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High Velocity Clouds Found to Dwell in Milky Way's Halo
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By NASA
5 min read
New NASA Mission to Reveal Earth’s Invisible ‘Halo’
A new NASA mission will capture images of Earth’s invisible “halo,” the faint light given off by our planet’s outermost atmospheric layer, the exosphere, as it morphs and changes in response to the Sun. Understanding the physics of the exosphere is a key step toward forecasting dangerous conditions in near-Earth space, a requirement for protecting Artemis astronauts traveling through the region on the way to the Moon or on future trips to Mars. The Carruthers Geocorona Observatory will launch from NASA’s Kennedy Space Center in Florida no earlier than Tuesday, Sept. 23.
Revealing Earth’s invisible edge
In the early 1970s, scientists could only speculate about how far Earth’s atmosphere extended into space. The mystery was rooted in the exosphere, our atmosphere’s outermost layer, which begins some 300 miles up. Theorists conceived of it as a cloud of hydrogen atoms — the lightest element in existence — that had risen so high the atoms were actively escaping into space.
But the exosphere reveals itself only via a faint “halo” of ultraviolet light known as the geocorona. Pioneering scientist and engineer Dr. George Carruthers set himself the task of seeing it. After launching a few prototypes on test rockets, he developed an ultraviolet camera ready for a one-way trip to space.
Apollo 16 astronaut John Young is pictured on the lunar surface with George Carruthers’ gold-plated Far Ultraviolet Camera/Spectrograph, the first Moon-based observatory. The Lunar Module “Orion” is on the right and the Lunar Roving Vehicle is parked in the background next to the American flag. NASA In April 1972, Apollo 16 astronauts placed Carruthers’ camera on the Moon’s Descartes Highlands, and humanity got its first glimpse of Earth’s geocorona. The images it produced were as stunning for what they captured as they were for what they didn’t.
“The camera wasn’t far enough away, being at the Moon, to get the entire field of view,” said Lara Waldrop, principal investigator for the Carruthers Geocorona Observatory. “And that was really shocking — that this light, fluffy cloud of hydrogen around the Earth could extend that far from the surface.” Waldrop leads the mission from the University of Illinois Urbana-Champaign, where George Carruthers was an alumnus.
The first image of UV light from Earth’s outer atmosphere, the geocorona, taken from a telescope designed and built by George Carruthers. The telescope took the image while on the Moon during the Apollo 16 mission in 1972. G. Carruthers (NRL) et al./Far UV Camera/NASA/Apollo 16 Our planet, in a new light
Today, the exosphere is thought to stretch at least halfway to the Moon. But the reasons for studying go beyond curiosity about its size.
As solar eruptions reach Earth, they hit the exosphere first, setting off a chain of reactions that sometimes culminate in dangerous space weather storms. Understanding the exosphere’s response is important to predicting and mitigating the effects of these storms. In addition, hydrogen — one of the atomic building blocks of water, or H2O — escapes through the exosphere. Mapping that escape process will shed light on why Earth retains water while other planets don’t, helping us find exoplanets, or planets outside our solar system, that might do the same.
NASA’s Carruthers Geocorona Observatory, named in honor of George Carruthers, is designed to capture the first continuous movies of Earth’s exosphere, revealing its full expanse and internal dynamics.
“We’ve never had a mission before that was dedicated to making exospheric observations,” said Alex Glocer, the Carruthers mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It’s really exciting that we’re going to get these measurements for the first time.”
Download this video from NASA’s Scientific Visualization Studio.
Journey to L1
At 531 pounds and roughly the size of a loveseat sofa, the Carruthers spacecraft will launch aboard a SpaceX Falcon 9 rocket along with NASA’s IMAP (Interstellar Mapping and Acceleration Probe) spacecraft and the National Oceanic and Atmospheric Administration’s SWFO-L1 (Space Weather Follow On – Lagrange 1) space weather satellite. After launch, all three missions will commence a four-month cruise phase to Lagrange point 1 (L1), a location approximately 1 million miles closer to the Sun than Earth is. After a one-month period for science checkouts, Carruthers’ two-year science phase will begin in March 2026.
Artist’s concept of the five Sun-Earth Lagrange points in space. At Lagrange points, the gravitational pull of two large masses counteract, allowing spacecraft to reduce fuel consumption needed to remain in position. The L1 point of the Earth-Sun system affords an uninterrupted view of the Sun and will be home to three new heliophysics missions in 2025: NASA’s Interstellar Mapping and Acceleration Probe (IMAP), NASA’s Carruthers Geocorona Observatory, and NOAA’s Space Weather Follow-On – Lagrange 1 (SWFO – L1). NASA’s Conceptual Image Lab/Krystofer Kim From L1, roughly four times farther away than the Moon, Carruthers will capture a comprehensive view of the exosphere using two ultraviolet cameras, a near-field imager and a wide-field imager.
“The near-field imager lets you zoom up really close to see how the exosphere is varying close to the planet,” Glocer said. “The wide-field imager lets you see the full scope and expanse of the exosphere, and how it’s changing far away from the Earth’s surface.”
The two imagers will together map hydrogen atoms as they move through the exosphere and ultimately out to space. But what we learn about atmospheric escape on our home planet applies far beyond it.
“Understanding how that works at Earth will greatly inform our understanding of exoplanets and how quickly their atmospheres can escape,” Waldrop said.
By studying the physics of Earth, the one planet we know that supports life, the Carruthers Geocorona Observatory can help us know what to look for elsewhere in the universe.
The Carruthers Geocorona Observatory mission is led by Lara Waldrop from the University of Illinois Urbana-Champaign. The Space Sciences Laboratory at the University of California, Berkeley leads mission implementation, design and development of the payload in collaboration with Utah State University’s Space Dynamics Laboratory. The Carruthers spacecraft was designed and built by BAE Systems. NASA’s Explorers and Heliophysics Projects Division at the agency’s Goddard Space Flight Center in Greenbelt, Maryland, manages the mission for the agency’s Heliophysics Division at NASA Headquarters in Washington.
By Miles Hatfield
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Sep 18, 2025 Related Terms
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By NASA
NASA; JAXA The Milky Way appears above Earth’s bright atmospheric glow in this Aug. 23, 2025, photograph from the International Space Station as it soared 261 miles above southern Iran at approximately 12:54 a.m. local time. The camera was configured for low light and long duration settings.
Our home galaxy has hundreds of billions of stars, enough gas and dust to make billions more stars, and at least ten times as much dark matter as all the stars and gas put together. NASA’s Nancy Grace Roman Space Telescope – slated to launch no later than May 2027 – will help scientists better understand the gas and dust strewn between stars in our galaxy, known as the interstellar medium.
Image credit: NASA; JAXA
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By NASA
3 min read
Weird Ways to Observe the Moon
Sun Funnels in action! Starting clockwise from the bottom left, a standalone Sun Funnel; attached to a small refractor to observe the transit of Mercury in 2019; attached to a large telescope in preparation for evening lunar observing; projection of the Moon on a funnel from a medium-size scope (5 inches). Night Sky Network International Observe the Moon Night is on October 4, 2025, this year– but you can observe the Moon whenever it’s up, day or night! While binoculars and telescopes certainly reveal incredible details of our neighbor’s surface, bringing out dark seas, bright craters, and numerous odd fissures and cracks, these tools are not the only way to observe details about our Moon. There are more ways to observe the Moon than you might expect, just using common household materials.
Put on a pair of sunglasses, especially polarized sunglasses! You may think this is a joke, but the point of polarized sunglasses is to dramatically reduce glare, and so they allow your eyes to pick out some lunar details! Surprisingly, wearing sunglasses even helps during daytime observations of the Moon.
One unlikely tool is the humble plastic bottle cap! John Goss from the Roanoke Valley Astronomical Society shared these directions on how to make your own bottle cap lunar viewer, which was suggested to him by Fred Schaaf many years ago as a way to also view the thin crescent of Venus when close to the Sun:
“The full Moon is very bright, so much that details are overwhelmed by the glare. Here is an easy way to see more! Start by drilling a 1/16-inch (1.5 mm) diameter hole in a plastic soft drink bottle cap. Make sure it is an unobstructed, round hole. Now look through the hole at the bright Moon. The image brightness will be much dimmer than normal – over 90% dimmer – reducing or eliminating any lunar glare. The image should also be much sharper because the bottle cap blocks light from entering the outer portion of your pupil, where imperfections of the eye’s curving optical path likely lie.” Many report seeing a startling amount of lunar detail!
You can project the Moon! Have you heard of a “Sun Funnel”? It’s a way to safely view the Sun by projecting the image from an eyepiece to fabric stretched across a funnel mounted on top. It’s easy to make at home, too – directions are here: bit.ly/sunfunnel. Depending on your equipment, a Sun Funnel can view the Moon as well as the Sun– a full Moon gives off more than enough light to project from even relatively small telescopes. Large telescopes will project the full Moon and its phases with varying levels of detail; while not as crisp as direct eyepiece viewing, it’s still an impressive sight! You can also mount your smartphone or tablet to your eyepiece for a similar Moon-viewing experience, but the funnel doesn’t need batteries.
Of course, you can join folks in person or online to celebrate our Moon on October 4, 2025, with International Observe the Moon Night – find details at moon.nasa.gov/observe.
Originally posted by Dave Prosper: September 2021
Last Updated by Kat Troche: March 2025
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By NASA
Explore Webb Science James Webb Space Telescope (JWST) NASA’s Webb Observes Immense… Webb News Latest News Latest Images Webb’s Blog 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 Webb Timeline Science Overview and Goals Early Universe Galaxies Over Time Star Lifecycle Other Worlds Science Explainers Observatory Overview Launch Deployment 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 Webb’s First Images Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 6 Min Read NASA’s Webb Observes Immense Stellar Jet on Outskirts of Our Milky Way
Webb’s image of the enormous stellar jet in Sh2-284 provides evidence that protostellar jets scale with the mass of their parent stars—the more massive the stellar engine driving the plasma, the larger the resulting jet. Full image shown below. Credits:
Image: NASA, ESA, CSA, STScI, Yu Cheng (NAOJ); Image Processing: Joseph DePasquale (STScI) A blowtorch of seething gasses erupting from a volcanically growing monster star has been captured by NASA’s James Webb Space Telescope. Stretching across 8 light-years, the length of the stellar eruption is approximately twice the distance between our Sun and the next nearest stars, the Alpha Centauri system. The size and strength of this particular stellar jet, located in a nebula known as Sharpless 2-284 (Sh2-284 for short), qualifies it as rare, say researchers.
Streaking across space at hundreds of thousands of miles per hour, the outflow resembles a double-bladed dueling lightsaber from the Star Wars films. The central protostar, weighing as much as ten of our Suns, is located 15,000 light-years away in the outer reaches of our galaxy.
The Webb discovery was serendipitous. “We didn’t really know there was a massive star with this kind of super-jet out there before the observation. Such a spectacular outflow of molecular hydrogen from a massive star is rare in other regions of our galaxy,” said lead author Yu Cheng of the National Astronomical Observatory of Japan.
Image A: Stellar Jet in Sh2-284 (NIRCam Image)
Webb’s image of the enormous stellar jet in Sh2-284 provides evidence that protostellar jets scale with the mass of their parent stars—the more massive the stellar engine driving the plasma, the larger the resulting jet. Image: NASA, ESA, CSA, STScI, Yu Cheng (NAOJ); Image Processing: Joseph DePasquale (STScI) This unique class of stellar fireworks are highly collimated jets of plasma shooting out from newly forming stars. Such jetted outflows are a star’s spectacular “birth announcement” to the universe. Some of the infalling gas building up around the central star is blasted along the star’s spin axis, likely under the influence of magnetic fields.
Today, while hundreds of protostellar jets have been observed, these are mainly from low-mass stars. These spindle-like jets offer clues into the nature of newly forming stars. The energetics, narrowness, and evolutionary time scales of protostellar jets all serve to constrain models of the environment and physical properties of the young star powering the outflow.
“I was really surprised at the order, symmetry, and size of the jet when we first looked at it,” said co-author Jonathan Tan of the University of Virginia in Charlottesville and Chalmers University of Technology in Gothenburg, Sweden.
Its detection offers evidence that protostellar jets must scale up with the mass of the star powering them. The more massive the stellar engine propelling the plasma, the larger the gusher’s size.
The jet’s detailed filamentary structure, captured by Webb’s crisp resolution in infrared light, is evidence the jet is plowing into interstellar dust and gas. This creates separate knots, bow shocks, and linear chains.
The tips of the jet, lying in opposite directions, encapsulate the history of the star’s formation. “Originally the material was close into the star, but over 100,000 years the tips were propagating out, and then the stuff behind is a younger outflow,” said Tan.
Outlier
At nearly twice the distance from the galactic center as our Sun, the host proto-cluster that’s home to the voracious jet is on the periphery of our Milky Way galaxy.
Within the cluster, a few hundred stars are still forming. Being in the galactic hinterlands means the stars are deficient in heavier elements beyond hydrogen and helium. This is measured as metallicity, which gradually increases over cosmic time as each passing stellar generation expels end products of nuclear fusion through winds and supernovae. The low metallicity of Sh2-284 is a reflection of its relatively pristine nature, making it a local analog for the environments in the early universe that were also deficient in heavier elements.
“Massive stars, like the one found inside this cluster, have very important influences on the evolution of galaxies. Our discovery is shedding light on the formation mechanism of massive stars in low metallicity environments, so we can use this massive star as a laboratory to study what was going on in earlier cosmic history,” said Cheng.
Unrolling Stellar Tapestry
Stellar jets, which are powered by the gravitational energy released as a star grows in mass, encode the formation history of the protostar.
“Webb’s new images are telling us that the formation of massive stars in such environments could proceed via a relatively stable disk around the star that is expected in theoretical models of star formation known as core accretion,” said Tan. “Once we found a massive star launching these jets, we realized we could use the Webb observations to test theories of massive star formation. We developed new theoretical core accretion models that were fit to the data, to basically tell us what kind of star is in the center. These models imply that the star is about 10 times the mass of the Sun and is still growing and has been powering this outflow.”
For more than 30 years, astronomers have disagreed about how massive stars form. Some think a massive star requires a very chaotic process, called competitive accretion.
In the competitive accretion model, material falls in from many different directions so that the orientation of the disk changes over time. The outflow is launched perpendicularly, above and below the disk, and so would also appear to twist and turn in different directions.
“However, what we’ve seen here, because we’ve got the whole history – a tapestry of the story – is that the opposite sides of the jets are nearly 180 degrees apart from each other. That tells us that this central disk is held steady and validates a prediction of the core accretion theory,” said Tan.
Where there’s one massive star, there could be others in this outer frontier of the Milky Way. Other massive stars may not yet have reached the point of firing off Roman-candle-style outflows. Data from the Atacama Large Millimeter Array in Chile, also presented in this study, has found another dense stellar core that could be in an earlier stage of construction.
The paper has been accepted for publication in The Astrophysical Journal.
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).
To learn more about Webb, visit:
https://science.nasa.gov/webb
Related Information
View more: Webb images of other protostar outflows – HH 49/50, L483, HH 46/47, and HH 211
View more: Data visualization of protostar outflows – HH 49/50
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Explore the jets emitted by young stars in multiple wavelengths: ViewSpace Interactive
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Related Images & Videos
Stellar Jet in Sh2-284 (NIRCam Image)
Webb’s image of the enormous stellar jet in Sh2-284 provides evidence that protostellar jets scale with the mass of their parent stars–the more massive the stellar engine driving the plasma, the larger the resulting jet.
Stellar Jet in Sh2-284 (NIRCam Compass Image)
This image of the stellar jet in Sh2-284, captured by NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera), shows compass arrows, scale bar, and color key for reference.
Immense Stellar Jet in Sh2-284
This video shows the relative size of two different protostellar jets imaged by NASA’s James Webb Space Telescope. The first image shown is an extremely large protostellar jet located in Sh2-284, 15,000 light-years away from Earth. The outflows from the massive central prot…
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Last Updated Sep 10, 2025 Location NASA Goddard Space Flight Center Contact Media Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov
Ray Villard
Space Telescope Science Institute
Baltimore, Maryland
Christine Pulliam
Space Telescope Science Institute
Baltimore, Maryland
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The journal paper by Y. Cheng et al.
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