NASA’s Webb Pinpoints Millions of Stars Within Cigar Galaxy - UNIVERSE

Located 12 million light-years away and undergoing rapid star formation, edge-on spiral galaxy Messier 82 (M82) is a scientifically unique sight to behold, and now NASA’s James Webb Space Telescope has revealed previously unseen details.

M82’s intense star formation, thought to be the result of a galaxy merger, will be a short-lived event in astronomical terms, estimated to last a few hundred million years in its entirety. This temporary phase of extreme star formation relative to the galaxy’s mass, as well as its location in the local universe, are among the factors that make M82, also known as the Cigar galaxy, a one-of-a-kind environment to study.

Image: M82 Cigar Galaxy (Webb + Hubble)

Scientists used NASA’s James Webb Space Telescope to image edge-on starburst galaxy Messier 82 and trace its evolutionary history. This Webb and Hubble composite image includes 16.5 million stars (blue-white), dust grains (red-orange), and ionized hydrogen gas (yellow).

Image: NASA, ESA, CSA, Adam Smercina (STScI, Tufts), Thomas Williams (University of Manchester); Image Processing: Alyssa Pagan (STScI)

A team of astronomers recently completed an imaging survey with the Webb telescope. This program entailed a total of 65 hours of observation time with Webb’s NIRCam (Near-Infrared Camera) instrument and revealed never-seen-before details of the starburst galaxy, including its distended disk structure and millions of individual stars. Webb’s high-resolution imaging, specifically of the main plane of the galactic disk, has unlocked vital information for astronomers as they seek to uncover M82’s formation history. Additionally, the Webb data will help scientists understand the current processes occurring within the starburst galaxy.

“M82 is a mess, but it’s a beautiful mess. We don’t fully understand what’s going on, especially concerning its evolutionary history. What could have triggered such an elevated rate of star formation? How long has this galaxy been driving plumes of material away from its center?” said principal investigator Adam Smercina, a NASA Hubble Fellow at the Space Telescope Science Institute in Baltimore, and incoming Assistant Professor at Tufts University in Massachusetts. “M82 is an ideal galaxy evolution laboratory because it has properties that allow us to probe important physical processes, such as how stars form in such environments and how that activity drives outflows. M82 provides a simultaneous window onto many astrophysical questions, in a way that no other galaxy in the local universe can.”

Image: M82 Cigar Galaxy (NIRCam Image)

NASA’s James Webb Space Telescope observed edge-on starburst galaxy Messier 82, peering through dust to reveal 16.5 million stars and the galaxy’s distended disk structure. Scientists seek to learn the galaxy’s evolutionary history with the Webb data.

Image: NASA, ESA, CSA, Adam Smercina (STScI, Tufts), Thomas Williams (University of Manchester); Image Processing: Alyssa Pagan (STScI)

Prior to Webb, many observatories looked at the starburst galaxy, including NASA’s Hubble and retired Spitzer space telescopes. However, the sheer volume of dust within that galaxy limited the amount of information astronomers could acquire on M82 at high resolution. While Webb has previously looked at this galaxy, the duration of the new imaging survey, combined with the telescope’s infrared sensitivity, enabled it to pierce through the thick dust.

Image: M82 Cigar Galaxy (Hubble/Webb Side-by-Side)

Side-by-side comparison of a portion of starburst galaxy Messier 82 (M82) as seen by NASA’s Hubble (left) and James Webb (right) space telescopes. Hubble detailed M82’s gas and dust structure, while Webb pierced through the dust and resolved millions of stars in infrared light.

Image: NASA, ESA, CSA, Adam Smercina (STScI, Tufts), Thomas Williams (University of Manchester); Image Processing: Alyssa Pagan (STScI)

The telescope’s near-infrared-light view is a snapshot of a scene that has been evolving over a couple hundred million years. Webb’s image contains approximately 16.5 million individual stars dispersed throughout the galaxy. The light from these stellar sources is depicted as luminous blue granules. This is only a small portion of the total amount of stars astronomers think reside in a galaxy like M82, with the majority too faint to be seen.

“The sheer number of stars that we were able to resolve with Webb is incredible,” said team member Benjamin Williams of the University of Washington. “It’s a whole different world from what we’ve been able to see with other telescopes. All of these stars collectively provide a detailed fossil record of the formation and evolution of M82.”

Moving inward, the increase in brightness and the asymmetrical shape of the galactic disk hints at the spiral galaxy’s unique underlying structure. The differing radii between the two sides suggests that M82 has a distorted shape, which can happen during intense galaxy mergers.

“At first glance, the disk of the galaxy may seem less spectacular because Webb sees through the dust,” said team member Eric Bell of the University of Michigan. “But M82 is a delightfully complex system. Webb’s observations will help us address some ongoing mysteries, such as how star formation has moved within M82 over the last few billion years.”

Video: M82 Cigar Galaxy (Webb + Hubble Fade)

NASA’s James Webb Space Telescope’s near-infrared observation of M82 is the most recent addition to overall data on this starburst galaxy. The Hubble Space Telescope is one observatory that has previously looked at M82, detailing the gas and dust structure seen in visible light.

Video: NASA, ESA, CSA, STScI, Alyssa Pagan (STScI)

Because of the extreme star formation within the galaxy, which is 10 times faster than the Milky Way galaxy’s star formation rate, stellar birth will eventually be disrupted. M82’s stellar frenzy is causing bipolar plumes of material to be ejected above and below the disk. Though it looks like a tumultuous region, the hourglass-shaped outflows appear to have a layered structure. The yellow tendrils of material closest to the galaxy’s disk represent ionized gas, whereas the orange material farther away depicts small dust grains. These grains are called polycyclic aromatic hydrocarbons and are helpful in tracing material in the space between the galaxy’s stars, also known as the interstellar medium.

The information collected as part of this Webb study is just one dataset scientists will analyze as they seek to piece together this starburst galaxy’s formation history.

“Galaxies are such intricate ecosystems that if you truly want to understand them, you have to pull datasets from different missions together,” said team member Kristen McQuinn of the Space Telescope Science Institute. “One mission cannot fully answer all of the questions we have about M82. Combining the data collected by different telescopes, like Webb and Hubble, is powerful. When you marry the datasets, you expand what you can probe, and the questions that you can pose are even more complex.”

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 CSA (Canadian Space Agency).

To learn more about Webb, visit: https://science.nasa.gov/webb 

Source: NASA’s Webb Pinpoints Millions of Stars Within Cigar Galaxy - NASA Science 

A thermodynamic approach to gravity could explain cosmic acceleration without dark energy - Physics - General Physics - Quantum Physics

A small causal diamond used as a tiny local laboratory for deriving gravity from thermal physics. Heat flows in and out across the light-like boundaries of the diamond, allowing the authors to ask what kind of gravitational theory emerges from a more general thermodynamic process that might happen inside the diamond. Credit: Isichei and Magueijo / Physical Review Letters.

Gravity, the force that attracts objects toward each other, is currently framed by Albert Einstein's theory of general relativity. This framework describes gravity as the curvature of spacetime, the invisible four-dimensional fabric of the universe.

While general relativity is now the central theory of gravity, it fails to explain some cosmological phenomena and mysteries, such as the so-called cosmological constant problem. This is the unexplained mismatch between the observed energy of empty space and the far greater values predicted by quantum theories.

In a recent paper published in Physical Review Letters, researchers at Imperial College London tried to frame gravity using thermodynamics, the framework that describes how energy and heat transform. Their study builds on a seminal paper by theoretical physicist Ted Jacobson, published more than three decades ago.

"I first came across Jacobson's seminal 1995 work when I was just out of my Ph.D., and I found the idea fascinating," João Magueijo, senior author of the paper, told Phys.org.

"He inverted the logic of Hawking and Bekenstein's arguments that Einstein gravity has temperature and entropy and instead used thermal physics to derive Einstein gravity. I wanted to do something with this idea for years, but all my attempts failed miserably. Then last year, while on holiday on a remote Greek island, part of which has no internet, which may have helped, I realized that most previous work had tried to retrofit existing theories of gravity into Jacobson's construction." 

The thermodynamic cycle proposed in the Letter. Standard Einstein gravity corresponds to the degenerate case in which only heat-flow legs are present. Allowing the additional work-producing legs opens the door to new gravitational theories, including ones in which matter-energy conservation is modified. Credit: Isichei and Magueijo / Physical Review Letters.

Building on this realization, Magueijo started exploring the possibility of describing gravity starting from thermal physics alone, without trying to determine what type of gravity theory would emerge. His hope was that this process would lead to entirely new theories of gravity that no one had thought of before.

Linking gravity, thermodynamics and the expanding universe

To further develop the ideas he had been contemplating, Magueijo started collaborating with Ray Isichei, a Ph.D. student he was supervising at Imperial College. Together, the two researchers started examining gravity from a thermodynamic standpoint, specifically framing it as an Otto cycle, a thermodynamic construct that describes how gasoline engines work.

"We asked what happens if the thermodynamic process behind gravity is not just heat flow," Magueijo explained. "In ordinary thermodynamics, heat is almost never the whole story: There may also be chemical reactions, expansion against a piston, work being done or other contributions. So, we added this missing 'something else' to the argument, without prejudice regarding what would come out the other side."

To their surprise, the researchers found that the gravitational theory they derived allowed matter and energy to be created or destroyed. This was a total shock, as the conservation of energy and matter is a fundamental physical principle. The fact that it could be violated almost prompted them to abandon their theory altogether.

"The idea did not end up in the garbage bin because we realized that, when applied to the universe as a whole, it could reproduce the observed acceleration of cosmic expansion without having to posit dark energy, a cosmological constant, or any of the usual ingredients invoked to explain it," Magueijo said.

"Normal matter should pull back and decelerate the expansion of the universe, but that assumes the usual conservation laws. In this model, normal matter whose conservation law is modified (allowing for continuous creation) can instead drive acceleration."

Fueling new theoretical studies

The team's study offers a fresh and unconventional theory of gravity, suggesting that Einstein's theory of relativity could also potentially be framed as a thermodynamic process. This theoretical framework could eliminate the need for a conventional cosmological constant, potentially helping to tackle a long-standing issue in cosmology.

While the new theory devised by Magueijo and Isichei is intriguing, it is still speculative and in its early stages. The researchers are now planning further studies aimed at developing it further and comparing its predictions with available cosmological evidence and experimental results.

"A lot of work now needs to be done comparing the model in detail with cosmological observations," Magueijo added. "When I started my Ph.D., back in 1990, you could still say almost anything in cosmology, because the paucity of data allowed it. Cosmology has since become a high-precision, data-driven subject. Any new idea now must pass the gauntlet of observation." 

Source: A thermodynamic approach to gravity could explain cosmic acceleration without dark energy