The Age of Interstellar Aliens

The Age of Interstellar Aliens
The Age of Interstellar Aliens

Recently, two interstellar objects have already been discovered - a comet and an asteroid, formed outside our solar system. Thanks to new research, scientists hope to find such objects more often in the future. According to the author, these interstellar wanderers can tell us a lot about the structure of the universe.

It's like science fiction: a tiny world formed by a distant star itself arrived in our cosmic environs for us to study. And yet it happened, and only twice in the last few months. And further in this decade it will be even more frequent.

The first known interstellar object - that is, formed outside our solar system - was discovered in late 2017 and was named 1I / Oumuamua. At first, scientists didn't know what to think. There was not much time for research - in just two weeks the asteroid rushed away from the Earth. Data about him is fragmentary. It was a small, elongated world the size of a skyscraper - smaller than most common comets and asteroids. Oumuamua's color was reddish - reddish hues predominate in the far reaches of the solar system, where a continuous rain of starlight interacts with carbon-rich molecules.

The second interstellar traveler, 2I / Borisov, is definitely a comet, and very similar to those that form on the icy outskirts of our own system. When comets approach the Sun, they "bloom": heavy with ice since the formation of the planets of our solar system, under the gentle warmth of our star, they grow impressive tails of gas and dust. In the light of these beams of sublimating vapor, imprints of the comet's chemical composition appear. Some of the frozen molecules and ions are well known to us - for example, ammonia and water. We determine their presence by the "offspring" separated by sunlight - the daughter of ammonia, the amino group NH2, and the son of water, hydroxyl OH. Borisov has a similar chemical composition - we found out when the comet approached the Sun last month. Borisov is close to our comets both in size - a little less than a kilometer - and a slow dissolution rate.

These interstellar ambassadors pique the interest of scientists because the samples frozen in the comet's tail reveal the chemical makeup of its home. Now, thanks to 2I / Borisov, we finally have a chance to learn about the surroundings of other stars first-hand. We can already assume that comets in the solar system and beyond are formed under the influence of the same processes. Oumuamua appeared too late to study it in detail, but Gennady Vladimirovich Borisov discovered his namesake much earlier, at the very beginning of her journey through the solar system, and this gave us months of study.

However, both objects were relatively faintly visible, and this made them difficult to observe and classify. Apparently, there were many such visitors in the past, but we can only find them now - thanks to technological advances. Telescopes that scan the skies looking for near-Earth asteroids and other diverse objects within the solar system are also good at detecting interstellar objects. Wide-angle cameras continuously photograph wide swaths of the sky, and software picks up any stray light sources, detecting newcomers. Our observation is becoming more accurate, and an even deeper search is ahead. The Telescope named after Vera Rubin will shoot the entire southern sky every three nights during the ten-year Trunk exploration of space and time. The stakes are rising, and astronomers hope this study will find interstellar aliens at least once a year.

This high frequency of discoveries is due to the fact that our galaxy is teeming with tiny wandering worlds. Each star, in one way or another, parted with most of the asteroids and comets, which it itself produces - including through gravitational shocks from migrating planets or when the attraction of a dying star to comets from a distant orbit weakens. Thus, our galaxy is not only a cluster of stars, but also countless interstellar asteroids and comets, and each star has contributed to their trillions. There are 10 of them in the entire galaxy to the 26th degree or so. Although collectively these travelers make up only a small fraction of the mass of the galaxy, we have yet to understand their role in planetary formation. Researchers are studying how these fugitive worlds are trapped where stars are born and disks of planetary systems form. Like supernovae - stellar explosions - that give birth to new stars, the life cycles of planetary systems also give rise to new planets, and this endless cycle continues throughout the history of the galaxy.

But that's not all. The galaxies themselves are formed as a result of the merger and interlacing of several host galaxies, once separated by vast distances. This process is a key part of their evolution, but the smallest details rarely come under attention. How planetary systems form in another galaxy nobody knows, but future interstellar objects may tell us - leaving an islet-sized chunk right at our doorstep.

Thanks to future data, we are very close to developing a coherent theory about the formation, growth and change of planetary systems. Until now, astrophysicists have studied only scattered parts of the system's life cycle, trying to somehow link up fragments that differ in age by more than a billion years, and in mass by 36 orders of magnitude. Samples from systems outside of our own provide a chance for specific experimental data. In the end, where did we get the idea that we weren't fantasizing? Even the meager data that we have collected about Oumuamua left a whole host of theories about its origin. Just a few months later, the New Horizons spacecraft showed that Arrocot, the primordial world in the Kuiper belt, has a strange shape, not foreseen by theory - it is a contact asteroid made of two neatly docked pancakes. Even if our solar system is fraught with such miracles, then what will the next interstellar wanderer bring us?

As for me, the appearance of planetary debris, born in another star, tells us that we are on the verge of a revolution - a shift that began hundreds of years ago that will fundamentally change the way we think about our own home. So, the orbit of Pluto showed that today the solar system has a different shape than when it was just formed, and among exoplanetary systems there is a wild variety of shapes and sizes that are not very similar to ours. Now we have learned that the chemical composition of our comets is by no means unique. The commonality of space means that what is happening here is in some way connected with what is happening on the other side of our galaxy - or even beyond. Truly, we are part of the big picture.

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