Recently have been binge-ing on planets and cosmos, and I saw this youtuber mentioned that we might discover the next planet after Neptune.
However from my understanding, humanity has discovered black holes, magnetars, stars and so on that are hundreds, thousands or even more than that in terms of the measurement of light years.
Our solar system is not in the measurement of light years, yet we can’t discover the next planet after Neptune. Why ?
In: Technology
Stars are bigger and make their own light. Easy to see.
Planets are smaller, and only reflect light from it’s nearby star. Harder to see.
Also, the principle way of discovering planets, and other bodies, in our own solar system is taking multiple pictures of the same part of the sky back to back and looking for moving points of light. Stars are so far away from us that they don’t appear to be moving compared to everything else, so something that is almost certainly is orbiting the sun closer by. Thing is, due to the way orbital mechanics work, the farther away from the sun you are, the slower your orbit it, as well as wider. So this means a planet beyond Neptune (and the one they are predicting is far, FAR beyond Neptune) would be moving not only very slowly, but covering an incredibly tiny distance visually from Earth.
Think of a circle with two points on it, an inch apart from each other. You sit at the middle, and the circle radius is three inches. Visually, from the center, the two points are roughly 20 degrees apart from each other. If a point of light moved from one point to the other, it’s be incredibly visible. Now imagine the circle is 100ft in radius, and the two points are a millimeter apart. The distance visually would be .00~1 degrees apart, much harder to notice, especially if the light reflecting off of it is dim and at risk of being drowned out by background light. Even if it is spotted, it can easily be mistaken for a star.
The sky is also flippin huge, so doing such a scan over the entire sky is just no feasible, and would take a hundred years to do. This is why you sort of have to predict where the Planet’s going to be before you go looking for it. This is actually how Neptune was discovered. Galileo was thought to map Neptune twice, but it moved so slowly he mistook it for a fixed star. Le Verrie, like many astronomers at the time, found that Uranus’ orbit didn’t make sense, and hypothesized that another planet was exerting gravity on it, messing with its orbit. Using Uranus’ orbital data, he calculated where this planet should be, and sent it to an observatory to look for the Planet. They found it the next night, right where it was predicted.
The same thing is happening now with the search for Planet Nine, but using the orbits of Oort Cloud comets instead of a planet, which unfortunately doesn’t narrow down the predicted location enough to find the planet in one night and the orbits are possibly explained by measurement bias in how we detect and track Oort cloud comets.
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