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By European Space Agency
Our understanding of planet formation in the Universe’s early days is challenged by new data from the NASA/ESA/CSA James Webb Space Telescope. Webb solved a puzzle by proving a controversial finding made with the NASA/ESA Hubble Space Telescope more than 20 years ago.
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By NASA
Webb Webb News Latest News Latest Images Blog (offsite) Awards X (offsite – login reqd) Instagram (offsite – login reqd) Facebook (offsite- login reqd) Youtube (offsite) Overview About Who is James Webb? Fact Sheet Impacts+Benefits FAQ Science Overview and Goals Early Universe Galaxies Over Time Star Lifecycle Other Worlds Observatory Overview Launch Orbit Mirrors Sunshield Instrument: NIRCam Instrument: MIRI Instrument: NIRSpec Instrument: FGS/NIRISS Optical Telescope Element Backplane Spacecraft Bus Instrument Module Multimedia About Webb Images Images Videos What is Webb Observing? 3d Webb in 3d Solar System Podcasts Webb Image Sonifications Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 7 Min Read NASA’s Webb Finds Planet-Forming Disks Lived Longer in Early Universe
This is a James Webb Space Telescope image of NGC 346, a massive star cluster in the Small Magellanic Cloud, a dwarf galaxy that is one of the Milky Way’s nearest neighbors. Credits:
NASA, ESA, CSA, STScI, Olivia C. Jones (UK ATC), Guido De Marchi (ESTEC), Margaret Meixner (USRA) NASA’s James Webb Space Telescope just solved a conundrum by proving a controversial finding made with the agency’s Hubble Space Telescope more than 20 years ago.
In 2003, Hubble provided evidence of a massive planet around a very old star, almost as old as the universe. Such stars possess only small amounts of heavier elements that are the building blocks of planets. This implied that some planet formation happened when our universe was very young, and those planets had time to form and grow big inside their primordial disks, even bigger than Jupiter. But how? This was puzzling.
To answer this question, researchers used Webb to study stars in a nearby galaxy that, much like the early universe, lacks large amounts of heavy elements. They found that not only do some stars there have planet-forming disks, but that those disks are longer-lived than those seen around young stars in our Milky Way galaxy.
“With Webb, we have a really strong confirmation of what we saw with Hubble, and we must rethink how we model planet formation and early evolution in the young universe,” said study leader Guido De Marchi of the European Space Research and Technology Centre in Noordwijk, Netherlands.
Image A: Protoplanetary Disks in NGC 346 (NIRCam Image)
This is a James Webb Space Telescope image of NGC 346, a massive star cluster in the Small Magellanic Cloud, a dwarf galaxy that is one of the Milky Way’s nearest neighbors. With its relative lack of elements heavier than hydrogen and helium, the NGC 346 cluster serves as a nearby proxy for studying stellar environments with similar conditions in the early, distant universe. Ten, small, yellow circles overlaid on the image indicate the positions of the ten stars surveyed in this study. NASA, ESA, CSA, STScI, Olivia C. Jones (UK ATC), Guido De Marchi (ESTEC), Margaret Meixner (USRA) A Different Environment in Early Times
In the early universe, stars formed from mostly hydrogen and helium, and very few heavier elements such as carbon and iron, which came later through supernova explosions.
“Current models predict that with so few heavier elements, the disks around stars have a short lifetime, so short in fact that planets cannot grow big,” said the Webb study’s co-investigator Elena Sabbi, chief scientist for Gemini Observatory at the National Science Foundation’s NOIRLab in Tucson. “But Hubble did see those planets, so what if the models were not correct and disks could live longer?”
To test this idea, scientists trained Webb on the Small Magellanic Cloud, a dwarf galaxy that is one of the Milky Way’s nearest neighbors. In particular, they examined the massive, star-forming cluster NGC 346, which also has a relative lack of heavier elements. The cluster served as a nearby proxy for studying stellar environments with similar conditions in the early, distant universe.
Hubble observations of NGC 346 from the mid 2000s revealed many stars about 20 to 30 million years old that seemed to still have planet-forming disks around them. This went against the conventional belief that such disks would dissipate after 2 or 3 million years.
“The Hubble findings were controversial, going against not only empirical evidence in our galaxy but also against the current models,” said De Marchi. “This was intriguing, but without a way to obtain spectra of those stars, we could not really establish whether we were witnessing genuine accretion and the presence of disks, or just some artificial effects.”
Now, thanks to Webb’s sensitivity and resolution, scientists have the first-ever spectra of forming, Sun-like stars and their immediate environments in a nearby galaxy.
“We see that these stars are indeed surrounded by disks and are still in the process of gobbling material, even at the relatively old age of 20 or 30 million years,” said De Marchi. “This also implies that planets have more time to form and grow around these stars than in nearby star-forming regions in our own galaxy.”
Image B: Protoplanetary Disks in NGC 346 Spectra (NIRSpec)
This graph shows, on the bottom left in yellow, a spectrum of one of the 10 target stars in this study (as well as accompanying light from the immediate background environment). Spectral fingerprints of hot atomic helium, cold molecular hydrogen, and hot atomic hydrogen are highlighted. On the top left in magenta is a spectrum slightly offset from the star that includes only light from the background environment. This second spectrum lacks a spectral line of cold molecular hydrogen.
On the right is the comparison of the top and bottom lines. This comparison shows a large peak in the cold molecular hydrogen coming from the star but not its nebular environment. Also, atomic hydrogen shows a larger peak from the star. This indicates the presence of a protoplanetary disk immediately surrounding the star. The data was taken with the microshutter array on the James Webb Space Telescope’s NIRSpec (Near-Infrared Spectrometer) instrument. Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI) A New Way of Thinking
This finding refutes previous theoretical predictions that when there are very few heavier elements in the gas around the disk, the star would very quickly blow away the disk. So the disk’s life would be very short, even less than a million years. But if a disk doesn’t stay around the star long enough for the dust grains to stick together and pebbles to form and become the core of a planet, how can planets form?
The researchers explained that there could be two distinct mechanisms, or even a combination, for planet-forming disks to persist in environments scarce in heavier elements.
First, to be able to blow away the disk, the star applies radiation pressure. For this pressure to be effective, elements heavier than hydrogen and helium would have to reside in the gas. But the massive star cluster NGC 346 only has about ten percent of the heavier elements that are present in the chemical composition of our Sun. Perhaps it simply takes longer for a star in this cluster to disperse its disk.
The second possibility is that, for a Sun-like star to form when there are few heavier elements, it would have to start from a larger cloud of gas. A bigger gas cloud will produce a bigger disk. So there is more mass in the disk and therefore it would take longer to blow the disk away, even if the radiation pressure were working in the same way.
“With more matter around the stars, the accretion lasts for a longer time,” said Sabbi. “The disks take ten times longer to disappear. This has implications for how you form a planet, and the type of system architecture that you can have in these different environments. This is so exciting.”
The science team’s paper appears in the Dec. 16 issue of The Astrophysical Journal.
Image C: NGC 346: Hubble and Webb Observations
Image Before/After The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
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 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.
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Media Contacts
Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Ann Jenkins – jenkins@stsci.edu, Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
Related Information
Past releases on NGC 346: Webb NIRCam image and MIRI image
Article: Highlighting other Webb Star Formation Discoveries
Simulation Video: Planetary Systems and Origins of Life
Animation Video: Exploring star and planet formation (English), and in Spanish
More Images of NGC 346 on AstroPix
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Last Updated Dec 15, 2024 Editor Marty McCoy Contact Laura Betz laura.e.betz@nasa.gov Related Terms
Astrophysics Galaxies Galaxies, Stars, & Black Holes Goddard Space Flight Center James Webb Space Telescope (JWST) Science & Research Stars The Universe View the full article
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By NASA
Artist’s concept of “hot Neptune” TOI-3261 b. NASA/JPL-Caltech/K. Miller (Caltech/IPAC) By Grace Jacobs Corban
The Discovery
A Neptune-sized planet, TOI-3261 b, makes a scorchingly close orbit around its host star. Only the fourth object of its kind ever found, the planet could reveal clues as to how planets such as these form.
Key Facts
An international team of scientists used the NASA space telescope, TESS (the Transiting Exoplanet Survey Satellite), to discover the exoplanet (a planet outside our solar system), then made further observations with ground-based telescopes in Australia, Chile, and South Africa. The measurements placed the new planet squarely in the “hot Neptune desert” – a category of planets with so few members that their scarcity evokes a deserted landscape. This variety of exoplanet is similar to our own Neptune in size and composition, but orbits extremely closely to its star. In this case, a “year” on TOI-3261 b is only 21 hours long. Such a tight orbit earns this planet its place in an exclusive group with, so far, only three other members: ultra-short-period hot Neptunes whose masses have been precisely measured.
Details
Planet TOI-3261 b proves to be an ideal candidate to test new computer models of planet formation. Part of the reason hot Neptunes are so rare is that it is difficult to retain a thick gaseous atmosphere so close to a star. Stars are massive, and so exert a large gravitational force on the things around them, which can strip the layers of gas surrounding a nearby planet. They also emit huge amounts of energy, which blow the gas layers away. Both of these factors mean that hot Neptunes such as TOI-3261 b might have started out as much larger, Jupiter-sized planets, and have since lost a large portion of their mass.
By modeling different starting points and development scenarios, the science team determined that the star and planet system is about 6.5 billion years old, and that the planet started out as a much larger gas giant. It likely lost mass, however, in two ways: photoevaporation, when energy from the star causes gas particles to dissipate, and tidal stripping, when the gravitational force from the star strips layers of gas from the planet. The planet also might have formed farther away from its star, where both of these effects would be less intense, allowing it to retain its atmosphere.
The remaining atmosphere of the planet, one of its most interesting features, will likely invite further atmospheric analysis, perhaps helping to unravel the formation history of this denizen of the “hot Neptune desert.” Planet TOI-3261 b is about twice as dense as Neptune, indicating that the lighter parts of its atmosphere have been stripped away over time, leaving only the heavier components. This shows that the planet must have started out with a variety of different elements in its atmosphere, but at this stage, it is hard to tell exactly what. This mystery could be solved by observing the planet in infrared light, perhaps using NASA’s James Webb Space Telescope – an ideal way to see the identifying fingerprints of the different molecules in the planet’s atmosphere. This will not just help astronomers understand the past of TOI-3261 b, but also begin to uncover the physical processes behind all hot, giant planets.
Fun Facts
The first-ever discovery of an ultra-short-period hot Neptune, LTT-9779 b, came in 2020. Since then, TESS discoveries TOI-849 b and TOI-332 b have also joined the elite ultra-short-period hot-Neptune club (with masses that have been precisely measured). Both LTT-9779 b and TOI-849 b are in the queue for infrared observations with the James Webb Space Telescope, potentially broadening our understanding of these planets’ atmospheres in the coming years.
The Discoverers
An international science team led by astronomer Emma Nabbie of the University of Southern Queensland published their paper on the discovery, “Surviving in the Hot Neptune Desert: The Discovery of the Ultrahot Neptune TOI-3261 b,” in The Astronomical Journal in August 2024.
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By NASA
Artist’s concept of a young, newly discovered planet, exposed to observation by a warped debris disk. Credit: Robert Hurt, Caltech-IPAC. The discovery
A huge planet with a long name – IRAS 04125+2902 b – is really just a baby: only 3 million years old. And because such infant worlds are usually hidden inside obscuring disks of debris, it is the youngest planet so far discovered using the dominant method of planet detection.
Key facts
The massive planet, likely still glowing from the heat of its formation, lies in the Taurus Molecular Cloud, an active stellar nursery with hundreds of newborn stars some 430 light-years away. The cloud’s relative closeness makes it a prime target for astronomers. But while the cloud offers deep insight into the formation and evolution of young stars, their planets are usually a closed book to telescopes like TESS, the Transiting Exoplanet Survey Satellite. These telescopes rely on the “transit method,” watching for the slight dip in starlight when a planet crosses the face of its host star. But such planetary systems must be edge-on, from Earth’s vantage point, for the transit method to work. Very young star systems are surrounded by disks of debris, however, blocking our view of any potentially transiting planets.
A research team has just reported an extraordinary stroke of luck. Somehow, the outer debris disk surrounding this newborn planet, IRAS 04125+2902 b, has been sharply warped, exposing the baby world to extensive transit observations by TESS.
Details
While the warped outer disk is a great coincidence, it’s also a great mystery. Possible explanations include a migration of the planet itself, moving closer to the star and, in the process, diverging from the orientation of the outer disk – so that, from Earth, the planet’s orbit is edge-on, crossing the face of the star, but the outer disk remains nearly face-on to us. One problem with this idea: Moving a planet so far out of alignment with its parent disk would likely require another (very large) object in this system. None has been detected so far.
The system’s sun happens to have a distant stellar companion, also a possible culprit in the warping of the outer disk. The angle of the orbit of the companion star, however, matches that of the planet and its parent star. Stars and planets tend to take the gravitational path of least resistance, so such an arrangement should push the disk into a closer alignment with the rest of the system – not into a radical departure.
Another way to get a “broken” outer disk, the study authors say, would not involve a companion star at all. Stellar nurseries like the Taurus Molecular Cloud can be densely packed, busy places. Computer simulations show that rains of infalling material from the surrounding star-forming region could be the cause of disk-warping. Neither simulations nor observations have so far settled the question of whether warped or broken disks are common or rare in such regions.
Fun facts
Combining TESS’s transit measurements with another way of observing planets yields more information about the planet itself. We might call this second approach the “wobble” method. The gravity of a planet tugs its star one way, then another, as the orbiting planet makes its way around the star. And that wobble can be detected by changes in the light from the star, picked up by specialized instruments on Earth. Such “radial velocity” measurements of this planet reveal that its mass, or heft, amounts to no more than about a third of our own Jupiter. But the transit data shows the planet’s diameter is about the same. That means the planet has a comparatively low density and, likely, an inflated atmosphere. So this world probably is not a gas giant like Jupiter. Instead, it could well be a planet whose atmosphere will shrink over time. When it finally settles down, it could become a gaseous “mini-Neptune” or even a rocky “super-Earth.” These are the two most common planet types in our galaxy – despite the fact that neither type can be found in our solar system.
The discoverers
A science team led by astronomer Madyson G. Barber of the University of North Carolina at Chapel Hill published the study, “A giant planet transiting a 3 Myr protostar with a misaligned disk,” in the journal Nature in November 2024.
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By NASA
2 min read
NASA-Funded Study Examines Tidal Effects on Planet and Moon Interiors
NASA-supported scientists have developed a new method to compute how tides affect the interiors of planets and moons. Importantly, the new study looks at the effects of body tides on objects that don’t have a perfectly spherical interior structure, which is an assumption of most previous models.
The puzzling, fascinating surface of Jupiter’s icy moon Europa looms large in this newly-reprocessed color view, made from images taken by NASA’s Galileo spacecraft in the late 1990s. This is the color view of Europa from Galileo that shows the largest portion of the moon’s surface at the highest resolution. NASA/JPL-Caltech/SETI Institute Body tides refer to the deformations experienced by celestial bodies when they gravitationally interact with other objects. Think of how the powerful gravity of Jupiter tugs on its moon Europa. Because Europa’s orbit isn’t circular, the crushing squeeze of Jupiter’s gravity on the moon varies as it travels along its orbit. When Europa is at its closest to Jupiter, the planet’s gravity is felt the most. The energy of this deformation is what heats up Europa’s interior, allowing an ocean of liquid water to exist beneath the moon’s icy surface.
“The same is true for Saturn’s moon Enceladus.” says co-author Alexander Berne of CalTech in Pasadena and an affiliate at NASA’s Jet Propulsion Laboratory in Southern California. “Enceladus has an ice shell that is expected to be much more non-spherically symmetric than that of Europa.”
The body tides experienced by celestial bodies can affect how the worlds evolve over time and, in cases like Europa and Enceladus, their potential habitability for life as we know it. The new study provides a means to more accurately estimate how tidal forces affect planetary interiors.
In this movie Europa is seen in a cutaway view through two cycles of its 3.5 day orbit about the giant planet Jupiter. Like Earth, Europa is thought to have an iron core, a rocky mantle and a surface ocean of salty water. Unlike on Earth, however, this ocean is deep enough to cover the whole moon, and being far from the sun, the ocean surface is globally frozen over. Europa’s orbit is eccentric, which means as it travels around Jupiter, large tides, raised by Jupiter, rise and fall. Jupiter’s position relative to Europa is also seen to librate, or wobble, with the same period. This tidal kneading causes frictional heating within Europa, much in the same way a paper clip bent back and forth can get hot to the touch, as illustrated by the red glow in the interior of Europa’s rocky mantle and in the lower, warmer part of its ice shell. This tidal heating is what keeps Europa’s ocean liquid and could prove critical to the survival of simple organisms within the ocean, if they exist. The giant planet Jupiter is now shown to be rotating from west to east, though more slowly than its actual rate. NASA/JPL-Caltech The paper also discusses how the results of the study could help scientists interpret observations made by missions to a variety of different worlds, ranging from Mercury to the Moon to the outer planets of our solar system.
The study, “A Spectral Method to Compute the Tides of Laterally Heterogeneous Bodies,” was published in The Planetary Science Journal.
For more information on NASA’s Astrobiology Program, visit:
https://science.nasa.gov/astrobiology
-end-
Karen Fox / Molly Wasser
Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
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