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Without wishing to dwell on it too much, but what is the frak's "Oumuamua?"
Oh, you remember Oumuamua. That made a lot of noise last year; previewed for the first time late 2017 by the pan-STARRS telescope in Hawaii, it was quickly discovered a very unusual orbit. Instead of the ellipse or the usual circle around the Sun, as for solar system objects, it turned out to have a hyperbolic orbit. This means that he was moving too fast to be tied to the sun, and this, in turn, means that it comes out of there. As really there: interstellar space, the void between the stars.
Subsequent observations have confirmed: "Oumuamua had just crossed the solar system, with so much extra speed (about 25 km / s) that it was moving faster than the exit speed of the Sun. It was a unique visitor screaming through the solar system and returning to The Black again.
This was certainly enough to be the subject of careful scrutiny. We had never seen anything from interstellar space crossing the solar system before! But what was it? At first it was classified as a comet, then an asteroid, then maybe a comet again (this confusion is reflected in its tentative designations, initially it was A / 2017 U1 for "asteroid ", then C / 2017 U1 for" comet ", then finally I / 2017 U1, for" interstellar "). It was hard to say what c & # 39; was; she was too small, too weak and too far away to make good observations, and worse yet, she was only seen when she was going out, so she was literally walking away from us every day.
Then, another very strange thing happened: more observations made it possible to better determine its trajectory and it was found that it did not slow down fast enough. When he moves away, the gravity of the Sun leans on it, slowing it down … but it does not slow down enough.
A force was acting on it, accelerating it very slightly. The comets are made of rock and ice, so maybe the ice was turning into gas, and as it was blown, it acted like a very soft rocket. The problem is that no such breakdown has been detected. If it looked like comets in our solar system, you would expect to see a lot of carbon monoxide (CO) and carbon dioxide (CO2) from it, but none was seen. So maybe it was another kind of ice, like water. But again, if it looks like our local comets, it would take so much water that we would have noticed.
It was then that two astronomers came up with something interesting: Maybe this force was a radiation pressure, literally the strength of the sunlight that was hitting it and giving it a little push. This makes sense, but for the calculation to work with the acceleration found, "Oumuamua had to be flat. As, really So flat that it looks more like a solar sail, a very thin sheet of material designed to capture sunlight and accelerate. But this, in turn, meant that "Oumuamua was artificial. Like in a spaceship.
Besides the obvious (this sounds like a big jump!), This idea is a problem for me. Since I wrote this, little has changed with this assumption, and if I would not rule out the fact that it is an extraterrestrial investigation, the evidence do not corroborate this conclusion and, in fact, corroborate it.
So, I ask again: What is the frak's Oumuamua?
A new document has been released that could have a solution, and it's really smart. Maybe 'Oumuamua is not flat. It may be fluffy.
When astronomers speculated that it was a thin, flat surface, which gave it a surface as large as a sail, they had to assume a density. Indeed, the amount of pressure exerted by the sunlight is very small. Therefore, if an object is large, it must be very thin and large to capture enough sunlight to speed it up enough to match the observations. They therefore assumed that it had a normal density in the range of 1 to 3 grams per cubic centimeter (approximately somewhere between the density of water and rock).
The new paper reverses the situation. Instead of assuming a density to find the area, assume that the size determined using normal methods is correct, use it to get an area, and then the density needed to match the observations.
– you measure the brightness and distance of an object, then you assume a reflectivity to get a size – is correct (somewhere between 50 and 130 meters), then, using the acceleration due to the light from the sun, use it to get the density.
Assuming a size for &umuamua from 50 to 130 meters, what they get is a very low density: about 0.00005 grams per cc C is incredibly low, and at first it seems ridiculous. It's 100 times less dense than air! No solid object can have such a low density!
… So if it is not solid?
I'm not saying that it's hollow, but it may be really porous. Like Styrofoam or Swiss cheese, but much more disturbing. Is there something natural like that?
It turns out that, surprisingly, yes. When the stars are very young, they are surrounded by a huge disk of material; it is from this material that the planets are formed. Far from the star, where the temperatures on the disc are cold, tiny grains of dust and water ice can form fun shapes, creating fractals. These are branched structures that are not regularly spaced like crystals; instead, they have a structure called self-similar: it looks the same regardless of the zoom you make. I know it sounds strange, but this video will help you:
We often see it in nature, including in snowflakes. Materials made in a fractal pattern can be very porous and, in fact, in this protoplanetary disk around a young star, physical models show that objects can grow fractally until they reach the size of "Oumuamua" and have this extremely low density counts for its strange behavior.
So, &umuamua does not have to be a spaceship. It just needs to be a snowflake! Snowflake of low density and extremely porous, built in three dimensions.
And in fact, that makes sense. The fact that we are seeing something like "Oumuamua coming from interstellar space means that we can try to estimate how many of them are there at any one time. By making some simple assumptions, the numbers you get are way too high to explain by the fact that the galaxy is filled with such beasts. It seems much more likely that objects such as' Oumuamua are relatively rare, which means that they probably come from a nearby place (if the objects came from further away, the odds are even higher weak that we would see one). In calculating the calculations, the new document suggests that it comes from a nearby, relatively young star (less than 100 million years old). It formed in the disc and was ejected in one way or another, probably from a planet forming nearby giving it a boost of its gravity.
I must say that I like that. It may not be as sexy or titillating as saying it's an extraterrestrial probe, but it's very clever, it uses known materials and calculations, and the conclusion even matches what we know of how planets are formed. That makes it pretty cool in itself. If I had to bet, I would put a lot more money for this idea to be correct because 'Oumuamua is an artifact of another civilization.
We may never know; it moves quite fast in relation to us and is very far now – it is currently more than 1.6 billion kilometers away. In a year, it will be 900 million km more. So, it's not like we can catch up with it anytime soon.
We will simply have to wait for another object of this type … which, according to this new idea, can take a lot of time. But we scan the heavens with better technology, we see more deeply, we see weaker objects, all the time now. I hope we will find more critters like this one. They can tell us a lot about the formation of planets in other star systems, which is quite difficult to understand from tens or hundreds of light years away. It's much easier when they send us bits and pieces of their building materials.
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