Hubble Examines a Star-Forming Chamaeleon

Chamaeleon Cloud I (Cha I)

Image Credit: NASA, ESA, K. Luhman and T. Esplin (Pennsylvania State University), et al., and ESO; Processing: Gladys Kober (NASA/Catholic University of America)

This NASA Hubble Space Telescope image captures one of three segments that comprise a 65-light-year wide star-forming region named the Chamaeleon Cloud Complex. The segment in this Hubble composite image, called Chamaeleon Cloud I (Cha I), reveals dusty-dark clouds where stars are forming, dazzling reflection nebulae glowing by the light of bright-blue young stars, and radiant knots called Herbig-Haro objects.

Herbig-Haro objects are bright clumps and arcs of interstellar gas shocked and energized by jets expelled from infant “protostars” in the process of forming. The white-orange cloud at the bottom of the image hosts one of these protostars at its center. Its brilliant white jets of hot gas are ejected in narrow torrents from the protostar’s poles, creating the Herbig-Haro object HH 909A.

The cross-like spikes around bright stars in the image occur when light waves from a very bright point source (like a star) bend around Hubble’s cross-shaped struts that support the telescope’s secondary mirror. As the light waves pass these struts, they coalesce on the other side, creating the bright, spikey starburst effect we see.

Hubble studied Cha I as part of a search for extremely dim, low-mass brown dwarfs. These “failed stars” lie somewhere in size between a large planet and a small star (10 to 90 times the mass of Jupiter), and do not have enough mass to ignite and sustain nuclear fusion in their cores. Hubble’s search found six new low-mass brown dwarf candidates that are helping astronomers better understand these objects.

This 315-million-pixel composite image is comprised of 23 observations made by Hubble’s Advanced Camera for Surveys. Gaps between those observations were filled by 20 Wide Field Planetary Camera 2 images. Any remaining gaps were filled with ground-based data from ESO’s VISTA VIRCAM. To download the full high-resolution version of this image, visit Hubble Captures Chamaeleon Cloud I.

Media Contact:

Claire Andreoli
NASA's Goddard Space Flight Center
301-286-1940

Editor: Andrea Gianopoulos

Source: NASA/Hubble

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Strike!

NGC 7764A

Credit: ESA/Hubble & NASA, J. Dalcanton, Dark Energy Survey, DOE, FNAL, DECam, CTIO, NOIRLab/NSF/AURA, ESO.  Acknowledgement: J. Schmidt

The subject of this image is a group of three galaxies, collectively known as NGC 7764A. They were imaged by the NASA/ESA Hubble Space Telescope, using both its Advanced Camera for Surveys (ACS) and Wide Field Camera  3 (WFC3). The two galaxies in the upper right of the image appear to be interacting with one another — indeed, the long trails of stars and gas extending from them both give the impression that they have both just been struck at great speed, thrown into disarray by the bowling-ball-shaped galaxy to the lower left of the image. In reality, however, interactions between galaxies happen over very long time periods, and galaxies rarely collide head-on with one another. It is also unclear whether the galaxy to the lower left is actually interacting with the other two, although they are so relatively close in space that it seems possible that they are. By happy coincidence, the collective interaction between these galaxies have caused the two on the upper right to form a shape, which from our Solar System's perspective, ressembles the starship known as the USS Enterprise from Star Trek!

NGC 7764A, which lies about 425 million light years from Earth in the constellation Phoenix, is a fascinating example of just how awkward astronomical nomenclature can be. The three galaxies are individually referred to as NGC 7764A1, NGC 7764A2 and NGC 7764A3, and just to be really difficult, an entirely separate galaxy, named NGC 7764, sits in the skies about a Moon’s distance (as seen from Earth) away. This rather haphazard naming makes more sense when we consider that many of the catalogues for keeping track of celestial bodies were compiled well over 100 years ago, long before modern technology made standardising scientific terminology much easier. As it is, many astronomical objects have several different names, or might have names that are so similar to other objects’ names that they cause confusion.

Source: ESA/Hubble/potw

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CU Boulder scientists bring stellar flares into clearer focus

At the top of the page: An artist’s impression of a superflaring star (NASA’s Goddard Space Flight Center). Above: This animation shows how a dip in the observed brightness of a star may indicate the presence of a planet passing in front of it, an occurrence known as a transit (NASA's Goddard Space Flight Center).

In work that has implications for the search for life elsewhere in the galaxy, scientists analyze data from 440 stellar flares and find them to be not just common and powerful, but also more complex than previously thought

Armed with a new statistical analysis of stellar flares on hundreds of distant stars, scientists are beginning to understand the likelihood that remote “exoplanets” might sustain life in our galaxy, research at the University of Colorado Boulder suggests.

The most-intense flares, which are more complex than previously observed, could have implications for the viability of life on nearby planets.

Ward Howard, a postdoctoral researcher who led the study, and Meredith MacGregor, assistant professor of astrophysical and planetary sciences at CU Boulder, conducted the first large-scale analysis of solar-flare data collected at 20-second intervals from NASA’s TESS mission. Their findings are soon to be published in The Astrophysical Journal.

TESS—the Transiting Exoplanet Survey Satellite—was launched in 2018 to search for planets outside of our solar system, including those that could support life.

The satellite detects those planets when they periodically block part of the light as they pass in front of their host stars, events called “transits.” The stars in question are M dwarf stars, which compose about 70% of the stars in our galaxy. Those stars are cooler and dimmer than Earth’s sun but are prone to explosive superflares—10 to 1,000 times larger than flares from our sun.

Superflares could destroy a nearby planet’s atmosphere, particularly because exoplanets in the “habitable zone” of these stars can be 20 times closer to their stars than we are to the sun.

“The sun is very well behaved,” Howard said. “Many of these red dwarf stars can emit flares 1,000 times larger than those from the sun, and you can only imagine what that might do to a planet or to life on the surface.”

The 20-second TESS data reveal the building blocks of the flare emission and informs how much radiation reaches the planets during the brief peaks of the flares.

By analyzing data from 440 large stellar flares from TESS, scientists are starting to “pull back the curtain” on questions of which exoplanets might have atmospheres that are conducive to life, and which would be “dead rocks,” Howard said.

Additionally, the new CU Boulder analysis of the flares shows the flares to be “super complicated, MacGregor said. “They have all sorts of weird structure in the light curves, which indicates that some of them are bursting multiple times.”

“We have historically had a very simple picture of stellar activity, where one loop breaks and we have one outburst of energy, and then it slowly dies away, and then we think about the frequency of that,” she continued. “That's the model that's been fed into everything we think about stars and their impact on planets, and it’s clearly just flat-out wrong.”

Although TESS’s primary mission is to detect exoplanets, the fact that TESS stares at certain parts of the sky for a month at a time also allows the instrument to detect stellar flares and superflares, which are rare and random events.

Solar and stellar flares result from entangled magnetic fields, and they release huge bursts of radiation and charged particles.

“Our sun does this, and we can get beautiful images where you see these loops of emission protruding out of the surface of the sun, and then they break and stream out into space,” MacGregor said. When those particles and radiation hit the Earth’s upper atmosphere, they can dissociate atmospheric molecules, causing the aurora borealis in northern latitudes and aurora australis in the southern.

“So we see beautiful lovely green lights,” MacGregor said. “What we're actually observing is the effect of our sun splitting apart molecules in our atmosphere and then the release of energy from that splitting of things like ozone and water.”

As originally deployed, TESS captured data every two minutes, a frequency sufficient to detect exoplanets but insufficient to gather detailed data on the incidence of stellar flares affecting those planets.

“It allows us to kind of have a statistical understanding of how often do certain things occur,” Howard said, adding that scientists have never before been able to determine how much radiation reaches planets during the peak of the superflares and how much complexity the flares have.

The James Webb Space Telescope, launched in December, is poised to further probe these questions, MacGregor and Howard said. In addition to seeking information about the earliest stages of the universe, it will look for atmospheres on exoplanets, aiming to determining what kind of atmospheres they have and whether they might support life.

“This field of astrobiology and exoplanet research is changing so quickly right now, that it makes it a really exciting area to work in,” MacGregor said.

By Clint Talbott

Source: University of Colorado Boulder (Colorado Arts and Sciences Magazine)

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Visualization explores a massive star's great eruption Eta Carinae: The Great Eruption of a Massive Star

 Eta Carinae: The Great Eruption of a Massive Star

Release videos

A new astronomical visualization from NASA's Universe of Learning showcases the multiwavelength emissions (from infrared light through X-rays) and three-dimensional structures surrounding Eta Carinae, one of the most massive and eruptive stars in our galaxy. The video, "Eta Carinae: The Great Eruption of a Massive Star," is being released today on hubblesite.org and universe-of-learning.org

Eta Carinae, or Eta Car, is famous for a brilliant and unusual outburst, called the "Great Eruption," observed in the 1840s. This briefly made it one of the brightest stars in the night sky, releasing almost as much visible light as a supernova explosion.

The star survived the outburst, and slowly faded away for the next five decades. The primary cause of this brightness change is a small nebula of gas and dust, called the Homunculus Nebula, that was expelled during the blast, and has blocked the light of the star.

Observations using NASA's Hubble Space Telescope and Chandra X-ray Observatory reveal the details in visible, ultraviolet, and X-ray light. Astronomers and artists at the Space Telescope Science Institute (STScI) in Baltimore, Maryland have developed three-dimensional models to represent the hourglass shape of the Homunculus and the clouds of glowing gas that encompass it. The result is a stunning tour of the nested emissions that brings the 2D images to 3D life.

"The team did such an amazing job representing the volumetric layers that viewers can immediately and intuitively comprehend the complex structure around Eta Car," said Frank Summers, principal visualization scientist at STScI and project lead. "We can not only tell the story of the Great Eruption, but also showcase the resulting nebula in 3D."

In addition, Eta Car is extremely bright at infrared wavelengths, and its radiation impacts the much larger Carina Nebula where it resides. Working with NASA's Spitzer Space Telescope observations, the team was able to place Eta Car in context of the dazzling infrared view of the star-forming region.

"Spitzer's infrared image lets us peer through the dust that obscures our view in visible light to reveal the intricate details and extent of the Carina Nebula around this brilliant star," commented Robert Hurt, lead visualization scientist at Caltech/IPAC and team member.

Extending the goals of NASA's Universe of Learning, the visualization assets promote learning beyond the video sequence. "We can take these models like the one for Eta Car and use them in 3D printing and augmented reality programs," noted Kim Arcand, visualization lead scientist at the Chandra X-ray Center in Cambridge, Massachusetts. "This means more people can put their hands on the data – literally and virtually – and this makes for better learning and engagement."

Eta Carinae is one of the most massive stars known. These exceptional stars are prone to outbursts during their lives. They will end their lives by collapsing into a black hole, probably accompanied by a supernova explosion. Eta Car is one of the nearest and best studied examples for learning about the energetic life and death of very massive stars.

Want to learn more? The visualization video and extensive related resources, which will include an upcoming Universe of Learning online live chat with Summers about the visualization, can be found at https://universeunplugged.ipac.caltech.edu/video/astroviz-eta-car .

NASA's Universe of Learning is part of the NASA Science Activation program. The Science Activation program connects NASA science experts, real content and experiences, and community leaders in a way that activates minds and promotes deeper understanding of our world and beyond. Using its direct connection to the science and the experts behind the science, NASA's Universe of Learning provides resources and experiences that enable youth, families, and lifelong learners to explore fundamental questions in science, experience how science is done, and discover the universe for themselves.

NASA's Universe of Learning materials are based upon work supported by NASA under cooperative agreement award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, and Jet Propulsion Laboratory.

Credits:

Media Contact:

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

Science Contact:

Frank Summers
Space Telescope Science Institute, Baltimore, Maryland

Contact Us:

Direct inquiries to the News Team.

Related Links and Documents:  NASA's Universe of Learning portal

Source: HubbleSite/News

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Sidewinding Young Stellar Jets Spied by Gemini South

The sinuous young stellar jet, MHO 2147, meanders lazily across a field of stars in this image captured from Chile by the international Gemini Observatory, a Program of NSF's NOIRLab. The stellar jet is the outflow from a young star that is embedded in an infrared dark cloud. Astronomers suspect its sidewinding appearance is caused by the gravitational attraction of companion stars. These crystal-clear observations were made using the Gemini South telescope’s adaptive optics system, which helps astronomers counteract the blurring effects of atmospheric turbulence. Credit: International Gemini Observatory/NOIRLab/NSF/AURA. Acknowledgments: PI: L. Ferrero (Universidad Nacional de Córdoba). Download  Large JPEG

The knotted young stellar jet, MHO 1502, is captured in this image from Chile by the international Gemini Observatory, a Program of NSF's NOIRLab. The stellar jet is embedded in an area of star formation known as an HII region. The bipolar jet is composed of a chain of knots, suggesting that its source, thought to be two stars, has been intermittently emitting material. These crystal-clear observations were made using the Gemini South telescope’s adaptive optics system, which helps astronomers counteract the blurring effects of atmospheric turbulence. Credit: International Gemini Observatory/NOIRLab/NSF/AURA. Acknowledgments: PI: L. Ferrero (Universidad Nacional de Córdoba). Download  Large JPEG

Young stellar jet MHO 2147 (wider crop). The sinuous young stellar jet, MHO 2147, meanders lazily across a field of stars in this image captured from Chile by the international Gemini Observatory, a Program of NSF's NOIRLab. The stellar jet is the outflow from a young star that is embedded in an infrared dark cloud. Astronomers suspect its sidewinding appearance is caused by the gravitational attraction of companion stars. These crystal-clear observations were made using the Gemini South telescope’s adaptive optics system, which helps astronomers counteract the blurring effects of atmospheric turbulence. Credit: International Gemini Observatory/NOIRLab/NSF/AURA. Acknowledgments: PI: L. Ferrero (Universidad Nacional de Córdoba). Download  JPEG

CosmoView Episode 40: Sidewinding Young Stellar Jets Spied by Gemini South. Sinuous stellar jets meander lazily across a field of stars in new images captured from Chile by the international Gemini Observatory, a Program of NSF's NOIRLab. The gently curving stellar jets are the outflow from young stars, and astronomers suspect their sidewinding appearances are caused by the gravitational attraction of companion stars. These crystal-clear observations were made using the Gemini South telescope’s adaptive optics system, which helps astronomers counteract the blurring effects of atmospheric turbulence. Credit: Images and videos: International Gemini Observatory/NOIRLab/NSF/AURA. Image processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani (NSF’s NOIRLab) & D. de Martin (NSF’s NOIRLab). Music: Stellardrone - Billions and Billions.

Crystal-clear images of meandering bipolar stellar jets from young stars captured with adaptive optics.

Sinuous stellar jets meander lazily across a field of stars in new images captured from Chile by the international Gemini Observatory, a Program of NSF's NOIRLab. The gently curving stellar jets are the outflow from young stars, and astronomers suspect their sidewinding appearances are caused by the gravitational attraction of companion stars. These crystal-clear observations were made using the Gemini South telescope’s adaptive optics system, which helps astronomers counteract the blurring effects of atmospheric turbulence.

Young stellar jets are a common by-product of star formation and are thought to be caused by the interplay between the magnetic fields of rotating young stars and the disks of gas surrounding them. These interactions eject twin torrents of ionized gas in opposite directions, such as those pictured in two images captured by astronomers using the Gemini South telescope on Cerro Pachón on the edge of the Chilean Andes. Gemini South is one half of the international Gemini Observatory, a Program of NSF's NOIRLab, that comprises twin 8.1-meter optical/infrared telescopes on two of the best observing sites on the planet. Its counterpart, Gemini North, is located near the summit of Maunakea in Hawai‘i.

The jet in the first image, named MHO 2147, is roughly 10,000 light-years from Earth, and lies in the galactic plane of the Milky Way, close to the boundary between the constellations Sagittarius and Ophiuchus. MHO 2147 snakes across a starry backdrop in the image — an appropriately serpentine appearance for an object close to Ophiuchus. Like many of the 88 modern astronomical constellations, Ophiuchus has mythological roots — in ancient Greece it represented a variety of gods and heroes grappling with a serpent. MHO 1502, the jet pictured in the second image, is located in the constellation of Vela, approximately 2000 light-years away.

Most stellar jets are straight but some can be wandering or knotted. The shape of the uneven jets is thought to be related to a characteristic of the object or objects that created them. In the case of the two bipolar jets MHO 2147 and MHO 1502, the stars which created them are obscured from view

In the case of MHO 2147, this young central star, which has the catchy identifier IRAS 17527-2439, is embedded in an infrared dark cloud — a cold, dense region of gas that is opaque at the infrared wavelengths represented in this image [1]. The sinuous shape of MHO 2147 is caused because the direction of the jet has changed over time, tracing out a gentle curve on either side of the central star. These almost unbroken curves suggest that MHO 2147 has been sculpted by continuous emission from its central source. Astronomers found that the changing direction (precession) of the jet may be due to the gravitational influence of nearby stars acting on the central star. Their observations suggest that IRAS 17527-2439 could belong to a triple star system separated by more than 300 billion kilometers (almost 200 billion miles).

MHO 1502, on the other hand, is embedded in a totally different environment — an area of star formation known as an HII region. The bipolar jet is composed of a chain of knots, suggesting that its source, thought to be two stars, has been intermittently emitting material.

These detailed images were captured by the Gemini South Adaptive Optics Imager (GSAOI), an instrument on the 8.1-meter-diameter Gemini South telescope. Gemini South is perched on the summit of Cerro Pachón, where dry air and negligible cloud cover provide one of the best observing sites on the planet. Even atop Cerro Pachón, however, atmospheric turbulence causes the stars to blur and twinkle. 

GSAOI works with GeMs, the Gemini Multi-Conjugate Adaptive Optics System, to cancel out this blurring effect using a technique called adaptive optics. By monitoring the twinkling of natural and artificial guide stars up to 800 times a second, GeMs can determine how atmospheric turbulence is distorting Gemini South’s observations [2]. A computer uses this information to minutely adjust the shape of deformable mirrors, canceling out the distortions caused by turbulence. In this case, the sharp adaptive optics images have made it possible to recognize more details in each knot of the young stellar jets than in previous studies.

Source: Gemini Observatory

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Notes

[1] Astronomical objects can appear very different at different wavelengths. For example, the dust surrounding newborn stars blocks visible light but is transparent at infrared wavelengths. Something similar also happens here on Earth — doctors can see right through you with an X-ray machine even though human bodies are not transparent at visible wavelengths. Astronomers therefore study the Universe across the electromagnetic spectrum to learn as much as possible about the Universe.

[2] Adaptive optics systems on telescopes often make use of "natural guide stars" which are bright stars that lie close to the target of an astronomical observation. Their brightness makes it easy to measure how atmospheric turbulence is distorting their appearance. Gemini South also uses artificial guide stars produced by shining powerful lasers into the upper atmosphere. 

Links

• Research paper 
• Photos of Gemini South
• Videos of Gemini South

Contacts

Leticia Ferrero
Universidad Nacional de Córdoba
Tel: ​+54 9 351 4331063/4/5 int: 105
Email:lvferrero@unc.edu.ar

Amanda Kocz
NSF’s NOIRLab Communications
Tel: +1 520 318 8591
Email:amanda.kocz@noirlab.edu

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Images at the Highest Angular Resolution in Astronomy

Fig. 1: The curved jet in the active galaxy OJ 287 from radio images taken at three different wavelengths and resolutions. Top left: RadioAstron at 1.3 cm wavelength - a global array including the space radio telescope Spektr-R in orbit around Earth. Top right: the Global mm-VLBI Array at 3.5 mm wavelength. Bottom: the Very Long Baseline Array at 2 cm wavelength - an array of ten antennas across the USA. The ellipses at the bottom left indicate the image resolution in each case, the angular and linear scale are shown by a horizontal white bar at the bottom. The top panel shows a record-breaking resolution of about 12 micro arc seconds, achieved when the space radio telescope is 15 earth diameters away from the ground telescopes (a distance of about 190.000 km, corresponding to half the distance between Moon and Earth). © Eduardo Ros/MPIfR (collage), Gómez et al., The Astrophysical Journal, 2022 (images).

Fig. 2: The Spektr-R satellite of the RadioAstron Space-VLBI project.

© A. Zakharov, IKI design

How a Binary Black Hole may be Bending the Relativistic Jet in the Quasar OJ 287

An international team of researchers including several scientists from the Max Planck Institute for Radio Astronomy has obtained an image of radio emission in the active galaxy OJ 287 at an angular resolution of 12 micro arcseconds, which is presently the highest resolution achieved in astronomical observations. This has been made possible with the technique of very long baseline interferometry (VLBI) which combines signals recorded at multiple radio telescopes simultaneously observing the same object and uses this combination to create a virtual telescope whose effective diameter is set by the largest distance between the participating telescopes. Combining together twelve radio telescopes distributed across the globe and an orbiting 10-metre antenna on board of the satellite Spektr-R launched and operated by the Russian Space Agency, the researchers have effectively constructed a radio telescope with a diameter of 193,000 km and used it to peer into the very heart of the galaxy OJ 287 believed to host a pair of supermassive black holes.

Their findings are published in the current issue of “The Astrophysical Journal”.

VLBI observations of the galaxy OJ 287 were performed at four different wavelengths. Observations including the space-borne antenna were carried out at a wavelength of 1.3 cm and amended with additional VLBI observations made with Earth-based telescopes only at wavelengths of 2, 0.7, and 0.3 cm wavelengths. The resulting images reach a record-breaking resolution of about 12 micro arcseconds at 1.3 cm, which is equivalent to being able to discern a 20 cent coin on the surface of the Moon.

The galaxy OJ 287, located at a distance of 5 billion light-years from Earth in the direction of the constellation Cancer, belongs to the class of blazar galaxies which manifest through powerful and variable emission originating in the close vicinity of the supermassive black hole residing in their centers.

The interferometric images at all four wavelengths consistently reveal several knots of emission in a strongly bent plasma jet. The jet bending becomes progressively stronger with increasing angular resolution and towards the jet origin, supporting the hypothesis of a supermassive binary black hole model powering the active galaxy. Analysis of the polarization properties reveals that the magnetic field has predominantly toroidal structure indicating that the innermost radio emitting region is threaded by a helical magnetic field, in agreement with jet formation models. The investigation of spectral properties demonstrates that the jet plasma is composed of electrons and positrons whose kinetic energy is balanced by the magnetic field. Repeated injections of more energetic particles into the jet plasma break this balance and flare up some portions of the inner jet.

OJ 287 is one of the best candidates for a binary supermassive black hole system we know so far in our cosmic neighborhood. The secondary black hole in this system is believed to be on a tight, elliptical orbit passing through the accretion disk of the primary twice every twelve years, producing powerful flares and driving the precession of the rotational axis of the primary black hole.

“One of the main questions related to the evolution of supermassive black holes today is how a pair of so massive black holes could end up merging – the so-called final parsec problem. Theory suggests that separation between the two black holes stops shrinking after they expel all surrounding stars and gas. This is where gravitational radiation comes into the game and causes the two black holes to keep approaching each other until they would ultimately merge,” says Andrei Lobanov from the Max Planck Institute for Radio Astronomy (MPIfR), one of the leading authors of the work. The expected binary supermassive black hole system in OJ287 is so close that it should emit gravitational waves which could soon be detectable with pulsar timing measurements. A substantial fraction of the energy released by the matter accreted by these black holes is channeled through bipolar jets of relativistic plasma jets which can be observed and studied in detail with VLBI. “The observed detailed fine structure of the inner jet region is ideally suited to the test the validity of the binary black hole model or if the observed jet bending is caused by other effects, such as helical magnetic fields, which are anchored in the rotating space time near the black hole”, adds Thomas Krichbaum, also from the MPIfR.

“These results helped us to move a step forward on broadening our knowledge on the morphology of relativistic jets close to the central engine, confirming the role of magnetic fields in jet launching and record one more time indirect signs of the existence of a proximate super massive black hole binary system deep in the heart of OJ 287”, says Thalia Traianou who is after her doctoral work at MPIfR at the Instituto de Astrofísica de Andalucía (IAA-CSIC) now.

“The objective of reaching the highest resolutions in astronomy has experienced a big step forward with the contribution of the RadioAstron mission and with the developments of millimetre-wavelength VLBI such as the MPIfR-operated Global mm-VLBI Array. Our pioneering work over the last decades is now collecting results, such as our exciting findings in OJ 287”, concludes J. Anton Zensus, director at the MPIfR, member of the RadioAstron International Science Council, and also co-author in the reported work.

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Further Information

The Earth-to-Space Interferometer RadioAstron consisted of a 10-metre orbiting radio telescope (Spektr-R) and a collection of about two dozen of the world’s largest ground-based radio telescopes. When the signals of individual telescopes were combined using the interference of radio waves, this array of telescopes provides a maximum angular resolution equivalent to a radio telescope of 350.000 km in diameter – almost the distance between the Earth and Moon. This made RadioAstron the highest angular resolution instrument in the history of astronomy. The RadioAstron project, active from July 2011 to May 2019, was led by the Astro Space Center of the Lebedev Physical Institute of the Russian Academy of Sciences and the Lavochkin Scientific and Production Association under a contract with the State Space Corporation ROSCOSMOS, in collaboration with partner organizations in Russia and other countries.

The "Global mm-VLBI Array" (GMVA) is an international network of radio observatories interested in performing astronomical VLBI observations at millimeter wavelengths and with open access for the scientific community. The GMVA performs regular, coordinated global VLBI observations in the 3mm/7mm band twice per year. The inclusion of the largest telescopes operating in these bands enhances sensitivity and image fidelity. The GMVA received support from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 730562.

The already very high angular resolution of Earth-based cm-wave VLBI can be increased further in two ways, either by using longer baselines or by observing at shorter wavelengths. The first approach leads to "space-VLBI" (VLBI with one or more orbiting antennas), the second approach to "millimeter-VLBI" (mm-VLBI). In the more distant future, both techniques may be combined. This will lead to space-VLBI at millimeter wavelengths ("mm-space-VLBI"). Both the RadioAstron and the GMVA data were processed at the MPIfR VLBI Correlator Centre in Bonn.

Following collaborators of the presented work are affiliated to the MPIfR, in order of appearance at the author list: Efthalia (Thalia) Traianou, Thomas P. Krichbaum, Andrei P. Lobanov, Yuri Y. Kovalev, Mikhail M. Lisakov, Rocco Lico, Uwe Bach, Carolina Casadio, Eduardo Ros, Tuomas Savolainen, and J. Anton Zensus.

Yuri Y. Kovalev acknowledges the Friedrich Wilhelm Bessel research prize of the Alexander von Humboldt foundation.

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Local Contact:

Dr. Andrei Lobanov
+49 228 525-191
alobanov@...
Max-Planck-Institut für Radioastronomie, Bonn

Dr. Efthalia Traianou
+34 958 1213-11
traianou@...
Instituto de Astrofisica de Andalucia, Granada, Spain

Prof. Dr. Eduardo Ros
+49 228 525-125
+49 228 525-229
ros@... 

Max-Planck-Institut für Radioastronomie, Bonn

Dr. Norbert Junkes
Press and Public Outreach
+49 228 525-399
njunkes@...
Max-Planck-Institut für Radioastronomie, Bonn

Source: Max Planck for Radio Astronomy/Press Release

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Hubble Finds a Black Hole Igniting Star Formation in a Dwarf Galaxy

A pullout of the central region of dwarf starburst galaxy Henize 2-10 traces an outflow, or bridge of hot gas 230 light-years long, connecting the galaxy's massive black hole and a star-forming region. Hubble data on the velocity of the outflow from the black hole, as well as the age of the young stars, indicates a causal relationship between the two. A few million years ago, the outflow of hot gas slammed into the dense cloud of a stellar nursery and spread out, like water from a hose impacting a mound of dirt. Now clusters of young stars are aligned perpendicular to the outflow, revealing the path of its spread. Credits: NASA, ESA, Zachary Schutte (XGI), Amy Reines (XGI); Image Processing: Alyssa Pagan (STScI)

Often portrayed as destructive monsters that hold light captive, black holes take on a less villainous role in the latest research from NASA's Hubble Space Telescope. A black hole at the heart of the dwarf galaxy Henize 2-10 is creating stars rather than gobbling them up. The black hole is apparently contributing to the firestorm of new star formation taking place in the galaxy. The dwarf galaxy lies 30 million light-years away, in the southern constellation Pyxis.

A decade ago this small galaxy set off debate among astronomers as to whether dwarf galaxies were home to black holes proportional to the supermassive behemoths found in the hearts of larger galaxies. This new discovery has little Henize 2-10, containing only one-tenth the number of stars found in our Milky Way, poised to play a big part in solving the mystery of where supermassive black holes came from in the first place.

"Ten years ago, as a graduate student thinking I would spend my career on star formation, I looked at the data from Henize 2-10 and everything changed," said Amy Reines, who published the first evidence for a black hole in the galaxy in 2011 and is the principal investigator on the new Hubble observations, published in the January 19 issue of Nature.

"From the beginning I knew something unusual and special was happening in Henize 2-10, and now Hubble has provided a very clear picture of the connection between the black hole and a neighboring star forming region located 230 light-years from the black hole," Reines said.

That connection is an outflow of gas stretching across space like an umbilical cord to a bright stellar nursery. The region was already home to a dense cocoon of gas when the low-velocity outflow arrived. Hubble spectroscopy shows the outflow was moving about 1 million miles per hour, slamming into the dense gas like a garden hose hitting a pile of dirt and spreading out. Newborn star clusters dot the path of the outflow's spread, their ages also calculated by Hubble.

This is the opposite effect of what's seen in larger galaxies, where material falling toward the black hole is whisked away by surrounding magnetic fields, forming blazing jets of plasma moving at close to the speed of light. Gas clouds caught in the jets' path would be heated far beyond their ability to cool back down and form stars. But with the less-massive black hole in Henize 2-10, and its gentler outflow, gas was compressed just enough to precipitate new star formation.

"At only 30 million light-years away, Henize 2-10 is close enough that Hubble was able to capture both images and spectroscopic evidence of a black hole outflow very clearly. The additional surprise was that, rather than suppressing star formation, the outflow was triggering the birth of new stars," said Zachary Schutte, Reines' graduate student and lead author of the new study.

Ever since her first discovery of distinctive radio and X-ray emissions in Henize 2-10, Reines has thought they likely came from a massive black hole, but not as supermassive as those seen in larger galaxies. Other astronomers, however, thought that the radiation was more likely being emitted by a supernova remnant, which would be a familiar occurrence in a galaxy that is rapidly pumping out massive stars that quickly explode.

"Hubble's amazing resolution clearly shows a corkscrew-like pattern in the velocities of the gas, which we can fit to the model of a precessing, or wobbling, outflow from a black hole. A supernova remnant would not have that pattern, and so it is effectively our smoking-gun proof that this is a black hole," Reines said. Reines expects that even more research will be directed at dwarf galaxy black holes in the future, with the aim of using them as clues to the mystery of how supermassive black holes came to be in the early universe. It's a persistent puzzle for astronomers. The relationship between the mass of the galaxy and its black hole can provide clues. The black hole in Henize 2-10 is around 1 million solar masses. In larger galaxies, black holes can be more than 1 billion times our Sun's mass. The more massive the host galaxy, the more massive the central black hole.

Current theories on the origin of supermassive black holes break down into three categories: 1) they formed just like smaller stellar-mass black holes, from the implosion of stars, and somehow gathered enough material to grow supermassive, 2) special conditions in the early universe allowed for the formation of supermassive stars, which collapsed to form massive black hole "seeds" right off the bat, or 3) the seeds of future supermassive black holes were born in dense star clusters, where the cluster's overall mass would have been enough to somehow create them from gravitational collapse.

So far, none of these black hole seeding theories has taken the lead. Dwarf galaxies like Henize 2-10 offer promising potential clues, because they have remained small over cosmic time, rather than undergoing the growth and mergers of large galaxies like the Milky Way. Astronomers think that dwarf galaxy black holes could serve as an analog for black holes in the early universe, when they were just beginning to form and grow.

"The era of the first black holes is not something that we have been able to see, so it really has become the big question: where did they come from? Dwarf galaxies may retain some memory of the black hole seeding scenario that has otherwise been lost to time and space," Reines said

Hubble finds a Black Hole Igniting Star Formation in a Dwarf Galaxy

Hubble imaging and spectroscopy of the dwarf starburst galaxy Henize 2-10 clearly show a gas outflow stretching from the black hole to a bright star birth region like an umbilical cord, triggering the already dense cloud into forming clusters of stars. Credits: NASA's Goddard Space Flight Center; Lead Producer: Paul Morris 

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C. 

 

Image Credit: NASA, ESA, Zachary Schutte (XGI), Amy Reines (XGI); Image Processing: Alyssa Pagan (STScI) Media Contacts:

Claire Andreoli

NASA's Goddard Space Flight Center

301-286-1940

Leah Ramsay

Space Telescope Science Institute, Baltimore, Maryland

Ray Villard

Space Telescope Science Institute, Baltimore, Maryland

Science Contact:

Amy Reines

eXtreme Gravity Institute, Montana State University, Bozeman, Montana

Editor: Andrea Gianopoulos

Source: NASA/Hubble

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Capturing All That Glitters in Galaxies With NASA’s Webb

This image of spiral galaxy NGC 3351 combines observations from several observatories to reveal details about its stars and gas. Radio observations from the Atacama Large Millimeter/submillimeter Array (ALMA) show dense molecular gas in magenta. The Very Large Telescope’s Multi Unit Spectroscopic Explorer (MUSE) instrument highlights where young massive stars illuminate their surroundings, set off in red. The Hubble Space Telescope’s images highlight dust lanes in white and newly formed stars in blue. High-resolution infrared images from the Webb Space Telescope will help researchers identify where stars are forming behind dust and study the earliest stages of star formation in this galaxy. Credits: Science: NASA, ESA, ESO-Chile, ALMA, NAOJ, NRAO; image processing: Joseph DePasquale (STScI)

This image of spiral galaxy NGC 1300 combines multiple observations to map stellar populations and gas. Radio light observed by the Atacama Large Millimeter/submillimeter Array (ALMA), represented in yellow, highlight the clouds of cold molecular gas that provide the raw material from which stars form. Data from the Very Large Telescope’s Multi Unit Spectroscopic Explorer (MUSE) instrument is represented in red and magenta, capturing the impact of young, massive stars on their surrounding gas. Visible and ultraviolet light captured by the Hubble Space Telescope highlights dust lanes in gold and very young, hot stars in blue. High-resolution infrared images from the Webb Space Telescope will help researchers identify where stars are forming behind dust and study the earliest stages of star formation in this galaxy. Credits: Science: NASA, ESA, ESO-Chile, ALMA, NAOJ, NRAO; image processing: Alyssa Pagan (STScI)

An international research team will survey the stars, star clusters, and dust that lie within 19 nearby galaxies.

Spirals are some of the most captivating shapes in the universe. They appear in intricate seashells, carefully constructed spider webs, and even in the curls of ocean waves. Spirals on cosmic scales – as seen in galaxies – are even more arresting, not only for their beauty, but also for the overwhelming amount of information they contain. How do stars and star clusters form? Until recently, a complete answer used to lie out of reach, blocked by gas and dust. Within the first year of operations, NASA’s James Webb Space Telescope will help researchers complete a more detailed sketch of the stellar life cycle with high-resolution infrared-light images of 19 galaxies.

The telescope will also provide a few key “puzzle pieces” that were missing until now. “JWST touches on so many different phases of the stellar life cycle – all in tremendous resolution,” said Janice Lee, Gemini Observatory chief scientist at the National Science Foundation’s NOIRLab in Tucson, Arizona. “Webb will reveal star formation at its very earliest stages, right when gas collapses to form stars and heats up the surrounding dust.”

Lee is joined by David Thilker of the Johns Hopkins University in Baltimore, Maryland, Kathryn Kreckel of Heidelberg University in Germany, and 40 additional members of the multi-wavelength survey program known as PHANGS (Physics at High Angular resolution in Nearby GalaxieS). Their mission? Not only to unravel the mysteries of star formation with Webb’s high-resolution infrared images, but also to share the datasets with the entire astronomical community to accelerate discovery.

The Rhythms of Star Formation

PHANGS is novel, in part, because it brought together more than 100 international experts to study star formation from beginning to end. They are targeting galaxies that can be seen face-on from Earth and that are, on average, 50 million light-years away. The large collaboration began with microwave light images of 90 galaxies from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Astronomers use this data to produce molecular gas maps to study the raw materials for star formation. Once the Very Large Telescope’s Multi Unit Spectroscopic Explorer (MUSE) instrument, also in Chile, came online, they obtained data known as spectra to study later phases of star formation of 19 galaxies, particularly after star clusters have cleared nearby gas and dust. The space-based Hubble Space Telescope has provided visible and ultraviolet light observations of 38 galaxies to add high-resolution images of individual stars and star clusters.

The missing elements, which Webb will fill in, are largely in areas of the galaxies that are obscured by dust – regions where stars are actively beginning to form. “We’re going to clearly see star clusters in the hearts of these dense molecular clouds that before we only had indirect evidence of,” Thilker said. “Webb gives us a way to look inside these ‘star factories’ to see the freshly assembled star clusters and measure their properties before they evolve.”

The new data will also help the team pinpoint the ages of stellar populations in a diverse sample of galaxies, which will help researchers build more accurate statistical models. “We’re always putting the context of the small scales into the big picture of galaxies,” explained Kreckel. “With Webb, we’ll trace the evolutionary sequence of each galaxy’s stars and star clusters.”

Another important answer they’re seeking involves the dust surrounding the stars, within the interstellar medium. Webb will help them determine which areas of the gas and dust are associated with specific star-forming regions, and which are free-floating interstellar material. “This couldn't be done before, beyond the nearest galaxies. It will be transformative,” Thilker added. The team is also working to understand the timing of the star-formation cycle. “Timescales are critical in astronomy and physics,” Lee said. “How long does each stage of star formation last? How might those timelines vary in different galaxy environments? We want to measure when these stars free themselves from their gas clouds to understand how star formation is disrupted.”

Science for All

These Webb observations will be taken as part of a Treasury program, which means they are not only available immediately to the public, but they will also be of broad and enduring scientific value. The team will work to create and release data sets that align Webb’s data to each of the complementary data sets from ALMA, MUSE, and Hubble, allowing future researchers to sift through each galaxy and their stellar populations easily, toggling on and off various wavelengths – and zoom into individual pixels of the images. They will provide inventories of different phases of the star-formation cycle, including regions of star formation, young stars, star clusters, and local dust properties.

This research will be conducted as part of Webb’s General Observer (GO) programs, which are competitively selected using a dual-anonymous review system, the same system that is used to allocate time on the Hubble Space Telescope.

The James Webb Space Telescope is the world's premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe 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.

Related Links and Documents

PHANGS Survey
PHANGS Hubble Observation

Editor: Rob Garner

Source: NASA/Webb Telescope

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Researchers uncover model for extremely luminous and fast rising supernova

Figure 1: Supernova AT 2018cow, nicknamed the COW. (Left) Following its explosion, COW reached peak luminosity on June 20, 2018, being much brighter than the galaxy’s center at upper left. (Right) By July 14, 2018, COW had become dimmer, becoming just as bright as the galaxy's center. Credit: Daniel Perley (Liverpool J. M. University), Kavli IPMU

Figure 2: Light curve of supernova SN 2018gep (GEP) shows it reaches a higher peak luminosity rapidly compared to ordinary Ic supernovae (solid lines). Credit: Anna Ho (Caltech), Kavli IPMU

Figure 3: Cartoon illustration of the shock-interaction picture. (Upper left) A massive star undergoes large pulsations due to electron-positron pair-creation and ejects some material to form dense circumstellar matter. (Upper right) The star explodes to form a shock wave, which propagates through the circumstellar matter. (Lower left) When the shock wave reaches the surface of the circumstellar matter, the kinetic energy is converted to the thermal and radiation energy. Then the surface of the circumstellar matter shines very brightly. Material ejected by supernova explosion expands at moderate speeds. (Lower right) Circumstellar matter rapidly expands and fades. Supernova ejecta also expands and fades. Credit: Shing-Chi Leung, Kavli IPMU

Figure 4: Theoretical shock-interaction models for the light curves and comparisons with observational data from the COW and the GEP. Solid lines are the models including the self-consistent CSM. Dashed line are the models assuming the CSM is artificially removed. Credit: Shing-Chi Leung, Kavli IPMU

Appearing ten to a hundred times brighter at its peak, and with a much faster rise toward the peak, stellar explosions AT 2018cow (nicknamed the COW) and SN 2018gep (nicknamed the GEP) represent a new type of supernova called Fast Blue Optical Transient (FBOT), reports two recent studies.

Thanks to recent extensive supernova observations by several telescopes worldwide, COW and GEP appeared in the night sky in 2018 and were well-observed from the early phase of their explosions (figure 1). But their origin was a mystery.

To find a theoretical model, Shing-Chi Leung, a former Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Researcher (currently a postdoctoral scholar at the California Institute of Technology), and Kavli IPMU Senior Scientist Ken’ichi Nomoto, organized two international teams of researchers to study each explosion, and have now succeeded in explaining COW and GEP features.

Observational data showed the COW had the brightest peak and the shortest rising time (about 1 day) among FBOTs. The GEP had a slightly lower brightness and a longer rising time (about 3 days), compared to the COW (figure 2).

Both research groups then successfully modeled the light curve, uncovering a clear picture of a possible sequence of events in both explosions (figure 3).

First, the star would have ejected its surface materials just before the explosion. These ejected materials would have formed a dense and opaque circumstellar matter (CSM) around the star, making the radius of the star much larger than ordinary presupernova stars. Such a presupernova mass ejection mechanism might have been caused by the pulsational pair-instability of very massive stars, which Leung and Nomoto had previously seen while studying the origin of massive black holes (see the related article).

When the supernova explosion occurred in the star, a strong shock wave would have formed and propagated through the CSM. When it reached the CSM surface, its kinetic energy would have converted into thermal and radiation energy, causing a sudden and a very bright event to occur, which is consistent with the very fast rise of the observed brightness of the supernova.

The CSM surface became as bright as observed peak of COW because of the large "radius", but once CSM quickly lost most of its energy and faded, it became transparent, giving way to an ordinary supernova light.

The theoretical supernova light curves powered by the shock-heating of the CSM the researchers created were found to be in good agreement with the observational data of the COW and the GEP, respectively (figure 4).

The researchers also found that without CSM, the rising of the light curve was much slower and the maximum luminosity was much lower, indicating FBOTs can be linked to CSM-heating.

The research teams are now proposing that the variation the CSM mass formed from the pulsational pair-instability of very massive stars would cause variation among FBOTs. If the CSM mass is large enough, the resulting supernova would be observed as a so-called Superluminous Supernova which is bright but shows much slower rising.

The next step is to confirm this hypothesis with more observations.

The results of both studies were published online in The Astrophysical Journal on 3 November 2020 [1] and 8 July 2021 [2].

Source: Klavi Institute for the Physics and Mathematics of the Universe (Klavi IPMU)

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Paper details

Paper [1]

Journal: The Astrophysical Journal

Paper title: A Model for the Fast Blue Optical Transient AT2018cow: Circumstellar Interaction of a Pulsational Pair-instability Supernova

Authors: Shing-Chi Leung (2,1), Sergei Blinnikov (1,3,4), Ken'ichi Nomoto (1), Petr Blakanov (3,5,6), Elena Sorokina (3,7) and Alexey Tolstov (8,1)

Author affiliations

1 Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan;

2 TAPIR, Walter Burke Institute for Theoretical Physics, Mailcode 350-17, Caltech, Pasadena, CA 91125, USA

3 National Research Center “Kurchatov institute,” Institute for Theoretical and Experimental Physics (ITEP), 117218 Moscow, Russia

4 Dukhov Automatics Research Institute (VNIIA), Suschevskaya 22, 127055 Moscow, Russia

5 National Research Nuclear University MEPhI, Kashirskoe sh. 31, Moscow 115409, Russia

6 Space Research Institute (IKI), Russian Academy of Sciences, Profsoyuznaya 84/32, 117997 Moscow, Russia

7 Sternberg Astronomical Institute, M.V. Lomonosov Moscow State University, Universitetski pr. 13, 119234 Moscow, Russia

8 The Open University of Japan, 2-11, Wakaba, Mihama-ku, Chiba, Chiba 261-8586, Japan

DOI: 10.3847/1538-4357/abba33 (published 3 November, 2020)
Paper abstract (The Astrophysical Journal)
Preprint (arXiv.org)

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Paper [2]

Journal: The Astrophysical Journal
Paper title: Fast Blue Optical Transients Due to Circumstellar Interaction and the Mysterious
Supernova SN 2018gep
Authors: Shing-Chi Leung (1), Jim Fuller (1), Ken’ichi Nomoto (2)
Author affiliations:
1 TAPIR, Walter Burke Institute for Theoretical Physics, Mailcode 350-17,
Caltech, Pasadena, CA 91125, USA
2 Kavli Institute for the Physics and Mathematics of the Universe (WPI),
The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan

DOI: 10.3847/1538-4357/abfcbe (published 8 July, 2021)
Paper abstract (The Astrophysical Journal)
Preprint (arXiv.org)

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Research contact

Ken'ichi Nomoto
Senior Scientist
Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), The University of Tokyo
E-mail: nomoto@astron.s.u-tokyo.ac.jp
Preprint (arXiv.org)

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Media contact:

Motoko Kakubayashi
Press officer
Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), The University of Tokyo
E-mail: press@ipmu.jp

Related article:

Researchers find the origin and the maximum mass of massive black holes observed by gravitational wave detectors.

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ALMA Catches “Intruder” Redhanded in Rarely Detected Stellar Flyby Event

Scientists have captured an intruder object disrupting the protoplanetary disk—birthplace of planets—in Z Canis Majors (Z CMa), a star in the Canis Majoris constellation. This artist’s impression shows the perturber leaving the star system, pulling a long stream of gas from the protoplanetary disk along with it. Observational data from the Subaru Telescope, Karl G. Jansky Very Large Array, and Atacama Large Millimeter/submillimeter Array suggest the intruder object was responsible for the creation of these gaseous streams, and its “visit” may have other as yet unknown impacts on the growth and development of planets in the star system. Credit: ALMA (ESO/NAOJ/NRAO), B. Saxton (NRAO/AUI/NSF). Hi-Res File

For the first time, scientists have captured an intruder object “breaking and entering” into a developing star system. Combining scattered light observations (H-band) from the Subaru Telescope (top right) with dust continuum emission observations from the VLA (Ka-band, 2nd image right) and ALMA’s Band 6 receiver (3rd image right), and the 13CO line (bottom right), scientists were able to gain a comprehensive understanding of just how much disruption this intruder caused, including the development of long streams of gas stretching far out from the protoplanetary disk surrounding Z Canis Majoris, a star in the Canis Majoris constellation. Just what consequences these disruptions will have on the birth of planets in the star system is yet to be seen. Credit: ALMA (ESO/NAOJ/NRAO), S. Dagnello (NRAO/AUI/NSF), NAOJ. Hi-Res File

As stars grow up, they often interact with their sibling stars—stars growing up near to them in space—but have rarely been observed interacting with outside, or intruder, objects. Scientists have now made observations of an intruder object disturbing the protoplanetary disk around Z Canis Majoris, a star in the Canis Major constellation, which could have major implications for the development of baby planets. Perturbations, including long streams of gas, were observed in detail by the Subaru Telescope in the H-band, the Karl G. Jansky Very Large Array in the Ka-band, and using the Atacama Large Millimeter/submillimeter Array’s Band 6 receiver. Credit: ALMA (ESO/NAOJ/NRAO), S. Dagnello (NRAO/AUI/NSF), NAOJ. Hi-Res File

cientists using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA) made a rare detection of a likely stellar flyby event in the Z Canis Majoris (Z CMa) star system. An intruder—not bound to the system—object came in close proximity to and interacted with the environment surrounding the binary protostar, causing the formation of chaotic, stretched-out streams of dust and gas in the disk surrounding it.

While such intruder-based flyby events have previously been witnessed with some regularity in computer simulations of star formation, few convincing direct observations have ever been made, and until now, the events have remained largely theoretical.

“Observational evidence of flyby events is difficult to obtain because these events happen fast and it is difficult to capture them in action. What we have done with our ALMA Band 6 and VLA observations is equivalent to capturing lightning striking a tree,” said Ruobing Dong, an astronomer at the University of Victoria in Canada and the principal investigator on the new study. “This discovery shows that close encounters between young stars harboring disks do happen in real life, and they are not just theoretical situations seen in computer simulations. Prior observational studies had seen flybys, but hadn’t been able to collect the comprehensive evidence we were able to obtain of the event at Z CMa.”

Perturbations, or disturbances, like those at Z CMa aren’t typically caused by intruders, but rather by sibling stars growing up together in space. Hau-Yu Baobab Liu, an astronomer at the Institute of Astronomy and Astrophysics at Academia Sinica in Taiwan and a co-author on the paper, said, “Most often, stars do not form in isolation. The twins, or even triplets or quadruplets, born together may be gravitationally attracted and, as a result, closely approach each other. During these moments, some material on the stars’ protoplanetary disks may be stripped off to form extended gas streams that provide clues to astronomers about the history of past stellar encounters.”

Nicolás Cuello, an astrophysicist and Marie Curie Fellow at Université Grenoble Alpes in France and a co-author on the paper added that in the case of Z CMa, it was the morphology, or structure, of these streams that helped scientists to identify and pinpoint the intruder. “When a stellar encounter occurs, it causes changes in disk morphology—spirals, warps, shadows, etc.—that could be considered as flyby fingerprints. In this case, by looking very carefully at Z CMa’s disk, we revealed the presence of several flyby fingerprints.”

These fingerprints not only helped scientists to identify the intruder but also led them to consider what these interactions might mean for the future of Z CMa and the baby planets being born in the system, a process that so far has remained a mystery to scientists. “What we now know with this new research is that flyby events do occur in nature and that they have major impacts on the gaseous circumstellar disks, which are the birth cradles of planets, surrounding baby stars,” said Cuello. “Flyby events can dramatically perturb the circumstellar disks around participant stars, as we’ve seen with the production of long streamers around Z CMa.”

Liu added, “These perturbers not only cause gaseous streams but may also impact the thermal history of the involved host stars, like Z CMa. This can lead to such violent events as accretion outbursts, and also impact the development of the overall star system in ways that we haven’t yet observed or defined.”

Dong said that studying the evolution and growth of young star systems throughout the galaxy helps scientists to better understand our own Solar System’s origin. “Studying these types of events gives a window into the past, including what might have happened in the early development of our own Solar System, critical evidence of which is long since gone. Watching these events take place in a newly forming star system provides us with the information needed to say, ‘Ah-ha! This is what may have happened to our own Solar System long ago.’ Right now, VLA and ALMA have given us the first evidence to solve this mystery, and the next generations of these technologies will open windows on the Universe that we have yet only dreamed of.”

Recently, the National Radio Astronomy Observatory (NRAO) received approval for its Central Development Laboratory (CDL) to develop a multi-million dollar upgrade to ALMA’s Band 6 receiver, and the Observatory’s next-generation VLA (ngVLA) received strong support from the astronomical community in the Astro2020 Decadal Survey. Technological advancements for both telescopes will lead to better observations, and a potentially significant increase in the discovery of difficult-to-see objects, like Z CMa’s stellar intruder. Both projects are funded in part by the National Science Foundation (NSF). “These observations highlight the synergy that can come from a newer instrument working in concert with a more seasoned one, and how good a workhorse the ALMA Band 6 receiver is,” said Dr. Joe Pesce, astrophysicist and ALMA Program Director at the NSF. “I look forward to the even-better results the upgraded ALMA Band 6 receiver will enable.”

Resource

Dong et. al, “A likely flyby of binary protostar Z CMa Caught in Action,” Nature Astronomy, 10.1038/s41550-021-01558-y

About ALMA

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 Ministry of Science and Technology (MOST) 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.

Media Contact:

Amy C. Oliver
Public Information Officer, ALMA
Public Information & News Manager, NRAO
+1 434 242 9584
aoliver@nrao.edu

Source: National Radio Astronomy Observatory (NRAO)/News

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