Merging galactic black holes focus of new survey - Canadanewsmedia
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Merging galactic black holes focus of new survey



These images show galactic nuclei in the process of merging, with supermassive black holes in the cores of each pair of galaxies gorging on stellar debris and rapidly growing in size. In the top image of NGC 6240, the approaching black holes are just 3,000 light years apart. Image: NASA, ESA, and M. Koss (Eureka Scientific, Inc.)

Astronomers are getting their best view yet of close pairs of supermassive black holes in the cores of colliding galaxies as the holes move closer and closer together, feasting on stellar debris and rapidly growing to enormous size as they near coalescence.

Michael Koss of Eureka Scientific Inc. used high-resolution images infrared images from the Hubble Space Telescope and the W.M. Keck Observatory to carry out the largest survey yet of nearby galactic cores, peering through thick clouds of gas and dust that shroud the growing supermassive black holes.

“Seeing the pairs of merging galaxy nuclei associated with these huge black holes so close together was pretty amazing,” Koss said. “In our study, we see two galaxy nuclei right when the images were taken. You can’t argue with it; it’s a very ‘clean’ result, which doesn’t rely on interpretation.”

Laura Blecha of the University of Florida said computer simulations of galactic collisions “show us that black holes grow fastest during the final stages of mergers, near the time when the black holes interact, and that’s what we have found in our survey.”

“The fact that black holes grow faster and faster as mergers progress tells us galaxy encounters are really important for our understanding of how these objects got to be so monstrously big.”

The team’s observations and results were posted in the journal Nature.

The images provide a preview of sorts, showing the eventual fates of the supermassive black holes in the nuclei of the Milky Way and the Andromeda galaxies, which are expected to crash together in five billion years or so. They also illustrate a phenomenon that was more common in the early universe when galactic mergers were more frequent.

Galaxy mergers take a billion years or more to run their course, kicking up huge quantities of gas and dust as the slow-motion gravitational encounter proceeds. The ejected material can form a thick “curtain” around the centres of the merging galaxies, providing a ready source of cosmic food for the central black holes to feast on.

The fastest growth occurs during the last 10 million to 20 million years of the merger. The Hubble and Keck Observatory images show the best views yet of this final stage, when the rapidly growing black holes in the galaxy merger known as NGC 6240 are just 3,000 light years apart.

“Gas falling onto the black holes emits X-rays, and the brightness of the X-rays tells you how quickly the black hole is growing,” Koss said. “I didn’t know if we would find hidden mergers, but we suspected, based on computer simulations, that they would be in heavily shrouded galaxies.Therefore we tried to peer through the dust with the sharpest images possible, in hopes of finding coalescing black holes.”

It wasn’t easy. The team first sifted through 10 years of X-ray data from the Neil Gehrels Swift Telescope and then worked through the Hubble archive, identifying the merging galaxies found in the X-ray data. They then used Keck for infrared observations of X-ray-producing black holes not found in the Hubble archive.

“People had conducted studies to look for these close interacting black holes before, but what really enabled this particular study were the X-rays that can break through the cocoon of dust,” Koss said. “We also looked a bit farther in the universe so that we could survey a larger volume of space, giving us a greater chance of finding more luminous, rapidly growing black holes.”

Future infrared telescopes will provide more detailed views of dusty galaxy collisions, allowing astronomers to measure the masses, growth rates and dynamics of close black hole pairs.

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From birds to fish, humans reshaping evolutionary history of species everywhere: paper




A theoretical biologist says the activities and presence of human beings have become one of the largest drivers of evolutionary change everywhere on the planet.

A white-winged crossbill sits in a tree near the Highwood Pass on Sept. 4, 2018. A new paper based on research from around the globe concludes that human beings have radically reshaped evolution for everything from birds to fish to plants.

Mike Drew/Postmedia

VANCOUVER — Swallows are evolving smaller, more manoeuvrable wings to help them dodge buildings and vehicles.

Some fish are growing mouths that are smaller and harder to hook.

Large animals from caribou to tuna are disappearing.

Meanwhile, it’s boom time for anything not too fussy about where it lives or what it eats.

“It’s a reshaping of the tree of life,” said Sarah Otto, a University of British Columbia researcher, whose paper was published Wednesday by the London-based Proceedings of the Royal Society.

Otto, a much-awarded and highly regarded theoretical biologist, says the activities and presence of human beings have become one of the largest drivers of evolutionary change everywhere on the planet.

“Human impacts on the world are not just local,” she said. “They are changing the course of evolutionary history for all species on the planet, and that’s a remarkable concept to ponder.”

Earth scientists have long discussed the idea of the Anthropocene — a period of Earth’s history defined by geological markers of human impact. Otto, after reviewing dozens of research papers, concludes the planet’s biology is becoming similarly marked as plants and animals respond to human pressure.

Her paper is replete with examples from bird species slowly forgetting to migrate to mosquito breeds adapted specifically to underground subway tunnels.

Backyard bird feeders are behind changes in the beak shape and strength of house finches. Different mammals are becoming nocturnal as a way to avoid human conflict. Introduced species change the ground rules for native plants and animals.

It’s a mistake to think evolution requires millennia, said Otto.

“Evolution happens really fast if the selection regimes are strong. We can see sometimes in plant populations evolutionary change in the course of years.”

If the changes come too fast for evolution to keep up, there’s always extinction.

Rates of species loss are now estimated to be 1,000 times higher than they were before human domination. More than one in five of all plant and animal species are considered at risk.

Extinctions have always happened. But Otto said they’re happening at such a pace and in response to such similar pressures that they are reducing the ability of evolution to respond to change.

“We’re losing the ability for evolution to bounce back.”

Forcing species into a human-formed box reduces variability, leaving evolution less to work with in response to future changes. And wiping species out removes them forever.

“If we’re eliminating the large-bodied mammals, even if humans went extinct on the planet, we’re not going to see an immediate return of ecosystems to have the right balance of small, medium and large species,” Otto said.

“We’re cutting off options. We’re cutting off options both within species by eliminating variability, and we’re also cutting off options at the tree of life level by cutting off species.”

Species that are doing well are generalists — crows, coyotes, dandelions.

“The ones that can both tolerate and thrive in human-altered environments,” said Otto. “The pigeons and the rats.”

The biggest single human-caused evolutionary pressure, Otto said, is climate change.

“The No. 1 thing we have to do is tackle climate change. If we don’t do that, we’re going to lose a lot more species.”

— By Bob Weber in Edmonton. Follow @row1960 on Twitter

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Nations gather to weigh the meaning of a kilogram




Carlos Sanchez, expert in metrology at the National Research Council of Canada, is working on the Kibble balance.


If things go as planned, by the end of this week, the world will have a new definition of the kilogram.

The change will not require any adjustments to bathroom scales, or alter the heft of a bag of potatoes. But the milestone will serve to make our universal unit of mass a lot more universal.

In short, instead of basing it on a lump of precious metal locked in a vault in France, scientists have decided to recast the kilogram as something truly immutable, tied by a mathematical umbilical cord to the fundamental constants of nature that have endured since the Big Bang banged.

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For those who play in the rarefied world of high-precision metrology − the science of measurement − it just doesn’t get any better.

“I’ve always said this is the best time to be the chief metrologist for your country,” said Alan Steele, who plays that role for Canada as director-general of the National Research Council’s Metrology Research Centre in Ottawa.

Dr. Steele is set to cast Canada’s vote to adopt the new kilogram definition on Friday.

The kilogram was originally devised as part of the metric system, a byproduct of the French revolution that sought to break with traditional measures such as the pound − an arbitrary quantity that harks back to the Roman libra − in favour of more scientifically derived units.

Initially, the kilogram was defined as the mass of a litre of water at the freezing point. But by 1889, the countries who were then part of the General Conference on Weights and Measures agreed that the value of the unit mass had to be pegged to something that could be measured far more precisely.

They settled on a reference weight machined out of a platinum-iridium alloy that has served as the world’s prototype kilogram ever since.

Canada was not among the original signatories, having joined the conference in 1907. But this time around, Canada has played a key role in supplanting the prototype with a new definition that no longer depends on a physical artifact.

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“It’s something we’re really proud of,” Dr. Steele said. “Metrology is about credibility and demonstrating you’re as good as you say you are.”

What Canada turns out to be good at is measuring an exceedingly small number, known as Planck’s constant, that serves as the fundamental increment of action in the universe. In theory, the constant emerges whenever you divide the energy in a particle of light by its frequency. In practice, it’s not so easy to measure. Right now, Canada holds the record for setting the value of the tiny constant with the least amount of uncertainty − about 9.1 parts per billion.

The device that made it possible is the Kibble balance, a supercharged version of the standard laboratory scale. But instead of comparing the masses of two objects, the Kibble balance very precisely sets the mass of one object against the magnetic force generated by an electric current flowing through a coil of wire. The ingenious design bridges the mechanical realm with the electromagnetic, and thereby allows the kilogram to be bound firmly to Planck’s constant for all time.

This has long been a goal of scientists who serve as the arbiters of measurement. The metre and the second have been defined by physical constants, such as the speed of light, for decades. But because of the difficulty of measuring Planck’s constant, the kilogram has been a holdout until now.

“It was only in the last two years or so that it became clear that we could vote for the redefinition,” said Michael Stock, director of physical metrology for the International Bureau of Weights and Measures in Sèvres, France. The effort, he said, is not driven by the needs of today but by the possibilities that more precise units of measurement open up for scientists in years to come.

Canada first got into the kilogram game in 2009 when it took over a Kibble balance from Britain and, in Dr. Steele’s words, “went to town and made almost every aspect of the experiment better and better.”

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The work ultimately allowed Canada’s blue-chip measurement to be included with a handful of other labs who have combined to set the value of Planck’s constant and, by extension, the kilogram.

Carlos Sanchez, who was part of the team that conducted the work at the NRC, said that the challenge was not just about being precise but about relentlessly beating down more than a dozen sources of uncertainty in the equipment for several years to get the cleanest possible result.

“It takes patience,” Dr. Sanchez said. “You have to have a plan, otherwise you can spend your life doing experiments that lead nowhere.”

Happily, the NRC’s experiments have led to the Palace of Versailles, where representatives from 60 countries have gathered to officially approve the new definition, not only for the kilogram but also for units of electric current (the ampere), temperature (the kelvin) and particulate quantity (the mole). A unanimous vote is expected, after which the global edifice of measurement, perhaps humanity’s greatest tribute to objective reality, will stand on firmer ground − all with nothing apparently having changed.

Which is precisely the point, Dr. Steele said. At the end of it all, “you want the kilogram to still weigh a kilogram.”

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Researchers walk back major ocean warming result





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Scripps Pier after sunset in La Jolla, California. Image via Hayne Palmour IV/ San Diego Union-Tribune/ os Angeles Times.

This is good news. It is less certain today that Earth’s oceans are 60% warmer than we thought (although they may still be that warm). As reported in the Los Angeles Times today (November 14, 2018), researchers with UC San Diego’s Scripps Institution of Oceanography and Princeton University have had to walk back a widely reported scientific result – based on a paper published in Nature last month – showing that showed Earth’s oceans were heating up dramatically faster than previously thought, as a result of climate change.

The October 31 paper in Nature stated the oceans had warmed 60% more than outlined by the United Nations’ Intergovernmental Panel on Climate Change (IPCC). On November 6, mathematician Nic Lewis posted his criticisms of the paper at Judith Curry’s blog. Both Lewis and Curry are critics of the scientific consensus that global warming is ongoing and human-caused.

In his November 6 blog post, Lewis pointed out flaws in the October 31 paper. The authors of the October 31 paper now say they’ve redone their calculations, and – although they find the ocean is still likely warmer than the estimate used by the IPCC – they agree that they “miffed” the range of probability. They can no longer support the earlier statement of a heat increase 60% greater than indicated. They now say there is a larger range of probability, between 10% and 70%, as other studies have already found.

A correction has been submitted to Nature.

The Los Angeles Times reported that one of the co-author’s on the paper – Ralph Keeling at the Scripps Institution of Oceanography – “took full blame” and thanked Lewis for alerting him to the mistake. Keeling told the Los Angeles Times:

When we were confronted with his insight it became immediately clear there was an issue there. We’re grateful to have it be pointed out quickly so that we could correct it quickly.

In the meantime, the Twitter-verse today has done the expected in a situation like this, where a widely reported and dramatic climate result has had to be walked back. Many are making comments like this one:

But cooler heads on Twitter and elsewhere in the media are also weighing in, pointing out – as has been necessary to point out time and again – that science is not a “body of facts.” Science is a process. Part of the reason scientists publish is so that other scientists can find errors in their work, so that the errors can be corrected.

All scientists know this. The Los Angeles Times explained it this way:

While papers are peer-reviewed before they’re published, new findings must always be reproduced before gaining widespread acceptance throughout the scientific community …

The Times quoted Gerald Meehl, a climate scientist at the National Center for Atmospheric Research in Boulder, Colorado, as saying:

This is how the process works. Every paper that comes out is not bulletproof or infallible. If it doesn’t stand up under scrutiny, you review the findings.

Bottom line: An error has been found in the October 31, 2018 paper published in Nature – showing an increase in ocean warming 60% greater than that estimated by the IPCC. The authors have acknowledged the error, and a correction has been submitted to Nature.

October 31 paper in Nature: Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition

November 6 blog post by Nic Lewis: A major problem with the Resplandy et al. ocean heat uptake paper

Deborah Byrd


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