What will happen in our universe in the future? Of course, astronomers are not prophets. However, if we can believe that the physical laws we understand now will operate the same way in the past, present, and distant future, then we can discuss what events might unfold in our universe. For example, in about 4 to 5 billion years, the Sun will eventually expand massively and completely disappear, leaving behind a planetary nebula. When we talk about the events that will occur in our universe, there is one event that always comes up: the collision and merger of our Milky Way galaxy with our neighboring Andromeda galaxy. In 2008, astronomers created a simulation consisting of 1.3 million particles to illustrate the gravitational interactions between our galaxy and Andromeda.

제한했습니다. 그 결과, 두 은하가 대략 50억 년 정도가 지났을 때 하늘에서 합쳐져 거대한 타원 은하가 된다는 결과를 얻었습니다. 이 결과는 빠르게 천문학계에서 받아들여지게 되었고, 이제 우리 은하가 안드로메다 은하와 충돌할 것이라는 이야기는 거의 기정 사실로 받아들여지고 있습니다. 그런데 최근 새로 업데이트된 결과를 통해 우리가 당연하다고만 생각했던 우리 은하의 미래 운명이 전혀 다른 방식으로 펼쳐질 수 있다는 아주 흥미로운 가능성이 제기되었습니다. 단적으로 말하자면, 우리 은하는 안드로메다 은하와 충돌하지 않을 수도 있습니다. 현재 타임즈의 예상과 달리, 무사할지도 모르는 우리 은하의 놀라운 운명에 관한 이야기를 소개합니다. 안드로메다 은하가 우리 은하를 향해 빠르게 다가오고 있다는 사실은 이미 오래전 천문학자 베스도 슬라이퍼의 스펙트럼 관측을 통해 알려지기 시작했습니다. 당시 슬라이퍼

The spectrum of the Andromeda Galaxy was found to be skewed toward very short wavelengths. This fact indicated that the two galaxies are approaching each other at a speed of nearly 110 kilometers per second. It means that the two galaxies are gradually being pulled together by each other's gravity. Many simulations conducted up until recently have supported the prediction that our galaxy and the Andromeda Galaxy will eventually merge into one. Impatient astronomers have even given a plausible name, Milkomeda, to the galaxy that will be formed after this merger, which is expected to be completed in about 5 to 7 billion years. Since this scenario is discussed so commonly in many places, such predictions feel very natural and obvious. However, predicting what will happen to our galaxy and the Andromeda Galaxy in the future is actually more complicated than one might think.

The process is as follows. First, surprisingly, astronomers still do not know the exact mass of our galaxy and the Andromeda galaxy. To determine the precise mass of a galaxy, one must consider not only the brightly shining stars but also the dark matter that fills the space between the stars. Naturally, dark matter cannot be seen directly. Instead, we can infer its presence by observing the movements of stars that are trapped in the overall gravitational pull of the galaxy, which allows us to estimate the strength of the galaxy's gravity, and thus its mass. Since we live in our galaxy, one might think that measuring its mass would be a piece of cake, but that is not the case at all. In fact, there is a more challenging aspect: the stars within the Milky Way are densely packed with clouds of gas, making it difficult to analyze each star individually.

Determining the mass of galaxies is very difficult. Astronomers still estimate that the mass of our Milky Way fluctuates by about two times. However, measuring the mass of Andromeda is not an easy task either. The distance to the Andromeda Galaxy is about 2.5 million light-years, which is quite ambiguous; it is far if you think about it, but close in the grand scheme of things. While it is relatively easy to distinguish satellite galaxies or globular clusters orbiting around Andromeda, observing individual stars remains a challenging issue. Unfortunately, astronomers still cannot accurately determine the masses of both our galaxy and the Andromeda Galaxy. They are not even sure which one is heavier. Another reason we find it difficult to answer the question of whether the Milkomeda Galaxy will form is the existence of numerous satellite galaxies orbiting each galaxy.

Galaxies, of course, have a mass that is only a fraction of that of the main galaxy at the center, typically between one hundredth to one thousandth. However, if their numbers are large, they cannot be ignored. The satellites are located at distances ranging from a few tens of thousands to a few hundred thousand light-years away. Gravity diminishes in effect the further away you get, so the influence of satellite galaxies that are relatively close by is significant, just like that of the much more distant Andromeda galaxy. To date, about 60 satellite galaxies have been discovered around our Milky Way, but astronomers estimate that there could be many more, ranging from a minimum of 100 to as many as 500, still hidden and yet to be discovered. The existence of these satellite galaxies obviously affects the orbits of both our Milky Way and the Andromeda galaxy. Therefore, if we cannot take all of them into account, predictions about the future of our galaxy cannot be perfect.

Currently, the Gaia satellite tracks not only the stars within our galaxy but also the movements of stars in relatively nearby satellite galaxies, including the Magellanic Clouds. It aims to create an accurate 3D spatial distribution map of the stars in our vicinity and to understand their detailed movements. Thanks to Gaia's significant contributions, we can now predict the future of the stars around us with greater precision than before. Recently, astronomers implemented refined simulations of galactic collisions based on the latest results from Gaia observations, and the findings are quite intriguing. When simulating the scenario where our galaxy and the Andromeda galaxy are set up, the possibility of the two galaxies actually colliding came out to be only about 50%. It may sound like an irresponsible prediction that there is a 50/50 chance of the two galaxies colliding or not colliding.

I don't know, but that's not the case at all. All this time, we have thought that the possibility of our galaxy colliding with Andromeda was obviously 100%. However, the prediction has suddenly dropped to half. But the interesting part doesn't end there. Astronomers have now included a larger satellite galaxy that orbits around Andromeda. This is the Triangulum Galaxy, which is the third heaviest galaxy in this local group of galaxies centered around our galaxy and the Andromeda Galaxy. Therefore, the gravity of this galaxy will also affect the possibility of a collision between the two massive galaxies. After including the Triangulum Galaxy, the collision possibility between our galaxy and Andromeda has increased to a level of about two minutes. But now, when we also consider the presence of the largest satellite galaxy, the Large Magellanic Cloud, which orbits our galaxy...

The possibility of a collision between our galaxy and Andromeda has dropped to 50%. Moreover, even in the 50% of cases where a collision might occur, the actual timing of the collision between the two galaxies is predicted to be 8 billion years from now. This is a stark contrast to previous predictions, which suggested that our galaxy would collide with Andromeda within the next 4 to 5 billion years and merge into one. In terms of both the likelihood of collision and the expected timing, the results are vastly different. Even if the two galaxies were to collide and form the Milkomeda Galaxy, the timing could be much further in the future than expected. By that time, it is highly likely that our solar system will have already disappeared. The Sun will have gone through its final stages, and Earth will likely have been completely absorbed into the Sun's surface. If the newly updated results are indeed true, we...

We may not need to worry about whether our solar system will be safe when the Milky Way collides with the Andromeda Galaxy, as by then, our Earth may no longer exist. It's not like we can predict when a small asteroid will crash into Earth, let alone when two massive galaxies, filled with countless stars, will collide or even if they will collide at all. The fact that making precise predictions about such events is so difficult illustrates how our universe can have its fate altered by even the smallest variables, revealing just how sensitive our universe is. I have confidently stated that our galaxy will eventually collide with Andromeda, but now I feel the need to respond more cautiously. Personally, I have been introducing myself...

Astronomers who study galaxy collisions have often talked about cosmic dust. Naturally, the galaxy collision I mentioned includes our Milky Way and the Andromeda Galaxy couple. However, perhaps we are destined to live in a relatively safe galaxy, far from collisions. This concludes today's episode of Cosmic Dust Times. Please subscribe and like as well. Thank you, Cosmic Dust viewers. Goodbye.

안드로메다와 우리은하는 충돌하지 않는다? 완전 뒤집힌 놀라운 예측 결과!

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