When you are trying to solve one of the biggest conundrums in cosmology, you should triple check your homework. The puzzle, called the "Hubble Tension," is that the current rate of the expansion of the universe is faster than what astronomers expect it to be, based on the universe's initial conditions and our present understanding of the universe’s evolution.
13.02.2024
NASA’s Webb, Hubble Telescopes Affirm Universe’s Expansion Rate, Puzzle Persists
Scientists using NASA's Hubble Space Telescope and many other telescopes consistently find a number that does not match predictions based on observations from ESA's (European Space Agency's) Planck mission. Does resolving this discrepancy require new physics? Or is it a result of measurement errors between the two different methods used to determine the rate of expansion of space?
This image of NGC 5468, a galaxy located about 130 million light-years from Earth, combines data from the Hubble and James Webb space telescopes. This is the farthest galaxy in which Hubble has identified Cepheid variable stars. These are important milepost markers for measuring the expansion rate of the universe. The distance calculated from Cepheids has been cross-correlated with a type Ia supernova in the galaxy. Type Ia supernovae are so bright they are used to measure cosmic distances far beyond the range of the Cepheids, extending measurements of the universe's expansion rate deeper into space.
Hubble has been measuring the current rate of the universe’s expansion for 30 years, and astronomers want to eliminate any lingering doubt about its accuracy. Now, Hubble and NASA’s James Webb Space Telescope have tag-teamed to produce definitive measurements, furthering the case that something else – not measurement errors – is influencing the expansion rate.
“With measurement errors negated, what remains is the real and exciting possibility we have misunderstood the universe,” said Adam Riess, a physicist at Johns Hopkins University in Baltimore. Riess holds a Nobel Prize for co-discovering the fact that the universe’s expansion is accelerating, due to a mysterious phenomenon now called “dark energy.”
As a crosscheck, an initial Webb observation in 2023 confirmed that Hubble measurements of the expanding universe were accurate. However, hoping to relieve the Hubble Tension, some scientists speculated that unseen errors in the measurement may grow and become visible as we look deeper into the universe. In particular, stellar crowding could affect brightness measurements of more distant stars in a systematic way.
The SH0ES (Supernova H0 for the Equation of State of Dark Energy) team, led by Riess, obtained additional observations with Webb of objects that are critical cosmic milepost markers, known as Cepheid variable stars, which now can be correlated with the Hubble data.
“We’ve now spanned the whole range of what Hubble observed, and we can rule out a measurement error as the cause of the Hubble Tension with very high confidence,” Riess said.
The team’s first few Webb observations in 2023 were successful in showing Hubble was on the right track in firmly establishing the fidelity of the first rungs of the so-called cosmic distance ladder.
Astronomers use various methods to measure relative distances in the universe, depending upon the object being observed. Collectively these techniques are known as the cosmic distance ladder – each rung or measurement technique relies upon the previous step for calibration.
But some astronomers suggested that, moving outward along the “second rung,” the cosmic distance ladder might get shaky if the Cepheid measurements become less accurate with distance. Such inaccuracies could occur because the light of a Cepheid could blend with that of an adjacent star – an effect that could become more pronounced with distance as stars crowd together and become harder to distinguish from one another.
The observational challenge is that past Hubble images of these more distant Cepheid variables look more huddled and overlapping with neighboring stars at ever farther distances between us and their host galaxies, requiring careful accounting for this effect. Intervening dust further complicates the certainty of the measurements in visible light. Webb slices though the dust and naturally isolates the Cepheids from neighboring stars because its vision is sharper than Hubble’s at infrared wavelengths.
At the center of these side-by-side images is a special class of star used as a milepost marker for measuring the universe’s rate of expansion – a Cepheid variable star. The two images are very pixelated because they are a very zoomed-in view of a distant galaxy. Each of the pixels represents one or more stars. The image from the James Webb Space Telescope is significantly sharper at near-infrared wavelengths than Hubble (which is primarily a visible-ultraviolet light telescope). By reducing the clutter with Webb’s crisper vision, the Cepheid stands out more clearly, eliminating any potential confusion. Webb was used to look at a sample of Cepheids and confirmed the accuracy of the previous Hubble observations that are fundamental to precisely measuring the universe’s expansion rate and age.
NASA, ESA, CSA, STScI, Adam G. Riess (JHU, STScI
“Combining Webb and Hubble gives us the best of both worlds. We find that the Hubble measurements remain reliable as we climb farther along the cosmic distance ladder,” said Riess.
The new Webb observations include five host galaxies of eight Type Ia supernovae containing a total of 1,000 Cepheids, and reach out to the farthest galaxy where Cepheids have been well measured – NGC 5468 – at a distance of 130 million light-years. “This spans the full range where we made measurements with Hubble. So, we've gone to the end of the second rung of the cosmic distance ladder,” said co-author Gagandeep Anand of the Space Telescope Science Institute in Baltimore, which operates the Webb and Hubble telescopes for NASA.
Hubble and Webb’s further confirmation of the Hubble Tension sets up other observatories to possibly settle the mystery. NASA’s upcoming Nancy Grace Roman Space Telescope will do wide celestial surveys to study the influence of dark energy, the mysterious energy that is causing the expansion of the universe to accelerate. ESA's Euclid observatory, with NASA contributions, is pursuing a similar task.
At present it’s as though the distance ladder observed by Hubble and Webb has firmly set an anchor point on one shoreline of a river, and the afterglow of the big bang observed by Planck’s measurement from the beginning of the universe is set firmly on the other side. How the universe’s expansion was changing in the billions of years between these two endpoints has yet to be directly observed. “We need to find out if we are missing something on how to connect the beginning of the universe and the present day,” said Riess.
These finding were published in the February 6, 2024 issue of The Astrophysical Journal Letters.
The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. Goddard also conducts mission operations with Lockheed Martin Space in Denver, Colorado. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble and Webb science operations for NASA.
The James Webb Space Telescope is the world's premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
Quelle: NASA
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Update: 14.03.2024
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JWST reveals a massive and ancient galaxy that challenges our models of the young Universe
Galaxies and stars developed faster after the Big Bang than expected
Detailed pictures of one of the very first galaxies show growth was much faster than we thought
JWST shows details of massive galaxy merger 13 billion years ago (insert of another early galaxy shows how significant the new JWST images are)
An international research team have made unprecedentedly detailed observations of the earliest merger of galaxies ever witnessed. They suggest stars developed much faster and more efficiently than we thought.
They used the James Webb Space Telescope (JWST) to observe the massive object as it was 510 million years after the Big Bang – i.e. around 13 billion years ago.
“When we conducted these observations, this galaxy was ten times more massive than any other galaxy found that early in the Universe,” says Dr Kit Boyett, an ASTRO 3D Research Fellow on First Galaxies, from the University of Melbourne. He is lead author on a paper published today in Nature Astronomy. The paper has 27 authors from 19 institutions in Australia, Thailand, Italy, the USA, Japan, Denmark and China.
JWST, launched in 2021, is enabling astronomers to see the early Universe in ways that were previously impossible. Objects that appeared as single points of light through earlier telescopes such as the Hubble Space Telescope, are revealing their complexity.
“It is amazing to see the power of JWST to provide a detailed view of galaxies at the edge of the observable Universe and therefore back in time” says Prof. Michele Trenti, ASTRO 3D First Galaxies theme leader and University of Melbourne node leader. “This space observatory is transforming our understanding of early galaxy formation” adds Prof. Trenti.
The observations in the current paper show a galaxy consisting of several groups with two components in the main group and a long tail, suggesting an ongoing merger of two galaxies into a larger one. “The merger hasn’t finished yet. We can tell this by the fact we still see two components. The long tail is likely produced by some of the matter being cast aside during the merger. When two things merge, they sort of throw away some of the matter. So, this tells us that there’s a merger and this is the most distant merger ever seen,” says Dr Boyett.
This and other observations using the JWST is causing astrophysicists to adjust their modelling of the early years of the Universe.
“With James Webb we are seeing more objects in the early cosmos than we expect to see, and those objects are more massive than we thought as well,” says Dr Boyett. “Our cosmology isn’t necessarily wrong, but our understanding of how quickly galaxies formed probably is, because they are more massive than we ever believed could be possible.”
Dr Boyett’s team’s findings show these galaxies were able to accumulate mass so fast by merging.
But it is not only the size of the galaxies and the speed with which they grew that surprises Dr Boyett. His paper for the first time describes the population of stars that make up the merging galaxies – another detail made possible by JWST.
“When we compared our spectrum analysis with our imaging, we found two different things. The image told us the population of stars was young, but the spectroscopy spoke of stars that are quite old. But it turns out both are correct because we don’t have one population of stars but two,” Boyett says.
“The old population has been there for a long time and what we believe happens is the merger of the galaxies produces new stars and that’s what we’re seeing in the imaging – new stars on top of the old population.”
Most studies of these very distant objects show very young stars, but this is because the younger stars are brighter and so their light dominates the imaging data. The JWST, however, allows for such detailed observations the two populations can be distinguished.
“It’s the fact that the spectroscopy is so detailed, we can see the subtle features of the old stars that tell us actually there’s more there than you think,” says Dr Boyett.
“This is not all that surprising, we know that over the history of a universe there are peaks of new star formation for various reasons, and that results in multiple populations.
“But it’s the first time we’ve really seen them at this distance.”
The paper has significant implications for current modelling.
“Our simulations can produce an object similar to the one we observed, roughly at the same age of a universe, and roughly the same mass, however, it’s incredibly rare. So rare there’s only one of these in the whole model. The chance of us observing that with our observations, then suggest we either incredibly lucky or our simulations are wrong, and this sort of object is more common than we think,” says Dr Boyett.
“The thing we think we’re missing is that stars were forming much more efficiently and that may be what we need to change in our models.”
About ASTRO 3D
The ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) is a $40m Research Centre of Excellence funded by the Australian Research Council (ARC) and nine collaborating Australian universities – The Australian National University, The University of Sydney, The University of Melbourne, Swinburne University of Technology, The University of Western Australia, Curtin University, Macquarie University, The University of New South Wales, and Monash University.
Quelle: scienceinpublic
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Update: 15.03.2024
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Cheers! NASA’s Webb Finds Ethanol, Other Icy Ingredients for Worlds
What do margaritas, vinegar, and ant stings have in common? They contain chemical ingredients that NASA’s James Webb Space Telescope has identified surrounding two young protostars known as IRAS 2A and IRAS 23385. Although planets are not yet forming around those stars, these and other molecules detected there by Webb represent key ingredients for making potentially habitable worlds.
An international team of astronomers used Webb’s MIRI (Mid-Infrared Instrument) to identify a variety of icy compounds made up of complex organic molecules like ethanol (alcohol) and likely acetic acid (an ingredient in vinegar). This work builds on previous Webb detections of diverse ices in a cold, dark molecular cloud.
Image A: Parallel Field to Protostar IRAS 23385 (MIRI Image)
This image at a wavelength of 15 microns was taken by MIRI (the Mid-Infrared Instrument) on NASA’s James Webb Space Telescope, of a region near the protostar known as IRAS 23385. IRAS 23385 and IRAS 2A (not visible in this image) were targets for a recent research effort by an international team of astronomers that used Webb to discover that the key ingredients for making potentially habitable worlds are present in early-stage protostars, where planets have not yet formed.
NASA, ESA, CSA, W. Rocha (Leiden University)
“This finding contributes to one of the long-standing questions in astrochemistry,” said team leader Will Rocha of Leiden University in the Netherlands. “What is the origin of complex organic molecules, or COMs, in space? Are they made in the gas phase or in ices? The detection of COMs in ices suggests that solid-phase chemical reactions on the surfaces of cold dust grains can build complex kinds of molecules.”
As several COMs, including those detected in the solid phase in this research, were previously detected in the warm gas phase, it is now believed that they originate from the sublimation of ices. Sublimation is to change directly from a solid to a gas without becoming a liquid. Therefore, detecting COMs in ices makes astronomers hopeful about improved understanding of the origins of other, even larger molecules in space.
Scientists are also keen to explore to what extent these COMs are transported to planets at much later stages of protostellar evolution. COMs in cold ices are thought to be easier to transport from molecular clouds to planet-forming disks than warm, gaseous molecules. These icy COMs can therefore be incorporated into comets and asteroids, which in turn may collide with forming planets, delivering the ingredients for life to possibly flourish.
The science team also detected simpler molecules, including formic acid (which causes the burning sensation of an ant sting), methane, formaldehyde, and sulfur dioxide. Research suggests that sulfur-containing compounds like sulfur dioxide played an important role in driving metabolic reactions on the primitive Earth.
Image B: Complex Organic Molecules in IRAS 2A
NASA’s James Webb Space Telescope’s MIRI (Mid-Infrared Instrument) has identified a variety of complex organic molecules that are present in interstellar ices surrounding two protostars. These molecules, which are key ingredients for making potentially habitable worlds, include ethanol, formic acid, methane, and likely acetic acid, in the solid phase. The finding came from the study of two protostars, IRAS 2A and IRAS 23385, both of which are so young that they are not yet forming planets.
Illustration: NASA, ESA, CSA, L. Hustak (STScI). Science: W. Rocha (Leiden University).
Of particular interest is that one of the sources investigated, IRAS 2A, is characterized as a low-mass protostar. IRAS 2A may therefore be similar to the early stages of our own solar system. As such, the chemicals identified around this protostar may have been in the first stages of development of our solar system and later delivered to the primitive Earth.
“All of these molecules can become part of comets and asteroids and eventually new planetary systems when the icy material is transported inward to the planet-forming disk as the protostellar system evolves,” said Ewine van Dishoeck of Leiden University, one of the coordinators of the science program. “We look forward to following this astrochemical trail step-by-step with more Webb data in the coming years.”
These observations were made for the JOYS+ (James Webb Observations of Young ProtoStars) program. The team dedicated these results to team member Harold Linnartz, who unexpectedly passed away in December 2023, shortly after the acceptance of this paper.
Quelle: NASA
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Update: 1.04.2024
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Webb telescope takes its first images of forming planetary systems
The observations help astronomers refine their theories about the processes involved in planet formation and shed light on what our sun did when it was very young.
This artist's concept shows a young star surrounded by a dusty protoplanetary disk. The disk contains the raw material from which planets may form at some point.NASA/JPL-Caltech/R. Hurt (SSC/Caltech)
By taking advantage of the dust-penetrating capabilities of the James Webb Space Telescope's infrared instruments, designed and built in part by University of Arizona scientists, astronomers have obtained the first direct observations with the new space telescope of gas and dust feeding a nascent planetary system with raw material for planet formation.
How planets form from a roiling maelstrom of gas and dust swirling around a young star is one of astronomy's most active fields of research. Much of the action during the early stages of planet formation remains shrouded in mystery – quite literally, as telescopes have historically struggled to peer through the dense clouds of dust surrounding planetary systems when they are in their infancy.
A team led by Jarron Leisenring at the UArizona Steward Observatory has obtained the deepest look yet into such planetary nurseries.
By combining JWST's images with prior observations by the Hubble Space Telescope and the Atacama Large Millimeter Array, or ALMA, in Chile, the researchers were able to piece together previously unseen interactions between the planet-forming disk and the envelope of gas and dust surrounding the young stars. The team presents its findings in three papers accepted in The Astrophysical Journal and two others in preparation.
Nascent planetary systems, also known as protoplanetary disks, are important targets of astronomical observation because they offer glimpses into how our own solar system came to be 4.6 billion years ago. Protoplanetary disks form when a vast cloud of interstellar gas and dust condenses under the effect of gravity before collapsing into a swirling "pancake" of matter. At its center shines a young star – only a few million years old.
Superimposed on the protoplanetary disk around HL Tau with its gaps and rings are features (shown in orange) detected by the James Webb Space Telescope. They reveal material in the envelope around the star, some of which is falling onto the disk, as well as an opening formed by material flowing out of the system.Camryn Mullin et al.
As microscopic dust particles coalesce into larger grains that stick together to form pebbles, and pebbles pile up to become planetesimals – "seedlings" that ultimately grow into planets – a planetary system is born. On astronomical time scales, protoplanetary disks are very short-lived. Typically, after 10 million years – at most – the material dissipates, clearing out from the disk. How that happens is not fully understood.
In the most likely scenario, much of the disk's material gets accreted onto the star, some is blown away by stellar radiation and the rest goes into forming planets, asteroids and comets. Although protoplanetary disks have been observed in various levels of detail, it is still extremely difficult to make out any planets that may be forming within. Rather, researchers have relied on features such as gaps and rings to infer the presence of planets as they plow through the disk.
JWST made its most striking observations in a protoplanetary disk around HL Tauri, or HL Tau for short, a young, sun-like star in the Taurus star forming region, about 457 light-years from Earth. HL Tau is hidden in visible light behind a massive envelope of dust and gas and surrounded by a protoplanetary disk with multiple rings and gaps. ALMA images reveal the presence of several gaps in the disk, hinting at the possibility that several planets the size of Jupiter or smaller might be plowing through the disk material on their orbits.
Based on the ALMA observations, the team set out to observe HL Tau along with two other protoplanetary disk systems, SAO 206462 and MWC 758, with JWST in hopes of detecting any planets that might be forming. Previous observations by the UArizona-led team revealed spiral arms forming in the protoplanetary disk of MWC 758, hinting at a massive planet orbiting its host star.
While no new planets were detected in the disk systems during the most recent observations, the sensitivity is groundbreaking, the researchers say, as it allows them to place the most stringent constraints yet on the suspected planets. For one, the results rule out the existence of additional planets in the outer regions of the MWC 758, consistent with a single giant planet driving the spiral arms.
"The lack of planets detected in HL Tau, and really in all three systems, tells us that the planets causing the gaps and spiral arms either are too close to their host stars or too faint to be seen with JWST," said Kevin Wagner, a NASA Hubble/Sagan Fellow at Steward Observatory who is a co-author on the HL Tau paper and lead author on the MWC 758 paper. "If the latter is true, it tells us that they're of relatively low mass, low temperature, enshrouded in dust, or some combination of the three – as is likely the case in MWC 758."
"While there is a ton of evidence for ongoing planet formation, HL Tau is too young with too much intervening dust to see the planets directly," Leisenring said. "We have already begun looking at other young systems with known planets to help form a more complete picture."
To the team's surprise, JWST revealed unexpected details of a different feature: the proto-stellar envelope – essentially a dense inflow of dust and gas surrounding the young star that is just beginning to coalesce, according to Leisenring, assistant research professor and principal investigator of the project. Under the influence of gravity, material from the interstellar medium falls inward onto the star and the disk, where it serves as the raw material for planets and their precursors.
"When I saw the JWST images of HL Tau, they just blew my mind," Wagner said. "I was expecting to see the disk or the rings, or maybe some planets in the rings, but instead, what we see are these features of the proto-stellar envelope resembling streams, clearly showing material flowing into the protoplanetary disk."
"We see a very complex and dynamic system with 'streamers' feeding material from the outer envelope into the inner regions of the disk, where we expect planets to be forming," Leisenring said.
The observations help scientists who study how planetary systems are being born refine their theories about the processes involved and shed light on what our sun did when it was very young. With the ongoing refinement of observational techniques and technological capabilities, and more advanced instruments coming online in the foreseeable future, astronomers hope to probe protoplanetary disks in greater detail and learn more about the conditions needed to build planets around stars other than our sun.
Quelle: University of Arizona
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