NASA's Webb Snaps Supersonic Outflow of Young Star

HH 211 (NIRCam Image)
Credits: Image: ESA/Webb, NASA, CSA, Tom Ray (Dublin)

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Herbig-Haro (HH) objects are luminous regions surrounding newborn stars, formed when stellar winds or jets of gas spewing from these newborn stars form shock waves colliding with nearby gas and dust at high speeds. This image of HH 211 from NASA’s James Webb Space Telescope reveals an outflow from a Class 0 protostar, an infantile analog of our Sun when it was no more than a few tens of thousands of years old and with a mass only 8% of the present-day Sun. (It will eventually grow into a star like the Sun.)

Infrared imaging is powerful in studying newborn stars and their outflows, because such stars are invariably still embedded within the gas from the molecular cloud in which they formed. The infrared emission of the star’s outflows penetrates the obscuring gas and dust, making a Herbig-Haro object like HH 211 ideal for observation with Webb’s sensitive infrared instruments. Molecules excited by the turbulent conditions, including molecular hydrogen, carbon monoxide, and silicon monoxide, emit infrared light that Webb can collect to map out the structure of the outflows.

The image showcases a series of bow shocks to the southeast (lower-left) and northwest (upper-right) as well as the narrow bipolar jet that powers them. Webb reveals this scene in unprecedented detail — roughly 5 to 10 times higher spatial resolution than any previous images of HH 211. The inner jet is seen to “wiggle” with mirror symmetry on either side of the central protostar. This is in agreement with observations on smaller scales and suggests that the protostar may in fact be an unresolved binary star.

Earlier observations of HH 211 with ground-based telescopes revealed giant bow shocks moving away from us (northwest) and moving towards us (southeast) and cavity-like structures in shocked hydrogen and carbon monoxide respectively, as well as a knotty and wiggling bipolar jet in silicon monoxide. Researchers have used Webb’s new observations to determine that the object’s outflow is relatively slow in comparison to more evolved protostars with similar types of outflows.

The team measured the velocities of the innermost outflow structures to be roughly 48-60 miles per second (80 to 100 kilometers per second). However, the difference in velocity between these sections of the outflow and the leading material they’re colliding with — the shock wave — is much smaller. The researchers concluded that outflows from the youngest stars, like that in the center of HH 211, are mostly made up of molecules, because the comparatively low shock wave velocities are not energetic enough to break the molecules apart into simpler atoms and ions.

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 the Canadian Space Agency

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About This Release

Credits:

Media Contact:

Bethany Downer
ESA/Webb, Baltimore, Maryland

Hannah Braun
Space Telescope Science Institute, Baltimore, Maryland

Science: Tom Ray (Dublin)

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team.

Related Links and Documents

• The ESA press release

Source: NASA's James Webb Space Telescope/News

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Webb Snaps Highly Detailed Infrared Image of Actively Forming Stars

Herbig-Haro 46/47 (NIRCam Image)
Credits: Image: NASA, ESA, CSA
Image Processing: Joseph DePasquale (STScI)

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Young stars are rambunctious!

NASA’s James Webb Space Telescope has captured the “antics” of a pair of actively forming young stars, known as Herbig-Haro 46/47, in high-resolution near-infrared light. To find them, trace the bright pink and red diffraction spikes until you hit the center: The stars are within the orange-white splotch. They are buried deeply in a disk of gas and dust that feeds their growth as they continue to gain mass. The disk is not visible, but its shadow can be seen in the two dark, conical regions surrounding the central stars.

The most striking details are the two-sided lobes that fan out from the actively forming central stars, represented in fiery orange. Much of this material was shot out from those stars as they repeatedly ingest and eject the gas and dust that immediately surround them over thousands of years.

When material from more recent ejections runs into older material, it changes the shape of these lobes. This activity is like a large fountain being turned on and off in rapid, but random succession, leading to billowing patterns in the pool below it. Some jets send out more material and others launch at faster speeds. Why? It’s likely related to how much material fell onto the stars at a particular point in time.

The stars’ more recent ejections appear in a thread-like blue. They run just below the red horizontal diffraction spike at 2 o’clock. Along the right side, these ejections make clearer wavy patterns. They are disconnected at points, and end in a remarkable uneven light purple circle in the thickest orange area. Lighter blue, curly lines also emerge on the left, near the central stars, but are sometimes overshadowed by the bright red diffraction spike.

All of these jets are crucial to star formation itself. Ejections regulate how much mass the stars ultimately gather. (The disk of gas and dust feeding the stars is small. Imagine a band tightly tied around the stars.)

Now, turn your eye to the second most prominent feature: the effervescent blue cloud. This is a region of dense dust and gas, known both as a nebula and more formally as a Bok globule. When viewed mainly in visible light, it appears almost completely black – only a few background stars peek through. In Webb’s crisp near-infrared image, we can see into and through the gauzy layers of this cloud, bringing a lot more of Herbig-Haro 46/47 into focus, while also revealing a deep range of stars and galaxies that lie well beyond it. The nebula’s edges appear in a soft orange outline, like a backward L along the right and bottom.

This nebula is significant – its presence influences the shapes of the jets shot out by the central stars. As ejected material rams into the nebula on the lower left, there is more opportunity for the jets to interact with molecules within the nebula, causing them both to light up.

There are two other areas to look at to compare the asymmetry of the two lobes. Glance toward the upper right to pick out a blobby, almost sponge-shaped ejecta that appears separate from the larger lobe. Only a few threads of semi-transparent wisps of material point toward the larger lobe. Almost transparent, tentacle-like shapes also appear to be drifting behind it, like streamers in a cosmic wind. In contrast, at lower left, look beyond the hefty lobe to find an arc. Both are made up of material that was pushed the farthest and possibly by earlier ejections. The arcs appear to be pointed in different directions, and may have originated from different outflows.

Take another long look at this image. Although it appears Webb has snapped Herbig-Haro 46/47 edge-on, one side is angled slightly closer to Earth. Counterintuitively, it’s the smaller right half. Though the left side is larger and brighter, it is pointing away from us.

Over millions of years, the stars in Herbig-Haro 46/47 will fully form – clearing the scene of these fantastic, multihued ejections, allowing the binary stars to take center stage against a galaxy-filled background.

Webb can reveal so much detail in Herbig-Haro 46/47 for two reasons. The object is relatively close to Earth, and Webb’s image is made up of several exposures, which adds to its depth.

Herbig-Haro 46/47 lies only 1,470 light-years away in the Vela Constellation.

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 the Canadian Space Agency.

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About This Release

Credits:

Media Contact:

Claire Blome
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Permissions: Content Use Policy

 Contact Us: Direct inquiries to the News Team.

Related Links and Documents

• The ESA press release
• ViewSpace Interactive: Herbig-Haro 46/47

Source: NASA's James Webb Space Telescope/News

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Cassini sheds Light on Cosmic Particle Accelerators

 Cassini at Saturn’s bow shock

The international Cassini spacecraft exploring the magnetic environment of Saturn. The image is not to scale. Saturn’s magnetosphere is depicted in grey, while the complex bow shock region – the shock wave in the solar wind that surrounds the magnetosphere – is shown in blue.

While crossing the bow shock on 3 February 2007, Cassini recorded a particularly strong shock (an Alfvén Mach number of approximately 100) under a ‘quasi-parallel’ magnetic field configuration, during which significant particle acceleration was detected for the first time. The findings provide insight into particle acceleration at the shocks surrounding the remnants of supernova explosions.Copyright ESA

During a chance encounter with an unusually strong blast of solar wind arriving at Saturn, the international Cassini spacecraft detected particles being accelerated to ultra-high energies, similar to the acceleration that takes place around supernova explosions. 

Shock waves are commonplace in the Universe, for example in the aftermath of a stellar explosion as debris accelerates outwards in a supernova remnant, or when the flow of particles from the Sun – the solar wind – impinges on the magnetic field of a planet to form a bow shock. 

Under certain magnetic field orientations and depending on the strength of the shock, particles can be accelerated to close to the speed of light at these boundaries. Indeed, very strong shocks at young supernova remnants are known to boost electrons to ultra-relativistic energies, and may be the dominant source of cosmic rays, high-energy particles that pervade our Galaxy. 

Space telescopes reveal evidence for accelerated electrons at supernova remnant shocks as X-ray emission, but these observations are made at great distances and thus the orientation of the local magnetic field can only be poorly measured at best. Without this crucial information, it is difficult to gain a full understanding of the shock acceleration process. 

Scientists want to understand how the acceleration of electrons in very strong shocks with large ‘Mach numbers’ depends on the angle between the magnetic field and a vector at right angles to the shock front. In particular, they are interested in what happens in a ‘quasi-parallel’ shock, where the field and vector are almost aligned, as may be found in supernova remnants. 

 Close up of magnetic fields

Illustration of quasi-parallel (top) and quasi-perpendicular (bottom) magnetic field conditions at a planetary bow shock. Under quasi-parallel conditions, the magnetic field is roughly pointing toward the shock surface, almost parallel to a vector at right angles to the shock front (red arrow). Under quasi-perpendicular conditions, the magnetic field is close to aligned with the shock surface, that is, almost perpendicular to the shock vector. Copyright ESA

Shocks in the solar wind in the Solar System are much more accessible and can be studied in greater detail. To date, however, particle acceleration has only been seen in ‘quasi-perpendicular’ shocks, where the magnetic field and shock vector are almost perpendicular. 

But this new study by Cassini describes the first detection of significant acceleration of electrons in a quasi-parallel shock at Saturn, coinciding with what may be the strongest shock ever encountered at the ringed planet. 

“Cassini has crossed Saturn’s bow shock hundreds of times, recording typical Alfvén Mach numbers of around 12. But during one particular crossing in early 2007, we measured a value of ~100, during which time the shock was quasi-parallel,” describes Adam Masters of the Institute of Space and Astronautical Science, Japan, and lead author of the paper reporting the results in Nature Physics.  

The findings confirm that, at high Mach numbers like those of the shocks surrounding supernova remnants, quasi-parallel shocks can become considerably more effective electron accelerators than previously thought. This result sheds new light on the complex process of cosmic particle acceleration. 

“Cassini has essentially given us the capability of studying the nature of a supernova shock in situ in our own Solar System, bridging the gap to distant high-energy astrophysical phenomena that are usually only studied remotely,” adds Dr Masters. 

“The Cassini observations have given us a glimpse of a process never before seen directly, providing new information on how high-energy particles, like cosmic rays, are accelerated to such high velocities by magnetic fields throughout the Universe,” says Nicolas Altobelli, ESA’s Cassini project scientist. 

Notes for Editors

“Electron acceleration to relativistic energies at a strong quasi-parallel shock wave” by A. Masters et al. is published in Nature Physics, 17 February 2013.

The electron observations were carried out using the Electron Spectrometer of the Cassini Plasma Spectrometer, and the Low-Energy Magnetospheric Measurements System of the Cassini Magnetospheric Imaging Instrument. The high Alfvén Mach number of M_A ~ 100 was measured on 3 February 2007.

The Cassini–Huygens mission is a cooperative project of NASA, ESA and ASI, the Italian space agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington.

Source: ESA