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Astronomy

What are the reasons behind the diverse shapes of galaxies?

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If prompted to depict a galaxy, it is likely that you would generate a spiral configuration such the one depicted above. Spiral galaxies possess significant benefits in capturing our attention, mostly due to their widespread admiration for their exceptional beauty. Additionally, they possess a greater number of attractive young individuals, making them more noticeable unless we properly examine them. Furthermore, one of them is our residence, resulting in an inherent prejudice.

However, not all galaxies exhibit a spiral shape, and even those that do can be classified into two primary categories. Why do certain galaxies get this magnificent configuration while others do not?

There remains a considerable degree of ambiguity around this inquiry; nonetheless, a certain set of explanations appears to be emerging as the prevailing perspective.

Spiral galaxies
Spiral galaxies exhibit a number of shared characteristics. All stars exhibit a relatively flat shape, characterized by a primary body that is significantly wider than its thickness. The disk is characterized by a center bulge that is densely populated with stars, extending both above and below it. Spiral galaxies typically possess a halo that, when regarded as a demarcation, would render them nearly spherical. Nevertheless, the presence of stars in the halo is so rare that it goes unnoticed, even when observing a spiral from a side-on perspective.

Although the spiral structure has received considerable research, its underlying causes remain incompletely comprehended. Partially, it embodies a fallacy. The spiral arms exhibit a significant amount of activity, mostly due to the heightened intensity of star formation inside these regions, resulting in a substantial presence of young, very energetic stars. This enhances the visibility of the arms compared to only observing the density of the material.

Spiral galaxies often have a core that predates their arms, but there are occasional exceptions. This observation implies that the core is believed to have originated earlier and then attracted the material that eventually formed the arms. The formation of large spirals, like in the Milky Way, occurs through the process of cannibalization against nearby smaller galaxies.

Spiral galaxies can be classified based on the degree of arm twisting as well as the number of arms, which can vary.

Remarkably, despite their significance to the cosmos and our own existence, our comprehension of the factors that give rise to spiral galaxy formation remains incomplete. Undoubtedly, we anticipate that the arms will coil securely around the center within significantly shorter timeframes compared to the lifespan of the spirals we are most familiar with. Dark matter accounts for a portion of our observed phenomena, but not all of them.

The disk-like nature of spiral galaxies can be readily elucidated, as a comparable phenomenon can be observed in the protoplanetary disks surrounding nascent stars. It is a result of the gravitational forces acting on particles that are in motion.

The spiral arms possess greater rigidity. The prevailing hypothesis is commonly referred to as “density wave theory.”. This observation implies that stars and dust do not constitute permanent components of arms. Conversely, density waves propagate inside the galaxy, causing the aggregation of matter as a crest traverses and then scattering it. Similar to how a water particle does not consistently occupy the highest point of a wave, stars undergo oscillatory motion within the arms of a wave, undergoing both inward and outward movements.

The exact origin of these density waves remains a mystery, although one possible catalyst could be the gravitational pull of neighboring galaxies disrupting their circular form. There are also suspicions about magnetic fields.

Deciding Whether or Not to Go to a Bar
One of the key distinctions among spiral galaxies is the presence or absence of a central bar, which can be observed in galaxies like our own.

Bars are increasingly prevalent as we approach us in space and time, indicating a rising frequency. Similar to the spiral shapes, it is believed that they are formed by density waves that originate from the galactic center instead of revolving around it.

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The Elliptical Galaxies
Elliptical galaxies are the other general shape that sets them apart, and they are also the biggest galaxies. The form might look like a rugby ball to people in some parts of the world. Americans might like to picture a football that is only slightly compressed and has some of its ends pushed in.

It was Edwin Hubble who first came up with the categories we use today (with some changes). He thought that elliptical galaxies were like an egg in space from which spiral galaxies grew, but this idea has since been disproved. Instead, elliptical galaxies tend to have stars that are much older than those in spiral galaxies because they have stopped making new stars for a long time. It seems that the jets that irregular galaxies’ supermassive black holes make mess up the gas that could form stars in other galaxies.

Some stars move in directions that don’t match those of their neighbors, even in spiral galaxies. Still, the vast majority of stars in spiral galaxies circle in a planned way. It is thought that stars in elliptical galaxies move around a lot less randomly, which makes the shape less stable.

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It is thought that irregular galaxies form when galaxies crash into each other. This is why they are old and don’t have a clear organization. Even though we know the Milky Way is made up of many galaxies, it has kept its shape. Ellipticals happen most often near the center of galaxy groups, which is also where galaxies are most likely to collide and fight. In all the bad things the Milky Way has been through, ellipticals have probably been through even worse.

Getting Messed Up
A lot of galaxies don’t fit into any of these groups, and their forms don’t follow a pattern. It’s easiest to understand these because a regular shape can get messed up when it meets a big force that changes things, like the gravity of a bigger galaxy. The galaxy might eventually come back together, but it may take so much time, especially if it is a smaller galaxy that is vulnerable to damage from larger galaxies, that it will be disorganized for a significant portion of its life.

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How the early universe looked
Galaxy forms that are close to us are easier to study, so that’s where most of what we know comes from. So, these galaxies are about the same age as ours, since we are not looking very far back in time. On the other hand, the JWST has shown us galaxies from when the universe was a lot smaller, and the forms are very different.

A recent report showed that scientists have compared shapes to sports gear, such as balls that are almost spherical and ones that look like frisbees, surfboards, and pool noodles.

Our galaxy’s aged, and we don’t know what happened to them. Even so, since these shapes aren’t common in our world, it seems likely that over time they will change into one of the shapes we see more often.

As Editor here at GeekReply, I'm a big fan of all things Geeky. Most of my contributions to the site are technology related, but I'm also a big fan of video games. My genres of choice include RPGs, MMOs, Grand Strategy, and Simulation. If I'm not chasing after the latest gear on my MMO of choice, I'm here at GeekReply reporting on the latest in Geek culture.

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Astronomy

This planet like Earth is the first one that has been proven to have an atmosphere

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Astronomers have successfully utilized the James Webb Space Telescope (JWST) to observe the presence of an atmosphere around a terrestrial exoplanet, marking the first such discovery beyond our solar system. Despite its inability to sustain life due to its likely magma ocean, this planet could provide valuable insights into the early geological development of Earth, as both planets share a rocky composition and a history of being molten.

Sara Seager, a planetary scientist at the Massachusetts Institute of Technology in Cambridge who was not part of the study, states that the discovery of a gaseous envelope surrounding an Earth-like planet is a significant achievement in the field of exoplanet research. The Earth’s tenuous atmosphere plays a vital role in supporting life, and the ability to detect atmospheres on comparable rocky planets is a significant milestone in the quest for extraterrestrial life.

JWST is currently studying the planet 55 Cancri e, which orbits a star similar to the Sun at a distance of 12.6 parsecs. It is classified as a super-Earth, meaning it is a terrestrial planet slightly larger than Earth. Specifically, it has a radius approximately twice that of Earth and a mass more than eight times greater. The paper published in Nature1 suggests that the atmosphere of the planet is likely to contain significant amounts of carbon dioxide or carbon monoxide. Additionally, the thickness of the atmosphere is estimated to be “up to a few percent” of the planet’s radius.

A mysterious world
55 Cancri e is also not a good place to live because it is very close to its star—about 1.6 times as close as Earth is to the Sun. Still, Aaron Bello-Arufe, an astrophysicist at the Jet Propulsion Laboratory (JPL) in Pasadena, California, and a co-author of the paper, says, “it’s perhaps the most studied rocky planet.” Its host star is bright at night, and the planet is big for a rocky one, so it’s easier to study than other places outside of the Solar System. “In astronomy, every telescope or other tool you can think of has pointed to this planet at some point,” says Bello-Arufe.

55 Cancribe was studied so much that when JWST was launched in December 2021, engineers pointed the infrared spectrometers of the spacecraft at it to test it. As these instruments soak up infrared wavelengths from starlight, they can find the chemical signatures of gases swirling around planets. Then Bello-Arufe and his coworkers chose to look into it more to find out for sure if the planet had an atmosphere.

Astronomers had changed their minds about 55 Cancri a huge number of times before the most recent observations. In 2004, the planet was found. Scientists first thought it might be the center of a gas giant like Jupiter. Researchers looked at 55 Cancri e as it passed in front of its star3 with the Spitzer Space Telescope in 2011. They found that it is a rocky super-Earth, much smaller and denser than a gas giant.

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After some time, scientists found that 55 C was cooler than it should have been for a planet that was so close to its star. This suggests that it probably has an atmosphere. One hypothesis was that the planet is a “water world” with supercritical water molecules all around it. Another was that it has a large, primordial atmosphere mostly made up of hydrogen and helium. But in the end, these ideas were shown to be wrong.

According to Renyu Hu, a planetary scientist at JPL and co-author of the new study, stellar winds would make it difficult for a planet this close to its star to retain volatile molecules in its atmosphere. He says there are still two options. The first was that the planet is completely dry and has a very thin layer of rock vapor in the air. The second reason was that it has a thick atmosphere made up of heavier, less volatile molecules that don’t easily escape.

A better picture
The most recent information shows that 55 Cancrie’s atmosphere has gases made of carbon, which points to option two. Seager says that the team did indeed find evidence of an atmosphere but that more observations are needed to fully understand its make-up, the amounts of gases present, and its exact thickness.

Laura Schaefer is a planetary geologist at California’s Stanford University. She wants to know how the atmosphere of 55 Cancrie affects things below the surface of the planet. The authors of the study say it’s still possible that stellar winds are carrying away parts of the atmosphere. However, rocks melting and releasing gases into the magma ocean could replace the gases.

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Astronomy

Why some physicists believe we live in a black hole

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Black holes are enigmatic entities that, despite our extensive knowledge, continue to perplex our comprehension of physics. Physicists have proposed unconventional hypotheses to address the paradoxes encountered during the study of these phenomena. One hypothesis suggests that these paradoxes indicate that our universe is actually a holographic representation. According to this idea, everything we observe and perceive is encoded at the boundary of our universe, which is a three-dimensional representation of a two-dimensional universe, including time. Moreover, there have been suggestions that this could potentially indicate that our universe exists inside a black hole within a larger universe.

Black holes are regions of space that result from the gravitational collapse of massive stars, exhibiting such intense gravity that even light cannot escape. Their presence presented a challenge when examining them from a thermodynamic perspective. After achieving stability, a black hole’s mass, angular momentum, and electric charge are the only factors that determine its final state.

“According to French astrophysicist Jean-Pierre Luminet’s 2016 review, in classical general relativity, a black hole effectively traps any particle or form of radiation within its cosmic confinement, preventing their escape.” “To an external observer, the moment a material body passes through an event horizon, all information regarding its material properties becomes inaccessible.” Only the updated values of mass (M), angular momentum (J), and electric charge (Q) are retained. Consequently, a black hole engulfs a vast quantity of information.

It may appear straightforward—or at least as straightforward as physics can be. However, if a black hole possesses mass (which is typically substantial), it should theoretically possess a temperature in accordance with the first law of thermodynamics. Furthermore, in accordance with the second law of thermodynamics, it should emit thermal radiation. Stephen Hawking demonstrated that black holes emit radiation, now known as Hawking radiation, which is generated at the boundary of a black hole.

“Hawking subsequently identified a paradox.” “If a black hole undergoes evaporation, a fraction of the information it possesses becomes permanently irretrievable,” Luminet elaborated. A black hole’s thermal radiation does not retain or replicate information about the matter it ate. The irrevocable loss of information contradicts one of the fundamental principles of quantum mechanics. The Schrödinger equation states that in physical systems that undergo changes over time, information cannot be created or destroyed. This property is referred to as unitarity.

This phenomenon is referred to as the black hole information paradox, and due to its apparent contradiction with our existing comprehension of the cosmos, it has been extensively examined and discussed.

Examining the thermodynamics of black holes within the context of string theory led to the discovery of an alternative solution. Gerard ‘t Hooft demonstrated that the total number of independent variables within a black hole is directly proportional to the surface area of its horizon, rather than its volume. This enables the examination of the entropy of a black hole.

“In terms of information, Luminet explains that each bit, represented as either a 0 or a 1, corresponds to four Planck areas. This correspondence enables the derivation of the Bekenstein-Hawking formula for entropy,” Luminet concludes. “To an external observer, it appears that the information regarding the entropy of the black hole, which was previously contained within the three-dimensional arrangement of objects that entered the event horizon, is no longer accessible.” However, according to this perspective, the data is encoded on the flat, two-dimensional surface of a black hole, similar to a hologram. Thus, Hooft concluded that the information consumed by a black hole could be fully recovered through the process of quantum evaporation.

Although it is consoling to know that black holes do not violate the second law of thermodynamics, this has given rise to the unusual idea that a three-dimensional space’s two-dimensional boundary can explain its physics.

It has been suggested that the universe itself could potentially function like a black hole, with all phenomena occurring at its boundary and our observations arising from these interactions. However, this concept does not apply to the space outside of a black hole. This idea is quite unconventional, with some unexpected additions. For example, there is a suggestion that gravity may emerge as a force from entanglement entropy at the boundary.

The theory falls short in its ability to provide a convincing explanation for our universe, as standard physics continues to offer the most accurate description of the observable universe. However, there are valid justifications for why individuals consider it of great importance.

In order for the model to be valid, it is crucial that the Hubble radius of the universe, which represents the radius of our observable universe, is equivalent to its Schwarzschild radius. This refers to the size of a black hole that would form if all the matter within it was compressed into a single point. These two figures are unexpectedly similar, although this could be attributed to a cosmic coincidence.

There are other factors to consider, like this comprehensive chart that indicates the possibility of our existence within a black hole within a larger universe. However, until a theory emerges with substantial evidence and predictions that surpass our current knowledge of physics, we recommend refraining from succumbing to an existential crisis. This applies regardless of whether you perceive yourself as a three-dimensional entity existing within conventional space-time or as a holographic projection originating from a two-dimensional boundary within a larger universe.

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Astronomy

A potential development of the first lunar railway is anticipated within the next ten years

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For people to live on the Moon’s surface permanently, they need to be able to use Moon resources. Not everything can be brought to Earth. But it’s not likely that the base will have everything it needs right there. Some things will need to be moved. It’s not a new idea to have cars (well, buggies) on the Moon, but now scientists are thinking about a very different idea: a railway system that floats.

FLOAT, which stands for “Flexible Levitation on a Track,” is the name of the project. The goal is to make payload transportation that is self-driving, dependable, and effective. As part of its mission, it will move payloads from spacecraft landing zones to the base and from mining sites to places where resources are taken out or where the soil is used for building.

Interesting about the technology is that the tracks are not fixed. Since they are unrolled right onto the lunar regolith, FLOAT doesn’t need much site preparation. Robots that can levitate will be able to move over the tracks. Since they don’t have wheels or legs, they don’t have to deal with the sharp regolith and its damaging power.

There is a layer of graphite on the flexible film track that lets diamagnetic levitation happen, and a flex circuit creates electromagnetic thrust. You don’t have to use the third layer, but if you do, it’s a solar panel that will power the system when it’s in the sun. The robots may be different sizes, but the team thinks that every day they can move 100 tons of stuff over several kilometers.

In phase II, six NASA Innovative Advanced Concepts (NIAC) have been moved forward. FLOAT is one of them. A new way to get astronauts to Mars quickly and an idea for a liquid space telescope are two others. For FLOAT, phase II will be all about designing and building a smaller version of the system that will be tested in a moon-like environment. This will also help us learn more about how the environment affects tracks and robots and what else is needed to make this idea a reality.

In a statement, John Nelson, NIAC program executive at NASA Headquarters in Washington, said, “These different, science fiction-like ideas make up a great group of Phase II studies.” “Our NIAC fellows always amaze and inspire us. This class makes NASA think about what’s possible in the future.”

These projects got $600,000 to keep looking into whether they were possible. As the leader of FLOAT, Ethan Schaler from NASA’s Jet Propulsion Laboratory is in charge. If the system keeps showing what it can do, it could be an important part of life on the Moon by the 2030s.

Phase I projects have also been announced. The ideas include new designs for telescopes, ways to make Mars less dangerous, and even a group of very small spacecraft that could reach our nearest stars in 20 years.

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