The National Oceanic and Atmospheric Administration (NOAA) reports:
The average U.S. temperature in 2017 was 54.6 degrees F (2.6 degrees F above average), making 2017 third warmest year in 123 years of record-keeping, according to scientists from NOAA’s National Centers for Environmental Information. In fact, the five warmest years on record for the U.S. all have occurred since 2006.
2017 was also was the 21st consecutive year that the annual average temperature exceeded the average. For the third consecutive year, every state across the contiguous U.S. and Alaska experienced above-average annual temperatures.
Bomb Cyclone Storm on January 4, 2018 off the Northeastern Shore
“‘Bomb cyclone’ blasting East Coast before polar vortex uncorks tremendous cold late this week. The most severe winter weather yet will assault the area late this week.” — washingtonpost.com (January 3, 2018)
The bomb cyclone blizzard was a 1,000 mile wide Nor’easter classified as a “bomb cyclone” because of its sharp drop in atmospheric pressure. “Bombogenesis, a popular term used by meteorologists, occurs when a midlatitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours,” said NOAA.
“We are not saying that the Earth’s temperature is just going to rise. In general, as energy is added to a system, the fluctuations in the system increase. So, we expect more storms, more droughts, more wildfires, more floods, more fluctuations of all kinds. What we are saying is that weather conditions will become more volatile due to the impact of humans,” said Sidd Mukherjee and Daniel Brouse (2004)
“What use to be a once-in-a-hundred year event is now an annual event.” (2017)
“I think the public and many policymakers don’t really take those 100-year forecasts very seriously,” said Myles Allen, an Oxford scientist who is now one of the world’s leading experts in attribution science. “They are much more seriously interested in the question of what is happening now and why—which boils down to attribution.”
It use to be that scientists were reluctant to relate any single weather event to climate change; however, that has changed.
NOAA now issues a report for extreme weather events, “This report provides information on direct economic losses, deaths, and other impacts for numerous weather and climate disasters including tropical cyclones, floods, droughts and heat waves, severe storms (e.g., tornadoes, hail, and straight-line winds), wildfires, crop freeze events, and winter storms.”
The Bulletin of the American Meteorological Society now issues a special report each year assessing the impact of climate change on the previous year’s extreme events.
Scientific American reported, Myles Allen had hinted about “litigation two years before Hurricane Katrina occurred. In his Nature commentary, he mused about the possibility of massive class-action lawsuits—carrying the potential for “up to six billion plaintiffs” around the world—attempting to hold greenhouse gas emitters liable for damages.
Attribution studies could help to apportion the blame, he noted. For instance, he wrote, “If, at a given confidence level, past greenhouse-gas emissions have increased the risk of a flood tenfold, and that flood occurs, then we can attribute, at that confidence level, 90% of any damage to those past emissions.”
About 2017, NPR reported, “This year will go down in history for its extreme weather. Researchers have now definitively attributed three major extreme weather events to climate change.”
LINDA WERTHEIMER, HOST:
If you’re listening to this program from the Midwest or East Coast, well, I hope you’re nice and warm inside your house or car. President Trump took note of the frigid temperatures in the East this holiday season with this tweet – perhaps we could use a little bit of that good, old global warming.
Climate scientists note that while parts of the U.S. are much colder than average now, the world as a whole this week is warmer than the average over recent decades. One thing climate scientists have long been reluctant to say is that specific extreme weather events are the result of climate change. But NPR’s Christopher Joyce says a little-noticed study this past year did prove a link.
CHRISTOPHER JOYCE, BYLINE: This was this – a study that determined that, yes, looking at events in 2016, 27 of them – they found three that were so off the charts that they had to be the result of what we have done to the planet. They’re just beyond what is expected to be a natural event.
WERTHEIMER: What are they? What are the three events?
JOYCE: Well, one was the incredible heat that we experienced – the average temperature around the globe in 2016. It was 1.7 degrees Fahrenheit above the average in the 20th century. And that is just enormous. The second one – extreme heat waves in Asia, especially India and Pakistan. Hundreds of people died. The temperatures were just beyond belief. And the third one – one not noticed that much – but something called the blob, which was a section of water in the Bering Sea off the coast of Alaska that was just unusually warm – again, so warm that it’s just beyond what could be modeled as being – as happening in a natural world.
WERTHEIMER: But still, how do they know that this was not just weird weather – certainly, extreme, unexpected, unusual?
JOYCE: You know, again, I have to use the word model, which people are afraid of. But they’re computer models. And what you basically do is you recreate the world as it was before the Industrial Revolution and certainly before the mid-20th century when we started warming it up. And you put in all of the atmosphere. You put in the oceans, the circulation, the temperature. And you sort of create this world before we changed it. And then you create another model of the world we’re in. And you take these events, and you put them in that model of what the world used to be like. And you can tell that they couldn’t have been created by the forces that were at work before we warmed the planet.
WERTHEIMER: So those three things could not have happened absent global warming.
JOYCE: Yeah. I talked to one of the scientists who did the work – who compiled the work – Stephanie Herring of the National Oceanic and Atmospheric Administration. And this is how she put it.
(SOUNDBITE OF ARCHIVED RECORDING)
STEPHANIE HERRING: Not even one in a million. They cannot replicate them in a world without climate change is what the scientists are saying. It’s a big result, yes. It’s – again, you know, we’ve been doing this for six years, 131 papers. This is our first time seeing this.
“Disaster on the Horizon: The Price Effect of Sea Level Rise”
Asaf Bernstein, Matthew Gustafson, and Ryan Lewis.
Sea level rise coming home, the market is paying attention (Halleluia! who woulda thunk it. The real estate market, especially on the coasts is a wretched hive of villainy))
The first sentence of the abstract is “Homes exposed to sea level rise (SLR) sell at a 7% discount relative to observably equivalent unexposed properties equidistant from the beach.”
More:
“This effect is primarily driven by properties unlikely to be inundated for over half a century, suggesting that it is driven by investors pricing long horizon concerns about SLR costs.”
” … the SLR exposure discount has increased substantially over the past decade, coinciding with both increased awareness and more pessimistic prognoses about the extent and speed of rising oceans. In particular, we document increased transaction volume and lower prices for sophisticated buyers following the significant revisions of the IPCC’s 2013 release, which increased SLR projects and awareness.”
” … properties that will experience ocean encroachment after 1 foot of global average sea level rise trading at a 22%, 2-3 feet at a 17% discount, 4-5 feet at a 9% discount and 6 feet at a 6% discount. [4] Using the long run discount rate provided by Giglio et al. (2014) and assuming complete loss at the onset of inundation, we estimate that markets expect 1 foot of sea level rise within 35 years, 2-3 feet within 45 years, 4-5 feet after 65 years, and 6 feet in 80 years. These results are consistent with the medium to high projections provided in Parris et al. (2012) and utilized by the NOAA in their 2012 report.
” … exposed non-owner occupied properties trade at a 10% to 11% discount, relative to comparable non-exposed properties. ”
” … expectations regarding future SLR have steadily increased over the course of our sample period … At the beginning of our sample in 2007 we find no significant difference between the prices of exposed and unexposed properties. By the end of our sample in 2016, exposed non-owner occupied properties are priced approximately 13.5% below comparable unexposed properties.”
” … we find evidence that the discount applied to non-owner occupied properties increased from 8.1% to 14.0% following the IPCC release.
” … consistent with the idea that as information about SLR risks comes to light, exposed properties should be more likely to transact, we find that the annual probability of turnover is approximately 0.2 percentage points higher for exposed properties between 2011 and 2016 (relative to a base transaction rate of approximately 11% for all properties). This is entirely driven by the period following the IPCC report where we see a 0.8 percentage point increase in the annual probability of an exposed property transacting.”
I see a remake of the “The Big Short” coming up. A good title might be “Underwater.”
Homeowners living in flood plain have learned the hard way that climate change has effected their ability to get a mortgage. As the sea level rises and extreme weather events intensify, homeowners have found their insurance rates increasing or their total inability to obtain insurance coverage. Without insurance it is very, very hard to get a mortgage.
Moody’s credit ratings are now going to have a similar impact on municipalities. “What we want people to realize is: If you’re exposed, we know that. We’re going to ask questions about what you’re doing to mitigate that exposure,” Lenny Jones, a managing director at Moody’s, said in an interview. “That’s taken into your credit ratings.”
Bloomberg news agency reports:
In its report, Moody’s lists six indicators it uses “to assess the exposure and overall susceptibility of U.S. states to the physical effects of climate change.” They include the share of economic activity that comes from coastal areas, hurricane and extreme-weather damage as a share of the economy, and the share of homes in a flood plain.
Based on those overall risks, Texas, Florida, Georgia and Mississippi are among the states most at risk from climate change. Moody’s didn’t identify which cities or municipalities were most exposed.
“If I was a city official, I’d be asking a whole lot of questions about what vulnerabilities their community has, and how each new proposed development adds to that vulnerability,” said Rob Moore, a senior policy analyst at the Natural Resources Defense Council. “Because at some point, your creditors certainly will.”
This is what I call the “Herb Insulation Air Purifier”. It’s very cheap and easy to use. As a matter of fact, it can pay for itself the first day.
On a cold day, it can insulate the window from letting cold air in or warm air out.
On a hot day, it can insulate the window from letting hot air in or cooler air out.
On every day, it can purify the air by adding O2, removing CO2, and emitting beneficial chemicals into the air for health and wellness.
On any day that you touch it, you will help prevent your own ills, as well as, the spreading of disease to others.
On the days you add them to your cooking, a metamorphosis and chemical reaction will occur that results in great things for your habitat and your diet.
Pictured in this Herb Insulation Air Purifier Mosaic (Healthy Snack) are parsley, rosemary, basil, onion greens, and oregano. Depending on the conditions and/or your appetite, any number of a herbs will do. The basil can’t stand frigid temperatures, so it is best left on the inner side for the winter. Here the oregano has two generations yielding both dried herbs and added insulation. Some of the parsley is in the second year of its bi-annual life. The first-year undergrowth adds a nice low buffer of insulation. Soil that is exposed during the cold months is a great insulator, absorbs the heat from sunlight during the day and stores it into the night. (Foraging for Food in the Winter offers additional advice on cold weather herbs.)
Also recommend are a wide variety of lettuce, aloe, scallions, thyme, sage, spinach, and whatever you like to eat. During hot months, aloe and cacti do well. The cacti can also be used to help keep cats out of the planters throughout the year.
Concentrations of carbon dioxide in the atmosphere surged at a record-breaking speed in 2016 to the highest level in 800,000 years, according to the World Meteorological Organization’s Greenhouse Gas Bulletin. The abrupt changes in the atmosphere witnessed in the past 70 years are without precedent.
Globally averaged concentrations of CO2 reached 403.3 parts per million in 2016, up from 400.00 ppm in 2015 because of a combination of human activities and a strong El Niño event. Concentrations of CO2 are now 145% of pre-industrial (before 1750) levels, according to the Greenhouse Gas Bulletin.
Rapidly increasing atmospheric levels of CO2 and other greenhouse gases have the potential to initiate unprecedented changes in climate systems, leading to “severe ecological and economic disruptions,” said the report.
The annual bulletin is based on observations from the WMO Global Atmosphere Watch Programme. These observations help to track the changing levels of greenhouse gases and serve as an early warning system for changes in these key atmospheric drivers of climate change.
Population growth, intensified agricultural practices, increases in land use and deforestation, industrialization and associated energy use from fossil fuel sources have all contributed to increases in concentrations of greenhouse gases in the atmosphere since the industrial era, beginning in 1750.
Since 1990, there has been a 40% increase in total radiative forcing – the warming effect on our climate – by all long-lived greenhouse gases, and a 2.5% increase from 2015 to 2016 alone, according to figures from the US National Oceanic and Atmospheric Administration quoted in the bulletin.
“Without rapid cuts in CO2 and other greenhouse gas emissions, we will be heading for dangerous temperature increases by the end of this century, well above the target set by the Paris climate change agreement,” said WMO Secretary-General Petteri Taalas. “Future generations will inherit a much more inhospitable planet, “ he said.
“CO2 remains in the atmosphere for hundreds of years and in the oceans for even longer. The laws of physics mean that we face a much hotter, more extreme climate in the future. There is currently no magic wand to remove this CO2 from the atmosphere,”said Mr Taalas.
The last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago, the temperature was 2-3°C warmer and sea level was 10-20 meters higher than now.
In a separate report, the United Nations (UN) released the Emissions Gap Report for 2017. The report concludes that world treaties are only slowing emissions by 1/3 of what is needed to meet the maximum 2 degree rise in temperature. A 2 degree Celsius rise in temperature would likely cause a 20-40 foot rise in sea levels.
“Living near the water is incredibly appealing for people around the country, but it also comes with additional considerations for buyers and homeowners,” Zillow chief economist Svenja Gudell wrote in a new report. “Homes in low-lying areas are also more susceptible to storm flooding and these risks could be realized on a much shorter timeline as we have seen time and time again.”
Climate change is causing the sea level to rise. The effects are already being felt in places like the Jersey Shore. Atlantic City, N.J. ranked third in the top ten U.S. areas that experience nuisance flooding with a 682% surge since 1957.
“As relative sea level increases, it no longer takes a strong storm or a hurricane to cause flooding”said William Sweet, Ph.D., oceanographer at NOAA’s Center for Operational Oceanographic Products and Services (CO-OPS) and the report’s lead author. “Flooding now occurs with high tides in many locations due to climate-related sea level rise, land subsidence and the loss of natural barriers. The effects of rising sea levels along most of the continental U.S. coastline are only going to become more noticeable and much more severe in the coming decades, probably more so than any other climate-change related factor.”
“We’ve seen the enormous impact flooding can have on a city and its residents,” said Gudell. “It’s harder for us to think about it on a long-term timeline, but the real risks that come with rising sea levels should not be ignored until it’s too late to address them.”
The Zillow report found:
Coastal homes are threatened by the prospect of rising sea levels
More than $900 billion worth of U.S. residential real estate could be lost by a 6-foot rise in sea levels
The rise in water levels projected by 2100 could destroy 2 million homes
A CNBC analysis of the report said, “Of the nation’s largest cities, Miami, New York, Boston, Tampa and Fort Myers, Florida, have the highest volume of homes at risk of flooding. Los Angeles, Charleston, South Carolina, Houston and New Orleans are also in the top 20 markets at risk.”
Flood insurance is usually needed to obtain a mortgage for a property located in a flood zone. Flood insurance is the only insurance offered by the federal government that can be obtained by anybody. The National Flood Insurance Program (NFIP) is made available by the Federal Emergency Management Agency (FEMA).
The NFIP offers coverage for: 1) Building Property, up to $250,000, and 2) Personal Property (Contents), up to $100,000. The coverage is cumulative which means NFIP will pay out a maximum of $250,000 for the structure. If you make a claim for $100,000 and then sell the property, the next owner can only get insurance for up to $150,000.
The Zillow study found:
One-third (32 percent) of underwater homes would be valued in the bottom third nationally, meaning $123 billion in losses.
Two in five (39 percent) underwater homes would be valued in the top third nationally, translating to $597 billion in lost high-end real estate.
In rural and suburban areas, homes in the top value tier may face particular risk, while in urban areas homes in the bottom value tier are more likely to be affected.
The Lancet Commission published a report on October 19, 2017 that outlined the results of pollution and health. The report concluded that 9 million people suffered premature deaths due to pollution in 2015.
“Pollution is the largest environmental cause of disease and premature death in the world today. Diseases caused by pollution were responsible for an estimated 9 million premature deaths in 2015—16% of all deaths worldwide—three times more deaths than from AIDS, tuberculosis, and malaria combined and 15 times more than from all wars and other forms of violence. In the most severely affected countries, pollution-related disease is responsible for more than one death in four,” the report states.
Air pollution is the leading cause of death followed by water pollution. The financial cost from pollution-related death, sickness and welfare costs about $4.6 trillion in annual losses.
The report highlights:
Air pollution was linked to 6.5 million premature deaths;
Water pollution was linked to 1.8 million premature deaths;
Workplace pollution was linked to 1 million premature deaths;
Premature deaths resulting from pollution-related diseases like heart disease and cancer outnumbered AIDS, tuberculosis, and malaria combined 3 to 1;
About 92% of all premature deaths linked to pollution occur in low and middle-income countries.
Up to one in four deaths can be attributed to pollution in countries like China, India, Pakistan, or Bangladesh.
In absolute numbers, China (1.8 million) and India (2.5 million) had the most pollution-related deaths for the year 2015.
The United States, home to the world’s biggest economy, saw 155,000 premature deaths linked to pollution in 2015.
Senegal is an African country on the west coast of the continent. The country is on the forefront of global warming’s impacts.
“Climate change makes life harder for Senegalese farmers in many different ways: shorter rainy seasons, more frequent and longer dry spells and droughts, a lower water table, floods, coastal erosion, destruction of mangroves, and disruption of fish stocks. But most pernicious of all is the salinization of soil across large tracts of coastal and riverine farmland,” reports the IRIN news agency.
Salinization is an example of a problem that is likely to effect many areas in the United States.
“For decades in Sine-Saloum, the soil, which used to be known for its quality and productivity, has been badly damaged by climate change, which has led to the salinization of the waterways of the delta,” explained Seydou Cissé, who works at Senegal’s National Institute of Pedology (the study of soils).
In an attempt to abate the problem, anti-salt dykes were built. They did help for a while; however, man’s plans do not compare to the force of nature. Already several islands along the Saint-Louis river have been washed away. “Three or four days after the rain, everything goes white. There are piles of salt. All the crops we sow die. All this is due to the salinity caused by the rising waters of the sea. And when we store valuables in our rooms, rust eats away little-by-little and eventually destroys them,” said Fatou Faye, a resident of Diamniadio island said in 2015. Since that time, the island has been washed away.
“When the sea enters in the river, because you have increasing of salt, it has killed many mangroves. And you know the mangroves are the nurseries of all the seafood,” said Aissata Dia of Actionaid Senegal.
“When the tide is high, the water goes into the kitchen and then gradually the water enters the rooms. My kitchen was rebuilt last year, but even today it is threatened by the rising waters. The high salinity of the seawater eventually breaks down even the cement. After three years, the building collapses,” said islander Faye.
In 2017, a sea wall built to help protect Senegal failed. The miles long breach is not repairable.
Reuters reported in May of 2017: “As Senegal’s coast crumbles, residents ponder move to safer ground”
“A French man told us once that there will be a time when this land won’t exist,” said Badiane, who lives in the working-class district of Guet Ndar. “Maybe in 30 years, maybe in 50. I don’t know.”
“(The people) are trying to fight, but in reality the phenomenon has become very serious,” said Abdou Sane, a former parliamentarian based in Dakar who has spearheaded efforts to reduce the threat of disasters. “It exceeds the means of the government, the means of communities,” he added.
Experts have urged the government to relocate other communities before they face a similar fate.
A UN-Habitat program in 2011 helped move about 60 families out of Guet Ndar to a settlement a short distance inland.
“That’s a way of being resilient,” said Mateugue Diack, a professor of agronomy and disaster risk reduction at the nearby Gaston Berger University.
But communication was lacking and people were reluctant to move, he said. The relocation effort fizzled out before it was completed.
Guet Ndar is populated primarily by fishermen whose families have lived there for generations. Most of those who have lost their homes have remained in the overcrowded area, squeezing in with relatives and neighbors.
“Unfortunately my country is one of those that has this huge problem. We always record that something may happen, that something has happened… but still do nothing,” said Diack.
Q: How do you make gold and platinum?
A: Collide two neutron stars
“It’s so beautiful. It’s so beautiful it makes me want to cry. It’s the fulfillment of dozens, hundreds, thousands of people’s efforts, but it’s also the fulfillment of an idea suddenly becoming real,” said Peter Saulson of Syracuse University.
Not only does a collision of neutron stars create heavy metals, it also causes a wrinkle in space-time. Gravitational waves had been an Albert Einstein theory until 2015. Since then, there have been three recordings of gravitational waves; however, they were all colliding black holes. This was the first recording of gravitational waves in light.
The observation was made by LIGO:
Laser Interferometer Gravitational-Wave Observatory
Supported by the National Science Foundation
Operated by Caltech and MIT
Gravitational waves are ripples in the curvature of spacetime that are generated in certain gravitational interactions and propagate as waves outward from their source at the speed of light. The possibility of gravitational waves was discussed in 1893 by Oliver Heaviside using the analogy between the inverse-square law in gravitation and electricity. In 1905 Henri Poincaré first proposed gravitational waves (ondes gravifiques) emanating from a body and propagating at the speed of light as being required by the Lorentz transformations. Predicted in 1916 by Albert Einstein on the basis of his theory of general relativity, gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation. Newton’s law of universal gravitation, part of classical mechanics, does not provide for the existence of gravitational waves, since that law is predicated on the assumption that physical interactions propagate at infinite speed—showing one of the ways that the methods of classical physics is unable to explain phenomena associated with relativity.
GW170817 Press Release
LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars
Discovery marks first cosmic event observed in both gravitational waves and light.
Watch the recording of a press conference announcing the discovery, at the National Press Club in Washington, DC:
Watch the recording of a seminar at Caltech titled “Seeing and Hearing the Cataclysmic Universe” following the announcement:
For the first time, scientists have directly detected gravitational waves — ripples in space-time — in addition to light from the spectacular collision of two neutron stars. This marks the first time that a cosmic event has been viewed in both gravitational waves and light.
The discovery was made using the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO); the Europe-based Virgo detector; and some 70 ground- and space-based observatories.
Neutron stars are the smallest, densest stars known to exist and are formed when massive stars explode in supernovas. As these neutron stars spiraled together, they emitted gravitational waves that were detectable for about 100 seconds; when they collided, a flash of light in the form of gamma rays was emitted and seen on Earth about two seconds after the gravitational waves. In the days and weeks following the smashup, other forms of light, or electromagnetic radiation — including X-ray, ultraviolet, optical, infrared, and radio waves — were detected.
GW170817: A Global Astronomy Event
The observations have given astronomers an unprecedented opportunity to probe a collision of two neutron stars. For example, observations made by the U.S. Gemini Observatory, the European Very Large Telescope, and the Hubble Space Telescope reveal signatures of recently synthesized material, including gold and platinum, solving a decades-long mystery of where about half of all elements heavier than iron are produced.
The LIGO-Virgo results are published today in the journal Physical Review Letters; additional papers from the LIGO and Virgo collaborations and the astronomical community have been either submitted or accepted for publication in various journals.
“It is tremendously exciting to experience a rare event that transforms our understanding of the workings of the universe,” says France A. Córdova, director of the National Science Foundation (NSF), which funds LIGO. “This discovery realizes a long-standing goal many of us have had, that is, to simultaneously observe rare cosmic events using both traditional as well as gravitational-wave observatories. Only through NSF’s four-decade investment in gravitational-wave observatories, coupled with telescopes that observe from radio to gamma-ray wavelengths, are we able to expand our opportunities to detect new cosmic phenomena and piece together a fresh narrative of the physics of stars in their death throes.”
A stellar sign
The gravitational signal, named GW170817, was first detected on Aug. 17 at 8:41 a.m. Eastern Daylight Time; the detection was made by the two identical LIGO detectors, located in Hanford, Washington, and Livingston, Louisiana. The information provided by the third detector, Virgo, situated near Pisa, Italy, enabled an improvement in localizing the cosmic event. At the time, LIGO was nearing the end of its second observing run since being upgraded in a program called Advanced LIGO, while Virgo had begun its first run after recently completing an upgrade known as Advanced Virgo.
Current operating facilities in the global network include the twin LIGO detectors—in Hanford, Washington, and Livingston, Louisiana— Virgo in Italy and GEO600 in Germany.
The NSF-funded LIGO observatories were conceived, constructed, and operated by Caltech and MIT. Virgo is funded by the Istituto Nazionale di Fisica Nucleare (INFN) in Italy and the Centre National de la Recherche Scientifique (CNRS) in France, and operated by the European Gravitational Observatory. Some 1,500 scientists in the LIGO Scientific Collaboration and the Virgo Collaboration work together to operate the detectors and to process and understand the gravitational-wave data they capture.
Each observatory consists of two long tunnels arranged in an L shape, at the joint of which a laser beam is split in two. Light is sent down the length of each tunnel, then reflected back in the direction it came from by a suspended mirror. In the absence of gravitational waves, the laser light in each tunnel should return to the location where the beams were split at precisely the same time. If a gravitational wave passes through the observatory, it will alter each laser beam’s arrival time, creating an almost imperceptible change in the observatory’s output signal.
On Aug. 17, LIGO’s real-time data analysis software caught a strong signal of gravitational waves from space in one of the two LIGO detectors. At nearly the same time, the Gamma-ray Burst Monitor on NASA’s Fermi space telescope had detected a burst of gamma rays. LIGO-Virgo analysis software put the two signals together and saw it was highly unlikely to be a chance coincidence, and another automated LIGO analysis indicated that there was a coincident gravitational wave signal in the other LIGO detector. Rapid gravitational-wave detection by the LIGO-Virgo team, coupled with Fermi’s gamma-ray detection, enabled the launch of follow-up by telescopes around the world.
The LIGO data indicated that two astrophysical objects located at the relatively close distance of about 130 million light-years from Earth had been spiraling in toward each other. It appeared that the objects were not as massive as binary black holes — objects that LIGO and Virgo have previously detected. Instead, the inspiraling objects were estimated to be in a range from around 1.1 to 1.6 times the mass of the sun, in the mass range of neutron stars. A neutron star is about 20 kilometers, or 12 miles, in diameter and is so dense that a teaspoon of neutron star material has a mass of about a billion tons.
While binary black holes produce “chirps” lasting a fraction of a second in the LIGO detector’s sensitive band, the Aug. 17 chirp lasted approximately 100 seconds and was seen through the entire frequency range of LIGO — about the same range as common musical instruments. Scientists could identify the chirp source as objects that were much less massive than the black holes seen to date.
LIGO’s data shows the “chirp” sound produced as the two neutron stars inspiral.
“It immediately appeared to us the source was likely to be neutron stars, the other coveted source we were hoping to see — and promising the world we would see,” says David Shoemaker, spokesperson for the LIGO Scientific Collaboration and senior research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “From informing detailed models of the inner workings of neutron stars and the emissions they produce, to more fundamental physics such as general relativity, this event is just so rich. It is a gift that will keep on giving.”
“Our background analysis showed an event of this strength happens less than once in 80,000 years by random coincidence, so we recognized this right away as a very confident detection and a remarkably nearby source,” adds Laura Cadonati, professor of physics at Georgia Tech and deputy spokesperson for the LIGO Scientific Collaboration. “This detection has genuinely opened the doors to a new way of doing astrophysics. I expect it will be remembered as one of the most studied astrophysical events in history.”
Theorists have predicted that when neutron stars collide, they should give off gravitational waves and gamma rays, along with powerful jets that emit light across the electromagnetic spectrum. The gamma-ray burst detected by Fermi, and soon thereafter confirmed by the European Space Agency’s gamma-ray observatory INTEGRAL, is what’s called a short gamma-ray burst; the new observations confirm that at least some short gamma-ray bursts are generated by the merging of neutron stars — something that was only theorized before.
“For decades we’ve suspected short gamma-ray bursts were powered by neutron star mergers,” says Fermi Project Scientist Julie McEnery of NASA’s Goddard Space Flight Center. “Now, with the incredible data from LIGO and Virgo for this event, we have the answer. The gravitational waves tell us that the merging objects had masses consistent with neutron stars, and the flash of gamma rays tells us that the objects are unlikely to be black holes, since a collision of black holes is not expected to give off light.”
But while one mystery appears to be solved, new mysteries have emerged. The observed short gamma-ray burst was one of the closest to Earth seen so far, yet it was surprisingly weak for its distance. Scientists are beginning to propose models for why this might be, McEnery says, adding that new insights are likely to arise for years to come.
A patch in the sky
Though the LIGO detectors first picked up the gravitational wave in the United States, Virgo, in Italy, played a key role in the story. Due to its orientation with respect to the source at the time of detection, Virgo recovered a small signal; combined with the signal sizes and timing in the LIGO detectors, this allowed scientists to precisely triangulate the position in the sky. After performing a thorough vetting to make sure the signals were not an artifact of instrumentation, scientists concluded that a gravitational wave came from a relatively small patch in the southern sky.
Virgo Helps Localize Gravitational-Wave Signals
“This event has the most precise sky localization of all detected gravitational waves so far,” says Jo van den Brand of Nikhef (the Dutch National Institute for Subatomic Physics) and VU University Amsterdam, who is the spokesperson for the Virgo collaboration. “This record precision enabled astronomers to perform follow-up observations that led to a plethora of breathtaking results.”
“This result is a great example of the effectiveness of teamwork, of the importance of coordinating, and of the value of scientific collaboration,” adds EGO Director Federico Ferrini. “We are delighted to have played our relevant part in this extraordinary scientific challenge: Without Virgo, it would have been very difficult to locate the source of the gravitational wave.
Fermi was able to provide a localization that was later confirmed and greatly refined with the coordinates provided by the combined LIGO-Virgo detection. With these coordinates, a handful of observatories around the world were able, hours later, to start searching the region of the sky where the signal was thought to originate. A new point of light, resembling a new star, was first found by optical telescopes. Ultimately, about 70 observatories on the ground and in space observed the event at their representative wavelengths.
“This detection opens the window of a long-awaited ‘multi-messenger’ astronomy,” says Caltech’s David H. Reitze, executive director of the LIGO Laboratory. “It’s the first time that we’ve observed a cataclysmic astrophysical event in both gravitational waves and electromagnetic waves — our cosmic messengers. Gravitational-wave astronomy offers new opportunities to understand the properties of neutron stars in ways that just can’t be achieved with electromagnetic astronomy alone.”
A fireball and an afterglow
Each electromagnetic observatory will be releasing its own detailed observations of the astrophysical event. In the meantime, a general picture is emerging among all observatories involved that further confirms that the initial gravitational-wave signal indeed came from a pair of inspiraling neutron stars.
Approximately 130 million years ago, the two neutron stars were in their final moments of orbiting each other, separated only by about 300 kilometers, or 200 miles, and gathering speed while closing the distance between them. As the stars spiraled faster and closer together, they stretched and distorted the surrounding space-time, giving off energy in the form of powerful gravitational waves, before smashing into each other.
Neutron Star Merger Seen in Gravity and Matter
At the moment of collision, the bulk of the two neutron stars merged into one ultradense object, emitting a “fireball” of gamma rays. The initial gamma-ray measurements, combined with the gravitational-wave detection, also provide confirmation for Einstein’s general theory of relativity, which predicts that gravitational waves should travel at the speed of light.
Theorists have predicted that what follows the initial fireball is a “kilonova” — a phenomenon by which the material that is left over from the neutron star collision, which glows with light, is blown out of the immediate region and far out into space. The new light-based observations show that heavy elements, such as lead and gold, are created in these collisions and subsequently distributed throughout the universe.
In the weeks and months ahead, telescopes around the world will continue to observe the afterglow of the neutron star merger and gather further evidence about various stages of the merger, its interaction with its surroundings, and the processes that produce the heaviest elements in the universe.
“When we were first planning LIGO back in the late 1980s, we knew that we would ultimately need an international network of gravitational-wave observatories, including Europe, to help localize the gravitational-wave sources so that light-based telescopes can follow up and study the glow of events like this neutron star merger,” says Caltech’s Fred Raab, LIGO associate director for observatory operations. “Today we can say that our gravitational-wave network is working together brilliantly with the light-based observatories to usher in a new era in astronomy, and will improve with the planned addition of observatories in Japan and India.”
More than 1,200 scientists and some 100 institutions from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration and the Australian collaboration OzGrav. Additional partners are listed at http://ligo.org/partners.php
The Virgo collaboration consists of more than 280 physicists and engineers belonging to 20 different European research groups: six from Centre National de la Recherche Scientifique (CNRS) in France; eight from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two in the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with the University of Valencia; and the European Gravitational Observatory, EGO, the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef.
High Res. versions of these graphics can be found in our gallery.
GW170817’s numbers
Masses of Neutron Stars and Black Holes
Current operating facilities in the global network include the twin LIGO detectors—in Hanford, Washington, and Livingston, Louisiana – Virgo in Italy, and GEO600 in Germany.
Neutron Star Merger Seen in Gravity and Matter
Virgo Helps Localize Gravitational-Wave Signals
GW170817: A Global Astronomy Event
Artist’s illustration of two merging neutron stars.
LIGO’s data shows the “chirp” sound produced as the two neutron stars inspiral.
Videos
Neutron star merger (Credit: Christopher W. Evans/Georgia Tech)
Jets and Debris from Neutron Star Collision (Credit: NASA/Goddard Space Flight Center/CI Lab)
Last Dance of Neutron Star Pair (Credit: W. Kastaun/T. Kawamura/B. Giacomazzo/R. Ciolfi/A. Endrizzi)
Ripples of Gravity, Flashes of Light (Credit: LIGO/Virgo)
Zooming in on the Source of Gravitational Waves (Credit: LIGO-Virgo)
Final Flight of Neutron Star Pair (Credit: LIGO-Virgo/Aaron Geller/Northwestern University)
Hearing the Wave (Credit: Alex Nitz/Max Planck Institute for Gravitational Physics/LIGO)
