Astronomy

New research offers the most precise measurements yet of pulsating Cepheid stars, which may hold clues about the immense size and scale of our universe.

In his classic book On the Structure of Scientific Revolutions, the philosopher Thomas Kuhn posited that, for a new scientific framework to take root, there has to be evidence that doesn’t sit well within the existing framework. For over a century now, Einstein’s theory of relativity and gravity has been the existing framework. However, cracks are starting to show, and a new paper from researchers at Case Western Reserve University added another one recently when they failed to find decreasing rotational energy in galaxies even millions of light years away from the galaxy’s center.

Galaxies are known to rotate – even our solar system travels in a circle around the center of the Milky Way galaxy at around 200 km per second, though we can’t perceive any motion on human time scales. According to Newtonian dynamics, this rotational speed should slow down the farther away a star is from the center of a galaxy. However, observations didn’t support this, showing that the speed kept up no matter how far away the star is.

That led scientists to create another force impacting the speed of rotation of the farthest-out stars. Today, we commonly call it dark matter. However, scientists have also spent decades trying to puzzle out what exactly dark matter is made of and have yet to come up with a coherent theory.

Anton dives into a weird quirk of galaxy rotation.
Credit – Anton Petrov YouTube Channel

But in some cases, even the existence of dark matter as we know it doesn’t match the observational data. Dr. Tobias Mistele, a post-doc at Case, found that the rotational speed of galaxies doesn’t drop off, no matter how far out they are and no matter how long they’ve been doing so. This data flies in the face of a traditional understanding of dark matter, where its gravitational influence is felt by a “halo” surrounding the dark matter itself. Even these dark matter halos have an effective area. Dr. Mistele and his co-authors found evidence of maintained rotational speed that should be well outside the sphere of influence of any dark matter halo existing in these galaxies.

To collect this data, the authors used a favorite tool of cosmologists – gravitational lensing. They collected data on galaxies that were far away and had their light amplified by a galaxy cluster or similarly massive object that was nearer. When collecting the data, Dr. Mistele analyzed the speed of rotation of the stars in a galaxy and plotted it against the distance of those stars from the galaxy’s center. This is known as a “Tully-Fisher” relation in cosmology.

The result was an almost perfectly straight line – the rotational speed of stars in a galaxy did not seem to diminish with distance from the galaxy’s center, as both traditional Newtonian dynamics and relativity via dark matter predicted it would. So, what alternative explanations are there?

Why do galaxy rotation curves matter? Nora explains.
Credit – Nora’s Guide to the Galaxy YouTube Channel

Paper co-author Stacy McGaugh points out in a press release that one theory in physics accurately predicted the data his team had collected—the modified Newtonian Dynamics (or MOND) theory. Designed explicitly to account for things like galaxy rotations, MOND was developed in 1983 and remains controversial to this day. It struggles with things like the gravitational lensing with which the paper’s data was collected. 

That disconnect points to the need for a deeper understanding of gravity – what Kuhn called a “crisis,” which many cosmologists already believe is afflicting the discipline. While there is no current consensus on what might resolve that crisis, the evidence is mounting for the need for resolution. If we’re truly going to understand our place in the universe, we will eventually need to figure out a solution – it just might take a while.

Learn More:
CWRU – New, groundbreaking research shows that rotation curves of galaxies stay flat indefinitely, corroborating predictions of modified gravity theory as an alternative to dark matter
Mistele et al. – Indefinitely Flat Circular Velocities and the Baryonic Tully-Fisher Relation from Weak Lensing
UT – Will Wide Binaries Be the End of MOND?
UT – New Measurements of Galaxy Rotation Lean Towards Modified Gravity as an Explanation for Dark Matter
UT – The Earliest Galaxies Rotated Slowly, Revving up Over Billions of Years

Lead Image:
Illustration of the galaxy rotation curve used in the research.
Credit – Mistele et al.

The post Rotation Curves of Galaxies Stay Flat Indefinitely appeared first on Universe Today.

In the years before the JWST’s launch, astronomers’ efforts to understand the early Universe were stymied by a stubborn obstacle: the light from the early Universe was red-shifted to an extreme degree. The JWST was built with extreme redshifts in mind, and one of its goals was to study Galaxy Assembly.

Once the JWST activated its segmented, beryllium eye, the Universe’s most ancient, red-shifted light became visible.

The light emitted by the first galaxies is not only faint but has been stretched by billions of years of cosmic expansion. The galaxies that emitted that light are called high-redshift galaxies, where redshift is indicated by the letter z. Since its shifted into the red, only infrared telescopes can see it. Telescopes like the Hubble and the Spitzer can see some redshifted light. But the JWST has far more power than its predecessors, allowing it to effectively see further back in time.

“Using advanced instruments such as JWST allows us to study more distant galaxies with greater detail than ever before.”

Yicheng Guo, Department of Physics and Astronomy, University of Missouri

Observations have shown that galaxies grow large through mergers and collisions and that up to 60% of all galaxies are spirals. But how did the process play out? When did the first spirals emerge? An answer to that question trickles down and affects other outstanding questions about galaxies.

Spiral arms host active star formation, where successive generations of stars create heavier elements. Those elements allow rocky planets to form and are also a requirement for life. So, an understanding of when spiral galaxies formed helps astronomers understand the parameters of star formation, rocky planet formation, and even, potentially, the appearance of life.

“Knowing when spiral galaxies formed in the universe has been a popular question in astronomy because it helps us understand the evolution and history of the cosmos.”

Vicki Kuhn, Department of Physics and Astronomy, University of Missouri

One of the JWST’s observing efforts is CEERS, the Cosmic Evolution Early Release Science Survey. In CEERS, the JWST was the first telescope to capture images of the Universe’s early galaxies. CEERS found the most distant active supermassive black hole and galaxies that existed in the distant past when the Universe was only about 500 to 700 million years old.

Image of CEERS scientists looking at the Epoch 1 NIRCam color mosaic in TACC’s visualization lab at UT Austin. Credit: R. Larson

New research published in The Astrophysical Journal Letters examined galaxies from CEERS to determine how many of these ancient galaxies were spirals. The title is “JWST Reveals a Surprisingly High Fraction of Galaxies Being Spiral-like at 0.5 ≤ z ≤ 4.” The first author is Vicki Kuhn, a graduate student in the University of Missouri’s Department of Physics and Astronomy.

“Scientists formerly believed most spiral galaxies developed around 6 to 7 billion years after the universe formed,” said Yicheng Guo, an associate professor in Mizzou’s (University of Missouri) Department of Physics and Astronomy and co-author of the study. “However, our study shows spiral galaxies were already prevalent as early as 2 billion years afterward. This means galaxy formation happened more rapidly than we previously thought.”

In their research letter, the authors examined 873 galaxies from CEERS with redshift 0.5 ≤ z ≤ 4 and stellar mass ≤ 1010 solar masses. They found that 216 of them had spiral structures. “This fraction is surprisingly high and implies that the formation of spiral arms, as well as disks, was earlier in the Universe,” the authors write in their paper.

This figure from the research shows some of the galaxies in the sample. Redshift increases from left to right, and the rows from top to bottom show the range of galaxies classified as spiral to nonspiral. “Spiral structure is easier to see at the lower redshift ranges and becomes less pronounced at higher redshifts.” the authors write. The top three rows show galaxies identified as spirals with strong confidence, the middle three rows show galaxies identified as spirals with less confidence, and the bottom row shows non-spirals. Image Credit: Kuhn et al. 2024

“Knowing when spiral galaxies formed in the universe has been a popular question in astronomy because it helps us understand the evolution and history of the cosmos,” said lead author Kuhn. “Many theoretical ideas exist about how spiral arms are formed, but the formation mechanisms can vary amongst different types of spiral galaxies. This new information helps us better match the physical properties of galaxies with theories — creating a more comprehensive cosmic timeline.”

Spiral galaxies started as disks of gas. These results, when combined with other studies of high-redshift galaxies, paint a picture of the history of galaxy evolution in the early Universe. Dynamically hot gaseous disks appear around z = 4 to 5. These disks settled down to become dynamically cold gaseous disks around z = 3 to 4. Since stars form when gas cools and clumps together, large numbers of dynamically cold stellar disks appeared at z = 3 to 4, as indicated by their spiral arms.

This research also illuminates the relationships between spiral arms and other galaxy substructures. Gas-rich disks at high redshifts are very turbulent, and gravitational instabilities form giant clumps of star formation. Later, hot stars disperse young galaxies’ velocities, allowing them to settle down and become less turbulent. These bulges of star formation can also merge, helping to further stabilize the disks. The conclusion is that gravitational instabilities primarily lead to spiral arms, with clumps playing a secondary role since they co-exist with spirals at high redshifts.

The authors point out some caveats in their work. Galaxies that are merging can appear as spirals. The long tails prevalent during mergers can look like spiral arms, so their numbers could be off a little. But on the other hand, spirals can also look like mergers, adding to the uncertainty. “This situation is more severe for galaxies at z > 2, as the merger fraction is believed to be higher then,” the authors write.

But these facts likely don’t affect the conclusion much. “The observed spiral fraction decreases with increasing redshift, from ~43% at z = 1 to ~4% at z = 3,” the researchers conclude. So, while spirals are rarer the further we look back in time, they’re still more plentiful earlier than thought.

“Using advanced instruments such as JWST allows us to study more distant galaxies with greater detail than ever before,” Guo said. “A galaxy’s spiral arms are a fundamental feature used by astronomers to categorize galaxies and understand how they form over time. Even though we still have many questions about the universe’s past, analyzing this data helps us uncover additional clues and deepens our understanding of the physics that shaped the nature of our universe.”

The post Almost a Third of Early Galaxies Were Already Spirals appeared first on Universe Today.

The FAA is holding a virtual public meeting this evening (June 17) about the potential environmental impact of SpaceX's Starship operations in Florida, and you can participate.

Boeing Starliner has seen its one-week test mission in space double to about two weeks. That allowed time for an incredible aurora show during thruster testing on June 15.

Many years ago, there was a viral YouTube video called “History of the entire world, i guess,” which has been an endless source of internet memes since its release. One of the most prominent is also scientifically accurate—when describing why animals couldn’t start living on land, the video’s creator, Bill Wurtz, intones, “The Sun is a deadly laser.” 

Early in planetary development, the X-ray and ultraviolet radiation level of a planet’s host stars could sterilize the entire planet’s surface, even if it is in the so-called “habitable zone.” To narrow down the search for potentially habitable planets, the team at the Chandra X-ray Observatory and XMM-Newton telescopes took a look at stars that had planets in their habitable zone and analyzed them for whether the star’s radiation itself might preclude life as we know it from developing there.

Over ten observational days on Chandra and 26 on XMM-Newton, scientists observed 57 stars close enough to Earth to have their exoplanets explored by the next generation of exoplanet-hunting telescopes, such as the Habitable Worlds Observatory. While not all of them had known exoplanets, at least some did. 

YouTube Video detailing the research.
Credit – Chandra X-ray Observatory YouTube Channel

However, those exoplanets were typically much larger than Earth, even if they were in the habitable zone. It is much easier to detect giant planets orbiting close to their stars using modern date exoplanet detection techniques like transiting and astrometry. A press release from Chandra notes how many more rocky exoplanets the size of Earth are likely hiding around these stars, but our limited detection methods are not yet capable of finding them.

That isn’t to say we can’t learn much about their host stars, though, and that is where the data from the paper presented to the 244 meeting of the American Astronomical Society in Madison, Wisconsin, comes in. Watching the X-ray emissions of these local stars allowed the team to narrow down what stars to look at for potentially habitable exoplanets, thereby allowing the future powerful planet hunters to focus their observational time on candidates that are more likely to produce results.

Fraser details the path towards detecting 100 million exoplanets over the next thirty years.

Some of the stars in the study were indeed promising, with X-ray exposure similar to, or even less than, that of Earth when life began forming here billions of years ago. The data measured several aspects of the star’s output, including their brightness, how much energy those X-rays pack, and how powerful the star’s flares are. All of those could significantly impact the ability of life to form on any orbiting planets.

Fifty-seven stars is a relatively small sample size. Still, the proof of concept for how Chandra and XMM-Newton can be used to scout potential systems for habitability can be scaled up before any long-term observing mission for the new planet finders—no doubt they will be shortly as HWF and other missions get closer to fruition.

However, Chandra itself is facing budgetary challenges, causing many in the media to speculate that it might soon go “dark.” XMM-Newton itself is almost a quarter century old at this point, and a new joint X-ray mission, XRISM, is facing its own technical challenges, with a stuck door limiting it from observing in some of its potential wavelengths.

With luck, X-ray astronomy will continue to evolve over the next few decades. Part of that mission might be leading the scouting team for one of the most important astronomical searches humanity is currently undergoing.

Learn More:
Chandra Press Room – Coming in Hot: NASA’s Chandra Checks Habitability of Exoplanets
UT – Chandra’s X-ray Vision Combined With JWST Reveals Even More Details About the Universe
UT – A Collection of New Images Reveal X-Rays Across the Universe
UT – Chandra and JWST Join Forces in a Stunning Series of Images

Lead Image:
Illustration of hot exoplanet.
Credit – NASA/CXC/M.Weiss

The post Which Stars are Lethal to their Planets? appeared first on Universe Today.

NASA's Lunar Reconnaissance Orbiter has taken its first look at China's Chang'e 6 spacecraft on the moon's far side.

Not content with shapes in two or three dimensions, mathematicians like to explore objects in any number of spatial dimensions. Now they have discovered shapes of constant width in any dimension, which roll like a wheel despite not being round

Not content with shapes in two or three dimensions, mathematicians like to explore objects in any number of spatial dimensions. Now they have discovered shapes of constant width in any dimension, which roll like a wheel despite not being round

Tribalism can be toxic, yet we need more of it if we are to meet today’s global challenges, argues one anthropologist. His research reveals how to create a “teratribe”

Tribalism can be toxic, yet we need more of it if we are to meet today’s global challenges, argues one anthropologist. His research reveals how to create a “teratribe”

“I feel that my larger purpose at NASA, which I've felt since I came on as an intern, is to leave NASA a better place than I found it." — Mallory Carbon, Management and Program Analyst, NASA Headquarters

In order to explain the presence of these heavier elements today, it’s necessary to find phenomena that can produce them. One type of event that fits the bill is a gamma-ray burst (GRB) – the most powerful class of explosion in the universe.

A robot named Musashi with a human-like "skeleton" and "musculature" can perform basic driving tasks – but this isn’t the safest approach to autonomous transport

A robot named Musashi with a human-like "skeleton" and "musculature" can perform basic driving tasks – but this isn’t the safest approach to autonomous transport

Meteoroids are difficult objects for aerospace and geophysics researchers like us to study, because we can’t usually predict when and where they will hit the atmosphere. But on very rare occasions, we can study artificial objects that enter the atmosphere much like a meteoroid would.

By combining two approaches to quantum computing into one device, Google has been able to simulate the behaviour of magnets in detail - and found discrepancies with our current understanding of certain magnet systems

By combining two approaches to quantum computing into one device, Google has been able to simulate the behaviour of magnets in detail - and found discrepancies with our current understanding of certain magnet systems

A young star that astronomers have studied for decades has been found to be part of a duo, encircled by a disk of material within which planets may have just begun coalescing.

Why is the sky near