A galaxy
about 9 billion light years away from us is the host galaxy of the gamma ray burst GRB 151229A.
In July 2022, through observations of these galaxies, astronomers gained a new understanding of a subcategory of gamma ray bursts, short bursts .
Hello everyone, I am Teng Bao. In this issue, we will talk about the history of the discovery of gamma ray bursts and recent research.
Discovery History
Gamma ray bursts can be said to be the most energetic and energetic bursts after the Big Bang.
People first noticed this outbreak in 1967.
was detected by a detector called VELA satellite launched by the United States.
VELA satellite
The original intention of this detector is to detect gamma rays released from nuclear weapons explosions.
Because in the 1950s and 1960s, as humans learned about atomic energy and then manufactured nuclear weapons, various countries were studying nuclear weapons one after another and conducting detonation experiments on the earth.
Such a large-scale detonation experiment would do untold harm to the earth.
Therefore, on August 5, 1963, the United States, the former Soviet Union and the United Kingdom signed a contract in Moscow. The content of the contract was that prohibited nuclear weapons experiments in the atmosphere, outer space, and underwater.. After
, other countries also signed this treaty.
But after signing, the United States was not at ease, so they developed a detector that specifically detects nuclear explosions to monitor the compliance of other countries. The detector
is the VeLa satellite detector we mentioned before.
The VeLa satellite can detect high-energy radiation released by nuclear weapon explosions, such as gamma rays.
On July 2, 1967, the VeLa 3 and 4 detectors detected gamma flashes that were unlike any nuclear weapons. At that time, no one knew where they came from.
After more data, it was confirmed that these gamma flashes did not come from the earth or the sun.
They come from the universe.
But where exactly it came from was unknown at the time.
Because it is not easy to determine the specific location of these gamma flashes, the flashes are fleeting from occurrence to disappearance, so it is difficult for researchers to find their optical counterparts.
until 1997.
On February 8, 1997, an X-ray detector launched by Italy and the Netherlands tracked the origin direction of a gamma ray burst numbered GRB 970228. Based on this direction, astronomers finally identified Here comes its optical counterpart.
GRB 970228
But it has been 30 years since the first gamma ray burst was discovered.
During those 30 years, people have always suspected that these bright gamma flashes came from the Milky Way . Because the energy of the flash is very high, it should not be very far away from us, but when we first saw it Astronomers were shocked when they discovered the optical counterpart!
Because it is not within the Milky Way, it comes from outside the Milky Way, a distant galaxy, but how far it is from us cannot be determined because the galaxy is too faint.
until May of the same year.
A gamma ray burst numbered GRB 970508 gave an astonishing answer. Astronomers also determined the optical counterpart of this gamma ray burst, and, based on this optical counterpart, Astronomers have measured its distance from us, and it is more than 6 billion light-years away.
GRB 970508
This is the first time humans have accurately determined the distance of a gamma ray burst.
I can’t imagine what kind of explosion this is. Even we, who are 6 billion light years away, can detect such amazing energy.
formation speculation
The first thing astronomers think of is the explosion of stars, supernova explosions .
But the explosion of supernova cannot reach this level.
Unless, it concentrates all the burst of energy together.
We know that the explosion of a supernova is a form of diffusion, and its energy is released in all directions.
Supernova
So if concentrates these scattered energies to form a form like a beam , then when such concentrated energy is directed at us, it can explain such high-energy gamma flashes.
How can we concentrate?
Astronomers believe that such a concentration should be formed when a massive star explodes .
Because after a massive star explodes as a supernova, its core will collapse into a black hole. When the black hole is formed, it will have a surrounding accretion disk . The accretion disk will make the black hole powerful. Magnetic field, so at this time, the magnetic field will concentrate the energy to the two poles and shoot it into the universe. As a result, there will be an ultra-high energy beam, a gamma ray burst.
Gamma ray burst formation indication
Therefore, such a powerful energy burst often heralds the creation of a black hole, but later astronomers believed that when the magnetar is formed, a gamma ray burst should also be produced.
Is that really the case?
Observations show that the origin of gamma ray bursts is far more complicated than we imagined.
Although gamma ray bursts are all bright high-energy flashes, when classified by duration, astronomers have found that there are two different subcategories, namely bursts longer than two seconds and bursts less than two seconds , that is What we are talking about now is that is long-term and is bad, and is short-term and is bad.
's observations of long bursts show that they basically come from galaxies. Star-forming regions, consistent with the theory of supernova explosions of massive stars.
Long bursts are basically near nebulae
But this is not the case for short bursts. Observations show that it seems to have nothing to do with supernovae. It may come from another kind of explosion, kilonova.
The afterglow of short bursts observed by Hubble is related to kilonova.
And, unlike long bursts, most of the short bursts observed do not see the host galaxy. They seem to explode alone in interstellar space.
In this regard, astronomers have proposed two possibilities. One is that the host galaxies of short bursts may be too faint for us to observe; the other is that they may be wanderers in the universe and have no host galaxies.
A kilonova refers to the merger of dense celestial bodies, such as neutron stars and neutron stars, or neutron stars and black holes.
Neutron star collision indication
Then, before they form such a dense celestial body, they have already experienced a supernova explosion, so the supernova explosion can blast them out of the host galaxy, thereby becoming flowrs, and finally, they are formed in interstellar space Short burst.
’s latest research (July 2022)
’s research this time is to understand the mystery of the short burst host galaxy.
In this study, researchers selected 31 unowned candidates from more than 100 short bursts.
Through joint observations with the Gemini Telescope, Keck Observatory , Hubble Telescope and other powerful telescopes, they finally found 18 host galaxies in this seemingly isolated 31 short burst. These galaxies They range from 130 million light-years to 10 billion light-years away from us. Although there are still 13 that have not been found, this study seems to mean that the first possibility is .
We have not seen the host galaxy of short bursts, probably because the host galaxy is too faint.
instead they originate from stray neutron star mergers.
In this case, short bursts may be more common than expected with .
This also means that the early universe was far more dangerous than imagined.
[More exciting astronomical videos can be viewed on the homepage]
Unless, it concentrates all the burst of energy together.
We know that the explosion of a supernova is a form of diffusion, and its energy is released in all directions.
Supernova
So if concentrates these scattered energies to form a form like a beam , then when such concentrated energy is directed at us, it can explain such high-energy gamma flashes.
How can we concentrate?
Astronomers believe that such a concentration should be formed when a massive star explodes .
Because after a massive star explodes as a supernova, its core will collapse into a black hole. When the black hole is formed, it will have a surrounding accretion disk . The accretion disk will make the black hole powerful. Magnetic field, so at this time, the magnetic field will concentrate the energy to the two poles and shoot it into the universe. As a result, there will be an ultra-high energy beam, a gamma ray burst.
Gamma ray burst formation indication
Therefore, such a powerful energy burst often heralds the creation of a black hole, but later astronomers believed that when the magnetar is formed, a gamma ray burst should also be produced.
Is that really the case?
Observations show that the origin of gamma ray bursts is far more complicated than we imagined.
Although gamma ray bursts are all bright high-energy flashes, when classified by duration, astronomers have found that there are two different subcategories, namely bursts longer than two seconds and bursts less than two seconds , that is What we are talking about now is that is long-term and is bad, and is short-term and is bad.
's observations of long bursts show that they basically come from galaxies. Star-forming regions, consistent with the theory of supernova explosions of massive stars.
Long bursts are basically near nebulae
But this is not the case for short bursts. Observations show that it seems to have nothing to do with supernovae. It may come from another kind of explosion, kilonova.
The afterglow of short bursts observed by Hubble is related to kilonova.
And, unlike long bursts, most of the short bursts observed do not see the host galaxy. They seem to explode alone in interstellar space.
In this regard, astronomers have proposed two possibilities. One is that the host galaxies of short bursts may be too faint for us to observe; the other is that they may be wanderers in the universe and have no host galaxies.
A kilonova refers to the merger of dense celestial bodies, such as neutron stars and neutron stars, or neutron stars and black holes.
Neutron star collision indication
Then, before they form such a dense celestial body, they have already experienced a supernova explosion, so the supernova explosion can blast them out of the host galaxy, thereby becoming flowrs, and finally, they are formed in interstellar space Short burst.
’s latest research (July 2022)
’s research this time is to understand the mystery of the short burst host galaxy.
In this study, researchers selected 31 unowned candidates from more than 100 short bursts.
Through joint observations with the Gemini Telescope, Keck Observatory , Hubble Telescope and other powerful telescopes, they finally found 18 host galaxies in this seemingly isolated 31 short burst. These galaxies They range from 130 million light-years to 10 billion light-years away from us. Although there are still 13 that have not been found, this study seems to mean that the first possibility is .
We have not seen the host galaxy of short bursts, probably because the host galaxy is too faint.
instead they originate from stray neutron star mergers.
In this case, short bursts may be more common than expected with .
This also means that the early universe was far more dangerous than imagined.
[More exciting astronomical videos can be viewed on the homepage]
