Month: June 2018

Astronomers Observe The Magnetic Field Of The Remains Of Supernova 1987A

For the first time, astronomers have directly observed the magnetism in one of astronomy’s most studied objects: the remains of Supernova 1987A (SN 1987A), a dying star that appeared in our skies over thirty years ago.

In addition to being an impressive observational achievement, the detection provides insight into the early stages of the evolution of supernova remnants and the cosmic magnetism within them.

“The magnetism we’ve detected is around 50,000 times weaker than a fridge magnet,” says Prof. Bryan Gaensler. “And we’ve been able to measure this from a distance of around 1.6 million trillion kilometres.”

“This is the earliest possible detection of the magnetic field formed after the explosion of a massive star,” says Dr. Giovanna Zanardo.

Gaensler is Director of the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto, and a co-author on the paper announcing the discovery being published in the Astrophysical Journal on June 29th. The lead author, Zanardo, and co-author Prof. Lister Staveley-Smith are both from the University of Western Australia’s node of the International Centre for Radio Astronomy Research.

SN 1987A was co-discovered by University of Toronto astronomer Ian Shelton in February 1987 from the then Southern Observatory of the University of Toronto in northern Chile. It is located in the Large Magellanic Cloud, a dwarf galaxy companion to the Milky Way Galaxy, at a distance of 168,000 light-years from Earth. It was the first naked-eye supernova to be observed since the astronomer Johannes Kepler witnessed a supernova over 400 years ago.

In the thirty years since the supernova occurred, material expelled by the blast, as well as the shockwave from the star’s death throes, have been travelling outward through the gas and dust that surrounded the star before it exploded. Today, when we look at the remnant, we see rings of material set aglow by the supernova’s expanding debris and shockwave.

Using the Australia Telescope Compact Array at the Paul Wild Observatory, Gaensler and his colleagues observed the magnetic field by studying the radiation coming from the object. By analyzing the properties of this radiation, they were able to trace the magnetic field.

“The picture shows what it would look like if you could sprinkle iron filings over the expanding cloud of debris, 170 thousand light years away,” says Gaensler.

What they found was that the remnant’s magnetic field was not chaotic but already showed a degree of order. Astronomers have known that as supernova remnants get older, their magnetic fields are stretched and aligned into ordered patterns. So, the team’s observation showed that a supernova remnant can bring order to a magnetic field in the relatively short period of thirty years.

The magnetic field lines of the Earth run north and south, causing a compass to point to the Earth’s poles. By comparison, the magnetic field lines associated with SN 1987A are like the spokes of a bicycle wheel aligned from the centre out.

“At such a young age,” says Zanardo, “everything in the stellar remnant is moving incredibly fast and changing rapidly, but the magnetic field looks nicely combed out all the way to the edge of the shell.”

Gaensler and his colleagues will continue to observe the constantly evolving remnant. “As it continues to expand and evolve,” says Gaensler, “we will be watching the shape of the magnetic field to see how it changes as the shock wave and debris cloud run into new material.”

Bali Volcano Eruption Halts Some Flights

Several flights were canceled or rescheduled on Thursday when Mount Agung volcano erupted on the Indonesian holiday island of Bali, sending a column of ash and smoke at least 2 km into the air, officials said.

Bali airport was operating normally, but some airlines said they had canceled flights to and from the island known for its beaches and temples.

“The eruption of Mount Agung today has impacted several of our flights to and from Bali,” budget carrier AirAsia said in a statement, adding at least 27 flights had been canceled or rescheduled.

Jetstar and Virgin Australia also canceled flights, according to media. Hundreds of passengers were expected to be affected. Airlines avoid flying through volcanic ash as it can damage aircraft engines, clog fuel and cooling systems and hamper visibility.

Mount Agung Erupts, But Airport Operations On Watch

Ngurah Rai International Airport in Bali is assessing whether to temporarily halt operations following Mount Agung’s latest eruption this week.

Airport authorities have issued a warning to airlines on the possibility of ash disrupting flights to and from the airport following the eruption, urging all airlines to remain cautious although the situation has yet to affect flight routes.

Mt. Agung emitted smoke 1,500 meters above its peak on Thursday, heading west. The increasing volcanic activity came after the highest mountain on the popular resort island erupted on Wednesday night.

“Mount Agung erupted but operations [at the airport] remain normal. We are trying to map all the routes,” Ngurah Rai’s communication and legal section head, Arie Ahsanurrohim, said in its notification to airlines on Thursday.

Japan Space Probe Reaches Asteroid In Search For Origin Of Life

A Japanese probe has reached an asteroid 300 million kilometres away to collect information about the birth of the solar system and the origin of life after a more than three-year voyage through deep space.

The Hayabusa2 probe successfully settled into an observation position 20 kilometres (12 miles) above the Ryugu asteroid, officials from the Japan Aerospace Exploration Agency (JAXA) said Wednesday.

Researchers broke out into cheers when the probe arrived in place, a feat JAXA described as “shooting from Japan at a six centimetre target in Brazil”.

“Today, we are at the beginning of a space science exploration that is unprecedented for humankind,” project manager Yuichi Tsuda told reporters.

The successful mission came just days before the UN’s International Asteroid Day on June 30, a global event to raise awareness about the hazards of an asteroid impact and technological progress to counter such a threat.

Scientists hope to glean clues about what gave rise to life on Earth from samples taken from Ryugu, which is thought to contain relatively large amounts of organic matter and water.

Photos of Ryugu—which means “Dragon Palace” in Japanese, a castle at the bottom of the ocean in an ancient Japanese tale—show an asteroid shaped a bit like a spinning top with a rough surface.

The Hayabusa2 probe was in good shape and now ready to start exploring the asteroid over the coming 18 months, JAXA said.

The next stage is to identify suitable sites to take samples from once the probe touches down on the asteroid, scientist Seiichiro Watanabe said.

‘Impactor’

Hayabusa2, about the size of a large fridge and equipped with solar panels, is the successor to JAXA’s first asteroid explorer, Hayabusa—Japanese for falcon.

That probe returned from a smaller, potato-shaped, asteroid in 2010 with dust samples despite various setbacks during its epic seven-year odyssey and was hailed as a scientific triumph.

The Hayabusa2 mission costs 30 billion yen ($274 million) and the probe was launched in December 2014. It will stay with the asteroid for 18 months before heading back to Earth with its samples.

Its total flight time was 1,302 days and it cruised 3.2 billion kilometres through space on a circuitous route to get to its target, Tsuda told reporters.

To collect its samples, it will release an “impactor” that will explode above the asteroid, shooting a two kilo (four pound) copper object into the surface to excavate a crater a few metres in diameter.

From this crater, the probe will collect “fresh” materials unexposed to millennia of wind and radiation, hoping for answers to some fundamental questions about life and the universe, including whether elements from space helped give rise to life on Earth.

The probe will observe the surface with its camera and sensing equipment but will also drop tiny MINERVA-II rover robots as well as a French-German landing package named Mobile Asteroid Surface Scout (MASCOT) for surface observation.

Seismologists Use Massive Earthquakes To Unlock Secrets Of The Outer Core

By applying new data and Princeton’s supercomputers to the classic question of what lies beneath our feet, Princeton seismologist Jessica Irving and an international team of colleagues have developed a new model for the Earth’s outer core, a liquid iron region deep in the Earth.

The outer core is churning constantly, sustaining the planet’s magnetic field and providing heat to the mantle. “Understanding the outer core is crucial for understanding the history of the magnetic field,” said Irving, an assistant professor of geosciences. Her team’s work appears today in the journal Science Advances.

“The model we have produced, EPOC—Elastic Parameters of the Outer Core—is going to be the background model, the one thing that underlies everything else,” said Irving. The researchers describe EPOC as an outer core update of the existing Preliminary Earth Reference Model (PREM), a model of how fundamental Earth properties vary with depth, which was developed almost 40 years ago.

The key data in the research came from “normal modes,” which are standing waves that can be measured after the very largest earthquakes, typically magnitude 7.5 or higher. Unlike the body waves and surface waves that most seismologists study, normal modes are “the vibration of the whole Earth at once, which is kind of an amazing thing to think about,” Irving said. “We could say that the Earth ‘rings like a bell,’ at characteristic frequencies.”

The new model, EPOC, was first envisioned at a four-week summer science workshop where Irving was housed with fellow seismologists Sanne Cottaar, at the University of Cambridge, and Vedran Leki?, at the University of Maryland-College Park.

“PREM is a venerable, very simple, well-regarded model, but it can’t represent any small-scale structures,” Irving said. “We thought, ‘Can we make a simple model, with even fewer parameters than PREM, that does the job just as well?’ It turned out we could make a model that does the job much better.”

For one, EPOC reduces the need for a “complicated little layer” at the boundary between the core and the mantle, she said. Researchers in recent decades had found discrepancies between the PREM-predicted body wave velocity and the data they were finding, especially at the top of the core, and some had argued that there must be an anomalously slow layer hidden there. They debated how thick it should be—estimates range from 50 to 300 miles—and exactly what it must be composed of.

Her team’s model doesn’t offer any more specifics than PREM, Irving said, “but we suggest that because EPOC fits the data better, maybe you don’t need this little layer.” And additionally, it provides information about the material properties of the outer core.

The outer core is vitally important to the thermal history of the planet and its magnetic field, said Irving, but “it’s not tangible. We can’t show you a rock from the outer core. But at the same time, it is such a huge section of our planet. The core has roughly 30 percent of the mass of the planet in it. The crust is insignificant by comparison. There is so much that we don’t understand about the deep earth—and these aren’t even the complicated properties. We’re just looking for the very slowly varying bulk properties.”

To create their model, Irving and fellow seismologists pooled their skills. Cottaar had experience with equations of state—the physics explaining the connections between temperature, pressure, volume and other fundamental characteristics—and Leki? was fluent in Bayesian techniques, a probabilistic approach that helped the team sift through countless possible models and find the most likely ones. And because of her background with normal mode seismology, Irving knew how to work with the newly updated dataset.

“So all three of us were seismologists with different specialized skill sets, and we liked to have coffee at breakfast together,” Irving said. “It’s so much fun doing science with friends.”

The researchers fed the equations of state into Princeton’s Tiger supercomputer cluster to generate millions of possible models of the outer core. “Every six seconds we created a new model,” Irving said. “Some we rejected because they looked wrong. We have scientific tests for ‘wrong,’ for models that say things like, ‘The mass of the Earth should be twice what we think it is.'”

The team then took the best of the models and used them to predict what frequencies the whole Earth would shake at after a massive earthquake. The researchers compared the measured frequencies of normal modes to the predictions from their models until they found their preferred model.

When teaching about normal modes, Irving uses the metaphor of two bells, one of brass and one of steel, both painted white. “If you hit those bells, you’ll get different notes out of them, and that will tell you that you have different materials in there,” she said. “The exact frequencies—the exact pitch that the Earth at shakes after these very large earthquakes—depends on the material properties of the Earth. Just like we can’t see through the paint on the bells, we can’t see through the planet, but we can listen for the pitch, the frequencies of these whole-Earth observations, and use them to make inferences about what’s going on deep in the Earth.”

Yosemite Granite ‘Tells A Different Story’ About Earth’s Geologic History

A team of scientists including Carnegie’s Michael Ackerson and Bjorn Mysen revealed that granites from Yosemite National Park contain minerals that crystallized at much lower temperatures than previously thought possible. This finding upends scientific understanding of how granites form and what they can teach us about our planet’s geologic history. Their work is published in Nature.

Granites are igneous rocks comprised predominately of the minerals quartz and feldspar. They are the link between igneous processes that occur within the Earth and volcanic rocks that solidified on Earth’s surface.

“Granites are the ultimate product of the processes by which our planet separated into layers and they are key to understanding the formation of the continental crust,” Ackerson said. “Minerals from granites record almost all of our planet’s history — from 4.4 billion years ago to today.”

So, understanding the conditions under which granites form is important to geoscientists trying to unravel the processes that have shaped the Earth.

Until now, the prevailing wisdom on granites was that the minerals that comprise them crystallize as the molten rock cools to temperatures between 650 and 700 degrees Celsius (or between about 1,200 and 1,300 degrees Fahrenheit). Below these temperatures, the granites have been assumed to be completely crystallized.

It was previously known that under certain conditions some of the minerals of which granite is comprised can solidify at lower temperatures. So, the team — which also included Nicholas Tailby of the American Museum of Natural History and Bruce Watson of the Rensselaer Polytechnic Institute — used lab analysis to determine the temperatures of granite crystallization in granites from Yosemite National Park.

The team employed a technique called titanium in quartz thermometry. By measuring the amount of titanium dissolved in the quartz crystals, the team was able to determine the temperatures at which it crystallized deep in the Earth when the granites formed 90 million years ago.

They demonstrated that quartz crystals in samples of a body of granite body called the Tuolumne Intrusive Suite in Yosemite crystallized at temperatures between 474 and 561 Celsius (or 885 and 1,042 degrees Fahrenheit) — up to 200 degrees cooler than previously thought possible for granites.

“These granites tell a different story,” Ackerson added. “And it could rewrite what we think we understand about how Earth’s continents form.”

These findings could influence our understanding of the conditions in which the Earth’s crust first formed during the Hadean and Archean. They could also explain some recent observations about the temperature at which volcanic magmas exist before eruption and the mechanisms through which economically important ore deposits form.

Scientists Find Evidence Of Complex Organic Molecules From Enceladus

Using mass spectrometry data from NASA’s Cassini spacecraft, scientists found that large, carbon-rich organic molecules are ejected from cracks in the icy surface of Saturn’s moon Enceladus. Southwest Research Institute scientists think chemical reactions between the moon’s rocky core and warm water from its subsurface ocean are linked to these complex molecules.

“We are, yet again, blown away by Enceladus. Previously we’d only identified the simplest organic molecules containing a few carbon atoms, but even that was very intriguing,” said SwRI’s Dr. Christopher Glein, a space scientist specializing in extraterrestrial chemical oceanography. He is coauthor of a paper in Nature outlining this discovery. “Now we’ve found organic molecules with masses above 200 atomic mass units. That’s over ten times heavier than methane. With complex organic molecules emanating from its liquid water ocean, this moon is the only body besides Earth known to simultaneously satisfy all of the basic requirements for life as we know it.”

Prior to its deorbit in September of 2017, Cassini sampled the plume of material emerging from the subsurface of Enceladus. The Cosmic Dust Analyzer (CDA) and the SwRI-led Ion and Neutral Mass Spectrometer (INMS) made measurements both within the plume and Saturn’s E-ring, which is formed by plume ice grains escaping Enceladus’ gravity.

“Even after its end, the Cassini spacecraft continues to teach us about the potential of Enceladus to advance the field of astrobiology in an ocean world,” Glein said. “This paper demonstrates the value of teamwork in planetary science. The INMS and CDA teams collaborated to reach a deeper understanding of the organic chemistry of Enceladus’ subsurface ocean than would be possible with only one data set.”

During Cassini’s close flyby of Enceladus on Oct. 28, 2015, INMS detected molecular hydrogen as the spacecraft flew through the plume. Previous flybys provided evidence for a global subsurface ocean residing above a rocky core. Molecular hydrogen in the plume is thought to form by the geochemical interaction between water and rocks in hydrothermal environments.

“Hydrogen provides a source of chemical energy supporting microbes that live in the Earth’s oceans near hydrothermal vents,” said SwRI’s Dr. Hunter Waite, INMS principal investigator who also was a coauthor of the new paper. “Once you have identified a potential food source for microbes, the next question to ask is ‘what is the nature of the complex organics in the ocean?’ This paper represents the first step in that understanding — complexity in the organic chemistry beyond our expectations!”

“The paper’s findings also have great significance for the next generation of exploration,” Glein said. “A future spacecraft could fly through the plume of Enceladus, and analyze those complex organic molecules using a high-resolution mass spectrometer to help us determine how they were made. We must be cautious, but it is exciting to ponder that this finding indicates that the biological synthesis of organic molecules on Enceladus is possible.”