Astrophysicists Detect Gravitational Waves Once Again

The hat-shaped Sombrero galaxy was not involved in the gravitational wave research, but it is lovely. Seen edge-on, it features an unusually large and extended central bulge composed of billions of old stars, while its dust rings harbor many younger and brighter stars. Its center is thought to house a large black hole. Image credit: NASA/Hubble Heritage Team

Just four months after the announcement of the first detection of gravitational waves, physicists say they’ve recorded another burst of these elusive ripples in space-time, again coming from a merging pair of black holes, far beyond our galaxy.

The first gravitation wave detection, announced with great fanfare in February, was sparked by a signal recorded at the twin LIGO detectors on September 14 of last year; this latest signal tripped the detectors on December 26. (The acronym stands for Laser Interferometer Gravitational-wave Observatory.)

“We now know that the first detection wasn’t just luck,” LIGO team member Duncan Brown, of Syracuse University, tells mental_floss. The odds of the earlier signal being a false alarm were on the order of a million to one—but, notes Brown, “people do win the lottery sometimes.” This second detection clinches it, he says. “This tells us that we will be making regular detections of binary black holes” in the coming years.

The LIGO team announced the discovery today at a meeting of the American Astronomical Society in San Diego. Their paper will be published in the journal Physical Review Letters

The paper, which examines data collected by LIGO from September 2015 to January 2016, also hints at a third gravitational wave event, recorded last October, although that event is less certain (and is being described only as a “candidate signal,” and not necessarily a “detection”).

Black holes form when massive stars collapse in the final stage of their evolution. Occasionally black holes end up orbiting other black holes, their orbits gradually shrinking as the system loses energy. Eventually they accelerate and merge, sending a blast of gravitational waves out across the universe.

Until this year, gravitational waves were purely theoretical, a prediction of Einstein’s general theory of relativity, published 100 years ago.

NASA created this visualization of two black holes merging when the discovery of gravitational waves was announced earlier this year.

The black holes that caused the December signal are smaller than those responsible for the earlier event; in this case their masses are believed to have been about 14 and about 17.5 times the mass of the Sun (in the earlier case, they were 29 and 36 times as massive as the Sun). Because of their smaller size, they took longer to execute their final orbits, Brown says. As a result, while the earlier signal was a mere blip, lasting about one-tenth of a second, this event lasted for a relatively leisurely 1.5 seconds. During that time, the two ultra-dense stars, having orbited each other for perhaps 100,000,000 years, performed their final loops. “This time we saw about 30 orbits, before they finally crashed into each other and merged,” Brown says.

The result is an even bigger black hole—though not quite as large as you’d expect by just adding up the masses of the two black holes that gave rise to it. That’s because roughly one solar mass was converted into energy, via Einstein’s famous equation, E = mc2. The magnitude of the explosion boggles the imagination. “When a nuclear bomb explodes, you’re converting about a gram of matter—about the weight of a thumbtack—into energy,” Brown explains. “Here, you’re converting the equivalent of the mass of the Sun into energy, in a tiny fraction of a second.”

As powerful as the blast was—for an instant, it would have produced more energy than all the stars in the universe—the ripples it unleashed were almost vanishingly small by the time they reached the Earth, having traveled across some 1.4 billion light years of space.            

For now, scientists can only estimate what direction these signals have come from; however, their ability to “triangulate” locations will greatly improve when another gravitational wave detector, Italy’s Virgo facility, is incorporated into the network of detectors, possibly as early as this autumn. India and Japan are also set to bring gravitational wave detectors online in the years ahead.

LIGO began operation in 2002, but with only a fraction of its current sensitivity. The detectors, located in Louisiana and in Washington state, were upgraded last fall in an effort known as “Advanced LIGO.” The facility is still operating at just one-third of its potential maximum sensitivity, Brown says.

As gravitational wave observations become routine, physicists will be able to tackle some of the outstanding problems in astrophysics and cosmology—many of which involve the puzzling properties of black holes, as University of Florida physicist Clifford Will tells mental_floss: “Where do black holes come from? Were they born small, and then grow? Or are there mechanisms that can produce 30 or 40 stellar mass black holes from the get-go? Did they form within binary systems? Or did one black hole capture another, later in life? These are the questions that astronomers and astrophysicists will be thinking about.”

Adds Brown: “The field of 'gravitational wave astronomy' is now open for business.”

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Ernest Hemingway’s Guide to Life, In 20 Quotes
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Though he made his living as a writer, Ernest Hemingway was just as famous for his lust for adventure. Whether he was running with the bulls in Pamplona, fishing for marlin in Bimini, throwing back rum cocktails in Havana, or hanging out with his six-toed cats in Key West, the Nobel and Pulitzer Prize-winning author never did anything halfway. And he used his adventures as fodder for the unparalleled collection of novels, short stories, and nonfiction books he left behind, The Sun Also Rises, A Farewell to Arms, Death in the Afternoon, For Whom the Bell Tolls, and The Old Man and the Sea among them.

On what would be his 119th birthday—he was born in Oak Park, Illinois on July 21, 1899—here are 20 memorable quotes that offer a keen perspective into Hemingway’s way of life.

ON THE IMPORTANCE OF LISTENING

"I like to listen. I have learned a great deal from listening carefully. Most people never listen."

ON TRUST

"The best way to find out if you can trust somebody is to trust them."

ON DECIDING WHAT TO WRITE ABOUT

"I never had to choose a subject—my subject rather chose me."

ON TRAVEL

"Never go on trips with anyone you do not love."


Ernest Hemingway Photograph Collection, John F. Kennedy Presidential Library and Museum, Boston. [1], Public Domain, Wikimedia Commons

ON THE RELATIONSHIP BETWEEN INTELLIGENCE AND HAPPINESS

"Happiness in intelligent people is the rarest thing I know."

ON TRUTH

"There's no one thing that is true. They're all true."

ON THE DOWNSIDE OF PEOPLE

"The only thing that could spoil a day was people. People were always the limiters of happiness, except for the very few that were as good as spring itself."

ON SUFFERING FOR YOUR ART

"There is nothing to writing. All you do is sit down at a typewriter and bleed."

ON TAKING ACTION

"Never mistake motion for action."

ON GETTING WORDS OUT

"I wake up in the morning and my mind starts making sentences, and I have to get rid of them fast—talk them or write them down."


Photograph by Mary Hemingway, in the Ernest Hemingway Photograph Collection, John F. Kennedy Presidential Library and Museum, Boston., Public Domain, Wikimedia Commons

ON THE BENEFITS OF SLEEP

"I love sleep. My life has the tendency to fall apart when I'm awake, you know?"

ON FINDING STRENGTH 

"The world breaks everyone, and afterward, some are strong at the broken places."

ON THE TRUE NATURE OF WICKEDNESS

"All things truly wicked start from innocence."

ON WRITING WHAT YOU KNOW

"If a writer knows enough about what he is writing about, he may omit things that he knows. The dignity of movement of an iceberg is due to only one ninth of it being above water."

ON THE DEFINITION OF COURAGE

"Courage is grace under pressure."

ON THE PAINFULNESS OF BEING FUNNY

"A man's got to take a lot of punishment to write a really funny book."


By Ernest Hemingway Photograph Collection, John F. Kennedy Presidential Library and Museum, Boston. - JFK Library, Public Domain, Wikimedia Commons

ON KEEPING PROMISES

"Always do sober what you said you'd do drunk. That will teach you to keep your mouth shut."

ON GOOD VS. EVIL

"About morals, I know only that what is moral is what you feel good after and what is immoral is what you feel bad after."

ON REACHING FOR THE UNATTAINABLE

"For a true writer, each book should be a new beginning where he tries again for something that is beyond attainment. He should always try for something that has never been done or that others have tried and failed. Then sometimes, with great luck, he will succeed."

ON HAPPY ENDINGS

"There is no lonelier man in death, except the suicide, than that man who has lived many years with a good wife and then outlived her. If two people love each other there can be no happy end to it."

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