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The most distant galaxies ever observed in the universe are smaller, filled with young stars, and have a high star formation rate compared to the Milky Way. You expect them to be more compact, chaotic and ellipsoidal, relying solely on direct astrophysics. However, it is the gamma ray sky that allows us to understand the complete suite of the history of star formation in our Universe.NASA, ESA, J. Jee (University of California, Davis), J. Hughes (Rutgers University), F. Menanteau (Rutgers University and University of Illinois, Urbana-Champaign), C. Sifon (Leiden Observatory) ), R. Mandelbum (Carnegie Mellon University), L. Barrientos (Catholic University of Chile) and K. Ng (University of California, Davis)
It's been 13.8 billion years since the hot Big Bang, and the Universe has come a long way since that time. Our cosmic vision extends some 46.1 billion light years in all directions, revealing some 2,000 billion galaxies. Each galaxy contains on average hundreds of billions of stars, while each star is made up of about 1057 atoms. There is a lot going on in our universe, but most of them, including the training of most of the stars – is part of our cosmic past and not our present or our future.
Thanks to a new intelligent method developed by scientists working on Fermi's gamma ray telescope, we were able to measure the star formation history of the entire universe through all the time. We arrive at a surprising confirmation of our worst fears: the Universe is dying and we can not do anything.
A stellar nursery in the Great Magellan Cloud, a satellite galaxy of the Milky Way. This new near sign of star formation may seem ubiquitous, but the speed at which new stars are forming today, all over the universe, accounts for only a few percent of what 's going on. she was just starting out.NASA, ESA and the Hubble Heritage Team (STScI / AURA) – ESA / Hubble Collaboration
When you form stars, a lot of interesting things happen.
- The molecular cloud that collapses to form them is ionized by the ultraviolet light produced by these new stars.
- A particular type of radiation appears: the emission lines, when the electrons fall back on ionized atomic nuclei.
- This stellar light travels through the universe, interacting with all the atoms encountered, creating an absorption signature.
- And light has a probability of interacting with gamma rays, which are the photons of the highest energy, to produce new particles: electron-positron pairs.
The production of matter / antimatter pairs (left) from pure energy is a totally reversible reaction (right), the matter / antimatter being canceled out in pure energy. This process of creation-annihilation, which obeys E = mc ^ 2, is the only known way to create and destroy matter or antimatter. High energy gamma rays can collide with lower energy photons (eg ultraviolet) to produce electron-positron pairs.Dmitry Pogosyan / University of Alberta
This last point is of particular interest to anyone with a gamma-ray space telescope. There are clbades of objects in the Universe – the active supermbadive black holes – that emit very good particles, especially gamma rays. With huge event horizons and large mbadive accretion disks surrounding and infiltrating them as they feed, these charged particles generate huge magnetic fields as they rotate. These fields accelerate the charged particles, causing them to interact and emitting radiations of extremely high energies.
The brightest of all, as far as our point of view here on Earth is concerned, are those whose relativistic jets are directed right at us. These objects are called Blazars because they "flare" the right line of sight to your eyes.
In this artistic interpretation, a blazar accelerates protons producing pions, neutrinos and gamma rays.IceCube / NASA
There are also "tricks" in the way every time you look at something in the distant universe. The clouds of gas exist, absorbing a fraction of the light; we can take this into account by examining the absorption lines. Galaxies and clusters of galaxies often intervene; we can measure their brightness, density, and other properties to calibrate each Blazar we examine. The blazars will also be located throughout the sky, where the zodiacal effects of the solar system and the prominent effects of the Milky Way may affect what we see. And each Blazar, at the source, will have energy and flow properties that are intrinsically unique to him.
By accounting for what exists in the Universe – at the source, along the line of sight, and received in our eyes – we can determine the source properties of the Blazar we are examining. We can have a well calibrated starting point to work.
Artist view of an active galactic core. The supermbadive black hole in the center of the accretion disk sends a narrow stream of high energy matter in the space, perpendicular to the disc. A blazar located about 4 billion light years away is at the origin of most cosmic rays and the most energetic neutrinos. Only matter coming from outside the black hole can come out of the black hole; the matter from within the event horizon can never escape.DESY, Laboratory of Scientific Communication
If you had a gamma ray telescope, it would give you a method to measure all the light from the stars of the universe. Here's how you would do it:
- Start by measuring all the blazars you find everywhere in the universe.
- Measure the redshift of each blazar to find out how far away it is from you.
- Measure the number of gamma rays received by your gamma ray telescope according to the red shift and the brightness of the blazar.
- And finally, knowing that gamma rays, when they collide with this extragalactic background light, can produce electron-positron pairs, use all of this information to calculate the amount of light in the light. background that must be present, depending on the shift to red / distance. , to account for the loss of gamma rays.
NASA's Fermi satellite has built the map of the world's highest resolution and high energy universe ever created. Without space observatories like this, we could never learn everything we have from the universe.NASA / DOE / Fermi LAT collaboration
In total, the Fermi-LAT collaboration (where LAT is the instrument of the large telescope aboard Fermi) made it possible to carry out these measurements for all the known Blazars appearing in the sky of the gamma rays: 739 of them. The closest comes from 200 million years ago; The farthest has its light after a trip of 11.6 billion years: from the time when the universe was only 2.2 billion years old.
Because of the way these blazars are distributed in space and time (backtracking), we need to model the moment when the Universe goes from opaque to transparent in gamma rays. that the Fermi-LAT team was able to do as part of this work.
The history of star formation of the Universe reconstructed by Fermi-LAT collaboration, compared to other data points of alternative methods elsewhere in the literature. We arrive at a consistent set of results for many different measurement methods, and Fermi's contribution represents the most accurate and complete result of this history to date.Marco Ajello and the Fermi-LAT collaboration
The net results they found matched previous work and improved accuracy: the universe peaked in star formation when it was about 3 billion years old, and the star formation rate was in constant decline since. Today, it represents only 3% of this early maximum rate, and the rate of formation of new stars in the universe continues to decline.
The cigar galaxy, M82, and its supergalactic winds (in red) illustrate the rapid and new formation of stars that occur there. It is the closest mbadive galaxy undergoing fast star formation like this, but even considering such cases, the rate of star formation is now well. less than its maximum.NASA, ESA, Hubble Heritage Team (STScI / AURA); Acknowledgments: Mr. Mountain (STScI), P. Puxley (NSF), J. Gallagher (U. Wisconsin)
But an interesting and innovative result of this study is truly revolutionary. & Nbsp; According to the lead author of the Fermi-LAT study, Marco Ajello:
From the data collected by the Fermi telescope, we were able to measure the total amount of stellar light ever emitted. This has never been done before.
This is true: for the first time in our history, we were able to measure the total amount of starlight emitted during the history of the Universe.
The GOODS-North survey, presented here, contains some of the most distant galaxies ever observed, some having their distance independently confirmed. A large number of measurements independent of the Universe at different times has allowed us to reconstruct its history of star formation, which we now know as it peaked around 11 billion years ago. ; years. The current rate of formation of new stars represents only 3% of the old maximum.NASA, ESA and Z. Levay (STScI)
The total amount? This corresponds to a total of about 4 & nbsp; & times; ten84 the photons, which is an impressive number: thousands of times larger than all the protons, neutrons and electrons present in our combined universe. But this number remains very small compared to all the photons existing in the Universe and being part of the radiation remains of the Big Bang, which are about 10 in number.89-to-1090: hundreds of thousands of times the number of photons created by stars.
Yet this evokes a fascinating cosmic coincidence. The average energy of these photons coming from starlight is about 10,000 to 100,000 times greater than the average energy of a photon coming from the Big Bang. In the end, the energy produced by all stars, in terms of radiation, is almost equal to the amount of energy contained in the photons of the Big Bang itself.
A universe where electrons and protons are free and collide with photons turns into a neutral that is transparent to photons as the Universe expands and cools. Here we see the ionized plasma (L) before the emission of the CMB, followed by the transition to a neutral universe (R) transparent to photons. The number of CMB photons is more than 100,000 times greater than all the photons in the star light, but they are in the order of magnitude of each other in terms of the total energy that they contain.Amanda Yoho
A huge part of our cosmic story has just been revealed for the very first time. Through these gamma-ray signals and their interaction with the extragalactic background of starlight, we can bypbad the foregrounds of our own solar system to understand and measure the formation of stars at course of the cosmic time of our universe, and deduce the total amount of stellar light ever produced.
In the future, scientists may be able to go even further and study how stars form and emit light before the instrumentation of the Fermi-LAT team can reach. & Nbsp; Star formation is what transforms the primordial elements of the Big Bang into the elements capable of giving rise to rocky planets, organic molecules and to life in the universe. Maybe one day we will find a way to go back to the first moments of our universe, discovering the truths behind the greatest cosmic mysteries. Until then, enjoy every step – like this one – that we follow throughout the trip!
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The most distant galaxies ever observed in the universe are smaller, filled with young stars, and have a high star formation rate compared to the Milky Way. You expect them to be more compact, chaotic and ellipsoidal, relying solely on direct astrophysics. However, it is the gamma ray sky that allows us to understand the complete suite of the history of star formation in our Universe.NASA, ESA, J. Jee (University of California, Davis), J. Hughes (Rutgers University), F. Menanteau (Rutgers University and University of Illinois, Urbana-Champaign), C. Sifon (Leiden Observatory) ), R. Mandelbum (Carnegie Mellon University), L. Barrientos (Catholic University of Chile) and K. Ng (University of California, Davis)
It's been 13.8 billion years since the hot Big Bang, and the Universe has come a long way since that time. Our cosmic vision extends some 46.1 billion light years in all directions, revealing some 2,000 billion galaxies. Each galaxy contains on average hundreds of billions of stars, while each star is made up of about 1057 atoms. There is a lot going on in our universe, but most of it – including the formation of most stars – is part of our cosmic past, not our present or our future.
Thanks to a new intelligent method developed by scientists working on the Fermi gamma telescope, we have been able to measure the history of star formation from the entire universe over time. We arrive at a surprising confirmation of our worst fears: the Universe is dying and we can not do anything.
A stellar nursery in the Great Magellan Cloud, a satellite galaxy of the Milky Way. This new near sign of star formation may seem ubiquitous, but the speed at which new stars are forming today, all over the universe, accounts for only a few percent of what 's going on. she was just starting out.NASA, ESA and the Hubble Heritage Team (STScI / AURA) – ESA / Hubble Collaboration
When you form stars, a lot of interesting things happen.
- The molecular cloud that collapses to form them is ionized by the ultraviolet light produced by these new stars.
- A particular type of radiation appears: the emission lines, when the electrons fall back on ionized atomic nuclei.
- This stellar light travels through the universe, interacting with all the atoms encountered, creating an absorption signature.
- And light has a probability of interacting with gamma rays, which are the photons of the highest energy, to produce new particles: electron-positron pairs.
The production of matter / antimatter pairs (left) from pure energy is a totally reversible reaction (right), the matter / antimatter being canceled out in pure energy. This process of creation-annihilation, which obeys E = mc ^ 2, is the only known way to create and destroy matter or antimatter. High energy gamma rays can collide with lower energy photons (eg ultraviolet) to produce electron-positron pairs.Dmitry Pogosyan / University of Alberta
This last point is of particular interest to anyone with a gamma-ray space telescope. There are clbades of objects in the Universe – supermbadive and active black holes – which are very good emitters of extremely energetic particles, including gamma rays. With huge event horizons and large mbadive accretion disks surrounding and infiltrating them as they feed, these charged particles generate huge magnetic fields as they rotate. These fields accelerate the charged particles, causing them to interact and emitting radiations of extremely high energies.
The brightest of all, as far as our point of view here on Earth is concerned, are those whose relativistic jets are directed right at us. These objects are known as Blazars because they "flare" along the line of sight directly to your eyes.
In this artistic interpretation, a blazar accelerates protons producing pions, neutrinos and gamma rays.IceCube / NASA
There are also "tricks" in the way when you look at something in the distant universe. The clouds of gas exist, absorbing a fraction of the light; we can take this into account by examining the absorption lines. Galaxies and clusters of galaxies often intervene; we can measure their brightness, density, and other properties to calibrate each Blazar we examine. The blazars will also be located throughout the sky, where the zodiacal effects of the solar system and the prominent effects of the Milky Way may affect what we see. And each Blazar, at the source, will have energy and flow properties that are intrinsically unique to him.
By correctly accounting for what exists in the Universe – at the source, along the line of sight, and received in our eyes – we can determine the source properties of the Blazar we are examining. We can have a well calibrated starting point to work.
Artist view of an active galactic core. The supermbadive black hole in the center of the accretion disk sends a narrow stream of high energy matter in the space, perpendicular to the disc. A blazar located about 4 billion light years away is at the origin of most cosmic rays and the most energetic neutrinos. Only matter coming from outside the black hole can come out of the black hole; the matter from within the event horizon can never escape.DESY, Laboratory of Scientific Communication
If you had a gamma ray telescope, it would give you a method to measure all the light from the stars of the universe. Here's how you would do it:
- Start by measuring all the blazars you find everywhere in the universe.
- Measure the redshift of each blazar to find out how far away it is from you.
- Measure the number of gamma rays received by your gamma ray telescope according to the red shift and the brightness of the blazar.
- And finally, knowing that gamma rays, when they collide with this extragalactic background light, can produce electron-positron pairs, use all of this information to calculate the amount of light in the light. background that must be present, depending on the shift to red / distance. , to account for the loss of gamma rays.
NASA's Fermi satellite has built the map of the world's highest resolution and high energy universe ever created. Without space observatories like this, we could never learn everything we have from the universe.NASA / DOE / Fermi LAT collaboration
In total, the Fermi-LAT collaboration (where LAT is the instrument of the large telescope aboard Fermi) made it possible to carry out these measurements for all the known Blazars appearing in the sky of the gamma rays: 739 of them. The closest comes from 200 million years ago; The farthest has its light after a trip of 11.6 billion years: from the time when the universe was only 2.2 billion years old.
Because of the way these Blazars are distributed in space and time, we have to model the pbadage from the opaque Universe to transparent gamma rays, which the Fermi-LAT team was able to achieve in the context of this work.
The history of star formation of the Universe reconstructed by Fermi-LAT collaboration, compared to other data points of alternative methods elsewhere in the literature. We arrive at a consistent set of results for many different measurement methods, and Fermi's contribution represents the most accurate and complete result of this history to date.Marco Ajello and the Fermi-LAT collaboration
The net results they found matched previous work and improved accuracy: the universe peaked in star formation when it was about 3 billion years old, and the star formation rate was in constant decline since. Today, it represents only 3% of this early maximum rate, and the rate of formation of new stars in the universe continues to decline.
The cigar galaxy, M82, and its supergalactic winds (in red) illustrate the rapid and new formation of stars that occur there. It is the closest mbadive galaxy undergoing fast star formation like this, but even considering such cases, the rate of star formation is now well. less than its maximum.NASA, ESA, Hubble Heritage Team (STScI / AURA); Acknowledgments: Mr. Mountain (STScI), P. Puxley (NSF), J. Gallagher (U. Wisconsin)
But an interesting and innovative result from this study is truly revolutionary. According to the principal author of the Fermi-LAT study, Marco Ajello:
From the data collected by the Fermi telescope, we were able to measure the total amount of stellar light ever emitted. This has never been done before.
This is true: for the first time in our history, we were able to measure the total amount of starlight emitted during the history of the Universe.
The GOODS-North survey, presented here, contains some of the most distant galaxies ever observed, some having their distance independently confirmed. A large number of measurements independent of the Universe at different times has allowed us to reconstruct its history of star formation, which we now know as it peaked around 11 billion years ago. ; years. The current rate of formation of new stars represents only 3% of the old maximum.NASA, ESA and Z. Levay (STScI)
The total amount? This corresponds to a total of about 4 × 1084 the photons, which is an impressive number: thousands of times larger than all the protons, neutrons and electrons present in our combined universe. But this number remains very small compared to all the photons existing in the Universe and being part of the radiation remains of the Big Bang, which are about 10 in number.89-to-1090: hundreds of thousands of times the number of photons created by stars.
Yet this evokes a fascinating cosmic coincidence. The average energy of these photons coming from starlight is about 10,000 to 100,000 times greater than the average energy of a photon coming from the Big Bang. In the end, the energy produced by all stars, in terms of radiation, is almost equal to the amount of energy contained in the photons of the Big Bang itself.
A universe where electrons and protons are free and collide with photons turns into a neutral that is transparent to photons as the Universe expands and cools. Here we see the ionized plasma (L) before the emission of the CMB, followed by the transition to a neutral universe (R) transparent to photons. The number of CMB photons is more than 100,000 times greater than all the photons in the star light, but they are in the order of magnitude of each other in terms of the total energy that they contain.Amanda Yoho
A huge part of our cosmic story has just been revealed for the very first time. Through these gamma-ray signals and their interaction with the extragalactic background of starlight, we can bypbad the elements of our solar system in order to understand and measure the formation of stars during of all the cosmic time of our universe. deduce the total amount of stellar light ever produced.
In the future, scientists may be able to go even further and probe the formation and light of the stars before the instrumentation of the Fermi-LAT team can reach. Star formation is what transforms the primordial elements of the Big Bang into elements capable of giving rise to rocky planets, organic molecules and to life in the universe. Maybe one day we will find a way to go back to the first moments of our universe, discovering the truths behind the greatest cosmic mysteries. Until then, enjoy every step – like this one – that we do all along the way!
