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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

NASA’s flyby of Europa shows that “something” is moving under the ice

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Europa’s surface has marks that show the icy crust is vulnerable to the water below. The most important thing is that Juno’s recent visit shows what might be plume activity. If this is real, it would let future missions take samples of the ocean inside the planet without having to land.

Even though it’s been almost two years since Juno got the closest to Europa, its data is still being looked at. Even though Juno has been going around Jupiter since 2016, the five pictures it took on September 29, 2022, were the closest views of Europa since Galileo’s last visit in 2000.

Some might say that’s a shocking lack of interest in one of the Solar System’s most interesting worlds, but it could also have been a good way to see how things had changed over time.

Europa is the smoothest object in the solar system because its ocean keeps it from sinking to the surface. Still, it’s not featureless; Juno saw some deep depressions with steep walls that are 20 to 50 kilometers (12 to 31 miles) wide, as well as fracture patterns that are thought to show “true polar wander.

In a statement, Dr. Candy Hansen of the Planetary Science Institute said, “True polar wander occurs if Europa’s icy shell is separated from its rocky interior. This puts a lot of stress on the shell, which causes it to break in predictable ways.”

The shell that sits on top of Europa’s ocean is thought to be rotating faster than the rest of the moon. This is what true polar wandering means. People think that the water below is moving and pulling the shell along with it. Ocean currents are thought to be causing this. The currents are most likely a result of heat inside Europa’s rocky core, which is heated up as a result of Jupiter and its larger moons pulling on Europa and turning it into a large stress ball.

The ocean and ice could stretch and compress parts of the ice, which is how the cracks and ridges that have been seen since Voyager 2 visited were made.

A group under the direction of Hansen is viewing images of Europa’s southern half. The scientist said, “This is the first time that these fracture patterns have been mapped in the southern hemisphere. This suggests that true polar wander has a bigger effect on Europa’s surface geology than was thought before.”

Ocean currents are not to blame for all of Europa’s map changes. It appears that optical tricks can even fool NASA. Hansen said, “Crater Gwern is no longer there.” “JunoCam data showed that Gwern, which was once thought to be a 13-mile-wide impact crater and one of Europa’s few known impact craters, was actually a group of ridges that crossed each other to make an oval shadow.”

But Juno gives more than it takes away. The team is interested in what they’re calling the Platypus because of its shape, not because it has a lot of parts that shouldn’t go together. Ridges on its edge look like they are collapsing into it. The scientists think this might be because pockets of salt water have partially broken through the icy shell.

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The Europa Clipper would find these pockets to be fascinating indirect targets for study, but the dark stains that cryovolcanic activity might have left behind are even more intriguing.

“These features suggest the possibility of current surface activity and the existence of liquid water beneath the surface on Europa,” stated Heidi Becker from the Jet Propulsion Laboratory. There is evidence of such activity in the geysers of Enceladus, but there is still uncertainty regarding whether it is currently happening on Europa.

Engaging in such an endeavor would enable the sampling of the interior ocean to detect signs of life simply by flying through a plume and gathering ice flakes without the need for landing or drilling.

It seems that in the past, there was a significant shift of over 70 degrees in the locations of features on Europa’s surface, although the reasons for this remain unknown. However, at present, polar wander only leads to minor adjustments.

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Astronomy

The Sun emitted the largest solar flare in the past 20 years, resulting in power outages

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Solar Cycle 25 is decidedly more turbulent than its predecessor. The Sun is currently experiencing heightened activity, characterized by solar storms, coronal mass ejections, and geomagnetic storms of unprecedented intensity in recent years. Currently, the sun has emitted its most powerful solar flare to date during this particular cycle.

The flare was quantified as an X8.7, indicating a considerably higher strength compared to the flares emitted last week. The event emitted highly energetic light in the extreme ultraviolet range, which resulted in the ionization of the uppermost layer of the atmosphere. Consequently, a radio blackout occurred over the Americas, adversely impacting aircraft and vessels that depend on signals with frequencies below 30 MHz.

Ionization of the atmosphere causes an expansion, resulting in increased drag on satellites in low Earth orbit. They will require strategic maneuvering to be moved away from Earth. Solar flares have the potential to interfere with satellite communications.

A gif of the Sun yesterday with two bright flashes corresponding to the flares on its limb

Sunspot AR 3664 is where it comes from. Last week, several strong flares were seen coming from this area, including the second strongest of this cycle at the time. The Sun also sent out a number of coronal mass ejections (CMEs), which hit Earth and caused the beautiful auroral display we saw last weekend.

Back then, the sunspot was right on the side of the Sun that could be seen, and anyone could see it. It’s sixteen times wider than Earth! As the Sun turns, the spot is now on its side, so we can only see it from the side. We might have seen a bigger flare if it had happened last week.

“Another X-ray flare was made by Region 3664 as it moved past the western solar limb!!” It was an X8.7 flare this time, the biggest of this solar cycle! NASA’s Space Weather Prediction Center said in a post that any coronal mass ejection (CME) linked to this flare “likely WILL NOT have any geomagnetic effects on Earth due to its location.” “As always, please check our website for news!”

Today, as the CME moves past Earth, there may be a small rise in auroral activity. It’s too bad that nothing as exciting will happen as last Friday.

The solar cycle has a high point and a low point every 11 years. Around the peak, which could happen at any time, the most intense events tend to happen, but every once in a while, there are exceptions. There have been 10 times as many powerful flares this century.

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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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