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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

Witness the rare celestial event of Mars and Jupiter reaching their closest proximity in the sky this week, a phenomenon that will not occur again until 2033.

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Mars and Jupiter will be only 0.3 degrees apart in the sky on August 14. From our point of view, this passage is very close. If you miss it, you won’t be able to see another one until 2033.

When two objects pass each other in the sky from our point of view, this is called a conjunction. Every time two planets came together, the closer one would block out the other because they would all be moving in a perfectly flat plane. The orbits of the planets are slightly different from those of the other planets, though, so they move slightly to the north and south of each other. Every time, that gap is a different size.

When two things happen close together, the results are especially stunning. Jupiter and Saturn were close enough to each other in 2020 that they could be seen in the same field of view through a telescope. This is a treat for people who like to observe the sky.

Being 0.5 degrees wide, the full moon will fit in any view that can hold the whole moon. This pair will also look good before and after the full moon.

But even with the naked eye, a close conjunction can make the sky look even more amazing. The contrast between the red of Mars and the white of Jupiter will be especially striking. However, Mars’ brightness changes a lot. When it’s at its brightest, it’s about the same brightness as Jupiter. Right now, it’s 16 times less bright. They are so bright that, unless there are clouds, you should be able to see them from all but the dirtiest cities.

Most people in the world will miss this sight, though, because they can’t see the pair of planets in the evening from anywhere on Earth. The exact time they rise depends on where you live, but it’s usually between midnight and 3 am. To see this, you will mostly need to get up before astronomical twilight starts so that you have time to get through the thickest part of the atmosphere.

For people in Europe, Africa, west Asia, and the Americas, the closest time will be 14:53 UTC, which is during the day. The mornings before and after, though, will look almost as close.

Mars and Jupiter meet about every two and a half years, but the most recent one was almost twice as far away and could only be seen in the morning. In 2029, the gaps will be just under two degrees. The next one will be even wider, at more than a degree.

When planets are close to each other, that doesn’t always mean that their distance from each other is very small. Mars has been around the Sun for 687 days, but it is now less than 100 days past its perihelion, which means it is closer than usual. Even though Jupiter is a little closer than usual, it’s not really that close. To be as close as possible to each other, Mars has to be at its farthest point, and Jupiter has to be at its closest point. So this one is not unusual.

But if you want to see something beautiful, you will have to wait more than nine years to see it again.

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Astronomy

It may not be long before we find “Earth’s Twin”

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To figure out if there is life in other parts of the universe, we start with Earth, where there is life now. Finding another Earth is a good way to find aliens. We have found more than 5,000 exoplanets, but we haven’t found Earth’s twin yet. This could change soon, though. Here comes the PLATO mission from the European Space Agency (ESA).

What does PLATO stand for? It stands for PLAnetary Transits and Oscillations of stars. Its goal is very clear. It will look for nearby stars like the Sun that might have habitable worlds like Earth.

“One of the main goals is to find a way to compare Earth and the Sun.” The size of Earth is in the habitable zone of a star like the Sun. “We want to find it around a star that’s bright enough that we can really figure out how heavy it is and how big it is,” Dr. David Brown from the University of Warwick told IFLScience. “If you like, that’s our main goal.”

The telescope is not only an observatory for looking for planets, but it is also an observatory for collecting data on a huge number of stars. The mission team thinks that the fact that it can do both is a key part of why this telescope will be so important.

“You have two parts of the mission.” One is exoplanets, and the other is the stars. “From a scientific point of view, I think it’s pretty cool that these two parts are working together to make the best science we can,” Dr. Brown said.

One of the secondary goals is to make a list of all the planets that are Earth-like and all the star systems that are out there. One more goal is to find other solar systems that are like ours. Even though we don’t know for sure if our little part of the universe is truly unique, it does seem to be different from everything else.

Dr. Brown told IFLScience, “We have a bunch of other scientific goals.” “Really, how well do we know how planetary systems change and grow over time?” Planetary systems are something we’re trying to understand as a whole, not just one planet at a time.

PLATO is different in more ways than just the goals. It is not just one telescope. In fact, it’s made up of 26 different ones. Two of the cameras are fast, and the other 24 are normal cameras set up in groups of six with a small gap between them. This makes the telescope work better, has a wider field of view, and lets you quickly rule out false positives.

It can be hard to tell which of the things you find when you transit exoplanets are real and which ones are not. With the help of several telescopes, we were able to block out some of the mimics that we would have seen otherwise. “Plus, it looks pretty cool,” Dr. Brown said with excitement. “This big square with all of these telescopes pointing at you looks really cool!”

This week, Dr. Brown gave an update on PLATO at the National Astronomy Meeting at the University of Hull. The telescope is being put together and has recently passed important tests. There are no changes to the planned launch date for December 2026. An Ariane 6 rocket, the same kind that made its first launch last week, will take off from French Guiana.

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Astronomy

You can watch and listen to gravitational waves coming from everywhere in the universe

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Gravitational waves can be turned into sound very easily. The little chirp changes into little sounds as soon as the blocks hit each other. One of those chirps is my ringtone when my phone has sound, which doesn’t happen very often. The people at Audio Universe have now made the gravitational wave data even better.

In a 3D video, the sounds of gravitational waves hit you from the direction in the sky where it is thought they came from. The sound effects and visualization are both great. There are tiny vibrations in space-time that can hit you as you move your mouse, phone, or VR headset.

Like other sonification projects, it gives blind and visually impaired people a way to get involved in astronomy. It works well with other methods like the Tactile Universe. But that’s not the only reason why they do it.

“We want to do this for three reasons.” It helps researchers look into big, complicated datasets with lots of dimensions. It could be used to make educational materials that are immersive and interesting. Rose Shepherd from Newcastle University says, “It can also make astronomy easier for more people to understand, which is an important thing.” “Making things easier to get makes them better for everyone.”

Being able to listen to the emission lines of celestial objects is one of the most interesting things about sonification for research. As an object moves, its light spectrum peaks spread out, and sonification can make something that is barely noticeable to the eye seem very clear to the ear.

This is helpful in more than one field, though. The group has thought about how adding sound to different datasets could make them better. Warming Stripes is a cool example of this. This is a simple image that shows changes in temperature over time by using a series of stripes, from blue to red. The stripes on the right side get redder as we move from the left to the right. The left side shows decades ago. It is great to see how the climate crisis is getting worse, and now sound adds a little more to it.

“By adding sounds, it can give your data an emotional meaning.” Shepherd explained, “You can use that to show the data how you feel.” “We didn’t mean for the Warming Stripes sonification to make people feel stressed, but it was interesting to see how they reacted instead of just watching the video.”

Audio Universe is making a sonic toolkit that many people can use to make their own resources.

She gave a talk about the audio universe at the National Astronomy Meeting at the University of Hull this week.

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