Despite being known to humans for many thousands of years, the planets in the Solar System are still active areas of study for astronomers. Each of the planets is unique in some way, allowing us to see how different conditions can produce very different results just within our own astronomical back yard. When you add in things like asteroids and comets, the Solar System is a very dynamic place!
In addition to our own Solar System, astronomers now study planets around other stars, which are called exoplanets. These planets are so small and far away that it is very difficult to learn anything about them, or if they are even there at all. However, astronomers have developed some complex techniques for studying them, allowing us to learn more about what our Solar System could have been like if things had been slightly different.
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You are correct that many meteor showers are the result of the Earth passing through the remains of a comet tail, but the conditions have to be just right for that to actually happen. Most comets are not actually aligned with the orbits of the planets, meaning that while all of the major planets more or less orbit in one flat circle, comets can go far outside that circle. This is the case for Neowise, which, as you can see in this 3D model of the Solar System, travels completely above/below the Earth’s orbit. So it’s tail may leave some debris in the orbit of Mercury (which can’t really have meteor showers since it doesn’t have an atmosphere) but it won’t really do anything for the Earth.
The short answer is essentially that it is very unlikely that a tidally locked planet could ever be habitable all the way around without some weather condition being unfavorable. Usually, astronomers don’t consider tidally locked planets to be inhabitable at all.
For a more detailed explanation, tidally locked planets have a number of problems, mainly due to the fact that one side is very hot all the time. The temperatures would be extreme, with temperatures far too hot for life under the sun and far too cold on the dark half of the planet. Favorable temperatures would only be found somewhere in the “sunset zone” around the edge of the planet where the sun is low on the horizon. If you imagine an ocean facing the sun all the time, it would eventually evaporate and have its moisture carried off elsewhere, likely to the other side of the planet where the temperatures are hundreds of degrees colder and the moisture would freeze out, depositing a large amount of water on the other side. Beyond this, heating up rock continuously leads to it expelling gas, leading to a Venus-like runaway greenhouse effect, further messing with the planet’s weather.
The only way I could see the temperature being somewhat consistent would be if there were extremely strong winds going in bands around the planet. These types of winds exist in some form on the Earth (I’m not a meteorologist so I don’t know the details), but if you had winds that distributed the sun’s energy more equally around the planet, it might extend the habitable zone a bit. Of course, this would cause lots of other habitability issues and extreme weather, so this probably wouldn’t be nice.
It is very difficult to measure rotation for planets outside the solar system (exoplanets) and stars, but mostly astronomers rely on looking for regular fluctuations in brightness. If an exoplanet or star has a dark cloud or surface feature on it, then you can expect that once per rotation, that dark cloud would reduce the overall amount of light that you see from that object. If astronomers see regular dips in brightness like this, then you can guess that the time in between the dips is one day for that thing.
We can’t even make any direct observations of our own Oort cloud, let alone any clouds around other stars! The furthest object we have ever seen (the imaginatively named FarFarOut) is only 132 AU away from the Sun, which is not even 10% of the distance to the inner edge of the Oort cloud. So how do we even know that the Oort cloud is there if we can’t see it? The comets we see streaking through the inner Solar System every once in a while have orbits that take them far away from the Sun and in all directions equally, implying that there must be some large spherical cloud of comets out there even if we can’t see it. There’s no reason to expect that our Sun’s debris cloud looks any different than any other similar star, so it’s probably safe to assume that there are Oort clouds around them as well, but it’s essentially impossible to see such dim, distant, and diffuse clouds of material.
This is an interesting question that I had to spend a bit thinking about. There are a number of factors at play here that make the answer to your question a bit complicated. The first thing to note is that usually when astronomers talk about what a given star is made of, they talk about its “metallicity.” Conceptually, this is the amount of heavy elements (heavier than helium) present in a star, and practically this is usually defined based off of the ratio of iron to hydrogen in a star (Fe/H). You have correctly pointed out that younger stars tend to have higher metallicities than older stars because they incorporate metals from previous generations of stars.
Typically, stars form in large clusters from a single cloud of gas that condenses down into numerous stars in close proximity. These stars stay together for a period of time (the Pleiades star cluster in the night sky is a good example of what this looks like) but after a few hundred million years, their movement through the galaxy carries them away from each other, scrambling up the stellar population throughout the galaxy. So to answer your immediate question, the Sun’s “siblings” i.e. stars that were born from the same gas cloud and thus have the same composition, are likely very far from the Sun now so there should be no local grouping of “similar planets.”
However, in a broader sense, we do expect there to be roughly similar planet trends around our Sun because there is a trend in stellar metallicity as you go radially outwards from the center of the galaxy. Since there is more stuff (i.e. stars, gas, dust, etc.) in the center of the galaxy, more stars are formed and more metals are created compared to the more sparse outskirts of the galaxy. Astronomers have also observed a correlation between the metallicity of a star and the number of planets that form around it, so at a given distance from the galactic center (i.e. for a certain metallicity), there will actually be some similarity in the number of planets in a given solar system. If you’re interested in some more technical reading, I recommend this paper from Fischer & Valenti in 2005 about the subject, specifically Figure 4 which shows that stars with more iron are more likely to have planets.
So the Sun isn’t particularly related to the stars immediately around it, but it does fit in with an overall trend through the whole galaxy that makes it so nearby stars may be somewhat similar planet-wise.