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By European Space Agency
Video: 00:04:31 The double-satellite Proba-3 is the most ambitious member yet of ESA’s Proba family of experimental missions. Two spacecraft will fly together as one, maintaining precise formation down to a single millimetre. One will block out the fiery disc of the Sun for the other, to enable prolonged observations of the Sun’s surrounding atmosphere, or ‘corona’, the source of the solar wind and space weather. Usually, the corona can only be glimpsed for a few minutes during terrestrial total solar eclipses. Proba-3 aims to reproduce such eclipses for up to six hours at a time, in a highly elliptical orbit taking it more than 60 000 km from Earth. The two spacecraft are being launched together by India’s PSLV-XL launcher from the Satish Dhawan Space Centre. Follow the mission’s deployment and commissioning, up to its first glimpse of the corona, in this overview video.
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By NASA
3 min read
Buckle Up: NASA-Funded Study Explores Turbulence in Molecular Clouds
This image shows the distribution of density in a simulation of a turbulent molecular cloud. NASA/E. Scannapieco et al (2024) On an airplane, motions of the air on both small and large scales contribute to turbulence, which may result in a bumpy flight. Turbulence on a much larger scale is important to how stars form in giant molecular clouds that permeate the Milky Way.
In a new NASA-funded study in the journal Science Advances, scientists created simulations to explore how turbulence interacts with the density of the cloud. Lumps, or pockets of density, are the places where new stars will be born. Our Sun, for example, formed 4.6 billion years ago in a lumpy portion of a cloud that collapsed.
“We know that the main process that determines when and how quickly stars are made is turbulence, because it gives rise to the structures that create stars,” said Evan Scannapieco, professor of astrophysics at Arizona State University and lead author of the study. “Our study uncovers how those structures are formed.”
Giant molecular clouds are full of random, turbulent motions, which are caused by gravity, stirring by the galactic arms and winds, jets, and explosions from young stars. This turbulence is so strong that it creates shocks that drive the density changes in the cloud.
The simulations used dots called tracer particles to traverse a molecular cloud and travel along with the material. As the particles travel, they record the density of the part of the cloud they encounter, building up a history of how pockets of density change over time. The researchers, who also included Liubin Pan from Sun Yat Sen University in China, Marcus Brüggen from the University of Hamburg in Germany, and Ed Buie II from Vassar College in Poughkeepsie, New York, simulated eight scenarios, each with a different set of realistic cloud properties.
This animation shows the distribution of density in a simulation of a turbulent molecular cloud. The colors represent density, with dark blue indicating the least dense regions and red indicating the densest regions. Credit: NASA/E. Scannapieco et al (2024) The team found that the speeding up and slowing down of shocks plays an essential role in the path of the particles. Shocks slow down as they go into high-density gas and speed up as they go into low-density gas. This is akin to how an ocean wave strengthens when it hits shallow water by the shore.
When a particle hits a shock, the area around it becomes more dense. But because shocks slow down in dense regions, once lumps become dense enough, the turbulent motions can’t make them any denser. These lumpiest high-density regions are where stars are most likely to form.
While other studies have explored molecular cloud density structures, this simulation allows scientists to see how those structures form over time. This informs scientists’ understanding of how and where stars are likely to be born.
“Now we can understand better why those structures look the way they do because we’re able to track their histories,” said Scannapieco.
This image shows part of a simulation of a molecular cloud. The colors represent density, with dark blue indicating the least dense regions and red indicating the densest regions. Tracer particles, represented by black dots, traverse the simulated cloud. By examining how they interact with shocks and pockets of density, scientists can better understand the structures in molecular clouds that lead to star formation. NASA/E. Scannapieco et al (2024) NASA’s James Webb Space Telescope is exploring the structure of molecular clouds. It is also exploring the chemistry of molecular clouds, which depends on the history of the gas modeled in the simulations. New measurements like these will inform our understanding of star formation.
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
New findings using data from NASA’s IXPE (Imaging X-ray Polarimetry Explorer) mission offer unprecedented insight into the shape and nature of a structure important to black holes called a corona.
A corona is a shifting plasma region that is part of the flow of matter onto a black hole, about which scientists have only a theoretical understanding. The new results reveal the corona’s shape for the first time, and may aid scientists’ understanding of the corona’s role in feeding and sustaining black holes.
This illustration of material swirling around a black hole highlights a particular feature, called the “corona,” that shines brightly in X-ray light. In this depiction, the corona can be seen as a purple haze floating above the underlying accretion disk, and extending slightly inside of its inner edge. The material within the inner accretion disk is incredibly hot and would glow with a blinding blue-white light, but here has been reduced in brightness to make the corona stand out with better contrast. Its purple color is purely illustrative, standing in for the X-ray glow that would not be obvious in visible light. The warp in the disk is a realistic representation of how the black hole’s immense gravity acts like an optical lens, distorting our view of the flat disk that encircles it. NASA/Caltech-IPAC/Robert Hurt Many black holes, so named because not even light can escape their titanic gravity, are surrounded by accretion disks, debris-cluttered whirlpools of gas. Some black holes also have relativistic jets – ultra-powerful outbursts of matter hurled into space at high speed by black holes that are actively eating material in their surroundings.
Less well known, perhaps, is that snacking black holes, much like Earth’s Sun and other stars, also possess a superheated corona. While the Sun’s corona, which is the star’s outermost atmosphere, burns at roughly 1.8 million degrees Fahrenheit, the temperature of a black hole corona is estimated at billions of degrees.
Astrophysicists previously identified coronae among stellar-mass black holes – those formed by a star’s collapse – and supermassive black holes such as the one at the heart of the Milky Way galaxy.
“Scientists have long speculated on the makeup and geometry of the corona,” said Lynne Saade, a postdoctoral researcher at NASA’s Marshall Space Flight Center in Huntsville, Alabama, and lead author of the new findings. “Is it a sphere above and below the black hole, or an atmosphere generated by the accretion disk, or perhaps plasma located at the base of the jets?”
Enter IXPE, which specializes in X-ray polarization, the characteristic of light that helps map the shape and structure of even the most powerful energy sources, illuminating their inner workings even when the objects are too small, bright, or distant to see directly. Just as we can safely observe the Sun’s corona during a total solar eclipse, IXPE provides the means to clearly study the black hole’s accretion geometry, or the shape and structure of its accretion disk and related structures, including the corona.
“X-ray polarization provides a new way to examine black hole accretion geometry,” Saade said. “If the accretion geometry of black holes is similar regardless of mass, we expect the same to be true of their polarization properties.”
IXPE demonstrated that, among all black holes for which coronal properties could be directly measured via polarization, the corona was found to be extended in the same direction as the accretion disk – providing, for the first time, clues to the corona’s shape and clear evidence of its relationship to the accretion disk. The results rule out the possibility that the corona is shaped like a lamppost hovering over the disk.
The research team studied data from IXPE’s observations of 12 black holes, among them Cygnus X-1 and Cygnus X-3, stellar-mass binary black hole systems about 7,000 and 37,000 light-years from Earth, respectively, and LMC X-1 and LMC X-3, stellar-mass black holes in the Large Magellanic Cloud more than 165,000 light-years away. IXPE also observed a number of supermassive black holes, including the one at the center of the Circinus galaxy, 13 million light-years from Earth, and those in galaxies NGC 1068 and NGC 4151, 47 million light-years away and nearly 62 million light-years away, respectively.
Stellar mass black holes typically have a mass roughly 10 to 30 times that of Earth’s Sun, whereas supermassive black holes may have a mass that is millions to tens of billions of times larger. Despite these vast differences in scale, IXPE data suggests both types of black holes create accretion disks of similar geometry.
That’s surprising, said Marshall astrophysicist Philip Kaaret, principal investigator for the IXPE mission, because the way the two types are fed is completely different.
“Stellar-mass black holes rip mass from their companion stars, whereas supermassive black holes devour everything around them,” he said. “Yet the accretion mechanism functions much the same way.”
That’s an exciting prospect, Saade said, because it suggests that studies of stellar-mass black holes – typically much closer to Earth than their much more massive cousins – can help shed new light on properties of supermassive black holes as well.
The team next hopes to make additional examinations of both types.
Saade anticipates there’s much more to glean from X-ray studies of these behemoths. “IXPE has provided the first opportunity in a long time for X-ray astronomy to reveal the underlying processes of accretion and unlock new findings about black holes,” she said.
The complete findings are available in the latest issue of The Astrophysical Journal.
More about IXPE
IXPE, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint NASA and Italian Space Agency mission with partners and science collaborators in 12 countries. IXPE is led by Marshall. Ball Aerospace, headquartered in Broomfield, Colorado, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder.
Learn more about IXPE’s ongoing mission here:
https://www.nasa.gov/ixpe
Elizabeth Landau
NASA Headquarters
elizabeth.r.landau@nasa.gov
202-358-0845
Lane Figueroa
NASA’s Marshall Space Flight Center
256-544-0034
lane.e.figueroa@nasa.gov
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Last Updated Oct 17, 2024 EditorBeth RidgewayLocationMarshall Space Flight Center Related Terms
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By European Space Agency
Video: 00:01:27 The ESA-led Solar Orbiter mission has experienced its second close encounter with the Sun. It is delivering more stunning data, and at higher resolution than ever before.
The moment of closest approach took place on 12 October at 19:12 UTC (21:12 CEST), when Solar Orbiter was just 29% of the Earth’s distance from the Sun. This movie comes from 13 October, when the spacecraft’s Extreme Ultraviolet Imager (EUI) returned the highest resolution movie of the quiet corona ever taken with any instrument.
Each pixel on this movie spans 105 km on the surface of the Sun. This means that if EUI were to look at the Earth from this distance, our entire planet would span just 120 pixels across. The movie itself contains 2048 across, meaning that 17 Earths would fit side by side across this image.
The corona is the Sun’s outer atmosphere. It is termed quiet when there is little appreciable solar activity such as flares or coronal mass ejections. This movie, and others taken during the encounter, show the dynamic nature of the Sun's million degree-hot corona. The electrically charged gas here, known as plasma, is in constant motion, guided and accelerated by changes of the Sun's magnetic field. The arches of bright plasma in the movie are being held in place by loops of magnetism that burst up into the corona from the Sun’s interior.
The Sun is currently ramping up for a peak in its activity levels, known as solar maximum, in 2025. So views of a quiet corona are likely to become rarer in the coming few years.
The Sun launches a solar wind of particles that streams out through the Solar System. It originates in the corona but the precise mechanism by which this happens is poorly understood. Investigating this phenomenon is a key focus for solar physicists, and one of Solar Orbiter’s main scientific objectives.
This particular encounter benefited from Solar Orbiter rapidly flying in the direction of Earth. This allowed much more data to be downlinked. It also allowed for coordinated observations of solar features to be made with Earth-based telescopes, from 21 October onwards.
“I am very much looking forward to data from all ten instruments being downloaded during the next few weeks, and then the world-wide science community will be very busy discovering new things using this unique data set,” says Daniel Müller, ESA Project Scientist for Solar Orbiter.
Solar Orbiter is a space mission of international collaboration between ESA and NASA, operated by ESA.
This movie was enhanced with Wavelet Optimized Whitening technique.
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By USH
Parker Solar Probe launched in 2018 to explore the mysteries of the Sun by traveling closer to it than any spacecraft before. Three years after launch and decades after first conception, Parker has finally arrived.
For the first time in history, a spacecraft has touched the Sun. NASA’s Parker Solar Probe has now flown through the Sun’s upper atmosphere – the corona – and sampled particles and magnetic fields there.
As Parker Solar Probe passed through the Sun's corona, the spacecraft flew by structures called coronal streamers. These structures can be seen as bright features moving upward and downward in the first video compiled from the spacecraft's WISPR (Wide-field Imager for Parker Solar Probe) instrument.
Such a view is only possible because the spacecraft flew above and below the streamers inside the corona. Until now, streamers have only been seen from afar. They are visible from Earth during total solar eclipses.
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