Month: September 2016

Black Hole Hidden Within Its Own Exhaust

Supermassive black holes, millions to billions of times the mass of our Sun, are found at the centers of galaxies. Many of these galactic behemoths are hidden within a thick doughnut-shape ring of dust and gas known as a torus. Previous observations suggest these cloaking, tire-like structures are formed from the native material found near the center of a galaxy.

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New data from the Atacama Large Millimeter/submillimeter Array (ALMA), however, reveal that the black hole at the center of a galaxy named NGC 1068 is actually the source of its own dusty torus of dust and gas, forged from material flung out of the black hole’s accretion disk.

This newly discovered cosmic fountain of cold gas and dust could reshape our understanding of how black holes impact their host galaxy and potentially the intergalactic medium.

“Think of a black hole as an engine. It’s fueled by material falling in on it from a flattened disk of dust and gas,” said Jack Gallimore, an astronomer at Bucknell University in Lewisburg, Pennsylvania, and lead author on a paper published in Astrophysical Journal Letters. “But like any engine, a black hole can also emit exhaust.” That exhaust, astronomers discovered, is the likely source of the torus of material that effectively obscures the region around the galaxy’s supermassive black hole from optical telescopes.

NGC 1068 (also known as Messier 77) is a barred spiral galaxy approximately 47 million light-years from Earth in the direction of the constellation Cetus. At its center is an active galactic nucleus, a supermassive black hole that is being fed by a thin, rotating disk of gas and dust known as an accretion disk. As material in the disk spirals toward the central black hole, it becomes superheated and blazes bright with ultraviolet radiation. The outer reaches of the disk, however, are considerably cooler and glow more appreciably in infrared light and the millimeter-wavelength light that ALMA can detect.

Using ALMA, an international team of astronomers peered deep into this region and discovered a sprinkling of cool clouds of carbon monoxide lifting off the outer portion of the accretion disk. The energy from the hot inner disk partially ionizes these clouds, enabling them to adhere to powerful magnetic field lines that wrap around the disk.

Like water being flung out of a rapidly rotating garden sprinkler, the clouds rising above the accretion disk get accelerated centrifugally along the magnetic field lines to very high speeds — approximately 400 to 800 kilometers per second (nearly 2 million miles per hour). This is up to nearly three times faster than the rotational speed of the outer accretion disk, fast enough to send the clouds hurtling further out into the galaxy.

“These clouds are traveling so fast that they reach ‘escape velocity’ and are jettisoned in a cone-like spray from both sides of the disk,” said Gallimore. “With ALMA, we can for the first time see that it is the gas that is thrown out that hides the black hole, not the gas falling in.” This suggests that the general theory of an active black hole is oversimplified, he concludes.

With future ALMA observations, the astronomers hope to work out a fuel budget for this black hole engine: how much mass per year goes into the black hole and how much is ejected as exhaust.

“These are fundamental quantities for understanding black holes that we really don’t have a good handle on at this time,” concludes Gallimore.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Gaia’s Billion Star Maps Hints At Treasures To Come

The first catalogue of more than a billion stars from ESA’s Gaia satellite was published today — the largest all-sky survey of celestial objects to date.

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On its way to assembling the most detailed 3D map ever made of our Milky Way galaxy, Gaia has pinned down the precise position on the sky and the brightness of 1142 million stars.

As a taster of the richer catalogue to come in the near future, today’s release also features the distances and the motions across the sky for more than two million stars.

“Gaia is at the forefront of astrometry, charting the sky at precisions that have never been achieved before,” says Alvaro Giménez, ESA’s Director of Science.

“Today’s release gives us a first impression of the extraordinary data that await us and that will revolutionise our understanding of how stars are distributed and move across our Galaxy.”

Launched 1000 days ago, Gaia started its scientific work in July 2014. This first release is based on data collected during its first 14 months of scanning the sky, up to September 2015.

“The beautiful map we are publishing today shows the density of stars measured by Gaia across the entire sky, and confirms that it collected superb data during its first year of operations,” says Timo Prusti, Gaia project scientist at ESA.

The stripes and other artefacts in the image reflect how Gaia scans the sky, and will gradually fade as more scans are made during the five-year mission.

“The satellite is working well and we have demonstrated that it is possible to handle the analysis of a billion stars. Although the current data are preliminary, we wanted to make them available for the astronomical community to use as soon as possible,” adds Dr Prusti.

Transforming the raw information into useful and reliable stellar positions to a level of accuracy never possible before is an extremely complex procedure, entrusted to a pan-European collaboration of about 450 scientists and software engineers: the Gaia Data Processing and Analysis Consortium, or DPAC.

In addition to processing the full billion-star catalogue, the scientists looked in detail at the roughly two million stars in common between Gaia’s first year and the earlier Hipparcos and Tycho-2 Catalogues, both derived from ESA’s Hipparcos mission, which charted the sky more than two decades ago.

By combining Gaia data with information from these less precise catalogues, it was possible to start disentangling the effects of ‘parallax’ and ‘proper motion’ even from the first year of observations only. Parallax is a small motion in the apparent position of a star caused by Earth’s yearly revolution around the Sun and depends on a star’s distance from us, while proper motion is due to the physical movement of stars through the Galaxy.

In this way, the scientists were able to estimate distances and motions for the two million stars spread across the sky in the combined Tycho-Gaia Astrometric Solution, or TGAS.

This new catalogue is twice as precise and contains almost 20 times as many stars as the previous definitive reference for astrometry, the Hipparcos Catalogue.

As part of their work in validating the catalogue, DPAC scientists have conducted a study of open stellar clusters — groups of relatively young stars that were born together — that clearly demonstrates the improvement enabled by the new data.

“With Hipparcos, we could only analyse the 3D structure and dynamics of stars in the Hyades, the nearest open cluster to the Sun, and measure distances for about 80 clusters up to 1600 light-years from us,” says Antonella Vallenari from the Istituto Nazionale di Astrofisica (INAF) and the Astronomical Observatory of Padua, Italy.

“But with Gaia’s first data, it is now possible to measure the distances and motions of stars in about 400 clusters up to 4800 light-years away.

For the closest 14 open clusters, the new data reveal many stars surprisingly far from the centre of the parent cluster, likely escaping to populate other regions of the Galaxy.”

Many more stellar clusters will be discovered and analysed in even greater detail with the extraordinary data that Gaia continues to collect and that will be released in the coming years.

The new stellar census also contains 3194 variable stars, stars that rhythmically swell and shrink in size, leading to periodic brightness changes.

Many of the variables seen by Gaia are in the Large Magellanic Cloud, one of our galactic neighbours, a region that was scanned repeatedly during the first month of observations, allowing accurate measurement of their changing brightness.

Details about the brightness variations of these stars, 386 of which are new discoveries, are published as part of today’s release, along with a first study to test the potential of the data.

“Variable stars like Cepheids and RR Lyraes are valuable indicators of cosmic distances,” explains Gisella Clementini from INAF and the Astronomical Observatory of Bologna, Italy.

“While parallax is used to measure distances to large samples of stars in the Milky Way directly, variable stars provide an indirect, but crucial step on our ‘cosmic distance ladder’, allowing us to extend it to faraway galaxies.”

This is possible because some kinds of variable stars are special. For example, in the case of Cepheid stars, the brighter they are intrinsically, the slower their brightness variations. The same is true for RR Lyraes when observed in infrared light. The variability pattern is easy to measure and can be combined with the apparent brightness of a star to infer its true brightness.

This is where Gaia steps in: in the future, scientists will be able to determine very accurate distances to a large sample of variable stars via Gaia’s measurements of parallaxes. With those, they will calibrate and improve the relation between the period and brightness of these stars, and apply it to measure distances beyond our Galaxy. A preliminary application of data from the TGAS looks very promising.

“This is only the beginning: we measured the distance to the Large Magellanic Cloud to test the quality of the data, and we got a sneak preview of the dramatic improvements that Gaia will soon bring to our understanding of cosmic distances,” adds Dr Clementini.

Knowing the positions and motions of stars in the sky to astonishing precision is a fundamental part of studying the properties and past history of the Milky Way and to measure distances to stars and galaxies, but also has a variety of applications closer to home — for example, in the Solar System.

In July, Pluto passed in front of a distant, faint star, offering a rare chance to study the atmosphere of the dwarf planet as the star gradually disappeared and then reappeared behind Pluto.

This stellar occultation was visible only from a narrow strip stretching across Europe, similar to the totality path that a solar eclipse lays down on our planet’s surface. Precise knowledge of the star’s position was crucial to point telescopes on Earth, so the exceptional early release of the Gaia position for this star, which was 10 times more precise than previously available, was instrumental to the successful monitoring of this rare event.

Early results hint at a pause in the puzzling pressure rise of Pluto’s tenuous atmosphere, something that has been recorded since 1988 in spite of the dwarf planet moving away from the Sun, which would suggest a drop in pressure due to cooling of the atmosphere.

“These three examples demonstrate how Gaia’s present and future data will revolutionise all areas of astronomy, allowing us to investigate our place in the Universe, from our local neighbourhood, the Solar System, to Galactic and even grander, cosmological scales,” explains Dr Brown.

This first data release shows that the mission is on track to achieve its ultimate goal: charting the positions, distances, and motions of one billion stars — about 1% of the Milky Way’s stellar content — in three dimensions to unprecedented accuracy.

“The road to today has not been without obstacles: Gaia encountered a number of technical challenges and it has taken an extensive collaborative effort to learn how to deal with them,” says Fred Jansen, Gaia mission manager at ESA.

“But now, 1000 days after launch and thanks to the great work of everyone involved, we are thrilled to present this first dataset and are looking forward to the next release, which will unleash Gaia’s potential to explore our Galaxy as we’ve never seen it before.”

Volcano Is Heating Up Again

Given its previous eruptions, Mount Ruapehu is one of the most closely watched volcanoes in New Zealand.

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Those monitoring the active volcano say there have been sharp increases in the temperature of a crater lake and a rise in volcanic tremors.

The crater lake reached its lowest recorded temperature of 12ºC in August but has since heated up to 17.6 ºC.

The volcano, part of the backdrop for Mordor in the Peter Jackson-directed trilogy, last erupted in September 2007.

“It’s certainly not a regular cycle but we typically see temperatures getting up to 40 degrees. The tremor has started again, and again we often see that at the same sort of time … the processes are all linked together,” duty volcanologist Michael Rosenberg told Stuff NZ.

“Obviously it is an active volcano and it has the potential to erupt at very short notice.”

In May this year, the alert level for Mount Ruapehu was raised after the mountain’s crater lake temperature almost doubled in just a few weeks.

At the time, earthquake and monitoring service GNS Science said recent visits to the volcano had shown an increase in the output of volcanic gas, sparking concerns that an eruption is imminent.

Contained deep within the Earth, volcanos are vents where molten rock, debris, and gases from the planet’s interior are emitted.

When thick magma and gas build up under the surface, volcanoes expel lava, rocks and ash into the air. The mountain-like mounds that we associate with volcanoes are what remains after material spewed during eruptions has hardened around the vent.

A large eruption can be extremely dangerous for people living near a volcano. Flows of searing lava can reach 1,250 degrees or more, burning everything in its path, including humans and entire towns. Ash and toxic gases can cause lung damage and other problems.
It’s estimated that more than 260,000 people have died in the past 300 years from volcanic eruptions and their aftermath.

About 1,900 volcanoes on Earth are considered active, meaning they show some level of activity and are likely to explode again.

Many other volcanoes are dormant, showing no current signs of exploding but likely to become active at some point in the future. Others are considered extinct.

Deep Sea Volcano Hot Spot For Mysterious Ocean Life

GEOLOGIST SEAMOUNTS, Hawaii – The turquoise waters became darker and darker, and squiggly glow-in-dark marine creatures began to glide past in the inky depths like ghosts.

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The three-man submarine went down, down, down into the abyss and drew within sight of something no human had ever laid eyes on: Cook seamount, a 13,000-foot extinct volcano at the bottom of the sea.

Scientists aboard the vessel Pisces V visited the volcano earlier this month to examine its geological features and its rich variety of marine life, and an Associated Press reporter was given exclusive access to the dive. It was the first-ever expedition to the Cook seamount by a manned submersible.

Among other things, the researchers from the University of Hawaii and the nonprofit group Conservation International spotted such wonders as a rare type of octopus with big fins that look like Dumbo’s ears, and a potentially new species of violet-hued coral they dubbed Purple Haze.

Conservation International hopes to study 50 seamounts, or undersea volcanoes, over the next five years.

“We don’t know anything about the ocean floor,” said Peter Seligmann, chairman, CEO and co-founder of Conservation International. “What we know is that each one of those seamounts is a refuge for new species, but we don’t know what they are. We don’t know how they’ve evolved. We don’t know what lessons they have for us.”

During the Sept. 6 dive, the submarine splashed into the water, and as it dove, the only sounds were radio communications from the surface, the hum of an air scrubber that removes carbon monoxide from the passenger chamber, and the voices of the crew. The thick, hot tropical air inside the steel sphere became cooler and drier as the submarine descended.

“We don’t know what we’re going to find,” said Conservation International’s Greg Stone, a marine biologist on board. “There will always be the unexpected when you go into the deep ocean.”

Halfway to the volcano’s summit, which is 3,000 feet below the surface of the Pacific, no sunlight penetrated. The only light that could be seen from the submarine’s face-sized windows was the bluish glow of the vessel’s own bright lights. Occasionally, bioluminescent creatures drifted past in the darkness.

Stone and subpilot Terry Kerby, who helps run the Hawaii Undersea Research Laboratory at the University of Hawaii, watched as the volcano and its rugged basalt walls hundreds of yards high came into view.

Seamounts are either active or dormant volcanoes that rise dramatically from the bottom of the ocean and never reach the surface. They are hotspots for marine life because they carry nutrient-rich water upward from the sea floor. Seamounts are believed to cover about 18 million square miles of the planet.

Cook, situated over 100 miles southwest of Hawaii’s Big Island, is part of a group of undersea volcanoes known as the Geologist Seamounts that are about 80 million years old and could hold many new animal species, as well as elements such as nickel and cobalt that mining companies could extract.

“My goal today is to … find out what’s living on them, find out how they support ocean life, what their effect is from ocean currents and essentially what drives the ocean, what makes the ocean what it is,” Stone said. “Seamounts are a key part of that, and something which humanity knows very little about.”

Within minutes of the vessel’s arrival at the summit, life began to appear — a starfish clinging to a rock, joined shortly after by eels, sharks, chimaera (also known as “ghost sharks”), shrimp, crabs and two rare Dumbo octopuses. One of the octopuses changed color from white to pink to reddish brown as it swam by.

Several types of deep-sea corals were found along the seamount’s cliffs, including a vibrant purple one.

“I need to go home, look through the literature … and also go and run some genetic analyses,” said Sonia Rowley, a postdoctoral researcher at the University of Hawaii who is taking part in the project. “But as this is a new seamount … that no one had dived on before, it won’t be any surprise to me whether this is going to be a new species.”

Two other seamounts were studied over three days of expeditions: McCall, home to a large number of small deep-sea sharks, and Lo’ihi, an active volcano.

Lo’Ihi has been extensively surveyed by manned submersibles over the past 30 years. The past few times Kerby was there, he saw a large Pacific sleeper shark lurking about the volcano’s crater.

As hot vents shot out volcanic gases around them, the team released bait in the water and the 7-foot shark appeared in front of the submarine. Kerby was delighted to see his “old friend.”

The team also saw 6-foot eels and a number of new geological formations around the crater. Scientists say Lo’ihi is likely to someday become the newest island in the Hawaii chain as volcanic activity pushes the summit upward.

Second Typhoon In Three Days Expected To Smash Taiwan

Taiwan is about to be soaked by its second severe storm in just three days, with typhoon Malakas forecast to pass by the northern end of the island early on Saturday.

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The tropical storm will tear past Taiwanese capital Taipei at around midday and is forecast to reach as high as a category four hurricane, with wind speeds exceeding 125 miles per hour (200 kilometers per hour).

It comes just two days after typhoon Meranti made landfall on the southern coast, leaving hundreds of thousands of homes without power.

On Friday afternoon, typhoon Malakas was hovering off the eastern coast of Taiwan and is forecast to curve up the country’s coastline, growing stronger and passing Taipei, before heading towards Japan.

“Even though the storm is not forecast to make a direct landfall on Taiwan at the moment, areas towards the north of Taitung county are forecast to receive tropical storm force winds beginning Saturday afternoon and lasting into Sunday morning,” CNN meteorologist Michael Guy said.

“Once the storm begins its track towards the northeast it will impact the Ryuku Islands with high surf, winds and rain.”

Taiwan’s Central Weather Bureau issued a typhoon warning for parts of the country on Friday, ahead of the storm’s arrival.

Tropical Storm Karl Forms in Eastern Atlantic

Tropical Storm Karl has formed in the far eastern Atlantic but currently poses no threat to land.

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Late Thursday night, Karl was located about 575 miles (930 km) west-northwest of the Cabo Verde Islands and about 1,930 miles (3,105 km) east of the Leeward Islands.

The National Hurricane Center in Miami says Karl is moving west at 14 mph (kph) with maximum sustained winds of 45 mph (75 kph). It was expected to continue toward the west or west-southwest for the next couple of days.

No coastal watches or warnings are in effect related to the storm.

Storm Julia Weakens Into A Depression, Meandering Off Of U.S. Coast

Tropical Storm Julia weakened into a depression and is expected to meander off the coast of Georgia and South Carolina for the next few days, the U.S. National Hurricane Center said on Thursday.

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Julia is located about 60 miles (95 km) south-southeast of Charleston, South Carolina with maximum sustained winds of 35 mph (55 kph), the Miami-based weather forecaster said.

“A slow and erratic motion is expected over the next couple of days, and the track forecast keeps Julia meandering offshore of the Georgia and southern South Carolina coastlines into Saturday,” the NHC said.

Julia, the 10th named storm of the 2016 Atlantic hurricane season, was moving northeast at 2 mph just off the U.S. coast, as little change TO its strength was expected during next two days, it said.

Heavy rain combined with high tides raised concerns of flooding in downtown Charleston, South Carolina, and other coastal parts of the state into Thursday morning, forecasters said.

Some residents in coastal communities were offered sandbags to prepare for flooding in low-lying areas.

Since late Tuesday, Julia has dumped heavy rains and toppled trees in the region, but has not caused significant damage, the National Weather Service said.

On Thursday morning, the hurricane center also was tracking a tropical depression that was expected to bring heavy rains to the Cape Verde islands off West Africa. On its forecasted track, the system would remain far away from the coastal United States through early next week.