This is an artist’s concept of a galaxy with a bright quasar star at its center. Quasars are very bright, distant, active supermassive black holes with masses of millions to billions of times the mass of the sun. Among the brightest things in the universe, the light of a quasar is superior to all the stars in its parent galaxy combined. Quasars feed on fallen matter and release jets of wind and radiation, forming the galaxies in which they live. Using Webb’s unique abilities, scientists will study the six most distant and brightest quasars in the universe. Credits: NASA, ESA, and J. Olmsted (STScI)
–Quasars outperform all the stars in their parent galaxy combined, and are among the brightest in the universe. These bright, distant, active supermassive black holes form the galaxies in which they live. Immediately after launch, scientists will use Webb to study the six brightest and most distant quasars, along with their parent galaxies, in the very young universe. They will examine the role quasars played in the evolution of these early galaxies. The team will also use quasars to study gases in intergalactic space in the infant universe. Only with Webb’s extreme sensitivity to low light levels and incredible angular resolution will this be possible.
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Quasars are very bright, distant, active black holes with masses of millions to billions of times the mass of the Sun. Usually located in the center of galaxies, they feed on fallen matter and release fantastic streams of radiation. Among the brightest things in the universe, the light of a quasar collectively illuminates all the stars in its parent galaxy, and its rays and winds make up the galaxy it belongs to.
Shortly after launch later this year, a team of scientists will train NASA’s James Webb Space Telescope on the six most distant and brightest quasars. They will study the properties of these quasars and their host galaxies, and how they related to each other during the early stages of galactic evolution in the very early universe. The team will also use quasars to examine gas in intergalactic space, particularly during the cosmic reionization period, which ended when the universe was very young. They will achieve this with Webb’s extreme sensitivity for low light levels and impressive angular resolution.
(Click on the image to view the full diagram.) More than 13 billion years ago, during the era of reionization, the universe was a completely different place. Intergalactic gas is too opaque for energetic light, making young galaxies difficult to observe. What allowed the universe to become completely ionized, or transparent, eventually leading to the “clear” state detected in most of the universe today? The James Webb Space Telescope will dig deep into space to gather more information about things that existed during the reionization era to help us understand this major change in the history of the universe. Credits: NASA, ESA, and J.Kang (STScI)
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Webb: Visiting the Young Universe
When Webb looks into the depths of the universe, he is actually looking into the past. The light from this distant quasar began its journey to the Webb when the universe was very young and took billions of years to reach. We will see things as they used to be, not as they are now.
“All the quasars we studied existed very early, when the universe was less than 800 million years old, or less than 6 percent of its current age. So these observations give us an opportunity to study the evolution of galaxies and their formation. the evolution of these early supermassive black holes. That’s a lot,” explains team member Santiago Arribas, Research Professor in the Department of Astrophysics at the Center for Astrobiology in Madrid, Spain. Arribas is also a member of Webb’s Near Infrared Spectrograph (NIRSpec) Instrument Science Team.
(Click on the image to view the full diagram.) The universe is expanding, and this expansion stretches light across space in a phenomenon known as cosmic redshift. The greater the redshift, the greater the distance traveled by the light. As a result, telescopes equipped with infrared detectors are needed to see light from the first and most distant galaxies. Credits: NASA, ESA, and L. Hustak (STSci)
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The light from this very distant object has been stretched due to the expansion of space. This is known as the cosmic redshift. The further away the light is, the greater the redshift. In fact, visible light from the early universe stretched out in such a way that it turned into infrared radiation when it reached us. With a variety of instruments tuned in infrared, Webb is uniquely suited to studying this type of light.
The study of quasars, their galaxies, their host environment, and their strong currents
The quasars the team will study are not only among the most distant in the universe, but also among the brightest. These quasars usually have the highest black hole mass, and they also have the highest accretion rate – the rate at which material falls into the black hole.
“We were interested in observing the brightest quasars because the extremely high amount of energy they generate in their cores should lead to the greatest impact on the host galaxy through mechanisms such as quasar flow and heating,” said Chris. Willott, a research scientist at the Herzberg Astronomy and Astrophysics Research Center of Canada’s National Research Council (NRC) in Victoria, British Columbia. Willott is also CSA’s Webb Project Scientist. “We wanted to observe these quasars at a time when they had the greatest impact on the host galaxy.”
A large amount of energy is released when matter is accumulated by a supermassive black hole. This energy heats up and pushes the surrounding gas outward, producing a powerful outflow that tore apart interstellar space like a tsunami, causing chaos in the host galaxy.
Watch how emissions and winds from supermassive black holes affect their host galaxy – and space hundreds of thousands of light years away for millions of years. Credits: NASA, ESA, and L. Hustak (STScI)
Outflows played an important role in the evolution of galaxies. Gas triggers star formation, so when gas is ejected due to outflow, the rate of star formation decreases. In some cases, the outflow is so strong that it emits large amounts of gas that can completely stop star formation within the parent galaxy. Scientists also believe that outflow is the primary mechanism by which gas, dust and elements are redistributed over great distances within galaxies or perhaps even ejected into intergalactic space – the intergalactic medium. This can trigger fundamental changes in the properties of the parent galaxy and the intergalactic medium.
Examining the properties of intergalactic space during the reionization era
More than 13 billion years ago, when the universe was very young, the scene was far from clear. Neutral gas between galaxies has made the universe opaque for some types of light. Over hundreds of millions of years, the neutral gas in the intergalactic medium has become charged or ionized, making it transparent to ultraviolet light. This period is called the reionization era. But what caused the reionization that creates the “clear” conditions detected in most of the universe today? Webb will investigate space to gather more information about this major transformation in the history of the universe. Observations will help us understand the era of reionization, one of the main frontiers in astrophysics.
The team will use the quasar as a backlight source to study the gas between us and the quasar. This gas absorbs quasar light at certain wavelengths. Through a technique called imaging spectroscopy, they will look for absorption lines in the interfering gas. And the brighter the quasar, the stronger the absorption line features in the spectrum. By determining whether a gas is neutral or ionized, scientists will study how neutral the universe is and how much of this reionization process occurs at any given point in time.
The James Webb Space Telescope will use an innovative instrument called the Integrated Field Unit (IFU) to capture both the image and the spectrum simultaneously. This video provides a basic overview of how IFU works. Credits: NASA, ESA, CSA, and L. Hustak (STScI)
“If you want to study the universe, you need a very bright background source. Quasars are perfect objects in the distant universe, because they are quite luminous,” said team member Camilla Pacifici, who is affiliated with the Canadian Space Agency but works as an instrument scientist at the Space Telescope Science Institute. So we can see it very well. In Baltimore, “We want to study the early universe because the universe evolved, and we want to know how it started.”
The team will analyze the light coming from the quasar using NIRSpec to look for what astronomers call “metals,” elements heavier than hydrogen and helium. These elements formed in the first stars and the first galaxies and were ejected by the outflow. The gas moves out of the galaxy in which it was originally located and into the intergalactic medium. The team plans to measure these first-generation “metals,” as well as the way they were pushed into the intergalactic medium by these early outflows.
The power of the web
The Webb is a very sensitive telescope capable of detecting very low levels of light. This is important, because even though the quasar is intrinsically very bright, what the team will observe is one of the most distant objects in the universe. In fact, they were so far apart that the signal Webb would receive was very, very low. Only with Webb’s extraordinary sensitivity can this knowledge be attained. Webb also provides excellent angular resolution, which makes it possible to separate the quasar’s light from its host galaxy.
The quasar program described here is Guaranteed time record involving the spectral capabilities of NIRSpec.
The James Webb Space Telescope will become the world’s premier space science observatory when it launches in 2021. Webb will solve the mysteries of our solar system, look beyond distant worlds around other stars, and investigate the mysterious structure and origins of the universe and our place. Inside that. Webb is an international program led by NASA with partners ESA (European Space Agency) and the Canadian Space Agency.
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