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Showing posts with label massive binary star system. Show all posts
Showing posts with label massive binary star system. Show all posts
From millions of light-years away, how can we tell if a galaxy
contains one supermassive black hole or two? It’s a tricky problem: the
gas around single supermassive black holes glows across the
electromagnetic spectrum and varies on timescales from hours to years,
and it’s not obvious how adding a second black hole changes these
behaviors. As a step toward differentiating the two scenarios, a team
led by John Ryan Westernacher-Schneider (Leiden University and Clemson
University) simulated the gas surrounding pairs of black holes. When
binary black hole systems ensnare gas from their surroundings, the gas
collects in a large accretion disk around both black holes and in
smaller disks around the individual black holes. These smaller disks are
called minidisks. Each frame above shows a simulated minidisk
with different physical parameters. Because of instabilities, the
simulated minidisks sometimes become extremely elongated, and if future
work suggests that this elongation is likely to happen in real disks, it
may provide a way to interpret variations in the light from distant
sources and pinpoint binary black holes. To learn more about these
minidisk simulations, be sure to check out the full article linked
below.
A thermal-infrared image of wr 112 captured with keck observatory's lws instrument in august 2004.
Credit: R. Lau et al./ISAS/JAXA/W. M. Keck Observatory
Maunakea, Hawaii – Astronomers using three Maunakea
Observatories have discovered one of the most prolific dust-making
Wolf-Rayet star systems known, remarkably producing an entire Earth mass
of dust every year.
With nearly two decades of images from the world’s largest
observatories – including W. M. Keck Observatory, Subaru Telescope, and
Gemini Observatory in Hawaii – a research team led by Ryan Lau of
Honolulu, Hawaii, an ʻIolani School alumnus and astronomer with the
Japan Aerospace Exploration Agency (JAXA) at the Institute of Space and
Astronautical Science (ISAS), has captured the beautiful, spiral motion
of newly-formed dust streaming from a massive binary star system called
Wolf-Rayet (WR) 112.
“WR 112 is incredibly hot and luminous with fast stellar winds
ejecting material at high velocities – over thousands of kilometers per
second,” said Lau, lead author of the study. “We’d expect dust to
incinerate from the intense radiation of heat and violent winds. The
fact that we see dust survive in this extreme environment is what makes
WR 112 so mysterious and unusual.”
Wolf-Rayet stars are one of the most extreme stars known; they are
over 20 times more massive and millions of times brighter than the Sun.
Because they are in the very late stage of stellar evolution, losing a
large amount of mass, Wolf-Rayet stars have short lives and therefore
are extremely rare.
WR 112 is composed of a Wolf-Rayet star and a companion star that’s
also much more massive than the Sun. A sequence of images taken since
2001, including observations using Keck Observatory’s Long Wavelength
Spectrometer (LWS), shows this system moving over time, with the two
stars orbiting around each other at timescales of about 20 years, thus
causing the appearance of a spiral rotation.
“Keck Observatory’s LWS was one of the few instruments capable of
capturing high-resolution thermal-infrared images and Maunakea is an
exceptional site for such observations,” said Lau. “These combined
capabilities allowed us to trace the decades-long evolution of the dusty
nebula around WR 112.”
Sequence
of 7 mid-infrared (~10 micrometers) images of WR 112 taken between 2001
– 2019 by Gemini North, Gemini South, Keck Observatory, the Very Large
Telescope (VLT), and Subaru Telescope. The length of the white line on
each image corresponds to about 6800 astronomical units. “Spurs” are the
structures formed in the past 20 years showing variations between
observations. “Nested shells” are expanding structures formed
previously. The X-like signature in the Subaru Telescope image is an
artifact due to property of the instrument. Credit: R. Lau et
al./ISAS/JAXA
The team determined dust forms in the region where stellar winds from these two stars interact.
“When the two winds collide, all hell breaks loose, including the
release of copious shocked-gas X-rays, but also the (at first blush
surprising) creation of copious amounts of carbon-based aerosol dust
particles in those binaries where one of the stars has evolved to
helium-burning, which produces 40% of carbon in their winds,” said
co-author Anthony Moffat, emeritus professor of astronomy at the
University of Montreal.
However, the dusty nebula around WR 112 is far more complex than a
simple pinwheel pattern. Decades of multi-wavelength observations
presented conflicting interpretations of its dusty outflow and orbital
motion. After almost 20 years uncertainty on WR 112, images from Subaru
Telescope’s COMICS instrument taken in Oct 2019 provided the final—and
unexpected—piece to the puzzle.
“We published a study in 2017 on WR 112 suggesting the dusty nebula was not moving at all,
so I thought our COMICS observation would confirm this,” said Lau. “To
my surprise, the COMICS image revealed the dusty shell had definitely
moved since the last image we took with the Very Large Telescope in
2016. It confused me so much that I couldn’t sleep after the observing
run—I kept flipping through the images until it finally registered in my
head that the spiral looked like it was tumbling towards us.”
Lau collaborated with researchers at the University of Sydney,
including Tuthill and undergraduate student Yinuo Han, who are experts
at modeling and interpreting the motion of the dusty spirals from binary
systems like WR 112.
“I shared the images of WR 112 with Peter and Yinuo and they were
able to produce an amazing preliminary model that confirmed the dusty
spiral stream is in fact revolving in our direction along our line of
sight,” said Lau.
With the revised picture of WR 112, the research team was able to
deduce how much dust this binary system is forming. To their surprise,
the team found WR 112’s dust output rate of 3×10-6 solar mass
per year was unusual given its 20-year orbital period—the most
efficient dust producers in this type of WR binary star system tend to
have shorter orbital periods of less than a year, like WR 104 with its
220-day period.
WR 112 therefore demonstrates the diversity of WR binary systems
capable of being highly-efficient dust factories and highlights their
potential role as significant sources of dust not only in the Milky Way,
but galaxies beyond our own.
Massive binary star systems like WR 112, as well as supernova
explosions, are regarded as sources of dust in the early universe, but
the process of dust production and the amount of the ejected dust are
still open questions. With the discovery of WR 112, astronomers now have
new insight into the origin of dust in the young universe.
Above: animated model of the spiral dust nebula around WR 112 (left) and
the actual corresponding observations (right). The φ symbol on the
model animation indicates the orbital phase of the central binary, where
φ = 0 is at the beginning of its 20-yr orbit, and φ = 1 is at the end
of its orbit. The animation pauses at each phase that is displayed in
the real observations. Credit: R. Lau et al./ISAS/JAXA
The W. M. Keck Observatory telescopes are among the most
scientifically productive on Earth. The two 10-meter optical/infrared
telescopes on the summit of Maunakea on the Island of Hawaii feature a
suite of advanced instruments including imagers, multi-object
spectrographs, high-resolution spectrographs, integral-field
spectrometers, and world-leading laser guide star adaptive optics
systems.
Some of the data presented herein were obtained at Keck Observatory,
which is a private 501(c) 3 non-profit organization operated as a
scientific partnership among the California Institute of Technology, the
University of California, and the National Aeronautics and Space
Administration. The Observatory was made possible by the generous
financial support of the W. M. Keck Foundation.
The authors wish to recognize and acknowledge the very significant
cultural role and reverence that the summit of Maunakea has always had
within the Native Hawaiian community. We are most fortunate to have the
opportunity to conduct observations from this mountain.
ALMA’s view of the IRAS-07299 star-forming region and the massive binary
system at its center. The background image shows dense, dusty streams
of gas (shown in green) that appear to be flowing towards the center.
Gas motions, as traced by the methanol molecule, that are towards us are
shown in blue; motions away from us in red. The inset image shows a
zoom-in view of the massive forming binary, with the brighter, primary
protostar moving toward us is shown in blue and the fainter, secondary
protostar moving away from us shown in red. The blue and red dotted
lines show an example of orbits of the primary and secondary spiraling
around their center of mass (marked by the cross).
Movie composed of images taken by ALMA showing the gas streams, as
traced by the methanol molecule, with different line-of-sight
color-coded velocities, around the massive binary protostar system. The
grey background image shows the overall distribution, from all
velocities, of dust emission from the dense gas streams.
Scientists from the RIKEN Cluster for Pioneering Research in Japan,the Chalmers University of Technology in Sweden,and the University of Virginia in the USA and collaborators used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe a molecular cloud that is collapsing to form two massive protostars that will eventually become a binary star system.
While it is known that most massive stars possess orbiting stellar companions it has been unclear how this comes about – for example, are the stars born together from a common spiraling gas disk at the center of a collapsing cloud, or do they pair up later by chance encounters in a crowded star cluster.
Understanding the dynamics of forming binaries has been difficult because the protostars in these systems are still enveloped in a thick cloud of gas and dust that prevents most light from escaping. Fortunately, it is possible to see them using radio waves, as long as they can be imaged with sufficiently high spatial resolution.
In the current research, published in Nature Astronomy, the researchers led by Yichen Zhang of the RIKEN Cluster for Pioneering Research and Jonathan C. Tan at the Chalmers University,and the University of Virginia, used ALMAto observe, at high spatial resolution, a star-forming region known as IRAS 07299-1651, which is located 1.68 kiloparsecs, or about 5,500 light years, away.
The observations showed that already at this early stage, the cloud contains two objects, a massive “primary” central star and another “secondary” forming star, also of high mass. For the first time, the research team was able to use these observations to deduce the dynamics of the system. The observations showed that the two forming stars are separated by a distance of about 180 astronomical units—a unit approximately the distance from the earth to the sun. Hence, they are quite far apart. They are currently orbiting each other with a period of at most 600 years and have a total mass at least 18 times that of our Sun.
According to Zhang, “This is an exciting finding because we have long been perplexed by the question of whether stars form into binaries during the initial collapse of the star-forming cloud or whether they are created during later stages. Our observations clearly show that the division into binary stars takes place early on, while they are still in their infancy.”
Another finding of the study was that the binary stars are being nurtured from a common disk fed by the collapsing cloud and favoring a scenario in which the secondary star of the binary formed as a result of fragmentation of the disk originally around the primary. This allows the initially smaller secondary protostar to “steal” infalling matter from its sibling and eventually they should emerge as quite similar “twins”.
Tan adds, “This is an important result for understanding the birth of massive stars. Such stars are important throughout the universe, not least for producing, at the ends of their lives, the heavy elements that make up our Earth and are in our bodies.”
Zhang concludes, “What is important now is to look at other examples to see whether this is a unique situation or something that is common for the birth of all massive stars.”
Scientists have made observations of a molecular cloud that is collapsing to form two massive protostars that will eventually become a binary star system. The observations showed that already at this early stage, the cloud contains two objects, a massive “primary” central star and another “secondary” forming star, also of high mass.
Additional Information
This research appeared in Nature Astronomy as ‘Dynamics of a massive binary at birth’ by Yichen Zhang, Jonathan C. Tan, Kei E. I. Tanaka, James M. De Buizer, Mengyao Liu, Maria T. Beltrán, Kaitlin Kratter, Diego Mardones, and Guido Garay. Doi: 10.1038/s41550-019-0718-y.
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.
RIKEN is Japan’s largest research institute for basic and applied research. Over 2500 papers by RIKEN researchers are published every year in leading scientific and technology journals covering a broad spectrum of disciplines including physics, chemistry, biology, engineering, and medical science. RIKEN’s research environment and a strong emphasis on interdisciplinary collaboration and globalization have earned a worldwide reputation for scientific excellence.
At the RIKEN Pioneering Research Cluster, outstanding researchers with rich research achievements and strong leadership abilities serve as leaders of Chief Scientist Laboratories, from where they carry out innovative fundamental research, pioneer new research fields, and carry on research that crosses disciplinary and organizational barriers.
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 Jens Wilkinson RIKEN Global Communications Japan Phone: +81-(0)48-462-1225 Email:pr@riken.jp
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
