Semi-heavy water ice detected around young Sun-like star

JWST image of the protostellar system L1527 IRS. The protostar is, embedded within a cloud of dust, gas and ice (including semi-heavy water ice), which feeds its growth. © NASA/ESA/CSA/STScI

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For the first time, a team at Leiden University led by Ewine van Dishoek, an external scientific member of MPE, has robustly detected semi-heavy water ice around a young, sun-like star. These results support the theory that some of the water in our solar system originated before the Sun and its planets formed. The researchers used the James Webb Space Telescope to make their discovery, which they have published in The Astrophysical Journal Letters.

One way astronomers trace the origin of water is by measuring its deuteration ratio. Deuterium is a stable isotope of hydrogen whose nucleus contains a neutron as well as the proton. Water composed of one deuterium atom and one hydrogen atom – HDO rather than H₂O – is also known as semi-heavy water. A high fraction of semi-heavy water indicates that the water formed in a very cold place, such as the primitive dark clouds of dust, ice, and gas from which stars are born.

In our oceans, comets, and icy moons, up to one in a couple of thousand water molecules consists of semi-heavy water. This is about ten times higher than expected based on the composition of the Sun. Therefore, astronomers hypothesise that some of the water pin our solar system originated as ice in dark clouds hundreds of thousands of years before the birth of the Sun. To confirm this, they must measure the deuteration ratio of water ice in star-forming regions.

An international team of astronomers has now detected a high ratio of semi-heavy water ice in a protostellar envelope. This is the cloud of material surrounding a star in its embryonic stages.

The astronomers used the James Webb Space Telescope. Prior to its launch, the water deuteration ratio in star-forming regions could only be reliably measured in the gas phase, where chemical alteration occurs."Now, with the unprecedented sensitivity of Webb, we observe a beautifully clear semi-heavy water ice signature toward a protostar," says Katie Slavicinska, the Leiden University (Netherlands) PhD student who led the study.

The L1527 water deuteration ratio is very similar to that of some comets, as well as to the protoplanetary disk of a more evolved young star. This suggests that the water found in all of these objects has similar cold and ancient chemical origins.

"This finding adds to the mounting evidence that the bulk of water ice makes its journey largely unchanged from the earliest to the latest stages of star formation," says co-author Ewine van Dishoeck, a professor of astronomy at Leiden University who has spent much of her career tracing the journey of water through space.

Source:  Max Planck Institute for Extraterrestrial Physics/Press Releases

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Contact:

Ewine van Dishoeck
external scientific member
tel: +49 89 30000-3592
fax: +49 89 30000-3569
ewine@mpe.mpg.de

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Original publication

K. Slavicinska, Ł. Tychoniec, M. G. Navarro, E. F. van Dishoeck, et al.
HDO ice detected toward an isolated low-mass protostar with JWST 2025 ApJL L19

Source | DOI

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More Information

Detection of semi-heavy water ice around young sunlike star

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Feeding a Baby Star Through a Whirlpool in Space

(Top) Optical image of the jet in the HH 111 protostellar system taken by the Hubble Space Telescope (Reipurth et al. 1999). (Bottom left) Accretion disk detected with ALMA in dust continuum emission at 850 micron. (Bottom middle) The disk turned (de-projected) to be face-on, showing a pair of faint spirals. (Bottom right) Annularly averaged continuum emission is subtracted to highlight the faint spirals in the disk. Credit: ALMA (ESO/NAOJ/NRAO)/Lee et al. Scientific Paper

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) detected a pair of spiral arms in an accretion disk around a baby star. Interestingly, these spiral density enhancements make the disk appear like a “space whirlpool.” The finding supports current theories of accretion disk feeding process, and potentially brings critical insights into the processes of grain growth and settling that are important to planet formation. These results appear in an article in Nature Astronomy led by Chin-Fei Lee at Academia Sinica Institute of Astronomy and Astrophysics (ASIAA, Taiwan).

“Thanks to the resolving power of ALMA, we finally detected a pair of spirals in a young accretion disk around a baby star. These spirals, long predicted in theory, play a crucial role in the transport of angular momentum. Which allows disk material to swirl towards the baby star”, says Lee with excitement. “Our detection of the spirals is an important milestone in understanding the feeding process of baby stars.”

Spirals detected in protoplanetary disks around somewhat older stars seem to be produced by interaction with unseen baby planets. Unlike those, the spirals here are induced by accretion of material from the surrounding molecular cloud onto the disk.

The protostar with its disk lies at the center of HH 111, a pair of supersonic jets emerging from a molecular cloud core located 1300 lightyears away in the constellation Orion. The protostar is about half a million years old, just one ten-thousandth the age of our Sun, and has a mass 50% greater than our Sun. A portion of the flow through the disk onto the budding star is diverted to form the spectacular jets. Previous observations with a resolution of 120 AU (An astronomical unit – AU – is the average distance from the Earth to the Sun) detected the accretion disk orbiting the protostar out to a radius of 160 AU. The new observations with ALMA have a resolution of 16 AU, almost eight times better. With this outstanding capability, astronomers were able to resolve the disk spatially. They detected a pair of spiral arms by the glow of thermal emission from dust particles concentrated there (Figure 1).

The team’s observations open up the exciting possibility of detecting spiral structures in the accretion disks around protostars through high-resolution and high-sensitivity imaging with ALMA, which allows studying accretion disk feeding processes in depth. Such observations also provide insight into accretion disks around other kinds of astrophysical objects, including the supermassive black holes found at the center of active galaxies. 

Source: Atacama Large Millimeter/submillimeter Array (ALMA)/Press Release

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Additional information

This research was presented in a paper “Spiral Structures in an Embedded Protostellar Disk Driven by Envelope Accretion,” by Lee et al. to appear in Nature Astronomy.

The team is composed of Chin-Fei Lee (ASIAA, Taiwan; National Taiwan University, Taiwan), Zhi-Yun Li (University of Virginia, USA), and Neal J. Turner (JPL/Caltech, USA).

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified

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Contact

Nicolás Lira
Education and Public Outreach Coordinator
Joint ALMA Observatory, Santiago - Chile
Phone: +56 2 2467 6519
Cell phone: +56 9 9445 7726
Email: nicolas.lira@alma.cl

Masaaki Hiramatsu
Education and Public Outreach Officer, NAOJ Chile
Observatory
, Tokyo - Japan
Phone: +81 422 34 3630
Email: hiramatsu.masaaki@nao.ac.jp

Iris Nijman
Public Information Officer
National Radio Astronomy Observatory Charlottesville, Virginia - USA
Cell phone: +1 (434) 249 3423
Email: alma-pr@nrao.edu

Mariya Lyubenova
ESO Outreach Astronomer
Garching bei München, Germany
Phone: +49 89 32 00 61 88
Email: mlyubeno@eso.org

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Magnetic fields found in a Jet from a Baby Star

Figure 1: ALMA detection of SiO line polarization in the HH 211 jet. (Top) A composite image showing the HH 211 jet and the outflow around it. The blue and red images show respectively the approaching (blueshifted) side and the receding (redshifted) side of the jet in SiO (adopted from Lee et al. 2009). Gray image shows the outflow in H2 (adopted from Hirano et al. 2006). (Bottom) A zoom-in to the innermost part of the jet within 700 au of the central protostar. Orange image shows the accretion disk recently detected with ALMA (Lee et al. 2018). Blue and red images show the blueshifted and redshifted sides of the innermost jet coming out from the disk, obtained in our observation. Yellow line segments show the orientations of the SiO line polarization in the jet. A size scale of our solar system is shown in the lower right corner for size comparison. In the two panels, asterisks mark the possible position of the central protostar. Credit: ALMA (ESO/NAOJ/NRAO)/Lee et al.

Figure 2: Possible helical magnetic fields in the HH 211 jet. Blue and red images show the blueshifted and redshifted sides of the jet coming out from the disk, as shown in the bottom panel of Figure 1. The greenish helical lines show the possible magnetic field morphology in the jet. The asterisk marks the possible position of the central protostar. A size scale of our solar system is shown in the lower right corner for size comparison. Credit: ALMA (ESO/NAOJ/NRAO)/Lee et al. 

Figure 3: Artist’s conception of the helical magnetic field in the jet coming from the accretion disk. Credit: Yin-Chih Tsai

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An international research team led by Chin-Fei Lee in the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) has made a breakthrough observation with the Atacama Large Millimeter/submillimeter Array (ALMA), confirming the presence of magnetic fields in a jet from a protostar (baby star). The jet is believed to play an important role in star formation, enabling the protostar to accrete mass from an accretion disk by carrying away angular momentum from the disk. It is highly supersonic and collimated, and predicted, in theory, to be launched and collimated by magnetic fields. The finding supports the theoretical prediction and confirms the role of the jet in star formation.

“Although it has been long predicted that protostellar jet is threaded with magnetic fields, no one is really sure about it. Thanks to the high-sensitivity of ALMA, we have finally confirmed the presence of magnetic fields in a protostellar jet with molecular line polarization detection. More interestingly, the magnetic fields in the jet could be helical, as seen in the jet from an active galactic nucleus (AGN). Perhaps, the same mechanism is at work to launch and collimate the jets from both protostar and AGN,” says Chin-Fei Lee at ASIAA.

“The detected polarization comes from a silicon monoxide (SiO) molecular line in the presence of magnetic fields”, says Hsiang-Chih Hwang, who was a former National Taiwan University (NTU) undergraduate student of Chin-Fei Lee modeling the polarization. “The polarized emission in the jet is so faint that we failed to detect it with the Submillimeter Array (SMA, Mauna Kea, Hawai). We are so excited to have finally detected it with ALMA.”

HH 211 is a well-defined jet from one of the youngest protostellar systems in Perseus at a distance of about 1,000 light-years. The central powering protostar has an age of only about 10,000 years (which is about 2 millionths of the age of our Sun) and a mass of about 0.05 solar mass. The jet is rich in SiO molecular gas and drives a spectacular molecular outflow around it (see the top panel in Figure 1).

With ALMA, we zoomed in to the innermost part of the jet within 700 au of the central protostar, where the emission is the brightest in SiO. We detected SiO line polarization toward the approaching (blueshifted) side of the jet (see the bottom panel in Figure 1). The polarization has a fraction of about 1.5% and an orientation roughly aligned with the jet axis. This line polarization is due to the Goldreich-Kylafis effect, confirming the presence of magnetic fields in the jet. The orientation of the magnetic fields could be either toroidal or poloidal. According to the current jet launching models, the magnetic fields are expected to be helical and should be mainly toroidal there where the polarization is detected, in order to collimate the jet. Deeper observations will be proposed to detect the line polarization in the receding (redshifted) side of the jet and check for consistent morphology of the polarization. Furthermore, additional SiO lines will be observed in order to confirm the field morphology.

The observation opens up an exciting possibility of directly detecting and characterizing magnetic fields in protostellar jets through high-resolution and high-sensitivity imaging with ALMA, which can improve the theories of jet formation and thus our understanding for the feeding process in the innermost region of star formation.

Additional Information

This research was presented in a paper titled “Unveiling a Magnetized Jet from a Low-Mass Protostar” by Lee et al. published in the Nature Communications 2018 November issue.

The team is composed of Chin-Fei Lee (ASIAA, Taiwan; National Taiwan University, Taiwan), Hsiang-Chih Hwang (National Taiwan University, Taiwan; Johns Hopkins University, USA), Tao-Chung Ching (National Tsing Hua University, Taiwan), Naomi Hirano (ASIAA, Taiwan), Shih-Ping Lai (National Tsing Hua University, Taiwan), Ramprasad Rao (ASIAA, Taiwan), and Paul T.P. Ho (ASIAA, Taiwan; East Asia Observatory)

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA

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Contacts

Nicolás Lira
Education and Public Outreach Coordinator
Joint ALMA Observatory, Santiago - Chile
Phone: +56 2 2467 6519
Cell phone: +56 9 9445 7726
Email: nicolas.lira@alma.cl

Masaaki Hiramatsu
Education and Public Outreach Officer, NAOJ Chile Observatory
, Tokyo - Japan
Phone: +81 422 34 3630
Email: hiramatsu.masaaki@nao.ac.jp

Calum Turner
ESO Assistant Public Information Officer
Garching bei München, Germany
Phone: +49 89 3200 6670
Email: calum.turner@eso.org

Charles E. Blue
Public Information Officer
National Radio Astronomy Observatory Charlottesville, Virginia - USA
Phone: +1 434 296 0314
Cell phone: +1 202 236 6324
Email: cblue@nrao.edu

Source: Atacama Large Millimeter/submillimeter Array (ALMA)

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The onset of an extra-solar system - feeding a baby star with a dusty hamburger

Figure 1: Jet and disk in the HH 212 protostellar system: (a) A composite image for the jet in different molecules, produced by combining the images from the Very Large Telescope (McCaughrean et al. 2002) and ALMA (Lee et al. 2015). Orange image around the center shows the dusty envelope+disk at submillimeter wavelength obtained with ALMA at 200 AU resolution. (b) A zoom-in to the very center for the dusty disk at 8 AU resolution. Asterisks mark the possible position of the central protostar. A dark lane is seen in the equator, causing the disk to appear as a "hamburger". A size scale of our solar system is shown in the lower right corner for size comparison. (c) An accretion disk model that can reproduce the observed dust emission in the disk.  Credit: ALMA (ESO/NAOJ/NRAO)/Lee et al.

An international research team, led by Chin-Fei Lee in Academia Sinica Institute of Astronomy and Astrophysics (ASIAA, Taiwan), has made a new high-fidelity image with the Atacama Large Millimeter/submillimeter Array (ALMA), catching a protostar (baby star) being fed with a dusty "Hamburger", which is a dusty accretion disk. This new image not only confirms the formation of an accretion disk around a very young protostar, but also reveals the vertical structure of the disk for the first time in the earliest phase of star formation. It not only poses a big challenge on some current theories of disk formation, but also potentially brings us key insights on the processes of grain growth and settling that are important to planet formation.

"It is so amazing to see such a detailed structure of a very young accretion disk. For many years, astronomers have been searching for accretion disks in the earliest phase of star formation, in order to determine their structure, how they are formed, and how the accretion process takes place. Now using the ALMA with its full power of resolution, we not only detect an accretion disk but also resolve it, especially its vertical structure, in great detail", says Chin-Fei Lee at ASIAA.

"In the earliest phase of star formation, there are theoretical difficulties in producing such a disk, because magnetic fields can slow down the rotation of collapsing material, preventing such a disk from forming around a very young protostar. This new finding implies that the retarding effect of magnetic fields in disk formation may not be as efficient as we thought before," says Zhi-Yun Li at University of Virginia.

HH 212 is a nearby protostellar system in Orion at a distance of about 1300 ly. The central protostar is very young with an age of only ~40,000 yrs (which is about 10 millionth of the age of Our Sun) and a mass of ~0.2 Msun. It drives a powerful bipolar jet and thus must accrete material efficiently. Previous search at a resolution of 200 AU only found a flattened envelope spiraling toward the center and a hint of a small dusty disk near the protostar. Now with ALMA at a resolution of 8 AU, which is 25 times higher, we not only detect but also spatially resolve the dusty disk at submillimeter wavelength.

The disk is nearly edge-on and has a radius of about 60 AU. Interestingly, it shows a prominent equatorial dark lane sandwiched between two brighter features, due to relatively low temperature and high optical depth near the disk midplane. For the first time, this dark lane is seen at submillimeter wavelength, producing a "hamburger"-shaped appearance that is reminiscent of the scattered-light image of an edge-on disk in optical and near infrared. The structure of the dark lane clearly implies that the disk is flared, as expected in an accretion disk model.

Our observations open up an exciting possibility of directly detecting and characterizing small disks around the youngest protostars through high-resolution imaging with ALMA, which provides strong constraints on theories of disk formation. Our observations of the vertical structure can also yield key insights on the processes of grain growth and settling that are important to planet formation in the earliest phase.

Paper and research team 

This research was presented in a paper "First Detection of Equatorial Dark Dust Lane in a Protostellar Disk at Submillimeter Wavelength," by Lee et al. to appear in the journal Science Advances.

The team is composed of Chin-Fei Lee (ASIAA, Taiwan; National Taiwan University, Taiwan), Zhi-Yun Li (University of Virginia, USA), Paul T.P. Ho (ASIAA, Taiwan; East Asia Observatory), Naomi Hirano (ASIAA, Taiwan), Qizhou Zhang (Harvard-Smithsonian Center for Astrophysics, USA), and Hsien Shang (ASIAA, Taiwan).

The figure above shows an artist's impression of an accretion disk feeding the central protostar and a jet coming out from the protostar. Credit: Yin-Chih Tsai/ASIAA  

Source: Atacama Large Millimeter/submillimeter Array (ALMA)

Searching for Orphan Stars Amid Starbirth Fireworks

The HH 24 jet complex emanates from a dense cloud core that hosts a small multiple protostellar system known as SSV63. The nebulous star to the south is the visible T Tauri star SSV59. Color image based on the following filters with composite image color assignments in parenthesis: g (blue), r (cyan), I (orange), hydrogen-alpha (red), sulfur II (blue)) images obtained with GMOS on Gemini North in 0.5 arcsecond seeing, and NIRI. Field of view is 4.2x5.1 arcminutes, orientation: north up, east left. Image produced by Travis Rector.  Credit: Gemini Observatory/AURA/B. Reipurth, C. Aspin, T. Rector.  Download JPG 945KB | TIFF 7.8MB 

A new Gemini Observatory image reveals the remarkable “fireworks” that accompany the birth of stars. The image captures in unprecedented clarity the fascinating structures of a gas jet complex emanating from a stellar nursery at supersonic speeds. The striking new image hints at the dynamic (and messy) process of star birth. Researchers believe they have also found a collection of runaway (orphan) stars that result from all this activity.

Gemini Observatory has released one of the most detailed images ever obtained of emerging gas jets streaming from a region of newborn stars. The region, known as the Herbig-Haro 24 (HH 24) Complex, contains no less than six jets streaming from a small cluster of young stars embedded in a molecular cloud in the direction of the constellation of Orion.

"This is the highest concentration of jets known anywhere," says Principal Investigator Bo Reipurth of the University of Hawaii’s Institute for Astronomy (IfA), who adds, "We also think the very dynamic environment causes some of the lowest mass stars in the area to be expelled, and our Gemini data are supporting that idea."

Reipurth along with co-researcher, Colin Aspin, also at the IfA, are using the Gemini North data from the Gemini Multi-Object Spectrograph (GMOS), as well as the Gemini Near-Infrared Imager, to study the region which was discovered in 1963 by George Herbig and Len Kuhi. Located in the Orion B cloud, at a distance of about 400 parsecs, or about 1,300 light-years from our Solar System, this region is rich in young stars and has been extensively studied in all types of light, from radio waves to X-rays.

"The Gemini data are the best ever obtained from the ground of this remarkable jet complex and are showing us striking new detail," says Aspin. Reipurth and Aspin add that they are particularly interested in the fine structure and "excitation distribution" of these jets.

"One jet is highly disturbed, suggesting that the source may be a close binary whose orbit perturbs the jet body," says Reipurth.

The researchers report that the jet complex emanates from what is called a Class~I protostar, SSV63, which high-resolution infrared imaging reveals to have at least five components. More sources are found in this region, but only at longer, submillimeter wavelengths of light, suggesting that there are even younger, and more deeply embedded sources in the region. All of these embedded sources are located within the dense molecular cloud core.

A search for dim optical and infrared young stars has revealed several faint optical stars located well outside the star-forming core. In particular, a halo of five faint Hydrogen-alpha emission stars (which emit large amounts of red light) has been found with GMOS surrounding the HH 24 Complex well outside the dense cloud core. Gemini spectroscopy of the hydrogen alpha emission stars show that they are early or mid-M dwarfs (very low-mass stars), with at least one of which being a borderline brown dwarf.

The presence of these five very low-mass stars well outside the star-forming cloud core is puzzling, because in their present location the gas is far too tenuous for the stars to have formed there. Instead they are likely orphaned protostars ejected shortly after birth from the nearby star-forming core. Such ejections occur when many stars are formed closely together within the same cloud core. The crowded stars start moving around each other in a chaotic dance, ultimately leading to the ejection of the smallest ones.

A consequence of such ejections is that pairs of the remaining stars bind together gravitationally. The dense gas that surrounds the newly formed pairs brakes their motion, so they gradually spiral together to form tight binary systems with highly eccentric orbits. Each time the two components are closest in their orbits they disturb each other, leading to accretion of gas, and an outflow event that we see as supersonic jets. The many knots in the jets thus represent a series of such perturbations.

Source: Gemini Observatory