среда, 5 февраля 2020 г.

ALMA catches beautiful outcome of stellar fight

ALMA image of HD101584 

Location of HD101584 in the constellation of Centaurus 

Wide-field view of the region of the sky where HD101584 is located



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ESOcast 216 Light: ALMA Catches Beautiful Outcome of Stellar Fight
ESOcast 216 Light: ALMA Catches Beautiful Outcome of Stellar Fight

Zooming into HD101584



Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, have spotted a peculiar gas cloud that resulted from a confrontation between two stars. One star grew so large it engulfed the other which, in turn, spiralled towards its partner provoking it into shedding its outer layers.

Like humans, stars change with age and ultimately die. For the Sun and stars like it, this change will take it through a phase where, having burned all the hydrogen in its core, it swells up into a large and bright red-giant star. Eventually, the dying Sun will lose its outer layers, leaving behind its core: a hot and dense star called a white dwarf.

“The star system HD101584 is special in the sense that this ‘death process’ was terminated prematurely and dramatically as a nearby low-mass companion star was engulfed by the giant,” said Hans Olofsson of the Chalmers University of Technology, Sweden, who led a recent study, published in Astronomy & Astrophysics, of this intriguing object.

Thanks to new observations with ALMA, complemented by data from the ESO-operated Atacama Pathfinder EXperiment (APEX), Olofsson and his team now know that what happened in the double-star system HD101584 was akin to a stellar fight. As the main star puffed up into a red giant, it grew large enough to swallow its lower-mass partner. In response, the smaller star spiralled in towards the giant’s core but didn’t collide with it. Rather, this manoeuvre triggered the larger star into an outburst, leaving its gas layers dramatically scattered and its core exposed.

The team says the complex structure of the gas in the HD101584 nebula is due to the smaller star’s spiralling towards the red giant, as well as to the jets of gas that formed in this process. As a deadly blow to the already defeated gas layers, these jets blasted through the previously ejected material, forming the rings of gas and the bright bluish and reddish blobs seen in the nebula.

A silver lining of a stellar fight is that it helps astronomers to better understand the final evolution of stars like the Sun. “Currently, we can describe the death processes common to many Sun-like stars, but we cannot explain why or exactly how they happen. HD101584 gives us important clues to solve this puzzle since it is currently in a short transitional phase between better studied evolutionary stages. With detailed images of the environment of HD101584 we can make the connection between the giant star it was before, and the stellar remnant it will soon become,” says co-author Sofia Ramstedt from Uppsala University, Sweden.

Co-author Elizabeth Humphreys from ESO in Chile highlighted that ALMA and APEX, located in the country’s Atacama region, were crucial to enabling the team to probe “both the physics and chemistry in action” in the gas cloud. She added: “This stunning image of the circumstellar environment of HD101584 would not have been possible without the exquisite sensitivity and angular resolution provided by ALMA.

While current telescopes allow astronomers to study the gas around the binary, the two stars at the centre of the complex nebula are too close together and too far away to be resolved. ESO’s Extremely Large Telescope, under construction in Chile’s Atacama Desert, “will provide information on the ‘heart’ of the object,” says Olofsson, allowing astronomers a closer look at the fighting pair.



More Information

This research was presented in a paper published in Astronomy & Astrophysics.

The team is composed of H. Olofsson (Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Sweden [Chalmers]), T. Khouri (Chalmers), M. Maercker (Chalmers), P. Bergman (Chalmers), L. Doan (Department of Physics and Astronomy, Uppsala University, Sweden [Uppsala]), D. Tafoya (National Astronomical Observatory of Japan), W. H. T. Vlemmings (Chalmers), E. M. L. Humphreys (European Southern Observatory [ESO], Garching, Germany), M. Lindqvist (Chalmers), L. Nyman (ESO, Santiago, Chile), and S. Ramstedt (Uppsala).

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 leadership and management of the construction, commissioning and operation of ALMA.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.



Links 



Contacts

Hans Olofsson
Chalmers University of Technology
Onsala, Sweden
Tel: +46 31 772 5535
Email: hans.olofsson@chalmers.se

Elizabeth Humphreys
European Southern Observatory (ESO)
Santiago, Chile
Tel: +56 2 2463 6912
Email: ehumphre@eso.org

Sofia Ramstedt
Uppsala University
Uppsala, Sweden
Tel: +46 18 471 5970
Email: sofia.ramstedt@physics.uu.se

Bárbara Ferreira
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: pio@eso.org

Source: ESO/News




* This article was originally published here

The ‘Stoupe Brow’ Decorated Neolithic Cairn Slab (Cast), Whitby Museum and Art Gallery,...

The ‘Stoupe Brow’ Decorated Neolithic Cairn Slab (Cast), Whitby Museum and Art Gallery, Whitby, North Yorkshire, 2.2.20.



* This article was originally published here

Arctic on red alert as lands grow greener


New research techniques are being adopted by scientists tackling the most visible impact of climate change -- the so-called greening of Arctic regions.

Arctic on red alert as lands grow greener
Drone image of a permafrost thaw slump on Qikiqtaruk Herschel Island in the Canadian Arctic
[Credit: Jeff Kerby, National Geographic Society]
The latest drone and satellite technology is helping an international team of researchers to better understand how the vast, treeless regions called the tundra is becoming greener.

As Arctic summer temperatures warm, plants are responding. Snow is melting earlier and plants are coming into leaf sooner in spring. Tundra vegetation is spreading into new areas and where plants were already growing, they are now growing taller.

Understanding how data captured from the air compare with observations made on the ground will help to build the clearest picture yet of how the northern regions of Europe, Asia and North America are changing as the temperature rises.


Now a team of 40 scientists from 36 institutions, led by two National Geographic Explorers, have revealed that the causes of this greening process are more complex -- and variable -- than was previously thought.

Researchers from Europe and North America are finding that the Arctic greening observed from space is caused by more than just the responses of tundra plants to warming on the ground. Satellites are also capturing other changes including differences in the timing of snowmelt and the wetness of landscapes.

Lead author Dr Isla Myers-Smith, of the University of Edinburgh's School of GeoSciences, said: "New technologies including sensors on drones, planes and satellites, are enabling scientists to track emerging patterns of greening found within satellite pixels that cover the size of football fields."

Professor Scott Goetz of the School of Informatics, Computing and Cyber Systems at Northern Arizona University, says this research is vital for our understanding of global climate change. Tundra plants act as a barrier between the warming atmosphere and huge stocks of carbon stored in frozen ground.


Changes in vegetation alter the balance between the amount of carbon captured and its release into the atmosphere. Small variations could significantly impact efforts to keep warming below 1.5 degrees centigrade -- a key target of the Paris Agreement. The study will help scientists to figure out which factors will speed up or slow down warming.

Co-lead author Dr Jeffrey Kerby, who was a Neukom Fellow at Dartmouth College while conducting the research, said: "Besides collecting new imagery, advances in how we process and analyse these data -- even imagery that is decades old -- are revolutionising how we understand the past, present, and future of the Arctic."

Alex Moen, Vice President of Explorer Programs at the National Geographic Society, said: "We look forward to the impact that this work will have on our collective understanding of the Arctic for generations to come."

The paper has been published in Nature Climate Change.

Source: University of Edinburgh [January 31, 2020]



* This article was originally published here

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Fossil Shell Prehistoric Necklace, Whitby Museum and Art Gallery, Whitby, North Yorkshire, 2.2.20.



* This article was originally published here

Scientists Complete ELM Survey, Discover 98 Double White Dwarf Stars

Artist's conception of extremely low mass detached double white dwarf binary.
Credit: Melissa Weiss.  High Resolution (jpg)

Cambridge, MA - Scientists at the Center for Astrophysics | Harvard & Smithsonian (CfA) have completed the Extremely Low Mass--also known as ELM--spectroscopic study of white dwarf stars in the Sloan Digital Sky Survey (SDSS). In process for more than a decade, the completed survey discovered 98 detached double white dwarf binaries.

"We targeted candidate low mass white dwarf stars and found that they are all ultra-compact binaries. It makes sense," said Dr. Warren Brown, astronomer at CfA and lead author on the survey. "The stars we studied lost so much of their mass during their evolution that they ended up as a low mass white dwarf."

White dwarf stars are the remnant core of a star, what is left over after the star has burned through its nuclear fuel. The stars catalogued in the ELM survey do not follow the traditional "rules" for the creation of white dwarfs.

"The universe isn't old enough to make such low mass white dwarfs on their own, and yet, here they are. That's because they have companions in close orbits. The universe can't make a low mass white dwarf unless it's part of a compact binary," said Brown. "The completed survey now represents more than half of the known detached double white dwarf binaries. This is a substantive piece of work that offers models for future studies and discoveries.”

The ELM Survey is just the beginning, said Dr. Mukremin Kilic, from the University of Oklahoma, and co-author on the survey. Pulling data from the SDSS and Gaia, paired with followups using the 6.5-m MMT at the Fred Lawrence Whipple Observatory in Amado, Arizona, the survey team was able to collect a well-defined sample of existing binary white dwarf stars. "The models estimate there's an order of a hundred million white dwarf binaries in our galaxy," said Kilic. “We’ve found and confirmed 100 of them. Our observations can anchor the models for future surveys, and allow us to observe a specific subset of white dwarfs and cut through the population."

The clean and complete data set also acts as a precursor to future gravitational wave studies. The LISA (Laser Interferometer Space Antenna) gravitational wave observatory—planned for launch in 2034—will detect MHz gravity-wave sources, and is expected to detect hundreds of thousands of binary white dwarf stars. "There are things you can do if you have sources with both light and gravity waves,” said Brown. "With light we can measure temperature, distance, velocity, but we don’t measure mass directly; gravity-wave measurements measure mass."

As new technology and new methodologies approach reality, scientists are keen to see what the future holds for the stars in the ELM survey. "The traditional response to these binaries was to call them supernova progenitors. Someday they will merge together and become something else, and it's unclear what," said Brown. "If there's one thing we know for certain, it is that the stars we’ve listed in the survey will be great sources for the LISA mission and for future white dwarf star and gravitational wave studies; they are gravity wave sources, they are the signature multi-messenger systems of the future."

The results of the survey are published in The Astrophysical Journal.

About Center for Astrophysics | Harvard & Smithsonian

Headquartered in Cambridge, Mass., the Center for Astrophysics | Harvard & Smithsonian (CfA) is a collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Amy Oliver
Public Affairs
Center for Astrophysics | Harvard & Smithsonian
Fred Lawrence Whipple Observatory
520-879-4402
amy.oliver@cfa.harvard.edu





* This article was originally published here

Prehistoric Pottery and Incense Burners, Whitby Museum and Art Gallery, North Yorkshire, 2.2.20.

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* This article was originally published here

The great and the good

Here's a quote from a new paper on the impact of genetics, and especially ancient DNA, on archeology and linguistics co-authored by archeologist James Mallory and geneticist Oleg Balanovsky: Just as the genetic evidence for a steppe homeland appeared to weaken a popular theory (among archaeologists more than linguists) that the Indo-European languages spread from an Anatolian homeland with the

* This article was originally published here

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* This article was originally published here

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* This article was originally published here

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Roman Glassware, Whitby Museum and Art Gallery, Whitby, North Yorkshire, 2.2.20.



* This article was originally published here

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* This article was originally published here

The Blue Acceleration: Recent colossal rise in human pressure on ocean quantified


Human pressure on the world's ocean accelerated sharply at the start of the 21st century and shows no sign of slowing, according to a comprehensive new analysis on the state of the ocean.

The Blue Acceleration: Recent colossal rise in human pressure on ocean quantified
Claiming ocean resources and space is not new to humanity, but the extent, intensity, and diversity of today’s
aspirations are unprecedented, according to new research [Credit: PxFuel]
Scientists have dubbed the dramatic rise the "Blue Acceleration". The researchers from the Stockholm Resilience Centre, Stockholm University, synthesized 50-years of data from shipping, drilling, deep-sea mining, aquaculture, bioprospecting and much more. The results are published in the journal One Earth.


The scientists say the largest ocean industry is the oil and gas sector, responsible for about one third of the value of the ocean economy. Sand and gravel are the ocean's most mined minerals to meet demand from the construction industry. As freshwater become an increasingly scarce commodity, around 16,000 desalination plants have sprung up around the world in the last 50 years with a steep rise since 2000, according to the analysis.

Lead author Jean-Baptiste Jouffray from the Stockholm Resilience Centre said, "Claiming ocean resources and space is not new to humanity, but the extent, intensity, and diversity of today's aspirations are unprecedented"

The industrialization of the ocean took off at the end of the last century, driven by a combination of technological progress and declining land-based resources.

The Blue Acceleration: Recent colossal rise in human pressure on ocean quantified
Global trends in use of the marine environment. Usage reached an inflection point
around the turn of the new millennium [Credit: One Earth]
"This Blue Acceleration is really a race for ocean resources and space, posing risks and opportunities for global sustainability"

The study highlights some positive human impacts. For example, the area protected from some exploitation has increased exponentially with a surge since 2000 that shows no signs of slowing. And offshore wind farm technology has reached commercial viability in this period allowing the world to reduce reliance on fossil fuels.


The authors conclude by calling for increased attention to who is driving the Blue Acceleration, what is financing it and who is benefiting from it? The United Nations is embarking on a "decade of the ocean" in 2021. The scientists say this is is an opportunity to assess the social-ecological impacts and manage ocean resources for long-term sustainability.

They highlight there is a high degree of consolidation relating the seafood industry, oil and gas exploitation and bioprospecting with just a small handful of multinational companies dominating each sector. The team suggests that banks and other investors could adopt more stringent sustainability criteria for ocean investments.

Source: Stockholm Resilience Centre [January 24, 2020]



* This article was originally published here

Patterns of thinning of Antarctica’s biggest glacier higher than expected


Using the latest satellite technology from the European Space Agency (ESA), scientists from the University of Bristol have been tracking patterns of mass loss from Pine Island -- Antarctica's largest glacier.

Patterns of thinning of Antarctica’s biggest glacier higher than expected
Pine Island Bay [Credit: Getty]
They found that the pattern of thinning is evolving in complex ways both in space and time with thinning rates now highest along the slow-flow margins of the glacier, while rates in the fast-flowing central trunk have decreased by about a factor of five since 2007. This is the opposite of what was observed prior to 2010.

Pine Island has contributed more to sea level rise over the past four decades than any other glacier in Antarctica, and as a consequence has become one of its most intensively and extensively investigated ice stream systems.


However, different model projections of future mass loss give conflicting results; some suggesting mass loss could dramatically increase over the next few decades, resulting in a rapidly growing contribution to sea level, while others indicate a more moderate response.

Identifying which is the more likely behaviour is important for understanding future sea level rise and how this vulnerable part of Antarctica is going to evolve over the coming decades.

Patterns of thinning of Antarctica’s biggest glacier higher than expected
Animation showing thinning of Pine Island Glacier
[Credit: University of Bristol]
The results of the new study, published in the journal Nature Geoscience, suggest that rapid migration of the grounding line, the place where the grounded ice first meets the ocean, is unlikely over that timescale, without a major change in ocean forcing. Instead, the results support model simulations that imply that the glacier will continue to lose mass but not at much greater rates than present.


Lead author Professor Jonathan Bamber from the University of Bristol's School of Geographical Sciences, said: "This could seem like a 'good news story' but it's important to remember that we still expect this glacier to continue to lose mass in the future and for that trend to increase over time, just not quite as fast as some model simulations suggested.

"It's really important to understand why the models are producing different behaviour in the future and to get a better handle on how the glacier will evolve with the benefit of these new observations.

"In our study, we didn't make projections but with the aid of these new data we can improve model projections for this part of Antarctica."

Source: University of Bristol [January 27, 2020]



* This article was originally published here

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