12.01.2024
NASA’s Webb Discovers Dusty ‘Cat’s Tail’ in Beta Pictoris System
Beta Pictoris, a young planetary system located just 63 light-years away, continues to intrigue scientists even after decades of in-depth study. It possesses the first dust disk imaged around another star — a disk of debris produced by collisions between asteroids, comets, and planetesimals. Observations from NASA’s Hubble Space Telescope revealed a second debris disk in this system, inclined with respect to the outer disk, which was seen first. Now, a team of astronomers using NASA’s James Webb Space Telescope to image the Beta Pictoris system (Beta Pic) has discovered a new, previously unseen structure.
The team, led by Isabel Rebollido of the Astrobiology Center in Spain, used Webb’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) to investigate the composition of Beta Pic’s previously detected main and secondary debris disks. The results exceeded their expectations, revealing a sharply inclined branch of dust, shaped like a cat’s tail, that extends from the southwest portion of the secondary debris disk.
“Beta Pictoris is the debris disk that has it all: It has a really bright, close star that we can study very well, and a complex cirumstellar environment with a multi-component disk, exocomets, and two imaged exoplanets,” said Rebollido, lead author of the study. “While there have been previous observations from the ground in this wavelength range, they did not have the sensitivity and the spatial resolution that we now have with Webb, so they didn’t detect this feature.”
A Star’s Portrait Improved with Webb
Even with Webb or JWST, peering at Beta Pic in the right wavelength range — in this case, the mid-infrared — was crucial to detect the cat’s tail, as it only appeared in the MIRI data. Webb’s mid-infrared data also revealed differences in temperature between Beta Pic’s two disks, which likely is due to differences in composition.
“We didn’t expect Webb to reveal that there are two different types of material around Beta Pic, but MIRI clearly showed us that the material of the secondary disk and cat’s tail is hotter than the main disk,” said Christopher Stark, a co-author of the study at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The dust that forms that disk and tail must be very dark, so we don’t easily see it at visible wavelengths — but in the mid-infrared, it’s glowing.”
To explain the hotter temperature, the team deduced that the dust may be highly porous “organic refractory material,” similar to the matter found on the surfaces of comets and asteroids in our solar system. For example, a preliminary analysis of material sampled from asteroid Bennu by NASA’s OSIRIS-REx mission found it to be very dark and carbon-rich, much like what MIRI detected at Beta Pic.
Image: Annotated Image
The Tail’s Puzzling Beginning Warrants Future Research
However, a major lingering question remains: What could explain the shape of the cat’s tail, a uniquely curved feature unlike what is seen in disks around other stars?
Rebollido and the team modeled various scenarios in an attempt to emulate the cat’s tail and unravel its origins. Though further research and testing is required, the team presents a strong hypothesis that the cat’s tail is the result of a dust production event that occurred a mere one hundred years ago.
“Something happens — like a collision — and a lot of dust is produced,” shared Marshall Perrin, a co-author of the study at the Space Telescope Science Institute in Baltimore, Maryland. “At first, the dust goes in the same orbital direction as its source, but then it also starts to spread out. The light from the star pushes the smallest, fluffiest dust particles away from the star faster, while the bigger grains do not move as much, creating a long tendril of dust.”
“The cat’s tail feature is highly unusual, and reproducing the curvature with a dynamical model was difficult,” explained Stark. “Our model requires dust that can be pushed out of the system extremely rapidly, which again suggests it’s made of organic refractory material.”
The team’s preferred model explains the sharp angle of the tail away from the disk as a simple optical illusion. Our perspective combined with the curved shape of the tail creates the observed angle of the tail, while in fact, the arc of material is only departing from the disk at a five-degree incline. Taking into consideration the tail’s brightness, the team estimates the amount of dust within the cat’s tail to be equivalent to a large main belt asteroid spread out across 10 billion miles.
A recent dust production event within Beta Pic’s debris disks could also explain a newly-seen asymmetric extension of the inclined inner disk, as shown in the MIRI data and seen only on the side opposite of the tail. Recent collisional dust production could also account for a feature previously spotted by the Atacama Large Millimeter/submillimeter Array in 2014: a clump of carbon monoxide (CO) located near the cat’s tail. Since the star’s radiation should break down CO within roughly one hundred years, this still-present concentration of gas could be lingering evidence of the same event.
“Our research suggests that Beta Pic may be even more active and chaotic than we had previously thought,” said Stark. “JWST continues to surprise us, even when looking at the most well-studied objects. We have a completely new window into these planetary systems.”
These results were presented in a press conference at the 243rd meeting of the American Astronomical Society in New Orleans, Louisiana.
The observations were taken as part of Guaranteed Time Observation program 1411.
Quelle: NASA
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Update: 19.01.2024
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James Webb Space Telescope discovers oldest and most distant black hole ever seen
The ravenous black hole that existed just 400 million years after the Big Bang could help explain how supermassive black holes grew so rapidly.
The galaxy GN-z11 as seen by the Hubble space telescope and an illustration of a feeding black hole (inset).(Image credit: NMASA, ESA, P. Oesch (Yale University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz) (Inset) Robert Lea )
A team of astronomers has used the James Webb Space Telescope (JWST) to discover the most distant and oldest black hole ever seen as it feasts upon its host galaxy.
The discovery could be a massive step forward in understanding how supermassive black holes reached masses equivalent to millions of billions of times that of the sun in the very early epochs of the universe.
The black hole dwells in the ancient galaxy GN-z11, which is 13.4 billion light years away and is thus seen as it was just 400 million years after the Big Bang. The black hole itself is around 6 million times as massive as the sun and seems to be feeding on matter from its surrounding galaxy five times more rapidly than the limit suggested is sustainable by current theories.
University of Cambridge Department of Physics and team leader Roberto Maiolino described the discovery as "a giant leap forward" for black hole science in a statement.
"It's very early in the universe to see a black hole this massive, so we've got to consider other ways they might form," Maiolino said in the statement. "Very early galaxies were extremely gas-rich, so they would have been like a buffet for black holes."
Are supermassive black holes overeaters?
The size of early supermassive black holes that formed when the universe was less than 1 billion years old is a problem for formation theories because reaching a mass of millions or billions of times that of the sun should take billions of years of constant feeding.
"It's like seeing a family walking down the street, and they have two six-foot teenagers, but they also have with them a six-foot tall toddler," Maynooth University research fellow John Reagan, who was not involved in this research, told Space.com in reference in to previous discovery. "That's a bit of a problem; how did the toddler get so tall? And it's the same for supermassive black holes in the universe. How did they get so massive so quickly?"
Scientists currently have two main routes that black holes could take to reach supermassive status in the early universe. They could start out as small black hole seeds that are created when massive stars collapse at the end of their lives and after millions or billions of years, or they could skip this stage entirely.
This could possibly occur if vast clouds of cold gas and dust collapse to immediately form a "heavy black hole seed" with a mass a few million times that of the sun. That way, the process gets to fast forward through millions or billions of years of stellar evolution, getting a headstart on the feeding and merger processes that help black hole seeds grow to supermassive black holes. The discovery of this new ancient black hole with a mass a few million times that of the sun favors that heavy seed theory.
The Event Horizon Telescope, a planet-scale array of eight ground-based radio telescopes forged through international collaboration, captured this image of the supermassive black hole in the center of the galaxy M87 and its shadow. (Image credit: EHT Collaboration)
Yet, on the flip side of this, the rate at which the black hole in GN-z11 is accreting matter could suggest that black holes may be capable of feeding much faster than other black holes discovered in the early universe have been observed to do so. This would be a leg up for small black hole seed theories.
A mathematical formula known as the Eddington limit marks how fast a body, like a star, can accumulate mass without the radiation it emits (its luminosity) pushing that mass away and thus cutting off that food supply.
While black holes don't emit light because they are bounded by a light-trapping boundary called an event horizon, their massive gravitational influence does cause the material that swirls around them to be violently churned and heated, emitting radiation in the process. The more rapidly a black hole feeds, the more intense the light from that region, called an active galactic nucleus (AGN), is.
Thus, the Eddington limit applies to this region, and it can similarly act to push material away and cut off a black hole's feeding frenzy.
This newly discovered black hole is accreting matter from its host galaxy at a rate five times higher than the Eddington limit. Periods of so-called "super-Eddington accretion" can occur but do so in limited bouts.
The team estimated that if this period of voracious feeding for this black hole had been proceeding for 100 million years, it might not have had to start life as a heavy black hole seed. It could have formed from a much lighter stellar-mass black hole seed between around 250 million and 370 million years after the Big Bang and rapidly grown to the mass it is as the JWST observes it 13.4 million years ago.
Feeding black hole may doom its host galaxy
One thing the team is fairly certain of is the intense feeding of this black hole is responsible for GN-z11 itself, which is around 100 times smaller than the Milky Way and highly luminous. But the gluttonous black hole is also likely to stunt the growth of its host galaxy.
Ultrafast winds of particles belched out from around the feeding black hole are likely to be pushing away gas and dust from the galaxy's heart. Cold clouds of gas and dust collapse to birth stars, so this means that the black hole is grinding stellar birth to a halt, in the process "killing" the growth of this small galaxy.
As well as learning more about this black hole and its galaxy, the team behind this research believes that the power of the JWST should help uncover more black holes in the early universe.
In particular, they are aiming to discover small black hole seeds in the infancy of the cosmos and put to bed the debate surrounding the premature growth of supermassive black holes.
"It's a new era: The giant leap in sensitivity, especially in the infrared, is like upgrading from Galileo's telescope to a modern telescope overnight," Maiolino concluded. "Before the JWST came online, I thought maybe the universe isn't so interesting when you go beyond what we could see with the Hubble Space Telescope. But that hasn't been the case at all: The universe has been quite generous in what it's showing us, and this is just the beginning."
The team's research was published on Wednesday, Jan. 17, in the journal Nature.
Quelle: SC