdale, California, prior to its first engine run. Engine runs are part of a series of integrated ground tests needed to ensure safe flight and successful achievement of mission goals. The X-59 is the centerpiece of NASA’s Quesst mission, which seeks to solve one of the major barriers to supersonic flight over land by making sonic booms quieter.NASA/Carla Thomas “The success of these runs will be the start of the culmination of the last eight years of my career,” said Paul Dees, NASA’s deputy propulsion lead for the X-59. “This isn’t the end of the excitement but a small steppingstone to the beginning. It’s like the first note of a symphony, where years of teamwork behind the scenes are now being put to the test to prove our efforts have been effective, and the notes will continue to play a harmonious song to flight.”
After the engine runs, the X-59 team will move to aluminum bird testing, where data will be fed to the aircraft under both normal and failure conditions. The team will then proceed with a series of taxi tests, where the aircraft will be put in motion on the ground. These tests will be followed by final preparations for first flight.
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Last Updated Nov 06, 2024 EditorLillian GipsonContactMatt Kamletmatthew.r.kamlet@nasa.gov Related Terms
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