Echoes Of Black Holes Eating Stars Discovered

Supermassive black holes, with their immense gravitational pull, are notoriously good at clearing out their immediate surroundings by eating nearby objects. When a star passes within a certain distance of a black hole, the stellar material gets stretched and compressed — or “spaghettified” — as the black hole swallows it.

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A black hole destroying a star, an event astronomers call “stellar tidal disruption,” releases an enormous amount of energy, brightening the surroundings in an event called a flare. In recent years, a few dozen such flares have been discovered, but they are not well understood.

Astronomers now have new insights into tidal disruption flares, thanks to data from NASA’s Wide-field Infrared Survey Explorer (WISE). Two new studies characterize tidal disruption flares by studying how surrounding dust absorbs and re-emits their light, like echoes. This approach allowed scientists to measure the energy of flares from stellar tidal disruption events more precisely than ever before.

“This is the first time we have clearly seen the infrared light echoes from multiple tidal disruption events,” said Sjoert van Velzen, postdoctoral fellow at Johns Hopkins University, Baltimore, and lead author of a study finding three such events, to be published in the Astrophysical Journal. A fourth potential light echo based on WISE data has been reported by an independent study led by Ning Jiang, a postdoctoral researcher at the University of Science and Technology of China.

Flares from black holes eating stars contain high-energy radiation, including ultraviolet and X-ray light. Such flares destroy any dust that hangs out around a black hole. But at a certain distance from a black hole, dust can survive because the flare’s radiation that reaches it is not as intense.

After the surviving dust is heated by a flare, it gives off infrared radiation. WISE measures this infrared emission from the dust near a black hole, which gives clues about tidal disruption flares and the nature of the dust itself. Infrared wavelengths of light are longer than visible light and cannot be seen with the naked eye. The WISE spacecraft, which maps the entire sky every six months, allowed the variation in infrared emission from the dust to be measured.

Astronomers used a technique called “photo-reverberation” or “light echoes” to characterize the dust. This method relies on measuring the delay between the original optical light flare and the subsequent infrared light variation, when the flare reaches the dust surrounding the black hole. This time delay is then used to determine the distance between the black hole and the dust.

Van Velzen’s study looked at five possible tidal disruption events, and saw the light echo effect in three of them. Jiang’s group saw it in an additional event called ASASSN-14li.

Measuring the infrared glow of dust heated by these flares allows astronomers to make estimates of the location of dust that encircles the black hole at the center of a galaxy.

“Our study confirms that the dust is there, and that we can use it to determine how much energy was generated in the destruction of the star,” said Varoujan Gorjian, an astronomer at NASA’s Jet Propulsion Laboratory, Pasadena, California, and co-author of the paper led by van Valzen.

Researchers found that the infrared emission from dust heated by a flare causes an infrared signal that can be detected for up to a year after the flare is at its most luminous. The results are consistent with the black hole having a patchy, spherical web of dust located a few trillion miles (half a light-year) from the black hole itself.

“The black hole has destroyed everything between itself and this dust shell,” van Velzen said. “It’s as though the black hole has cleaned its room by throwing flames.”

JPL manages and operates WISE for NASA’s Science Mission Directorate in Washington. The spacecraft was put into hibernation mode in 2011, after it scanned the entire sky twice, thereby completing its main objectives. In September 2013, WISE was reactivated, renamed NEOWISE and assigned a new mission to assist NASA’s efforts to identify potentially hazardous near-Earth objects.

Astronomers Capture Best View Ever Of Disintegrating Comet

Astronomers have captured the sharpest, most detailed observations of a comet breaking apart 67 million miles from Earth, using NASA’s Hubble Space Telescope. The discovery is published online in Astrophysical Journal Letters.

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In a series of images taken over three days in January 2016, Hubble showed 25 fragments consisting of a mixture of ice and dust that are drifting away from the comet at a pace equivalent to the walking speed of an adult, said UCLA astrophysicist David Jewitt, who led the research team.

The images suggest that the roughly 4.5-billion-year-old comet, named 332P/Ikeya-Murakami, or comet 332P, may be spinning so fast that material is ejected from its surface. The resulting debris is now scattered along a 3,000-mile-long trail, larger than the width of the continental United States.

These observations provide insight into the volatile behavior of comets as they approach the sun and begin to vaporize, unleashing powerful forces.

“We know that comets sometimes disintegrate, but we don’t know much about why or how,” Jewitt said. “The trouble is that it happens quickly and without warning, so we don’t have much chance to get useful data. With Hubble’s fantastic resolution, not only do we see really tiny, faint bits of the comet, but we can watch them change from day to day. That has allowed us to make the best measurements ever obtained on such an object.”

The three-day observations show that the comet shards brighten and dim as icy patches on their surfaces rotate into and out of sunlight. Their shapes change, too, as they break apart. The icy relics comprise about four percent of the parent comet and range in size from roughly 65 feet wide to 200 feet wide. They are separating at only a few miles per hour as they orbit the sun at more than 50,000 miles per hour.

The Hubble images show that the parent comet changes brightness frequently, completing a rotation every two to four hours. A visitor to the comet would see the sun rise and set in as little as an hour, Jewitt said.

The comet is much smaller than astronomers thought, measuring only 1,600 feet across, about the length of five football fields.

Comet 332P was discovered in November 2010, after it surged in brightness and was spotted by two Japanese amateur astronomers.

Based on the Hubble data, the research team suggests that sunlight heated the surface of the comet, causing it to expel jets of dust and gas. Because the nucleus is so small, these jets act like rocket engines, spinning up the comet’s rotation, Jewitt said. The faster spin rate loosened chunks of material, which are drifting off into space. The research team calculated that the comet probably shed material over a period of months, between October and December 2015.

Jewitt suggested that some of the ejected pieces have themselves fallen to bits in a kind of cascading fragmentation. “We think these little guys have a short lifetime,” he said.

Hubble’s sharp vision also spied a chunk of material close to the comet, which may be the first salvo of another outburst. The remnant from still another flare-up, which may have occurred in 2012, is also visible. The fragment may be as large as comet 332P, suggesting the comet split in two. But the remnant wasn’t spotted until Dec. 31, 2015, by a telescope in Hawaii.

That discovery prompted Jewitt and colleagues to request Hubble Space Telescope time to study the comet in detail.

“In the past, astronomers thought that comets die when they are warmed by sunlight, causing their ices to simply vaporize away,” Jewitt said. “But it’s starting to look like fragmentation may be more important. In comet 332P we may be seeing a comet fragmenting itself into oblivion.”

The researchers estimate that comet 332P contains enough mass for 25 more outbursts. “If the comet has an episode every six years, the equivalent of one orbit around the sun, then it will be gone in 150 years,” Jewitt said. “It’s just the blink of an eye, astronomically speaking. The trip to the inner solar system has doomed it.”

The icy visitor hails from the Kuiper belt, a vast swarm of objects at the outskirts of our solar system. As the comet traveled across the system, it was deflected by the planets, like a ball bouncing around in a pinball machine, until Jupiter’s gravity set its current orbit, Jewitt said.

Co-authors include Harold Weaver Jr., research professor at the Johns Hopkins University Applied Physics Laboratory.

Explaining Why The Universe Can Be ‘Transparent’: Universe’s Reionization Is Based On A Galaxy’s Dust Content

Two papers published by an assistant professor at the University of California, Riverside and several collaborators explain why the universe has enough energy to become transparent.

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The study led by Naveen Reddy, an assistant professor in the Department of Physics and Astronomy at UC Riverside, marks the first quantitative study of how the gas content within galaxies scales with the amount of interstellar dust.

This analysis shows that the gas in galaxies is like a “picket fence,” where some parts of the galaxy have little gas and are directly visible, whereas other parts have lots of gas and are effectively opaque to ionizing radiation. The findings were just published in The Astrophysical Journal.

The ionization of hydrogen is important because of its effects on how galaxies grow and evolve. A particular area of interest is assessing the contribution of different astrophysical sources, such as stars or black holes, to the budget of ionizing radiation.

Most studies suggest that faint galaxies are responsible for providing enough radiation to ionize the gas in the early history of the universe. Moreover, there is anecdotal evidence that the amount of ionizing radiation that is able to escape from galaxies depends on the amount of hydrogen within the galaxies themselves.

The research team led by Reddy developed a model that can be used to predict the amount of escaping ionizing radiation from galaxies based on straightforward measurements on how “red,” or dusty, their spectra appear to be.

Alternatively, with direct measurements of the ionizing escape fraction, their model may be used to constrain the intrinsic production rate of ionizing photons at around two billion years after the Big Bang.

These practical applications of the model will be central to the interpretation of escaping radiation during the cosmic “dark ages,” a topic that is bound to flourish with the coming of 30-meter telescopes, which will allow for research unfeasible today, and the James Webb Space Telescope, NASA’s next orbiting observatory and the successor to the Hubble Space Telescope.

The research ties back to some 400,000 years after the Big Bang, when the universe entered the cosmic “dark ages,” where galaxies and stars had yet to form amongst the dark matter, hydrogen and helium.

A few hundred million years later, the universe entered the “Epoch of Reionization,” where the gravitational effects of dark matter helped hydrogen and helium coalesce into stars and galaxies. A great amount of ultraviolet radiation (photons) was released, stripping electrons from surrounding neutral environments, a process known as “cosmic reionization.”

Reionization, which marks the point at which the hydrogen in the Universe became ionized, has become a major area of current research in astrophysics. Ionization made the Universe transparent to these photons, allowing the release of light from sources to travel mostly freely through the cosmos.

The data for this research was acquired through the low resolution imaging spectrograph on the W.M. Keck Observatory.

The collaborators of this research are Charles Steidel (Caltech), Max Pettini (University of Cambridge), Milan Bogosavljevic (Astronomical Observatory, Belgrade) and Alice Shapley (UCLA).

Icy Giant Planet Growing Around A Nearby Star

Astronomers found signs of a growing planet around TW Hydra, a nearby young star, using the Atacama Large Millimeter/submillimeter Array (ALMA). Based on the distance from the central star and the distribution of tiny dust grains, the baby planet is thought to be an icy giant, similar to Uranus and Neptune in our Solar System. This result is another step towards understanding the origins of various types of planets.

icy-planet

A number of extrasolar planets have been found in the past two decades and now researchers agree that planets can have a wide variety of characteristics. However, it is still unclear how this diversity emerges. Especially, there is still debate about how the icy giant planets, such as Uranus and Neptune, form.

To take a close look at the planet formation site, a research team led by Takashi Tsukagoshi at Ibaraki University, Japan, observed the young star TW Hydrae. This star, estimated to be 10 million years old, is one of the closest young stars to Earth. Thanks to the proximity and the fact that its axis of rotation points roughly in Earth’s direction, giving us a face-on-view of the developing planetary system, TW Hydrae is one of the most favorable targets for investigating planet formation.

Past observations have shown that TW Hydrae is surrounded by a disk made of tiny dust particles. This disk is the site of planet formation. Recent ALMA observations revealed multiple gaps in the disk. Some theoretical studies suggest that the gaps are evidence of planet formation.

The team observed the disk around TW Hydrae with ALMA in two radio frequencies. Since the ratio of the radio intensities in different frequencies depends on the size of the dust grains, researchers can estimate the size of dust grains. The ratio indicates that smaller, micrometer-sized, dust particles dominate and larger dust particles are absent in the most prominent gap with a radius of 22 astronomical units.

Why are smaller dust particles selectively located in the gap in the disk? Theoretical studies have predicted that a gap in the disk is created by a massive planet, and that gravitational interaction and friction between gas and dust particles push the larger dust out from the gap, while the smaller particles remain in the gap. The current observation results match these theoretical predictions.

Researchers calculated the mass of the unseen planet based on the width and depth of the 22 au gap and found that the planet is probably a little more massive than the Neptune. “Combined with the orbit size and the brightness of TW Hydrae, the planet would be an icy giant planet like Neptune,” said Tsukagoshi.

Following this result, the team is planning further observations to better understand planet formation. One of their plans is to observe the polarization of the radio waves. Recent theoretical studies have shown that the size of dust grains can be estimated more precisely with polarization observations. The other plan is to measure the amount of gas in the disk. Since gas is the major component of the disk, the researchers hope to attain a better estimation of the mass of the forming planet.

Study: Full Moon Can Trigger Big Earthquakes

Could California’s long-dreaded “Big One” be triggered by a full moon?

Perhaps, says a new study out Monday that claims large earthquakes are more likely during unusually high tides, which occur during full and new moons.

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Stepper-temp

High tides, which typically occur twice a day, are caused when ocean water is moved by the gravitational pull of the moon. But twice a month, during a full or new moon, tides are especially high because the moon, earth and sun all line up together. (These twice-monthly tides are known as “spring” tides.)

Big quakes can occur when this additional weight of tidal water strains geological faults, according to the study. Though this theory is not new, this is the first study to display a firm, statistical link.

“The probability of a tiny rock failure expanding to a gigantic rupture increases with increasing tidal stress levels,” the study said.

Precisely how large earthquakes occur is not fully understood, but scientists say they may grow via a cascading process where a tiny fracture builds up into a large-scale rupture. If so, the authors’ results imply that the likelihood of a small fracture cascading into a large earthquake are greater during high tides.

The study was led by Satoshi Ide, a seismologist at the University of Tokyo and appeared in the peer-reviewed British journal Nature Geoscience.

Ide found that some of the most devastating recent earthquakes, such as the 2004 Sumatra quake that killed 230,000 people and the 2011 quake in Japan that killed 15,000, both hit during periods of high tide. In fact, his research team determined that nine of the 12 biggest quakes on record happened near or on days with full or new moons.

The scientists found no clear correlation between high tides and small earthquakes.

The study could help improve earthquake forecasting, the authors say, in places that are especially vulnerable to high seismic activity

“Scientists will find this result, if confirmed, quite interesting,” said University of Washington seismologist John Vidale, who was not part of the study. He cautions that “even if there is a strong correlation of big earthquakes with full or new moons, the chance any given week of a deadly earthquake remains miniscule,” making predictions rather unhelpful.

The study’s other authors are Suguru Yabe and Yoshiyuki Tanaka, also of the University of Tokyo.

Strong 6.0 Magnitude Earthquake Rocks Colombia

A strong earthquake has rocked Colombia, striking close to one of the country’s largest cities and forcing people to run for their lives during a mass evacuation of the surrounding area.

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More than 400 people had to flee their homes in Citadel Sevilla, Medellin – the home city of infamous cocaine drud lord Pablo Escobar.

People at the scene were “terrified” by the sizeable 6.0 magnitude quake, which is believed to have lasted around 30 seconds and was followed by an intense aftershock.

The local authority has initiated its Disaster Risk Management plan amid fears of landslides taking place in the rural region, which has been battered by heavy rains in recent days.

The quake, which took place aroun 8pm local time, was also felt in Bogota – 400km away.

Mayler Parra, who was near the epicentre in Mutatá, said: “The trucks on the roads were shaking, alarms of cars rang out, all the people in hotels took to the streets.”

Express.co.uk spoke to two tourists currently staying in nearby Sabaneta.

Tegan and Daniel, from New Zealand, said: “It was pretty scary! We are staying on the sixth floor in an apartment block and we shook for about a minute. It was a bit daunting not knowing what was going to happen. I guess a lot of people would have felt the same, the city is full of apartments!”

Other locals reported a 13 storey hotel building shaking ominously during the tremor.

Fears are growing for the surrounding population, especially considering a weaker 5.6 magnitude earthquake in 2008 killed 11 people in El Calvario.

The tremor originated 45 miles below the surface, according to geologists, and the region is located in a subduction zone, meaning earthquakes occur inland.

George Donnelly tweeted from Colombia to say he felt the earthquake and he claimed it went on for a long time.

There are no reports of fatalities as yet.

At the time of the earthquake a football match was taking place in the Atanasio Girardot in Medellin between Nacional de Medellín and Bolivar in the South American Cup – Medellin won 1-0.

New Discovery Shatters Previous Beliefs About Earth’s Origin

A new study led by Western University’s all-star cosmochemist Audrey Bouvier proves that the Earth and other planetary objects formed in the early years of the Solar System share similar chemical origins — a finding at odds with accepted wisdom held by scientists for decades.

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The findings were published today by the journal Nature.

Bouvier, the Canada Research Chair (CRC) in Planetary Materials and an Isotope Cosmochemistry professor in Western’s Department of Earth Sciences, made the game-changing discovery in collaboration with Maud Boyet from the Magmas and Volcanoes Laboratory at Blaise Pascal University in Clermont-Ferrand, France.

With data uncovered through thermal ionization mass spectrometry, Bouvier and Boyet demonstrated that the Earth and other extraterrestrial objects share the same initial levels of Neodymium-142 (142Nd) — one of seven isotopes found in the chemical element neodymium — which is widely distributed in the Earth’s crust and most commonly used for magnets in commercial products like microphones and in-ear headphones.

In 2005, a small variation in 142Nd was detected between chondrites, which are stony meteorites considered essential building blocks of the Earth, and terrestrial rocks. These results were widely interpreted as an early differentiation of the interior of the Earth (including the crust and mantle) and these chondrites within the first 30 million years of its history.

These new results from Bouvier and Boyet show that these differences in 142Nd were in fact already present during the growth of Earth and not introduced later, as was previously believed.

“How the Earth was formed and what type of planetary materials were part of that formation are issues that have puzzled generations of scientists,” says Bouvier, Curator of the Western Meteorite Collection and also a principal investigator at Western’s Centre for Planetary Science and Exploration (CPSX). “And these new isotopic measurements of meteorites provide exciting answers to these questions about our origins and what made the Earth so special.”

By using vastly improved measurement techniques, Bouvier and Boyet deduced that different meteoritical objects found in the Solar System incorporated the elements neodymium (Nd) and samarium (Sm) but with slightly different isotopic compositions. These variations in stable isotopes also show that the Solar System was not uniform during its earliest times and that materials formed from previous generations of stars were incorporated in various proportions into the building blocks of planets.

This study was supported by the National Science Foundation, France-Canada Research Fund, the Natural Sciences and Engineering Research Council of Canada (NSERC) CRC and Discovery Grant programs, the Institute of Earth Sciences of the French National Center for Scientific Research (CNRS) and ClerVolc, the Clermont-Ferrand Centre for Volcano Research.