Connect with us

Science

Astronomers discover 'extraordinary' unknown radio signal from heart of Milky Way – CNET

Published

 on


Across the vast desert plains of Western Australia, on the lands of the Wajarri Yamatji people, lies one of the most capable radio telescope arrays in the world. Containing 36 dish antennas, the Australian Square Kilometre Array Pathfinder, ASKAP, is an eye to the universe. The three dozen antennas watch for radio waves that crash over the Earth.

Over the last two years the antennas have, on occasion, been pointed toward the heart of the Milky Way, our home galaxy. And, on occasion, they’ve detected a highly unusual radio signal — one that does not seem to fit with any object we currently know is lurking in the cosmos.

The detection of the signal appears in the Astrophysical Journal on Oct. 12. It was first published as a preprint on arXiv in September.

The name of the strange signal is a mouthful: ASKAP J173608.2-321635. We’re going to call it the Ghost. Between April 2019 and August 2020, the Ghost was spotted 13 times but without any consistent timing.

It exhibits a range of characteristics that make it highly unusual and unlike other radio sources from the depths of the Milky Way. 

“This object was unique in that it started out invisible, became bright, faded away and then reappeared,” said Tara Murphy, an astrophysicist at the University of Sydney and co-author on the paper, in a press release. “This behaviour was extraordinary.”

Originally, the team thought the radio signal might be emanating from a pulsar, a kind of neutron star that is incredibly dense and throws off electromagnetic radiation while spinning rapidly in space. The team went searching for the pulsar using the Murriyang telescope at the Parkes observatory in Australia. They came up empty. 

Further searches through data obtained by NASA’s Neil Gehrels Swift Observatory found no X-rays associated with the signal and data from the VISTA telescope, in Chile, also showed no near-infrared signal.

The Ghost left little trace. 

Paraneutron activity

In an attempt to hunt down the Ghost, the team turned to the Meerkat array in South Africa, which is very similar to ASKAP — with double the antennas.

Listening in with Meerkat, the signal reappeared. But the Ghost had morphed into something new. No longer was the radio signal lasting for weeks, it now disappeared within a day. 

This irregular buzzing is one confusing aspect of the discovery, but perhaps the most unusual feature is the Ghost’s circular polarization. Polarization relates to how the radio wave moves through space and time — we’re not going to get into it here, but this entry on Wikipedia is actually quite good at explaining it. What you need to know is circular polarization is a rare phenomenon in the cosmos, making this radio signal rather interesting. 

“Much less than 1% of sources are circularly polarized,” says Ziteng Wang, a doctoral student at the University of Sydney, Australia and first author on the study, adding “usually polarized sources are associated with magnetic fields.” 

Potentially, the magnetic field of an object is messing with the radio signal on its way to Earth. That might be something as common as a dusty debris field or it could be something else entirely. 

Magnetic fields are likely associated with another kind of weird radio signal from the depths of the cosmos, known as a fast radio burst. Tracing these signals leads back to a type of dead star known as a magnetar. You can see the similarities, perhaps, but Wang points out that these signals are different from the Ghost and that FRBs last for much shorter time periods or repeat on much clearer timeframes. Nevertheless, magnetic fields appear to be a powerful way to mess with a radio signal.

There is another group of objects, known as galactic center radio transients, that might explain the Ghost, too, but Wang has reservations about this hypothesis. “The timescale of this signal and GCRTs are different,” he says, noting that these transients are still a mystery to astronomers, too, and if the Ghost is another GCRT, we’re not much closer to working out what that really means. 

We do know that, lurking within the heart of our Milky Way is a gigantic black hole known as Sagittarius A*, but there’s no indication it has anything to do with the Ghost, either.

One of the limitations of the study is the “sparse sampling” of the Ghost, Wang says. He also notes that it’s hard to say exactly how often the Ghost might repeat, because the amount of observations is still quite small. He doesn’t rule out that it’s a pulsar or star, but says the observations don’t fit with either of these objects.

So what is it? I know what you’re thinking, but we never jump to the “A” word around here. It’s almost certainly not aliens.

It definitely is a mystery — for now. Further observations should be able to refine the characteristics of the Ghost a little more, bringing its murky origins into clearer view. 

Adblock test (Why?)



Source link

Continue Reading

Science

Orionid meteor shower to reach peak on Thursday, but full moon may interfere – CTV News

Published

 on


TORONTO —
The Orionid meteor shower is expected to reach its peak in the early hours of Thursday morning, but the full moon may obstruct the show for celestial watchers.

According to NASA, the Orionid meteor shower is active from Oct. 2 to Nov. 7 with the height of activity expected early Oct. 21.

Unfortunately, this falls on the day after the full moon, or “Hunter’s Moon,” reaches its peak illumination on Wednesday morning, appearing full from Monday night through Thursday morning. This means the light of the full moon will interfere with spectators’ ability to see the meteors this year, NASA said.

Usually, the Orionids are considered to be “one of the most beautiful showers of the year,” according to the space agency, and they’re known for their brightness and for their speed.

Due to their speed – they travel at approximately 66 km/s into the Earth’s atmosphere – they can leave “glowing trains” or incandescent bits of debris in the wake of the meteor, which last for several seconds to minutes.

“Fast meteors can also sometimes become fireballs: Look for prolonged explosions of light when viewing the Orionid meteor shower,” NASA said. “The Orionids are also framed by some of the brightest stars in the night sky, which lend a spectacular backdrop for these showy meteors.”

Meteors are formed from leftover comet particles and bits from broken asteroids, according to NASA. When comets travel around the sun, they create a dusty trail around their orbits, which the Earth then passes through every year. When the bits collide with Earth’s atmosphere, they disintegrate to create “fiery and colourful streaks” in the sky.

In the case of the Orionids, the meteors originate from the ice and dust from Halley’s Comet when it returns to the inner solar system.

While the full moon is expected to hamper the view of the shower this year, those in the Northern and Southern hemispheres can still try to catch a glimpse of the meteors during the hours after midnight on Thursday.

According to NASA, hopeful viewers should try to find an area away from city or street lights. They should bring a sleeping bag, blanket, or lawn chair and lie flat on their backs with their feet facing southeast (if they’re in the Northern Hemisphere) and look up. 

Adblock test (Why?)



Source link

Continue Reading

Science

Crop diversity is needed today for tomorrow's food security and nutrition – Phys.org

Published

 on


by The Alliance of Bioversity International and the International Center for Tropical Agriculture

Bean diversity at the CGIAR gene bank in Colombia. Credit: Neil Palmer / CIAT

Although scientists have been ringing bells for more than 100 years about the decline of crop diversity in agriculture, questions about the magnitude, causes, and significance of this loss remain unanswered.

A team of 15 scientists from a wide range of research centers and universities set out 18 months ago to answer these persisting questions, resulting in the largest review ever conducted of evidence about change in crop diversity over time worldwide. The team reviewed hundreds of primary literature sources published over the last 80 years that examine potential crop diversity loss, also called “genetic erosion”. The global collaborative effort found that 95% of all studies reported diversity change, and almost 80% found evidence of loss.

Economic, agricultural, technological, climatic, and political changes during the last 100 years have together led to the decline or disappearance of diversity important to agriculture, both from cultivated fields and from wild habitats. Much of the crop diversity that remains continues to face the threat of erosion or even extinction, while also becoming more homogenous across local landscapes and around the world.

“The global picture that emerges from our review is that of enormous loss over a relatively short period of time of traditional agricultural diversity, which was nurtured by many cultures around the world over the last 10,000 years,” said lead author Colin Khoury, Senior Director for Science and Conservation at San Diego Botanic Garden and research scientist at the Alliance of Bioversity International and the International Center for Tropical Agriculture (CIAT). “Yet the picture also provides hope, as considerable crop diversity persists, and because it shows that agriculture can be re-diversified.”

Khoury collaborated with scientists at international and national agricultural research centers in the U.S., Colombia, Germany, Italy, Mexico, and Peru, as well as universities including El Colegio de la Frontera Sur (Chiapas, Mexico), Ohio State University, Saint Louis University, the University of Arizona, the University of California at Davis, the University of Cambridge, and the University of Illinois to carry out the study, which published in New Phytologist as a Tansley review. This review series was named after the famous English botanist and ecologist Arthur Tansley, who coined the term ecosystem in 1935.

Crop diversity is a critically important resource for agriculture and for human nutrition. This diversity keeps crops productive as they face pests and diseases, provides resilience during extreme weather and other shocks and offers the potential to adapt to changing climates and meet new market demands. In contributing to crop productivity and also to dietary diversity, it underpins food security and nutrition.

“The magnitude of crop diversity loss we have seen in some regions of the world underscores the importance of conserving this diversity outside of these ecosystems as well as within them,” said Luigi Guarino, Director of Science at the Crop Trust, and one of the study’s authors. “Collections of crop diversity such as those in agricultural genebanks and botanic gardens can mitigate local and regional losses, enable the future reestablishment of diversity on farms, and preserve the availability of crops for future use by all. We need to strengthen these repositories and duplicate unique collections in other locations to insure against the risk of loss,” he said.

There are approximately 1,750 genebanks worldwide, maintaining over seven million samples of crop diversity, with , universities, nonprofits, community seed banks, and local conservation networks further contributing to ex-situ conservation. However, more work is needed to conserve the full range of diversity at risk of disappearing from farmers’ fields and, in the case of crop wild relatives, the wild progenitors and cousins of cultivated plants, from grasslands, forests and other natural habitats.

The study analyzed the change in the diversity of traditional crop varieties, or landraces, cultivated on farms; of modern crop cultivars in agriculture; of crop wild relatives in their natural habitats; and of crop genetic resources held in ex situ conservation repositories. The extent of change over time in these environments, while considerable, varied by crop, location, and analytical approach.

“The good news is that while we found evidence of enormous diversity loss over the past decades in each of the environments we studied, we also saw significant maintenance of that diversity in some contexts, and even marked increases in specific instances,” said Stephen Brush, second author for the study and Professor Emeritus of Human Ecology and former Master Adviser for International Agricultural Development at UC Davis.

Diversity of traditional crops remains high on farms and in gardens where landraces are valued for their unique agricultural and societal uses. One-third of the 139 studies of changes in traditional crop varieties reported the maintenance of this diversity over time, and almost one-quarter found evidence for the appearance of new diversity. Also, crop breeders have made significant strides toward diversifying modern crop cultivars in recent decades.

“For crop diversity to continue evolving alongside pests and diseases, in response to climate change, and to meet demands for improved that provide both economic products and ecological services, we need to redouble support for conservation efforts in situ, or in the field, as well as ex situ,” said co-author Allison Miller, Member and Principal Investigator at the Danforth Plant Science Center and Professor of Biology at Saint Louis University.

“In reviewing global change in the that underpins everyone’s food security and nutrition, it’s obvious that there has been major loss, but also that the tools, methods, and knowledge exist to stop its further erosion,” said Khoury. “It is a matter of priorities and resources. To go a major step further and start to reverse the diversity trend, though, is a much bigger task. It requires no less than reframing our food systems, and even the societies they nourish, as -supportive processes.”


Explore further

First comprehensive network of wild crop species will help breeders tackle food insecurity


More information:
Colin K. Khoury et al, Crop genetic erosion: understanding and responding to loss of crop diversity, New Phytologist (2021). DOI: 10.1111/nph.17733

Provided by
The Alliance of Bioversity International and the International Center for Tropical Agriculture

Citation:
Crop diversity is needed today for tomorrow’s food security and nutrition (2021, October 20)
retrieved 20 October 2021
from https://phys.org/news/2021-10-crop-diversity-today-tomorrow-food.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

Adblock test (Why?)



Source link

Continue Reading

Science

Vikings crossed the Atlantic before Columbus, reaching Newfoundland: Scientists – Toronto Sun

Published

 on


Article content

Long before Columbus crossed the Atlantic, eight timber-framed buildings covered in sod stood on a terrace above a peat bog and stream at the northern tip of Newfoundland, evidence that the Vikings had reached the New World first.

Advertisement

Article content

But precisely when the Vikings journeyed to establish the L’Anse aux Meadows settlement had remained unclear – until now.

Scientists on Wednesday said a new type of dating technique using a long-ago solar storm as a reference point revealed that the settlement was occupied in 1021 AD, exactly a millennium ago and 471 years before the first voyage of Columbus. The technique was used on three pieces of wood cut for the settlement, all pointing to the same year.

The Viking voyage represents multiple milestones for humankind. The settlement offers the earliest-known evidence of a transatlantic crossing. It also marks the place where the globe was finally encircled by humans, who thousands of years earlier had trekked into North America over a land bridge that once connected Siberia to Alaska.

Advertisement

Article content

“Much kudos should go to these northern Europeans for being the first human society to traverse the Atlantic,” said geoscientist Michael Dee of the University of Groningen in the Netherlands, who led the study published in the journal Nature.

The Vikings, or Norse people, were seafarers with Scandinavian homelands: Norway, Sweden and Denmark. They ventured through Europe, sometimes colonizing and other times trading or raiding. They possessed extraordinary boat-building and navigation skills and established settlements on Iceland and Greenland.

“I think it is fair to describe the trip as both a voyage of discovery and a search for new sources of raw materials,” Dee said. “Many archaeologists believe the principal motivation for them seeking out these new territories was to uncover new sources of timber, in particular. It is generally believed they left from Greenland, where wood suitable for construction is extremely rare.”

Advertisement

Article content

Their wooden vessels, called longboats, were propelled by sail and oars. One surviving example, called the Oseberg ship, is roughly 70 feet (21.6 metres long).

The Viking Age is traditionally defined as 793-1066 AD, presenting a wide range for the timing of the transatlantic crossing. Ordinary radiocarbon dating – determining the age of organic materials by measuring their content of a particular radioactive isotope of carbon – proved too imprecise to date L’Anse aux Meadows, which was discovered in 1960, although there was a general belief it was the 11th century.

The new dating method relies on the fact that solar storms produce a distinctive radiocarbon signal in a tree’s annual growth rings. It was known there was a significant solar storm – a burst of high-energy cosmic rays from the sun – in 992 AD.

Advertisement

Article content

In all three pieces of wood examined, from three different trees, 29 growth rings were formed after the one that bore evidence of the solar storm, meaning the wood was cut in 1021, said University of Groningen archaeologist Margot Kuitems, the study’s first author.

It was not local indigenous people who cut the wood because there is evidence of metal blades, which they did not possess, Dee said.

The length of the occupation remains unclear, though it may have been a decade or less, and perhaps 100 Norse people were present at any given time, Dee said. Their structures resembled Norse buildings on Greenland and Iceland.

We apologize, but this video has failed to load.

Oral histories called the Icelandic Sagas depict a Viking presence in the Americas. Written down centuries later, they describe a leader named Leif Erikson and a settlement called Vinland, as well as violent and peaceful interactions with the local peoples, including capturing slaves.

The 1021 date roughly corresponds to the saga accounts, Dee said, adding: “Thus it begs the question, how much of the rest of the saga adventures are true?”

Advertisement

Comments

Postmedia is committed to maintaining a lively but civil forum for discussion and encourage all readers to share their views on our articles. Comments may take up to an hour for moderation before appearing on the site. We ask you to keep your comments relevant and respectful. We have enabled email notifications—you will now receive an email if you receive a reply to your comment, there is an update to a comment thread you follow or if a user you follow comments. Visit our Community Guidelines for more information and details on how to adjust your email settings.

Adblock test (Why?)



Source link

Continue Reading

Trending