Groundbreaking
gravitational wave discovery shows Einstein's brilliance yet again
Miriam Kramer, Mashable
Even
100 years after the fact, Albert Einstein is still getting his due.
On
Monday, more than a thousand astronomers and physicists around the world
celebrated the announcement of a landmark discovery. For the first time,
researchers saw the immediate aftermath of the merger of two neutron stars —
leftover stellar remnants packed with more mass than our sun but with the
diameter as small as the city of Boston.
Researchers
detected both the ripples in space and time sent out by the colliding neutron
stars as well as the light signature from the event. This marks the first time
a cosmic collision has been seen in both light and gravity.
It
also represents another passing grade for Einstein's general theory of
relativity, which he developed in 1915.
On
the morning of August 17, the two LIGO detectors in Washington and Louisiana,
as well as the Virgo detector in Italy, felt the subtle distortion of the
fabric of space and time caused by the ripples — or gravitational waves — sent
out by the colliding neutron stars. This collision created heavy elements like
gold, platinum, and lead.
“What’s
amazing with this discovery is that theoretically all of this that was observed
on August 17th was actually predicted. Over a century ago, Einstein predicted
that two orbiting objects will emit gravitational waves as they spiral in, and
astrophysicists predicted that as two compact objects — especially neutron
stars — collide, they should emit gamma-rays in jets," LIGO scientist
Vicky Kalogera said during a press conference.
"And
the cascade of light across the whole electromagnetic spectrum was predicted,
and the production of heavy elements that might include gold and platinum
should be produced," she added.
"So
it’s amazing to think that in one day, in a few hours and the weeks that
followed, all of these predictions were confirmed."
Einstein's
theory offers an elegant explanation for these gravitational waves.
Think
of our universe as a top sheet laid across a bed. If you put two large objects
on that sheet, it would create an indentation.
Our
universe is similar. Massive objects like stars or black holes depress parts of
the fabric of our universe. When two of these objects — like the two neutron
stars — orbit one another, falling in toward each other and eventually merging,
it can ripple that fabric, sending those waves out into the universe.
Artist's
illustration of the neutron star collision.
Image:
caltech
Scientists had previously
spotted gravitational waves sent out by black holes, but the August detection
marks the first time LIGO or Virgo has observed colliding neutron stars.
At nearly that same time as
LIGO and Virgo were riding the colliding neutron stars' gravitational wave,
scientists also caught sight of a gamma-ray burst associated with that
collision.
One of the things that the #GravitationalWaves #NeutronStar collision discovery confirms is that
light and gravity travel at the same speed.
We
had good evidence for this from previous data, but this is very direct:
gravitational waves & light travelling together, we time arrival.
This is very strong evidence that light and gravitational waves move at the
same speed, something else that Einstein originally predicted. Being
able to observe cosmic events in light and gravitational waves is a huge deal
for researchers.
While
gravitational waves carry with them signatures of the objects that created
them, being able to use more traditional observatories to see the event using
light — whether it be in the infrared, X-ray, visible, or ultraviolet spectrum
— can let scientists gather more information than ever before.
Science Astronomers
just measured a whole lot more than gravitational waves
Mallory Locklear,Engadget 1
hour 10 minutes ago
A
couple of weeks ago, the LIGO (Laser Interferometer Gravitational-Wave
Observatory) and Virgo teams announced the detection of another set
of gravitational waves -- the fourth since
LIGO's first detection in September of 2015. The
observations of these ripples in spacetime are extraordinary in and of
themselves, no matter how many times we record them. However, while the first three sets of gravitational waves recorded
were by the two LIGO observatories, the fourth was also detected by a newly
established third -- Virgo -- located in Italy. And having three detectors
allows researchers to triangulate the source of those waves with extraordinary
precision.
The
importance of that precision was made clear today when the LIGO and Virgo teams
announced a fifth gravitational wave detection, the source of which was able to
be quickly located. This allowed dozens of other observatories to hone in on it
and collect additional data including visual, X-ray, infrared, ultraviolet and
radio wave recordings -- meaning researchers all around the world just
collected, and are continuing to collect, a massive trove of information that
has given us the most detailed look at a gravitational wave-generating event
ever.
The
previously recorded gravitational waves were caused by black holes merging many
millions of light-years away. However, these new waves, recorded on August
17th, originated from the merging of two neutron stars -- very small but
incredibly massive stars. They're what's left over after a massive star
collapses and all of the protons and electrons get packed tightly together.
They're around the size of a city, but 1.3 to 2.5 times the mass of our Sun.
Just a teaspoon of a neutron star's matter can weigh more than one billion
tons. The gravitational wave recordings indicated that this latest event was
much closer than previous ones, around 130 million light-years from Earth.
Around
the same time that LIGO and Virgo picked up the signal, a bright flash of gamma
rays was detected by NASA's Fermi space telescope, and combined, those data
allowed researchers to pinpoint which direction the waves were coming from.
Armed with that knowledge, thousands of researchers around the world, manning
more than 70 ground- and space-based observatories, were mobilized and all of
them began collecting additional data from the neutron star merger. "This
event has the most precise sky localization of all detected gravitational waves
so far," Jo van den Brand, spokesperson for the Virgo collaboration, said
in a statement. "This record precision enabled astronomers to perform
follow-up observations that led to a plethora of breathtaking results."
This
strategy, called multi-messenger astronomy, has been a goal of LIGO researchers
from the very beginning because observing these sorts of events with
gravitational waves and light at nearly the same time can provide far more
detail than either can alone. "This detection opens the window of a long-awaited
'multi-messenger' astronomy," David Reitze, executive director of the LIGO
Laboratory, said in a statement. "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."
And
the collection of data was truly a team effort. Once astronomers around the
world were notified of the detection, the hunt began for the source. David
Cook, a postdoc at Caltech, quickly made a list of 50 possible galaxies that
could be hosting the neutron star merger. A few hours later the Swope Telescope
located in Chile detected an optical signal that seemed to match the
gravitational wave and gamma ray signals in a galaxy called NGC 4993. Shortly
after that, the Gemini South telescope -- also in Chile -- detected an infrared
signal from the same area.
So
what have we learned from this event so far? Quite a lot actually, and more
information is still being collected. The head of Caltech's astrophysical data
analysis group for LIGO, Alan Weinstein, said, "The detection of
gravitational waves from a binary neutron star merger is something that we have
spent decades preparing for. On that morning, all of our dreams came
true."
One
major finding was that neutron stars give off gamma ray bursts when they merge,
which had only been theorized before. But Fermi's initial recording, along with
the confirmation from the European Space Agency's INTEGRAL gamma ray
observatory, have finally provided researchers with solid evidence.
Secondly,
a big question about where the heavy elements of our universe come from may
have been answered. The lightest elements, hydrogen and helium, are thought to
have been formed during the Big Bang while heavier elements from lithium up to
iron are generated by stars. But where most of the other elements come from has
been a bit of an unknown. That is, until now. Infrared observations from the
likes of the Gemini Observatory, the European Very Large Telescope and the
Hubble Space Telescope showed that the neutron star merger produced those
heavier elements. "For the very first time, we see unequivocal evidence of
a cosmic mine that is forging about 10,000 earth-masses of heavy elements, such
as gold, platinum and neodymium," said Mansi Kasliwal, leader of the
Global Relay of Observatories Watching Transients Happen project, a
collaboration made up of dozens of astronomers and 18 telescopes on six
continents.
There
were a handful of surprises, though. The gamma ray signals that spewed out of
the merger were surprisingly weak. And, even a week after the gravitational
wave detection, researchers still hadn't observed any X-rays or radio waves.
X-rays were eventually detected by NASA's Chandra X-ray Observatory nine days
after the merger. It took 16 days for the Very Large Array in New Mexico to
pick up any radio waves. These delayed waves and wimpy gamma ray signals
spurred Kasliwal and her colleagues to design an explanatory model wherein a
pressurized cocoon-like structure forms during the merger that traps the waves.
While
the radio waves may be the slowest to arrive, they stick around much longer
than the others and bring with them a ton of information, which could include
how much energy was in the explosion, how much mass was spewed out and whether
the merger might have an impact on star formation. "The radio emission
arrives last but persists much longer than emissions at other wavebands,"
said Caltech astronomer Gregg Hallinan. "Radio comes late, and it comes
slow, but it brings amazing information about the cosmic cataclysm."
This
event is the most intensively studied transient astronomical occurrence in
history and it's hard to overstate just how important it is. It has not only
provided scientists with far more data than they've ever had on such an event,
it demonstrated just how wildly effective multi-messenger astronomy is. With a
global web of observatories all focused on the same target, we stand to make
substantial advances in our understanding of how the universe formed and
continues to evolve. "The story that is unfolding for this event is more
complete than for any previous event in astronomical history," said
Hallinan in a statement. "This complete story -- both hearing and seeing
the violent universe -- is the gift of multi-messenger astronomy," he
continued. Laura Cadonati, a physics professor at Georgia Tech and the
spokesperson for the LIGO Scientific Collaboration said, "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."
The
data described today in a handful of papers published in Science and Physical
Review Letters are just the beginning. Observatories around the world
will be releasing more findings in the weeks and months to come and many will
continue to observe the effects of the neutron star merger for months, even
years. And this is just one event. "We even more eagerly anticipate the
detection of gravitational waves from different kinds of known, extremely
energetic astrophysical objects, like rapidly spinning pulsars, supernovae and
neutron star quakes," said Weinstein, "and, especially, from
heretofore unknown astrophysical objects." It is truly an astoundingly
exciting time.
Images:
LIGO-Virgo/Frank Elavsky/Northwestern (Stellar Masses); UC Santa Cruz and
Carnegie Observatories/Ryan Foley (Swope Telescope Optical Image); LIGO-Virgo
(Participating Observatories)
Neutron
star smashup seen for first time, 'transforms' understanding of Universe
Mariëtte
Le Roux, AFP
Paris
(AFP) - Scientists have for the first time witnessed the crash of two ultra-dense
neutron stars, cataclysmic events now known to have generated at least half the
gold in the Universe, excited research teams revealed Monday.
Shockwaves
and light flashes emitted by the cosmic fireball travelled some 130 million
light-years to be captured by Earthly detectors on August 17, they revealed at
simultaneous press conferences around the globe as a dozen science papers were
published in top academic journals.
"We
witnessed history unfolding in front of our eyes: two neutron stars drawing
closer, closer... turning faster and faster around each other, then colliding
and scattering debris all over the place," co-discoverer Benoit Mours of
France's CNRS research institute told AFP.
The
groundbreaking observation solved a number of physics riddles and sent ripples
of anticipation through the scientific community.
Most
jaw-dropping for many, the data finally revealed where much of the gold,
platinum, mercury and other heavy elements in the Universe came from.
Telescopes
saw evidence of newly-forged material in the fallout, the teams said -- a
source long suspected, now confirmed.
"It
makes it quite clear that a significant fraction, maybe half, maybe more, of
the heavy elements in the Universe are actually produced by this kind of
collision," said physicist Patrick Sutton, a member of the Laser
Interferometer Gravitational-Wave Observatory (LIGO) which contributed to the
find.
Neutron
stars are the condensed, burnt-out cores that remain when massive stars run out
of fuel, blow up, and die.
Some
20 kilometres (12 miles) in diameter, with slightly more mass than our sun,
they are highly radioactive and ultra-dense -- a handful of material from one
weighs as much as Mount Everest.
-
'Too beautiful' -
It
had been theorised that mergers of two such exotic bodies would create ripples
in the fabric of space-time known as gravitational waves, as well as bright
flashes of high-energy radiation called gamma ray bursts.
On
August 17, detectors witnessed both phenomena, 1.7 seconds apart, coming from
the same spot in the constellation of Hydra.
"It
was clear to us within minutes that we had a binary neutron star
detection," said David Shoemaker, another member of LIGO, which has
detectors in Livingston, Louisiana and Hanford, Washington.
"The
signals were much too beautiful to be anything but that," he told AFP.
The
observation was the fruit of years of labour by thousands of scientists at more
than 70 ground- and space-based observatories scattered around the globe.
Along
with LIGO, they included teams from Europe's Virgo gravitational wave detector
in Italy, and a number of ground- and space-based telescopes including NASA's
Hubble.
"This
event marks a turning point in observational astronomy and will lead to a
treasure trove of scientific results," said Bangalore Sathyaprakash from
Cardiff University's School of Physics and Astronomy.
The
detection is another feather in the cap for German physicist Albert Einstein,
who first predicted gravitational waves more than 100 years ago.
Three
LIGO pioneers, Barry Barish, Kip Thorne and Rainer Weiss, were awarded the
Nobel Physics Prize this month for the observation of gravitational waves,
without which the latest discovery would not have been possible.
The
ripples have been observed four times before now -- the first time by LIGO in
September 2015.
The
fifth and latest gravitational wave observation is the first from a neutron
star fusion. The other four were from black hole mergers which are even more
violent but unlike neutron stars, emit no light.
-
'Earlier' than expected -
The
latest wave observation, on the other hand, was accompanied by flashes of gamma
rays, which scientists said came from closer in the Universe and were less
bright than expected.
"What
this event is telling us is that there may be many more of these short gamma
ray bursts going off nearby in the Universe than we expected," Sutton
said.
"This
might be the tip of the iceberg of short gamma ray bursts produced by
collisions and mergers of neutron stars" -- an exciting prospect for
scientists hoping to uncover further secrets of the Universe.
Among
other things, it is hoped that data from neutron star collisions will one day
reveal the rate of expansion of the cosmos, which in turn would tell us how old
it is and how much matter it contains.
"It
is tremendously exciting to experience a rare event that transforms our
understanding of the workings of the Universe," said France Cordova,
director of the National Science Foundation which funds LIGO.
Secret
of gold finally found: precious metals are forged in cataclysmic collision of
neutron stars
Sarah Knapton,The Telegraph 1
hour 10 minutes ago
The
secret of creating gold has fascinated alchemists for thousands of years, but
now scientists have finally solved the mystery.
Precious
metals are forged in the cataclysmic collision of neutron stars and then flung
out into the universe where they eventually aggregate with other stardust into
larger bodies, like planets or comets.
Previously
scientists had theorised that such cosmic smashes could create the vast amount
of energy needed to create gold, platinum and silver, but for the first time,
they have actually recorded it happening.
On
August 17, astronomers in the US picked up a signal from two neutron stars
crashing together 130 million years ago, when dinosaurs still roamed the Earth.
The
impact, known as a ‘kilanova’ was so powerful that it shook not only space but
also time, sending ripples - or gravitational waves - through the fabric of
the universe.
The
neutron star crash was so powerful it shook time and space sending a ripple out
across the universe Credit: LSC/Sonoma State University
After
the ripple was detected on Earth, astronomers across the world pointed their
telescopes to the area of space from which it had originated and soon also
picked up the bright afterglow from the collision. Inside that light were the
distinct chemical signatures for gold, silver and platinum.
Dr
Joe Lyman, of the University of Warwick, who was observing at
the European
Southern Observatory, in Germany, was the first to alert the
scientific community to the fact they were witnessing a completely new event.
“The
observations showed we were observing a kilonova, an object whose light is
powered by extreme nuclear reactions,” he said.
“This
tells us that the heavy elements, like the gold or platinum in jewellery, are
the cinders, forged in the billion degree remnants of a merging neutron star.”
Neutron
stars are created when giant stars die in spectacular supernovas. Their cores
collapse, allowing protons and electrons to meld together to form neutrons,
creating small yet incredibly dense stars. Just a teaspoon of neutron star
material would have a mass of about a billion tons.
The
two stars which were detected in August were as heavy as our Sun, yet only six
miles (10km) across. They existed in a galaxy called NGC 4993.
The
pair drew towards each other over millions of years, and revolved around each
other increasingly quickly as they got closer – eventually spinning around each
other five hundred times per second, until they crashed, forming either a
larger neutron star or collapsing into a black hole.
The
spacetime ripples created by the collision were detected by the Advanced Laser
Interferometer Gravitational-Wave Observatory in Washington and Louisiana
(Ligo). It was here the first discovery of gravitational waves was made in September
2015, confirming a prediction made by Albert Einstein 100 years ago and earning three pioneers of the project a Nobel Prize.
In
that instance, black holes collided so only the ripples were detected because
everything else was swallowed inside. But neutron stars are relatively
lighter than black holes, so when they collide and merge, a small part of their
mass and radiation does escape and can be detected along with gravitational
waves.
The
Theory of Relativity
Professor
David Wiltshire, Department of Physics & Astronomy, University of
Canterbury, said: “The first discovery of gravitational waves from
the merger of two neutron stars is an historic event.
“It
is every bit as exciting as the first discovery of gravitational waves from
merging black holes. Since this involves neutron stars that radiate light, for
the first time we can also see what is going on in an extreme astronomical
event that shakes up space-time.”
Dr
J.J. Eldridge, astrophysicist at the University of Auckland, added: “We’re all
made of stardust, but gold, silver and platinum are made of neutron stardust.
“In
this particular event, it’s likely that 100s or 1000s of Earth masses of gold
and other elements were made. If the rate of neutron stars mergers is as high
as we now think, these dying stars are now the source of most of these elements
in the universe.”
The
discovery has also solved the mystery of what creates short wave gamma ray
bursts which are picked up on Earth and could help pinpoint how fast the
universe is expanding.
Dr
Samantha Oates, of Warwick’s Astronomy and Astrophysics group added: “This
discovery has answered three questions that astronomers have been puzzling for
decades: what happens when neutron stars merge? What causes the short duration
gamma-ray bursts? Where are the heavy elements, like gold, made? In the space
of about a week all three of these mysteries were solved.”
The
new findings were published in research papers in the journals Nature, Nature
Astronomy and Science.
