You can login if you already have an account or register by clicking the button below.
Registering is free and all you need is a username and password. We never ask you for your e-mail.
Dr. Kalogera, who was in Utah hiking and getting ready for August’s total solar eclipse when she got the alarm, recalled thinking: “Oh my God, this is it. This 50-year-old mystery, the holy grail, is solved.”
Together the two signals told a tale of a pair of neutron stars spiraling around each other like the blades of a kitchen blender.
But where?
Luckily the European Virgo antenna had joined the gravitational wave network only two weeks before, and it also showed a faint chirp at the same time. The fact that it was so weak allowed the group to localize the signal to a small region of the sky in the Hydra constellation that was in Virgo’s blind spot.
The hunt was on. By then Hydra was setting in the southern sky. It would be 11 hours before astronomers in Chile could take up the chase.
One of them was Ryan Foley, who was working with a team on the Swope telescope run by the Carnegie Institution on Cerro Las Campanas in Chile. His team made a list of the biggest galaxies in that region and set off to photograph them all systematically.
The fireball showed up in the ninth galaxy photographed, as a new bluish pinprick of light in the outer regions of NGC 4993, a swirl of stars about 130 million light-years from here. “These are the first optical photons from a kilonova humankind has ever collected,” Dr. Foley
Within 10 minutes, another group of astronomers, led by Marcelle Soares-Santos of Brandeis University and using the Dark Energy Camera, which could photograph large parts of the sky with a telescope at the nearby Cerro Tololo Interamerican Observatory, had also spotted the same speck of light.
Emails went flying about in the Chilean night.
When it was first identified, the fireball of 8,000-degree gas was about the size of Neptune’s orbit and radiating about 200 million times as much energy as the sun.
Nine days later, the orbiting Chandra X-ray Observatory detected X-rays coming from the location of the burst, and a week after that, the Very Large Array in New Mexico recorded radio emissions. By then the fireball faded from blue to red.
From all this, scientists have begun patching together a tentative story of what happened in the NGC 4993 galaxy.
“It’s actually surprising how well we were able to anticipate what we’re seeing,” said Brian David Metzger, a theorist at Columbia University who coined the term kilonova back in 2010.
As they tell it, the merging objects were probably survivors of stars that had been orbiting each other and had each puffed up and then died in the supernova explosions in which massive stars end their luminous lives some 11 billion years ago, according to an analysis by Dr. Kalogera. Making reasonable assumptions about their spins, these neutron stars were about 1.1 and 1.6 times as massive as the sun, smack in the known range of neutron stars.
As they approached each other swirling a thousand times a second, tidal forces bulged their surfaces outward. Quite a bit of what Dr. Metzger called “neutron star guts” were ejected and formed a fat doughnut around the merging stars.
At the moment they touched , a shock wave squeezed more material out of their polar regions, but the doughnut and extreme magnetic fields confined the material into an ultra-high-speed jet emitting a blitzkrieg of radiation, the gamma rays.
As the jet slowed down, encountering interstellar gas in the galaxy, it began to glow in X-rays and then radio waves.
The subatomic nuggets known as neutrons meanwhile were working their cosmic alchemy. The atoms in normal matter are mostly empty space: a teeny tiny nucleus of positively charged protons and electrically neutral neutrons enveloped in a fluffy cloud of negatively charged electrons. Under the enormous pressures of a supernova explosion, however, the electrons get squeezed back into the protons turning them into neutrons packed into a ball denser than an atomic nucleus.
The big splat liberates these neutrons into space where they inundate the surrounding atoms, transmuting them into heavy elements. The radioactivity of these newly created elements keeps the fireball hot and glowing.
Dr. Metzger estimated that an amount of gold equal to 40 to 100 times the mass of the Earth could have been produced over a few days and blown into space. In the coming eons, it could be incorporated into new stars and planets and in some far, far day become the material for an alien generation’s jewels.
The discovery filled a long-known chink in the accepted explanation of how the chemistry of the universe evolved from pure hydrogen and helium into the diverse place it is today. Stars and supernovas could manufacture the elements up to iron or so, according to classic papers in the 1950s but heavier elements required a different thermonuclear chemistry called r-process and lots of free neutrons floating around. Where would they have come from?
One idea was neutron star collisions, or kilonovas, which now seem destined to take their place on the laundry list of cosmic catastrophes along with the supernova explosions and black hole collisions that have shaped the history of the universe.
Until now there was only indirect evidence of kilonovas. Astronomers found a fireball from a gamma-ray burst in 2013, but there was no proof that neutron stars were involved. Now astronomers know they are, completing the picture of the origin of bling.
One burning question is what happened to the remnant of this collision. According to the LIGO measurements, it was about as massive as 2.6 suns. Scientists say that for now they are unable to tell whether it collapsed straight into a black hole, formed a fat neutron star that hung around in this universe for a few seconds before vanishing, or remained as a neutron star. They may never know, Dr. Kalogera said.
Neutron stars are the densest form of stable matter known. Adding any more mass over a certain limit will cause one to collapse into a black hole, but nobody knows what that limit is.
Future observations of more kilonovas could help physicists understand where the line of no return actually is.
Dr. Holz, the University of Chicago astrophysicist, said, “I still can’t believe how lucky we all are,” reciting a list of fortuitous circumstances. They had three detectors running for only a few weeks, and it was the closest gamma-ray burst ever recorded and the loudest gravitational wave yet recorded. “It’s all just too good to be true. But as far as we can tell it’s really true. We’re living the dream.”
Correction: October 16, 2017
An earlier version of this article misstated the number of authors of a paper published in an astronomy journal. It is 3,500 authors, not 4,500.
Correction: October 18, 2017
An article on Monday about the detection of a collision of neutron stars misidentified the journal in which a paper written by thousands of authors describing the event appeared. It was in Astrophysical Journal Letters, not Physical Review Letters.
view the rest of the comments →
[–] Inara__Serra 0 points 1 point 1 point (+1|-0) ago
Dr. Kalogera, who was in Utah hiking and getting ready for August’s total solar eclipse when she got the alarm, recalled thinking: “Oh my God, this is it. This 50-year-old mystery, the holy grail, is solved.”
Together the two signals told a tale of a pair of neutron stars spiraling around each other like the blades of a kitchen blender.
But where?
Luckily the European Virgo antenna had joined the gravitational wave network only two weeks before, and it also showed a faint chirp at the same time. The fact that it was so weak allowed the group to localize the signal to a small region of the sky in the Hydra constellation that was in Virgo’s blind spot.
The hunt was on. By then Hydra was setting in the southern sky. It would be 11 hours before astronomers in Chile could take up the chase.
One of them was Ryan Foley, who was working with a team on the Swope telescope run by the Carnegie Institution on Cerro Las Campanas in Chile. His team made a list of the biggest galaxies in that region and set off to photograph them all systematically.
The fireball showed up in the ninth galaxy photographed, as a new bluish pinprick of light in the outer regions of NGC 4993, a swirl of stars about 130 million light-years from here. “These are the first optical photons from a kilonova humankind has ever collected,” Dr. Foley
Within 10 minutes, another group of astronomers, led by Marcelle Soares-Santos of Brandeis University and using the Dark Energy Camera, which could photograph large parts of the sky with a telescope at the nearby Cerro Tololo Interamerican Observatory, had also spotted the same speck of light.
Emails went flying about in the Chilean night.
When it was first identified, the fireball of 8,000-degree gas was about the size of Neptune’s orbit and radiating about 200 million times as much energy as the sun.
Nine days later, the orbiting Chandra X-ray Observatory detected X-rays coming from the location of the burst, and a week after that, the Very Large Array in New Mexico recorded radio emissions. By then the fireball faded from blue to red.
From all this, scientists have begun patching together a tentative story of what happened in the NGC 4993 galaxy.
“It’s actually surprising how well we were able to anticipate what we’re seeing,” said Brian David Metzger, a theorist at Columbia University who coined the term kilonova back in 2010.
As they tell it, the merging objects were probably survivors of stars that had been orbiting each other and had each puffed up and then died in the supernova explosions in which massive stars end their luminous lives some 11 billion years ago, according to an analysis by Dr. Kalogera. Making reasonable assumptions about their spins, these neutron stars were about 1.1 and 1.6 times as massive as the sun, smack in the known range of neutron stars.
As they approached each other swirling a thousand times a second, tidal forces bulged their surfaces outward. Quite a bit of what Dr. Metzger called “neutron star guts” were ejected and formed a fat doughnut around the merging stars.
At the moment they touched , a shock wave squeezed more material out of their polar regions, but the doughnut and extreme magnetic fields confined the material into an ultra-high-speed jet emitting a blitzkrieg of radiation, the gamma rays.
As the jet slowed down, encountering interstellar gas in the galaxy, it began to glow in X-rays and then radio waves.
The subatomic nuggets known as neutrons meanwhile were working their cosmic alchemy. The atoms in normal matter are mostly empty space: a teeny tiny nucleus of positively charged protons and electrically neutral neutrons enveloped in a fluffy cloud of negatively charged electrons. Under the enormous pressures of a supernova explosion, however, the electrons get squeezed back into the protons turning them into neutrons packed into a ball denser than an atomic nucleus.
The big splat liberates these neutrons into space where they inundate the surrounding atoms, transmuting them into heavy elements. The radioactivity of these newly created elements keeps the fireball hot and glowing.
Dr. Metzger estimated that an amount of gold equal to 40 to 100 times the mass of the Earth could have been produced over a few days and blown into space. In the coming eons, it could be incorporated into new stars and planets and in some far, far day become the material for an alien generation’s jewels.
The discovery filled a long-known chink in the accepted explanation of how the chemistry of the universe evolved from pure hydrogen and helium into the diverse place it is today. Stars and supernovas could manufacture the elements up to iron or so, according to classic papers in the 1950s but heavier elements required a different thermonuclear chemistry called r-process and lots of free neutrons floating around. Where would they have come from?
One idea was neutron star collisions, or kilonovas, which now seem destined to take their place on the laundry list of cosmic catastrophes along with the supernova explosions and black hole collisions that have shaped the history of the universe.
Until now there was only indirect evidence of kilonovas. Astronomers found a fireball from a gamma-ray burst in 2013, but there was no proof that neutron stars were involved. Now astronomers know they are, completing the picture of the origin of bling.
One burning question is what happened to the remnant of this collision. According to the LIGO measurements, it was about as massive as 2.6 suns. Scientists say that for now they are unable to tell whether it collapsed straight into a black hole, formed a fat neutron star that hung around in this universe for a few seconds before vanishing, or remained as a neutron star. They may never know, Dr. Kalogera said.
Neutron stars are the densest form of stable matter known. Adding any more mass over a certain limit will cause one to collapse into a black hole, but nobody knows what that limit is.
Future observations of more kilonovas could help physicists understand where the line of no return actually is.
Dr. Holz, the University of Chicago astrophysicist, said, “I still can’t believe how lucky we all are,” reciting a list of fortuitous circumstances. They had three detectors running for only a few weeks, and it was the closest gamma-ray burst ever recorded and the loudest gravitational wave yet recorded. “It’s all just too good to be true. But as far as we can tell it’s really true. We’re living the dream.” Correction: October 16, 2017
An earlier version of this article misstated the number of authors of a paper published in an astronomy journal. It is 3,500 authors, not 4,500. Correction: October 18, 2017
An article on Monday about the detection of a collision of neutron stars misidentified the journal in which a paper written by thousands of authors describing the event appeared. It was in Astrophysical Journal Letters, not Physical Review Letters.