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By NASA
X-rays are radiated by matter hotter than one million Kelvin, and high-resolution X-ray spectroscopy can tell us about the composition of the matter and how fast and in what direction it is moving. Quantum calorimeters are opening this new window on the Universe. First promised four decades ago, the quantum-calorimeter era of X-ray astronomy has finally dawned.
Photo of the XRISM/Resolve quantum-calorimeter array in its storage container prior to integration into the instrument. The 6×6 array, 5 mm on a side, consists of independent detectors – each one a thermally isolated silicon thermistor with a HgTe absorber. The spectrometer consisting of this detector and other essential technologies separates astrophysical X-ray spectra into about 2400 resolution elements, which can be thought of as X-ray colors.NASA GSFC A quantum calorimeter is a device that makes precise measurements of energy quanta by measuring the temperature change that occurs when a quantum of energy is deposited in an absorber with low heat capacity. The absorber is attached to a thermometer that is somewhat decoupled from a heat sink so that the sensor can heat up and then cool back down again. To reduce thermodynamic noise and the heat capacity of the sensor, operation at temperatures less than 0.1 K is required.
The idea for thermal measurement of small amounts of energy occurred in several places in the world independently when scientists observed pulses in the readout of low-temperature thermometers and infrared detectors. They attributed these spurious signals to passing cosmic-ray particles, and considered optimizing detectors for sensitive measurement of the energy of particles and photons.
The idea to develop such sensors for X-ray astronomy was conceived at Goddard Space Flight Center in 1982 when X-ray astronomers were considering instruments to propose for NASA’s planned Advanced X-ray Astrophysics Facility (AXAF). In a fateful conversation, infrared astronomer Harvey Moseley suggested thermal detection could offer substantial improvement over existing solid-state detectors. Using Goddard internal research and development funding, development advanced sufficiently to justify, just two years later, proposing a quantum-calorimeter X-ray Spectrometer (XRS) for inclusion on AXAF. Despite its technical immaturity at the time, the revolutionary potential of the XRS was acknowledged, and the proposal was accepted.
The AXAF design evolved over the subsequent years, however, and the XRS was eliminated from its complement of instruments. After discussions between NASA and the Japanese Institute of Space and Astronautical Science (ISAS), a new XRS was included in the instrument suite of the Japanese Astro-E X-ray observatory. Astro-E launched in 2000 but did not reach orbit due to an anomaly in the first stage of the rocket. Astro-E2, a rebuild of Astro-E, was successfully placed in orbit in 2005 and renamed Suzaku, but the XRS instrument ceased operation before observations started due to loss of the liquid helium, an essential part of the detector cooling system, caused by a faulty storage system.
A redesigned mission, Astro-H, that included a quantum-calorimeter instrument with a redundant cooling system was successfully launched in 2016 and renamed Hitomi. Hitomi’s Soft X-ray Spectrometer (SXS) obtained high resolution spectra of the Perseus cluster of galaxies and a few other sources before a problem with the attitude control system caused the mission to be lost roughly one month after launch. Even so, Hitomi was the first orbiting observatory to obtain a scientific result using X-ray quantum calorimeters. The spectacular Perseus spectrum generated by the SXS motivated yet another attempt to implement a spaceborne quantum-calorimeter spectrometer.
The X-ray Imaging and Spectroscopy Mission (XRISM) was launched in September 2023, with the spectrometer aboard renamed Resolve to represent not only its function but also the resolve of the U.S./Japan collaboration to study the Universe through the window of this new capability. XRISM has been operating well in orbit for over a year.
Development of the Sensor Technology
Development of the sensor technology employed in Resolve began four decades ago. Note that an X-ray quantum-calorimeter spectrometer requires more than the sensor technology. Other technologies, such as the coolers that provide a
The sensors used from XRS through Resolve were all based on silicon-thermistor thermometers and mercury telluride (HgTe) X-ray absorbers. They used arrays consisting of 32 to 36 pixels, each of which was an independent quantum calorimeter. Between Astro-E and Astro-E2, a new method of making the thermistor was developed that significantly reduced its low-frequency noise. Other fabrication advances made it possible to make reproducible connections between absorbers and thermistors and to fit each thermistor and its thermal isolation under its X-ray absorber, making square arrays feasible.
Through a Small Business Innovation Research (SBIR) contract executed after the Astro-E2 mission, EPIR Technologies Inc. reduced the specific heat of the HgTe absorbers. Additional improvements made to the cooler of the detector heat sink allowed operation at a lower temperature, which further reduced the specific heat. Together, these changes enabled the pixel width to be increased from 0.64 mm to 0.83 mm while still achieving a lower heat capacity, and thus improving the energy resolution. From Astro-E through Astro-H, the energy resolution for X-rays of energy around 6000 eV improved from 11 eV, to 5.5 eV, to 4 eV. No changes to the array design were made between Astro-H and XRISM.
Resolve detector scientist Caroline Kilbourne installing the flight Resolve quantum-calorimeter array into the assembly that provides its electrical, thermal, and mechanical interfaces.NASA GSFC Over the same period, other approaches to quantum-calorimeter arrays optimized for the needs of future missions were developed. The use of superconducting transition-edge sensors (TES) instead of silicon (Si) thermistors led to improved energy resolution, more pixels per array, and multiplexing (a technique that allows multiple signals to be carried on a single wire). Quantum-calorimeter arrays with thousands of pixels are now standard, such as in the NASA contribution to the future European New Advanced Telescope for High-ENergy Astrophysics (newAthena) mission. And quantum calorimeters using paramagnetic thermometers — which unlike TES and Si thermistors require no dissipation of heat in the thermometer for it to be read out — combined with high-density wiring are a promising route for realizing even larger arrays. (See Astrophysics Technology Highlight on these latest developments.)
The Resolve instrument aboard XRISM (X-ray Imaging and Spectroscopy Mission) captured data from the center of galaxy NGC 4151, where a supermassive black hole is slowly consuming material from the surrounding accretion disk. The resulting spectrum reveals the presence of iron in the peak around 6.5 keV and the dips around 7 keV, light thousands of times more energetic that what our eyes can see. Background: An image of NGC 4151 constructed from a combination of X-ray, optical, and radio light.Spectrum: JAXA/NASA/XRISM Resolve. Background: X-rays, NASA/CXC/CfA/J.Wang et al.; optical, Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope; radio, NSF/NRAO/VLA Results from Resolve
So, what is Resolve revealing about the Universe? Through spectroscopy alone, Resolve allows us to construct images of complex environments where collections of gas and dust with various attributes exist, emitting and absorbing X-rays at energies characteristic of their various compositions, velocities, and temperatures. For example, in the middle of the galaxy known as NCG 4151 (see figure above), matter spiraling into the central massive black hole forms a circular structure that is flat near the black hole, more donut-shaped further out, and, according to the Resolve data, a bit lumpy. Matter near the black hole is heated up to X-ray-emitting temperatures and irradiates the matter in the circular structure. The Resolve spectrum has a bright narrow emission line (peak) from neutral iron atoms that must be coming from colder matter in the circular structure, because hotter material would be ionized, and would have a different emission signature. Nonetheless, the shape of the iron line needs three components to describe it, each coming from a different lump in the circular structure. The presence of absorption lines (dips) in the spectrum provides further detail about the structure of the infalling matter.
A second example is the detection of X-ray emission by Resolve from the debris of stars that have exploded, such as N132D (see figure below), that will improve our understanding of the explosion mechanism and how the elements produced in stars get distributed, and allow us to infer the type of star each was before ending in a supernova. Elements are identified by their characteristic emission lines, and shifts of those lines via the Doppler effect tell us how fast the material is moving.
XRISM’s Resolve instrument captured data from supernova remnant N132D in the Large Magellanic Cloud to create the most detailed X-ray spectrum of the object ever made. The spectrum reveals peaks associated with silicon, sulfur, argon, calcium, and iron. Inset at right is an image of N132D captured by XRISM’s Xtend instrument.JAXA/NASA/XRISM Resolve and Xtend These results are just the beginning. The rich Resolve data sets are identifying complex velocity structures, rare elements, and multiple temperature components in a diverse ensemble of cosmic objects. Welcome to the quantum calorimeter era! Stay tuned for more revelations!
Project Leads: Dr. Caroline Kilbourne, NASA Goddard Space Flight Center (GSFC), for silicon-thermistor quantum calorimeter development from Astro-E2 through XRISM and early TES development. Foundational and other essential leadership provided by Dr. Harvey Moseley, Dr. John Mather, Dr. Richard Kelley, Dr. Andrew Szymkowiak, Mr. Brent Mott, Dr. F. Scott Porter, Ms. Christine Jhabvala, Dr. James Chervenak (GSFC at the time of the work) and Dr. Dan McCammon (U. Wisconsin).
Sponsoring Organizations and Programs: The NASA Headquarters Astrophysics Division sponsored the projects, missions, and other efforts that culminated in the development of the Resolve instrument.
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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
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Last Updated Dec 15, 2024 Editor Marty McCoy Contact Laura Betz laura.e.betz@nasa.gov Related Terms
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
A scientific balloon is inflated during NASA’s 2023 Antarctic campaign in McMurdo, Antarctica. NASA/Scott Battaion NASA’s Scientific Balloon Program has returned to Antarctica’s icy expanse to kick off the annual Antarctic Long-Duration Balloon Campaign, where two balloon flights will carry a total of nine missions to near space. Launch operations will begin mid-December from the agency’s Long Duration Balloon camp located near the U.S. National Science Foundation’s McMurdo Station on the Ross Ice Shelf.
“Antarctica is our cornerstone location for long-duration balloon missions, and we always look forward to heading back to ‘the ice,’” said Andrew Hamilton, acting chief of NASA’s Balloon Program Office at the agency’s Wallops Flight Facility in Virginia. “It’s a tremendous effort to stage a campaign like this in such a remote location, and we are grateful for the support provided to us by the U.S. National Science Foundation, New Zealand, and the U.S. Air Force.”
This year’s Antarctic campaign includes investigations in astrophysics, space biology, heliospheric research, and upper atmospheric research, along with technology demonstrations. The campaign’s two primary missions include:
GAPS (General Anti-Particle Spectrometer), led by Columbia University in New York, is an experiment to detect anti-matter particles produced by dark matter interactions. The anti-particles stemming from these interactions in our galaxy can only be observed from a suborbital platform or in space, since Earth’s atmosphere shields us from the cosmic radiation. GAPS aims to provide an unprecedented level of sensitivity to certain classes of anti-particles, allowing the exploration of a currently unexplored energy regime of the elusive dark matter. Salter Test Flight Universal, led by NASA’s Columbia Scientific Balloon Facility in Palestine, Texas, will test and validate long-duration balloon and subsystems, while supporting several piggyback missions on the flight. Piggyback missions, or smaller payloads, riding along with the Salter Test Flight Universal mission include:
MARSBOx (Microbes in Atmosphere for Radiation, Survival, and Biological Outcomes Experiments), led by the U.S. Naval Research Laboratory, will expose melanized fungus, called Aspergillus niger, to the stratosphere’s extreme radiation and temperature fluctuations, low atmospheric pressure, and absence of water — conditions much like the surface of Mars. Knowledge of how this fungus adapts to protect itself in this harsh environment could lead to the development of treatments to protect astronauts from high radiation exposure. EMIDSS-6 (Experimental Module for Iterative Design of Satellite Subsystems 6), led by National Polytechnical Institute − Mexico, is a technological platform with experimental design and operational validation of instrumentation that will collect and store data from the stratospheric environment to contribute to the study of climate change. SPARROW-6 (Sensor Package for Attitude, Rotation, and Relative Observable Winds – 6), led by NASA’s Balloon Program Office at NASA Wallops, will demonstrate relative wind measurements using an ultrasonic anemometer designed for the balloon float environment. WALRUSS (Wallops Atmospheric Light Radiation and Ultraviolet Spectrum Sensor), led by the Balloon Program Office at NASA Wallops, is a technology demonstration of a sensor package capable of measuring the total ultraviolet wavelength spectrum and ozone concentration. INDIGO (INterim Dynamics Instrumentation for Gondolas), led by the Balloon Program Office at NASA Wallops, is a data recorder meant to measure the shock, rotation, and attitude of the gondola during the launch, float, and landing phases of flight. Data will be used to improve understanding of the dynamics of flight and to inform the design of future components and hardware. The remaining two piggyback missions are led by finalists of NASA’s FLOATing DRAGON (Formulate, Lift, Observe, And Testing; Data Recovery And Guided On-board Node) Balloon Challenge, sponsored by the Balloon Program Office at NASA Wallops and managed by the National Institute of Aerospace. The challenge was created for student teams to design, build, and fly an autonomous aerial vehicle, deployed from a gondola during a high-altitude balloon flight. The teams’ student-built data vaults will be safely dropped from around 120,000 feet with the capability to target a specific landing point on the ground to manage risk. The missions participating in the Antarctic campaign are Purdue University’s Purdue DRAGONfly, and University of Notre Dame’s IRIS v3.
NASA’s zero-pressure balloons, used in the Antarctic campaign, are made of a thin plastic film and are capable of lifting up to 8,000 pounds of payload and equipment to altitudes above 99.8% of Earth’s atmosphere. Zero-pressure balloons, which typically have a shorter flight duration from the loss of gas during the day-to-night cycle, can support long-duration missions in polar regions during summer. The constant daylight of Antarctica’s austral summer and stable stratospheric wind conditions allow the balloon missions to remain in near space for days to weeks, gathering large amounts of scientific data as they circle the continent.
NASA’s Long Duration Balloon camp is located about eight miles from the U.S. National Science Foundation’s McMurdo Station on Antarctica’s Ross Ice Shelf. NASA/Scott Battaion NASA’s Wallops Flight Facility in Virginia manages the agency’s scientific balloon flight program with 10 to 15 flights each year from launch sites worldwide. Peraton, which operates NASA’s Columbia Scientific Balloon Facility in Palestine, Texas, provides mission planning, engineering services, and field operations for NASA’s scientific balloon program. The Columbia team has launched more than 1,700 scientific balloons over some 40 years of operations. NASA’s balloons are fabricated by Aerostar. The NASA Scientific Balloon Program is funded by the NASA Headquarters Science Mission Directorate Astrophysics Division. NASA balloon launch operations from Antarctica receive logistical support from the U.S. National Science Foundation’s Office of Polar Programs, which oversees the U.S. Antarctic Program.
For mission tracking, click here. For more information on NASA’s Scientific Balloon Program, visit: https://www.nasa.gov/scientificballoons.
By Olivia Littleton
NASA’s Wallops Flight Facility, Wallops Island, Va.
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Last Updated Dec 10, 2024 EditorOlivia F. LittletonContactOlivia F. Littletonolivia.f.littleton@nasa.govLocationWallops Flight Facility Related Terms
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By NASA
Artist’s concept depicts new research that has expanded our understanding of exoplanet WASP-69 b’s “tail.” NASA/JPL-Caltech/R. Hurt (IPAC) The Planet
WASP-69 b
The Discovery
The exoplanet WASP-69 b has a “tail,” leaving a trail of gas in its wake.
Key Takeaway
WASP-69 b is slowly losing its atmosphere as light hydrogen and helium particles in the planet’s outer atmosphere escape the planet over time. But those gas particles don’t escape evenly around the planet, instead they are swept into a tail of gas by the stellar wind coming from the planet’s star.
Details
Hot Jupiters like WASP-69 b are super-hot gas giants orbiting their host stars closely. When radiation coming from a star heats up a planet’s outer atmosphere, the planet can experience photoevaporation, a process in which lightweight gases like hydrogen and helium are heated by this radiation and launched outward into space. Essentially, WASP-69 b’s star strips gas from the planet’s outer atmosphere over time.
What’s more, something called the stellar wind can shape this escaping gas into an exoplanetary tail.
The stellar wind is a continuous stream of charged particles that flow outwards into space from a star’s outer atmosphere, or corona. On Earth, the Sun’s stellar wind interacts with our planet’s magnetic field which can create beautiful auroras like the Northern Lights.
On WASP-69 b, the stellar wind coming from its host star actually shapes the gas escaping from the planet’s outer atmosphere. So, instead of gas just escaping evenly around the planet, “strong stellar winds can sculpt that outflow in tails that trail behind the planet,” said lead author Dakotah Tyler, an astrophysicist at the University of California, Los Angeles, likening this gaseous tail to a comet’s tail.
Because this tail is created by the stellar wind, however, that means it’s subject to change.
“If the stellar wind were to taper down, then you could imagine that the planet is still losing some of its atmosphere, but it just isn’t getting shaped into the tail,” Tyler said, adding that, without the stellar wind, that gas escaping on all sides of the planet would be spherical and symmetrical. “But if you crank up the stellar wind, that atmosphere then gets sculpted into a tail.”
Tyler likened the process to a windsock blowing in the breeze, with the sock forming a more structured shape when the wind picks up and it fills with air.
The tail that Tyler and his research team observed on WASP-69 b extended more than 7.5 times the radius of the planet, or over 350,000 miles. But it’s possible that the tail is even longer. The team had to end observations with the telescope before the tail’s signal disappeared, so this measurement is a lower limit on the tail’s true length at the time.
However, keep in mind that because the tail is influenced by the stellar wind, changes in the stellar wind could change the tail’s size and shape over time. Additionally changes in the stellar wind influence the tail’s size and shape, but since the tail is visible when illuminated by starlight, changes in stellar activity can also affect tail observations.
Exoplanet tails are still a bit mysterious, especially because they are subject to change. The study of exoplanet tails could help scientists to better understand how these tails form as well as the ever-changing relationship between the stellar and planetary atmospheres. Additionally, because these exoplanetary tails are shaped by stellar activity, they could serve as indicators of stellar behavior over time. This could be helpful for scientists as they seek to learn more about the stellar winds of stars other than the star we know the most about, our very own Sun.
Fun Facts
WASP-69 b is losing a lot of gas — about 200,000 tons per second. But it’s losing this gaseous atmosphere very slowly — so slowly in fact that there is no danger of the planet being totally stripped or disappearing. In general, every billion years, the planet is losing an amount of material that equals the mass of planet Earth.
The solar system that WASP-69 b inhabits is about 7 billion years old, so even though the rate of atmosphere loss will vary over time, you might estimate that this planet has lost the equivalent of seven Earths (in mass) of gas over that period.
The Discoverers
A team of scientists led by Dakotah Tyler of the University of California, Los Angeles published a paper in January, 2024 on their discovery, “WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 Rp,” in the journal, “The Astrophysical Journal.” The observations described in this paper were made by Keck/NIRSPEC (NIRSPEC is a spectrograph designed for Keck II).
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