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Astronomers are using NASA’s James Webb Space Telescope to peer deeper into the universe and farther back in time than ever before.
Already, the team has discovered hundreds of galaxies that existed when the universe was less than 600 million years old—just 4% of its current age.
The Webb Telescope, or JWST, also has observed galaxies sparkling with a multitude of young, hot stars formed during what researchers call “surprisingly episodic bursts of star formation.”
They made the observations as part of the JWST Advanced Deep Extragalactic Survey, or JADES, which is dedicated to uncovering and studying extremely faint, distant galaxies. Thirty-two days of observing time have been devoted to JADES, which is one of the largest observing programs in Webb’s first year of science.
The key to JWST’s ability to sniff out the extremely faint signatures of distant objects is its large, light-gathering mirror and infrared sensitivity.
“With JADES, we want to answer questions such as, ‘How did the earliest galaxies assemble themselves? How fast did they form stars? Why do some galaxies stop forming stars?'” says Marcia Rieke, a professor of astronomy at the University of Arizona Steward Observatory and a co-lead of the JADES program.
During his doctoral research at Steward Observatory, JADES team member Ryan Endsley, who is now a postdoctoral fellow at the University of Texas at Austin, led an investigation into galaxies that existed 500 to 850 million years after the Big Bang, a crucial time known as the “Epoch of Reionization.”
“Star formation in the early universe is much more complicated than we thought.”
For hundreds of millions of years, the young universe was filled with a gaseous fog that made it opaque to energetic light such as ultraviolet light or X-rays. About 1 billion years after the Big Bang, the fog had cleared and the universe became transparent during a process known as reionization.
Scientists have debated whether active, supermassive black holes or galaxies full of hot, young stars were the primary cause of reionization. As part of the JADES program, Endsley and his colleagues studied these galaxies specifically to look for signatures of star formation—and found them in abundance.
“Almost every single galaxy that we are finding shows these unusually strong emission line signatures indicating intense recent star formation,” Endsley says. “These early galaxies were very good at creating hot, massive stars.”
These bright, massive stars pumped out torrents of ultraviolet light, which transformed surrounding gas from opaque to transparent by ionizing atoms, unbinding their electrons from the nuclei. Since these early galaxies had such a large population of hot, massive stars, they may have been the main driver of the reionization process. The later reuniting of the electrons and nuclei produces the distinctively strong emission lines.
Endsley and his colleagues also found evidence that these young galaxies underwent periods of rapid star formation interspersed with quiet periods during which fewer stars formed. These fits and starts may have occurred as galaxies captured clumps of the gaseous raw materials needed to form stars. Alternatively, since massive stars are short-lived before they explode, they may have injected energy into the surrounding environment periodically, preventing gas from condensing to form new stars.
Another element of the JADES program involves the search for the earliest galaxies that existed when the universe was less than 400 million years old. By studying these galaxies, astronomers can explore how star formation in the early years after the Big Bang was different from today. The light from faraway galaxies is stretched to longer wavelengths and redder colors by the expansion of the universe—a phenomenon called redshift. By measuring a galaxy’s redshift, astronomers can learn how far away it is and, therefore, at what time it existed in the early universe.
“Before JWST, there were only a few dozen galaxies observed above a redshift of 8, when the universe was younger than 650 million years old, but JADES is now uncovering nearly a thousand of these extremely distant galaxies,” Rieke says.
The JADES team identified more than 700 candidate galaxies above redshift 8, which will completely overhaul astronomers’ understanding of early galaxy formation. The sheer number of these sources far exceeded predictions based on observations made before the launch of JWST. Webb’s fine resolution and sensitivity allow astronomers to get an unprecedented view of these distant galaxies.
“Previously, the earliest galaxies we could see just looked like little smudges,” says JADES team member Kevin Hainline, an assistant research professor at Steward Observatory. “And yet those smudges represent millions, or even billions, of stars at the beginning of the universe. Now, we can see, incredibly, that some of them are actually groupings of stars being born only a few hundred million years after the beginning of time.”
“What all this tells us,” Rieke says, “is that star formation in the early universe is much more complicated than we thought.”
The team presented their latest observations at the 242nd meeting of the American Astronomical Society in Albuquerque, New Mexico.
Source: University of Arizona
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Mitchell (right) at the 2007 FAMB convention with former Twin Galaxies referee Todd Rogers and what appears to be a Donkey Kong cabinet with a modified joystick. (credit: David Race)
Over the years, King of Kong star Billy Mitchell has seen his world-record Donkey Kong scores stripped, partially reinstated, and endlessly litigated, both in actual court and the court of public opinion. Through it all, Mitchell has insisted that every one of his records was set on unmodified Donkey Kong arcade hardware, despite some convincing technical evidence to the contrary.
Now, new photos from a 2007 performance by Mitchell seem to show obvious modifications to the machine used to earn at least one of those scores, a fascinating new piece of evidence in the long, contentious battle over Mitchell's place in Donkey Kong score-chasing history.
The photos in question were taken at the Florida Association of Mortgage Brokers (FAMB) Convention, which hosted Mitchell as part of its "80s Arcade Night" promotion in July 2007. Mitchell claims to have achieved a score of 1,050,200 points at that event, a performance that was recognized by adjudicator Twin Galaxies as a world record at the time (but which by now would barely crack the top 30).
Astronomers suggest more galaxies formed in the early universe than previously thought.
In their new study, the researchers discovered 87 galaxies that could be the earliest known galaxies in the universe.
“…we might need to revise our previous understanding of galaxy formation.”
The finding gets the astronomers one step closer to finding out when galaxies first appeared in the universe—about 200-400 million years after the Big Bang, says Haojing Yan, associate professor of physics and astronomy at the University of Missouri and lead author of the study.
The researchers used data from NASA’s James Webb Space Telescope (JWST) Early Release Observations.
“Finding such a large number of galaxies in the early parts of the universe suggests that we might need to revise our previous understanding of galaxy formation,” Yan says. “Our finding gives us the first indication that a lot of galaxies could have been formed in the universe much earlier than previously thought.”
In the study, the astronomers searched for potential galaxies at “very high redshifts.” Yan says the concept of redshifts in astronomy allows astronomers to measure how far away distant objects are in the universe—like galaxies—by looking at how the colors change in the waves of light that they emit.
“If a light-emitting source is moving toward us, the light is being ‘squeezed,’ and that shorter wavelength is represented by blue light, or blueshift,” Yan says. “But if that source [of light] is moving away from us, the light it produces is being ‘stretched,’ and changes to a longer wavelength that is represented by red light, or redshift.”
Yan says Edwin Hubble’s discovery in the late 1920s that our universe is ever-expanding is key to understanding how redshifts are used in astronomy.
“Hubble confirmed that galaxies external to our Milky Way galaxy are moving away from us, and the more distant they are, the faster they are moving away,” Yan says. “This relates to redshifts through the notion of distances—the higher the redshift an object is at, such as a galaxy, the further away it is from us.”
Therefore, Yan says the search for galaxies at very high redshifts gives astronomers a way to construct the early history of the universe.
“The speed of light is finite, so it takes time for light to travel over a distance to reach us,” Yan says. “For example, when we look at the sun, we aren’t looking at it what it looks like in the present, but rather what it looked like some eight minutes ago. That’s because that’s how long it takes for the sun’s radiation to reach us. So, when we are looking at galaxies which are very far away, we are looking at their images from a long time ago.”
Using this concept, Yan’s team analyzed the infrared light captured by the JWST to identify the galaxies.
“The higher the redshift a galaxy is at, the longer it takes for the light to reach us, so a higher redshift corresponds to an earlier view of the universe,” Yan says. “Therefore, by looking at galaxies at higher redshifts, we are getting earlier snapshots of what the universe looked like a long time ago.”
The JWST was critical to this discovery because objects in space like galaxies that are located at high redshifts—11 and above—can only be detected by infrared light, according to Yan. This is beyond what NASA’s Hubble Space Telescope can detect because the Hubble telescope only sees from ultraviolet to near-infrared light.
“JWST, the most powerful infrared telescope, has the sensitivity and resolution for the job,” Yan says. “Up until these first JWST data sets were released [in mid-July 2022], most astronomers believed that the universe should have very few galaxies beyond redshift 11. At the very least, our results challenge this view. I believe this discovery is just the tip of the iceberg because the data we used only focused on a very small area of the universe. After this, I anticipate that other teams of astronomers will find similar results elsewhere in the vast reaches of space as JWST continues to provide us with a new view of the deepest parts of our universe.”
The research appears in The Astrophysical Journal Letters. Additional coauthors are from the University of Missouri, University of Massachusetts-Amherst, and the Chinese Academy of Sciences South America Center for Astronomy and National Astronomical Observatories of China.
Source: University of Missouri
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Astronomers have captured a radio signal from a distant galaxy at a specific wavelength known as the 21 cm line.
With the help of the Giant Metrewave Radio Telescope in India, this is the first time this type of radio signal has been detected at such a large distance.
How do stars form in distant galaxies? Astronomers have long been trying to answer this question by detecting radio signals emitted by nearby galaxies. However, these signals become weaker the further away a galaxy is from Earth, making it difficult for current radio telescopes to pick up.
“A galaxy emits different kinds of radio signals. Until now, it’s only been possible to capture this particular signal from a galaxy nearby, limiting our knowledge to those galaxies closer to Earth,” says Arnab Chakraborty, a postdoctoral researcher at McGill University under the supervision of Matt Dobbs, a professor in the physics department.
“But thanks to the help of a naturally occurring phenomenon called gravitational lensing, we can capture a faint signal from a record-breaking distance. This will help us understand the composition of galaxies at much greater distances from Earth.”
“It’s the equivalent to a look-back in time of 8.8 billion years.”
For the first time, the researchers were able to detect the signal from a distant star-forming galaxy known as SDSSJ0826+5630 and measure its gas composition. The researchers observed the atomic mass of the gas content of this particular galaxy is almost twice the mass of the stars visible to us.
The signal the team detected was emitted from this galaxy when the universe was only 4.9 billion years old, allowing the researchers to glimpse into the secrets of the early universe.
“It’s the equivalent to a look-back in time of 8.8 billion years,” says Chakraborty.
“Gravitational lensing magnifies the signal coming from a distant object to help us peer into the early universe. In this specific case, the signal is bent by the presence of another massive body, another galaxy, between the target and the observer.
“This effectively results in the magnification of the signal by a factor of 30, allowing the telescope to pick it up,” says coauthor Nirupam Roy, an associate professor in the physics department at the Indian Institute of Science.
According to the researchers, these results demonstrate the feasibility of observing faraway galaxies in similar situations with gravitational lensing. It also opens exciting new opportunities for probing the cosmic evolution of stars and galaxies with existing low-frequency radio telescopes.
The study appears in the Monthly Notices of the Royal Astronomical Society.
The Giant Metrewave Radio Telescope was built and is operated by NCRA-TIFR. The research was funded by McGill University and the Indian Institute of Science.
Source: McGill University
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