Enduring ‘Radio Rebound’ Powered By Jets From Gamma-Ray Burst

In the blink of an eye, a massive star more than 2 billion light-years away lost a million-year-long fight against gravity and collapsed, triggering a supernova and forming a black hole at its center.

This newborn black hole belched a fleeting yet astonishingly intense flash of gamma rays known as a gamma-ray burst (GRB) toward Earth, where it was detected by NASA’s Neil Gehrels Swift Observatory on 19 December 2016.

While the gamma rays from the burst disappeared from view a scant seven seconds later, longer wavelengths of light from the explosion — including X-ray, visible light, and radio — continued to shine for weeks. This allowed astronomers to study the aftermath of this fantastically energetic event, known as GRB 161219B, with many ground-based observatories, including the National Science Foundation’s Very Large Array.

The unique capabilities of the Atacama Large Millimeter/submillimeter Array (ALMA), however, enabled a team of astronomers to make an extended study of this explosion at millimeter wavelengths, gaining new insights into this particular GRB and the size and composition of its powerful jets.

“Since ALMA sees in millimeter-wavelength light, which carries information on how the jets interact with the surrounding dust and gas, it is a powerful probe of these violent cosmic explosions,” said Tanmoy Laskar, an astronomer at the University of California, Berkeley, and a Jansky Postdoctoral Fellow of the National Radio Astronomy Observatory. Laskar is lead author of the study, which appears in the Astrophysical Journal.

These observations enabled the astronomers to produce ALMA’s first-ever time-lapse movie of a cosmic explosion, which revealed a surprisingly long-lasting reverse shockwave from the explosion echoing back through the jets. “With our current understanding of GRBs, we would normally expect a reverse shock to last only a few seconds. This one lasted a good portion of an entire day,” Laskar said.

A reverse shock occurs when material blasted away from a GRB by its jets runs into the surrounding gas. This encounter slows down the escaping material, sending a shockwave back down the jet.

Since jets are expected to last no more than a few seconds, a reverse shock should be an equally short-lived event. But that now appears not to be the case.

“For decades, astronomers thought this reverse shock would produce a bright flash of visible light, which has so far been really hard to find despite careful searches. Our ALMA observations show that we may have been looking in the wrong place, and that millimeter observations are our best hope of catching these cosmic fireworks,” said Carole Mundell of the University of Bath, and co-author of the study.

Instead, the light from the reverse shock shines most brightly at the millimeter wavelengths on timescales of about a day, which is most likely why it has been so difficult to detect previously. While the early millimeter light was created by the reverse shock, the X-ray and visible light came from the blast-wave shock riding ahead of the jet.

“What was unique about this event,” Laskar adds, “is that as the reverse shock entered the jet, it slowly but continuously transferred the jet’s energy into the forward-moving blast wave, causing the X-ray and visible light to fade much slower than expected. Astronomers have always puzzled where this extra energy in the blast wave comes from. Thanks to ALMA, we know this energy — up to 85 percent of the total in the case of GRB 161219B — is hidden in slow-moving material within the jet itself.”

The bright reverse shock emission faded away within a week. The blast wave then shone through in the millimeter band, giving ALMA a chance to study the geometry of the jet.

The visible light from the blast wave at this critical time, when the outflow has slowed just enough for all of the jet to become visible at Earth, was overshadowed by the emerging supernova from the exploded star. But ALMA’s observations, unencumbered by supernova light, enabled the astronomers to constrain the opening angle of the outflow from the jet to about 13 degrees.

Understanding the shape and duration of the outflow from the star is essential for determining the true energy of the burst. In this case, the astronomers find the jets contained as much energy as our Sun puts out in a billion years.

“This is a fantastical amount of energy, but it is actually one of the least energetic events we have ever seen. Why this is so remains a mystery,” says Kate Alexander, a graduate student at Harvard University who led the VLA observations reported in this study. “Though more than two billion light-years away, this GRB is actually the nearest such event for which we have measured the detailed properties of the outflow, thanks to the combined power of ALMA and the VLA.”

The VLA, which observes at longer wavelengths, continued observing the radio emission from the reverse shock after it faded from ALMA’s view.

This is only the fourth gamma-ray burst with a convincing, multi-frequency detection of a reverse shock, the researchers note. The material around the collapsing star was about 3,000 times less dense than the average density of gas in our galaxy, and these new ALMA observations suggest that such low-density environments are essential for producing reverse shock emission, which may explain why such signatures are so rare.

“Our rapid-response observations highlight the key role ALMA can play in following up transients, revealing the energy source that powers them, and using them to map the physics of the universe to the dawn of the first stars,” concludes Laskar. “In particular, our study demonstrates that ALMA’s superb sensitivity and new rapid-response capabilities makes it the only facility that can routinely detect reverse shocks, allowing us to probe the nature of the relativistic jets in these energetic transients, and the engines that launch and feed them.”

X-Ray Technology Reveals Never-Before-Seen Matter Around Black Hole

In an international collaboration between Japan and Sweden, scientists clarified how gravity affects the shape of matter near the black hole in binary system Cygnus X-1. Their findings, which were published in Nature Astronomy this month, may help scientists further understand the physics of strong gravity and the evolution of black holes and galaxies.

Near the center of the constellation of Cygnus is a star orbiting the first black hole discovered in the universe. Together, they form a binary system known as Cygnus X-1. This black hole is also one of the brightest sources of X-rays in the sky. However, the geometry of matter that gives rise to this light was uncertain. The research team revealed this information from a new technique called X-ray polarimetry.

Taking a picture of a black hole is not easy. For one thing, it is not yet possible to observe a black hole because light cannot escape it. Rather, instead of observing the black hole itself, scientists can observe light coming from matter close to the black hole. In the case of Cygnus X-1, this matter comes from the star that closely orbits the black hole.

Most light that we see, like from the sun, vibrates in many directions. Polarization filters light so that it vibrates in one direction. It is how snow goggles with polarized lenses let skiers see more easily where they are going down the mountain — they work because the filter cuts light reflecting off of the snow.

“It’s the same situation with hard X-rays around a black hole,” Hiroshima University Assistant Professor and study coauthor Hiromitsu Takahashi said. “However, hard X-rays and gamma rays coming from near the black hole penetrate this filter. There are no such ‘goggles’ for these rays, so we need another special kind of treatment to direct and measure this scattering of light.”

The team needed to figure out where the light was coming from and where it scattered. In order to make both of these measurements, they launched an X-ray polarimeter on a balloon called PoGO+. From there, the team could piece together what fraction of hard X-rays reflected off the accretion disk and identify the matter shape.

Two competing models describe how matter near a black hole can look in a binary system such as Cygnus X-1: the lamp-post and extended model. In the lamp-post model, the corona is compact and bound closely to the black hole. Photons bend toward the accretion disk, resulting in more reflected light. In the extended model, the corona is larger and spread around the vicinity of the black hole. In this case, the reflected light by the disk is weaker.

Since light did not bend that much under the strong gravity of the black hole, the team concluded that the black hole fit the extended corona model.

With this information, the researchers can uncover more characteristics about black holes. One example is its spin. The effects of spin can modify the space-time surrounding the black hole. Spin could also provide clues into the evolution of the black hole. It could be slowing down in speed since the beginning of the universe, or it could be accumulating matter and spinning faster.

“The black hole in Cygnus is one of many,” Takahashi said. “We would like to study more black holes using X-ray polarimetry, like those closer to the center of galaxies. Maybe we better understand black hole evolution, as well as galaxy evolution.”

Vanuatu: Ambae Island Evacuated Again Over Volcano Eruption

A Vanuatu island is being fully evacuated for a second time as its volcano erupts again.

The Manaro Voui volcano began spewing ash in recent days, prompting officials to order thousands of residents on tiny Ambae island to leave immediately.

The volcano began rumbling in September last year, which led to the island’s first full evacuation.

Now officials in the South Pacific nation say it once again presents a danger to life.

Foreign Minister Ralph Regenvanu tweeted that Friday’s evacuation was compulsory. Residents are being moved to neighbouring islands.

One Ambae resident told media outlet news.com.au that it had been hard to sleep because of noise from the volcano, adding that the ash was aggravating children’s asthma.

“I want to leave, but I don’t know where I’m going to live,” said Lillian Garae.

Pictures taken from Ambae several days ago showed grey skies with little visibility.

Others showed relief supplies being prepared for residents on the island.

Authorities said last weekend that the volcano was in a “minor eruption” state. Observation flights recorded “explosions and ejection of hot rocks” and ash being emitted.

But the activity intensified over the past week, with heavy ash blanketing many parts of the island.

The US National Oceanic and Atmospheric Administration released satellite footage showing the latest eruption.

In September, the volcano had been seen emitting clouds of smoke, with signs of hot lava emerging to the surface in its crater. More than 11,000 people fled their homes at the time.

Another evacuation was conducted in May, but this was not compulsory and many islanders said they wanted to stay.

In a 2005 eruption, Manaro Voui displaced around 5,000 people.

The volcano sits on the Pacific Ring of Fire, a geologically active area which experiences earthquakes regularly and has hundreds of active volcanoes.

Longest Total Lunar Eclipse Of 21st Century Wows Star-Gazers For Over 100 Minutes

The longest total lunar eclipse of the century transformed the moon into a reddish orange color for more than 100 minutes, according to NASA.

The eclipse was not visible from North America, Noah Petro, a scientist for the NASA Goddard Space Flight Center, told ABC News. Star-gazers in areas near the Middle East, south or eastern Africa, western and southeast Asia and India were be able to catch a glimpse of the celestial event as long as the weather permits, Petro said.

In those areas, the totality of the lunar eclipse — when the moon will retain its red color — lasted for about an hour and 42 minutes. The entire event will last about six hours and 13 minutes, Petro said.

Residents in Australia were able to see the lunar eclipse as the moon sets, while those in eastern Brazil and western Europe could see it as the moon is rising.

Petro suggested either renting a boat and driving it to the middle of the Indian Ocean or visiting relatives in Ethiopia for the “best seat in the house.”

A San Antonio couple named Miguel and Sara who experienced the eclipse from Cairo, Egypt described it as a “beautiful” sight.

“It looks like a giant tangerine,” Miguel told ABC News, adding that Cairo” was “a little bit colder than Texas right now.”

Cloudy weather conditions in cities like London, Moscow and Hong Kong obstructed views of the blood moon in those areas.

ABC News correspondent Matt Gutman described the sight of the lunar eclipse from Hong Kong as “more like a gray smudge,” due to the weather.

However, cities like Rome and Cairo, as well as several areas in Africa, had a clear picture of the moon.

In the U.S., the lunar eclipse began around 1:14 p.m. ET, with the maximum period of totality will starting around 4:21 p.m. ET, making it too light outside for the blood moon to be visible, Petro said.

Although U.S. residents weren’t able to see the eclipse, they should still note that the Lunar Reconnaissance Orbiter — NASA’s robotic spacecraft orbiting the moon — experienced it first-hand, Petro said. The LRO was launched in June 2009 to provide detailed maps to identify “safe and interesting” landing sites on the moon for future human and robotic exploration.

“The moon really holds the secret to understanding how the solar system works,” Petro said.

It’s a good time for Americans to start getting excited about the moon, as NASA will begin celebrating the 50th anniversary of Apollo 11, the spaceflight that made astronauts Neil Armstrong and Buzz Aldrin the first two people on the moon, in October, Petro said. Armstrong and Aldrin landed on the moon on July 20, 1969.

The next total lunar eclipse visible in the U.S. will be on Jan. 21, 2019, according to NASA. It will be a super moon as well, which is a full moon or new moon that coincides with the moon’s position at it’s closest to the Earth.

A partial lunar eclipse — which looks “like someone took a bite out of the moon — will also be visible in the U.S. in July 2019, Petro said. The partial lunar eclipse involves the southern half of the moon passing into the earth’s shadow, he added.

What exactly is a blood moon?

A blood moon is a term used to describe a total lunar eclipse, which is when the moon appears darkened as it passes through the Earth’s shadow.

The total lunar eclipse is given the “blood” nickname because of the “beautiful” red color caused by the projection of all of the Earth’s sunrises and sunsets onto its surface, Petro told ABC News earlier this year, before the super blue blood moon event that took place on Jan. 31.

Yellowstone Super-Volcano Has A Different History Than Previously Thought

The long-dormant Yellowstone super-volcano in the American West has a different history than previously thought, according to a new study by a Virginia Tech geoscientist.

Scientists have long thought that Yellowstone Caldera, part of the Rocky Mountains and located mostly in Wyoming, is powered by heat from the Earth’s core, similar to most volcanoes such as the recently active Kilauea volcano in Hawaii. However, new research published in Nature Geoscience by Ying Zhou, an associate professor with the Virginia Tech College of Science’s Department of Geosciences, shows a different past.

“In this research, there was no evidence of heat coming directly up from the Earth’s core to power the surface volcano at Yellowstone,” Zhou said. “Instead, the underground images we captured suggest that Yellowstone volcanoes were produced by a gigantic ancient oceanic plate that dove under the Western United States about 30 million years ago. This ancient oceanic plate broke into pieces, resulting in perturbations of unusual rocks in the mantle which led to volcanic eruptions in the past 16 million years.”

The eruptions were very explosive, Zhou added. A theoretical seismologist, Zhou created X-ray-like images of the Earth’s deep interior from USArray — part of the Earthscope project funded by the National Science Foundation — and discovered an anomalous underground structure at a depth of about 250 to 400 miles right beneath the line of volcanoes.

“This evidence was in direct contradiction to the plume model,” Zhou said.

In her study, Zhou found the new images of the Earth’s deep interior showed that the oceanic Farallon plate, which used to be where the Pacific Ocean is now, wedged itself beneath the present-day Western United States. The ancient oceanic plate was broken into pieces just like the seafloor in the Pacific today. A section of the subducted oceanic plate started tearing off and sinking down to the deep earth.

The sinking section of oceanic plate slowly pushed hot materials upward to form the volcanoes that now make up Yellowstone. Further, the series of volcanoes that make up Yellowstone have been slowly moving, achingly so, ever since. “The process started at the Oregon-Idaho border about 16 million years ago and propagated northwestward, forming a line of volcanoes that are progressively younger as they stretched northwest to present-day Wyoming,” Zhou added.

The previously-held plume model was used to explain the unique Yellowstone hotspot track — the line of volcanoes in Oregon, Idaho, and Wyoming that dots part of the Midwest. “If the North American plate was moving slowly over a position-fixed plume at Yellowstone, it will displace older volcanoes towards the Oregon-Idaho border and form a line of volcanoes, but such a deep plume has not been found.” Zhou said. So, what caused the track? Zhou intends to find out.

“It has always been a problem there, and scientists have tried to come up with different ways to explain the cause of Yellowstone volcanoes, but it has been unsuccessful,” she said, adding that hotspot tracks are more popular in oceans, such as the Hawaii islands. The frequent Geyser eruptions at Yellowstone are of course not volcanic eruptions with magna, but due to super-heated water. The last Yellowstone super eruption was about 630,000 years ago, according to experts. Zhou has no predictions on when or if Yellowstone could erupt again.

The use of the X-ray-like images for this study is unique in itself. Just as humans can see objects in a room when a light is on, Zhou said seismometers can see structures deep within the earth when an earthquake occurs. The vibrations spread out and create waves when they hit rocks. The waves are detected by seismometers and used in what is known as diffraction tomography.

“This is the first time the new imaging theory has been applied to this type of seismic data, which allowed us to see anomalous structures in the Earth’s mantle that would otherwise not be resolvable using traditional methods,” Zhou said.

Zhou will continue her study of Yellowstone. “The next step will be to increase the resolution of the X-ray-like images of the underground rock,” she added.

“More detailed images of the unusual rocks in the deep earth will allow us to use computer simulation to recreate the fragmentation of the gigantic oceanic plate and test different scenarios of how rock melting and magma feeding system work for the Yellowstone volcanoes.”

Galaxy Outskirts Likely Hunting Grounds For Dying Massive Stars And Black Holes

Findings from a Rochester Institute of Technology study provide further evidence that the outskirts of spiral galaxies host massive black holes. These overlooked regions are new places to observe gravitational waves created when the massive bodies collide, the authors report.

The study winds back time on massive black holes by analyzing their visible precursors — supernovae with collapsing cores. The slow decay of these massive stars creates bright signatures in the electromagnetic spectrum before stellar evolution ends in black holes.

Using data from the Lick Observatory Supernova Search, a survey of nearby galaxies, the team compared the supernovae rate in outer spiral galaxies with that of known hosts — dwarf/satellite galaxies — and found comparable numbers for typical spiral outskirts and typical dwarf galaxies, roughly two core-collapse supernovae per millennium.

The study, “Supernova Rate beyond the Optical Radius,” will appear in an upcoming issue of Astrophysical Journal Letters.

Low levels of elements heavier than hydrogen and helium found in dwarf/satellite galaxies create favorable conditions for massive black holes to form and create binary pairs. A similar galactic environment in the outer disks of spiral galaxies also creates likely hunting grounds for massive black holes, said Sukanya Chakrabarti, lead author and assistant professor in the RIT School of Physics and Astronomy.

“If these core-collapse supernovae are the predecessors to the binary black holes detected by LIGO (Laser Interferometer Gravitational-wave Observatory), then what we’ve found is a reliable method of identifying the host galaxies of LIGO sources,” said Chakrabarti. “Because these black holes have an electromagnetic counterpart at an earlier stage in their life, we can pinpoint their location in the sky and watch for massive black holes.”

The study’s findings complement Chakrabarti’s 2017 study, which showed that the outer parts of spiral galaxies could contribute to LIGO detection rates. The regions form stars at a comparable rate to dwarf galaxies and are low in heavy element content, creating a conducive home for massive black holes. The current study isolates potential candidates within these favorable galactic environments.

“We see now that these are both important contributors,” Chakrabarti said. “The next step is to do deeper surveys to see if we can improve the rate.”

Co-author Brennan Dell, a recent graduate from RIT’s computer science program, analyzed the data with Chakrabarti during his undergraduate co-op.

“This work may help us determine which galaxies to be on the lookout for electromagnetic counterparts of massive black holes,” Dell said.

Total Lunar Eclipse 2018: How To Watch The July ‘Blood Moon’ Live

A total lunar eclipse will turn the moon blood red today, but even if the celestial show isn’t visible from your corner of the world, there are still ways to watch the eclipse live.

The entire event will last 3 hours and 55 minutes. The period when the moon is completely engulfed in Earth’s shadow — a phenomenon known as totality — will last 1 hour and 43 minutes, making it the longest total lunar eclipse of this century.

“This eclipse is special because just by chance it happens that the moon will cross the shadow of the Earth almost along its diameter, which makes the eclipse a few minutes longer than usual,” Francisco Diego, an astronomer at University College London in the U.K., told NBC News MACH in an email.

During totality, which begins at around 3:30 p.m. EDT (19:30 UTC), the moon will be immersed in Earth’s shadow and will be “illuminated by red light filtered by the [Earth’s] atmosphere,” Diego said. For this eclipse, Diego says skywatchers can expect to see a “bright red-orange moon.”

Skywatchers can witness the eclipse in parts of South America, the Middle East, eastern Africa and central Asia. The sky show will not be visible from North America, but there’s still a way to catch all the action surrounding the “blood moon” online. NBC News will be hosting a livestream — part of a digital special hosted by Simone Boyce called “Space Is Awesome” — starting at 4 p.m. EDT (20:00 UTC).

If you happen to be in the Eastern Hemisphere, you’re in luck. According to NASA, the best places to witness the celestial event from start to finish are eastern Africa, the Middle East, India and central Asia. Skywatchers in southern Africa and the Middle East will be able to see totality around midnight local time. Viewers in central Asia will see the moon pass into Earth’s shadow at 10:44 p.m. local time and can expect the eclipse to peak at around midnight.

The sky show will be partially visible as the moon rises just after sunset in parts of Europe, West Africa and South America. In eastern Asia, Australia, and parts of the western Pacific, the eclipse will be visible before sunrise on Saturday (July 28), as the moon sets.

Lunar eclipses occur up to three times a year, so if you miss this week’s sky show, there will be other opportunities in the future. The next total lunar eclipse will happen on Jan. 21, 2019, and will be visible from North America, South America, and parts of Africa, Europe and the central Pacific. The period of totality for this eclipse will last 1 hour and 2 minutes. Skywatchers in South America, Europe, Africa, Asia and Australia will also be able to see a partial lunar eclipse on July 16, 2019.